http://www.cfd-online.com/W/index.php?title=Special:Contributions/ForMat&feed=atom&limit=50&target=ForMat&year=&month=CFD-Wiki - User contributions [en]2016-12-03T08:19:58ZFrom CFD-WikiMediaWiki 1.16.5http://www.cfd-online.com/Wiki/Ansys_FAQAnsys FAQ2006-10-04T06:09:28Z<p>ForMat: added one Q and A</p>
<hr />
<div>This article contains answers for Ansys related FAQ. <br />
Please feel free to add questions and answers here!<br />
<br />
== CFX-5 ==<br />
<br />
=== Preprocessing ===<br />
<br />
=== Solver related questions ===<br />
==== How to avoid 6000 - 7000 K temperatures using finite rate chemistry model ====<br />
Edit the def file and add the following to the edited ccl file.<br />
(You can do it by simply clicking the EDIT button in cfx5solver or using cfx5cmds command)<br />
Add these lines to the EXPERT section: <br />
EXPERT PARAMETERS:<br />
stiff chemistry = t<br />
END<br />
<br />
If you don't have this section, you can create it and then add a line there<br />
(see the manual).<br />
<br />
=== Postprocessing ===<br />
<br />
<br />
== FSI (Fluid Structure Interaction) ==<br />
=== General ===<br />
==== Which programms are necessary to solve a FSI simulation? ====<br />
Beginning with Ansys 11.0, Ansys Workbench with Simulation and CFX are required.<br />
<br />
==== Which Ansys licenses are required for FSI in Ansys? ====<br />
Working with Ansys 10.0 or older, a Muliphysics and a CFX license are required. Ansys 11.0 requests an Ansys Product and a CFX license.<br />
<br />
==== What kind of coupling methods are possible? ====<br />
One-way or two-way FSI coupling.<br />
<br />
==== Is it possible to perform a steady-state FSI simulation? ====<br />
Yes, Ansys 11.0 enables steady state and transient FSI simulations as well.<br />
<br />
==== What is the general procedure for a FSI simulation in Ansys 11.0? ====<br />
1. Define the Solid setup in Ansys Simulation (Ansys Workbench). This includes an Fluid-Solid-Interface.<br />
<br />
2. Write an Ansys Input File (.inp) of this setup.<br />
<br />
3. Define the Fluid setup in Ansys CFX-Pre. A link to the Ansys Input File is required.<br />
<br />
4. Write an Ansys Definition File (.def) of this setup. <br />
<br />
5. Solve the Definition File with Ansys CFX-Solver.<br />
<br />
6. Postprocess the data in CFX-Post.<br />
<br />
<br />
=== CFX Setup ===<br />
<br />
<br />
=== Ansys Setup ===<br />
<br />
<br />
=== Solving ===<br />
==== How do I start an FSI simulation in Ansys 11.0? ====<br />
Start the CFX Solver Manager and load the .def File. Ansys will load the .inp file automatically.<br />
<br />
==== Is it necessary to define the Ansys Insallation Root in "Define Run" in Ansys 11.0? ====<br />
On a Windows PC it is not, on Unix it is necessary.<br />
<br />
==== Is it possible to stop a running FSI simulation in Ansys 11.0? ====<br />
No, the "Stop"-button does not work for FSI simulations.<br />
<br />
==== Is it possible to write back-up files of a FSI simulation in Ansys 11.0? ====<br />
<br />
==== The solver terminates with the error message "A negative volume appeared". What went wrong? ====<br />
This error often appears with FSI simulations. Normally it comes together with a large deflection simulation of the solid part. Mostly the CFD-mesh deformation is too big and negative elements appear. Possible solutions might be<br />
* a better fluid mesh<br />
* meshsiffness 1/wall distance<br />
* smaller timesteps<br />
<br />
<br />
=== Postprocessing ===<br />
==== If I open the FSI simulation in CFX-Post 11.0 only the fluid data are available. Where are the solid data? ====<br />
CFX-Post only opens the .res file by default. If you want to postprocess fluid and solid data together you have to load the solid data additionally: File -> Load Result -> Load the Ansys .rst or similar data an activate the radio button "add data". Now you can postprocess all data in CFX-Post.<br />
<br />
<br />
== Ansys Workbench ==<br />
<br />
== ICEM CFD ==<br />
<br />
== CFX-Mesh ==<br />
<br />
== How should I ask my question on the CFX forum to get the best possible answer? ==<br />
<br />
The most important point to understand about the CFX forum is that the quality of the answer to your question will depend entirely on the quality of your question!<br />
<br />
Most of the questions posed on the CFX forum are so poorly posed that it's impossible to understand what the poster is actually asking. If you want effective help with your problem adhere to the following guidelines:<br />
<br />
# Make sure your question is as clear, concise and as intelligible as possible. Use punctuation. Other forum readers are not going to spend time trying to decipher a garbled question.<br />
# Give a clear general description of what class of problem and/or application you are working on BEFORE you start asking specific questions. This will aid other forum readers to better understand your specific questions.<br />
# Describe precisely what you have done yourself to try and solve your problem, giving examples.<br />
# Depending on your problem you should always include the following:<br />
#*A copy of your command file as a file attachment. Many simple problems can be spotted in a command file by an expert user.<br />
#*If you are asking a mesh quality related question then include some sample images of your mesh, including the boundary layer.<br />
#*If you are asking a user Fortran and/or user CEL question then include a copy of your existing code file as an attachment.<br />
<br />
Dont's:<br />
* Dont ask over broad questions e.g. "How do I simulate a 4-stroke engine". Nobody is going to type out fifty pages of guidance. They have better things to do.<br />
<br />
* Don't shorten the words. It's a web forum, not a SMS text message. It's very hard to read it. Or R U 2 lazy? People may tend to be lazy to decipher and answer.<br />
<br />
Example of a well posed question:<br><br />
FIXME<br />
<br />
Examples of questions that are unanswerable:<br><br />
FIXME<br />
<br />
How to upload images: <br />
* Create the image on your local machine e.g. skew_mesh.jpg<br />
* Upload the image to [http://www.imageshack.us Imageshack]<br />
* Copy the link "Thumbnail for websites"<br />
* Paste the link into your post e.g. <i><nowiki><a href="http://img91.imageshack.us/my.php?image=pipeym8.jpg" target="_blank"><img src="http://img91.imageshack.us/img91/5681/pipeym8.th.jpg" border="0" alt="Free Image Hosting at www.ImageShack.us" /></a></nowiki></i><br />
<br />
How to share non-image files as attachments:<br />
* If you have more than one file, zip them into a single file.<br />
* Upload the file to [http://www.rapidshare.de Rapidshare] <br />
* Scroll down to "I don't want a collector's account right now. Just give me the download-link." and click it.<br />
* Scroll down until you see the link e.g. <i><nowiki>http://rapidshare.de/files/33808646/audio.log.html</nowiki></i><br />
<br />
[[Category: FAQ's]]<br />
<br />
{{Stub}}</div>ForMathttp://www.cfd-online.com/Wiki/CombustionCombustion2005-10-02T14:33:13Z<p>ForMat: /* Infinitely fast chemistry */</p>
<hr />
<div>== What is combustion -- Physics versus modelling ==<br />
<br />
Combustion phenomena consists of many physical and chemical processes with <br />
broad range of time scales. Mathematical description of combustion is not <br />
always trivial. Analytical solutions exists only for basic situations of <br />
laminar flame and <br />
because of its assumptions it is often restricted to few problems solved <br />
usually in zero or one-dimensional space. <br />
<br />
Problems solved today concern mainly turbulent flows, gas as well as liquid <br />
fuels, pollution issues (products of combustion as well as for example noise <br />
pollution). These problems require not only extensive experimental <br />
work, but also numerical modelling. All combustion models must be validated <br />
against the experiments as each one has its own drawbacks and limits. However here <br />
the modelling part will be mainly addressed.<br />
<br />
<br />
== Reaction mechanisms ==<br />
<br />
The combustion is mainly chemical process and although we can, to some extend, <br />
describe flame without any chemistry informations, for modelling of flame <br />
propagation we need to know the speed of reactions, product concentrations, <br />
temperature and other parameters. <br />
Therefore more or less detailed information about reaction kinetics is <br />
essential for any combustion model. <br />
Mixture will generally combust, if the reaction of fuel and oxidiser is fast enough to <br />
maintain until all of the mixture is burned into products. If the reaction <br />
is too slow, the flame will extinguish, if too fast, explosion or even <br />
detonation will occur. The reaction rate of typical combustion reaction <br />
is influenced mainly by concentration of reactants, temperature and pressure. <br />
<br />
A stoichiometric equation of an arbitrary equation can be written as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\sum_{j=1}^{n}\nu' (M_j) = \sum_{j=1}^{n}\nu'' (M_j),<br />
</math></td></tr></table><br />
<br />
where $\nu$ is the stoichiometric coefficient, <math>M_j</math> is arbitrary species. One <br />
prime specifies the reactants and double prime products of the reaction. <br />
<br />
Reaction rate, expressing the rate of disappearance of reactant <b>i</b><br />
of such a reaction, is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
RR_i = k \, \prod_{j=1}^{n}(M_j)^{\nu'},<br />
</math></td></tr></table><br />
<br />
in which <b>k</b> is the specific reaction rate constant. Arrhenius found that this <br />
constant is a function only of temperature and this function is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
k= A T^{\beta} \, exp \left( \frac{-E}{RT}\right)<br />
</math></td></table><br />
<br />
where <b>A</b> is pre--exponential factor, <b>E</b> is activation energy and <math>\beta</math> is <br />
temperature exponent. <br />
These constants for given reactions can be found in literature. <br />
The reaction mechanism can be given from experiments for every reaction <br />
resolved, it could be also constructed numerically by automatic generation <br />
method (see [Griffiths (1994)] for review on reaction mechanisms).<br />
For simple hydrocarbon tens to hundreds of reactions are involved. <br />
By analysis and systematic reduction of reaction mechanisms global reaction <br />
(from one to five step reactions) can be found (see [Westbrook (1984)]).<br />
<br />
== Governing Equations ==<br />
<br />
The mass fraction transport equation for <i>k-th</i> species <math> Y_k </math> <br />
<br />
<table width="100%"><br />
:<math><br />
\frac{\partial}{\partial t} \left( \rho Y_k \right) +<br />
\frac{\partial}{\partial x_j} \left( \rho u_j Y_k\right) = <br />
\frac{\partial}{\partial x_j} \left( \rho D_k \frac{\partial Y_k}{\partial x_j}\right)+ w_k<br />
</math><br />
</td><td>(1)</td></tr><br />
<tr><td><br />
</table><br />
<br />
where Ficks law is assumed for scalar diffusion and <br />
<math> w_k </math> is the species reaction rate.<br />
<br />
== Infinitely fast chemistry ==<br />
All combustion models can be divided into two main groups according to the <br />
assumptions on the reaction kinetics.<br />
We can either assume the reactions to be infinitely fast - compared to <br />
e.g. mixing of the species, or of the comparable time scale of the mixing <br />
process. The simpler approach assuming chemistry fast enough, that the limiting <br />
process is mixing of the species is historically older approach and even today can<br />
be appropriate approach. It is simpler to solve then [[#Finite rate chemistry]] models, <br />
but introduces errors to the solution which may or may not be important. <br />
<br />
=== Premixed Combustion ===<br />
Premixed flame occurs in mixtures of fuel and oxidiser,<br />
homogeneously premixed prior to the flame. These flames are not <br />
limited only to gas fuels, but also to the pre-vaporised fuels.<br />
Typical example of premixed laminar flame is bunsen burner, where <br />
the air enters the fuel stream. The mixture burns in the wake of the <br />
riser tube walls forming nice stable flame.<br />
The premixed flames has many advantages in terms of control of temperature and <br />
products and pollution concentration, but introduce also some dangers like the autoignition (in the supply system).<br />
<br />
==== Turbulent flame speed model ====<br />
<br />
==== Eddy Break-Up model ====<br />
<br />
The Eddy Break-Up model is the typical example of mixed-is-burnt combustion model. <br />
It is based on the work of Magnussen and Hjertager, <br />
and Spalding and can be found in all CFD packages. <br />
The model assumes the reactions to be completed in the moment of mixing, so that the reaction rate is completely controlled by turbulent mixing. <br />
The combustion is described by a single step global chemical reaction:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
F + \nu_s O \rightarrow (1+\nu_s) P<br />
</math></td><td width="5%"></td></tr></table><br />
<br />
in which <b>F</b> stands for fuel, <b>O</b> for oxidiser and <b>P</b> for products of the reaction. Alternativelly we can have multistep scheme, where each reaction has its own mean reaction rate.<br />
The mean reaction rate is given by:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\bar{\dot\omega}_F=A_{EB} \frac{\epsilon}{k} <br />
min\left[\bar{C}_F,\frac{\bar{C}_O}{\nu},<br />
B_{EB}\frac{\bar{C}_P}{(1+\nu)}\right]<br />
</math></td><td width="5%"></td></tr></table><br />
<br />
<br />
<math>\bar{C}</math> denotes mean concentrations for fuel, oxidiser and products <br />
respectively, <b>A</b> and <b>B</b> are model constants with typical values of 0.5 <br />
and 4.0 respectively. The values of these constants are fitted according <br />
to the experimental results and they are suitable for most of the general cases. <br />
Still they are just constants based on experimental fitting and they need not <br />
be suitable for <b>all</b> the situations. <br />
Care must be taken especially in highly strained regions, where the ratio of <math>k</math> <br />
to <math>\epsilon</math> is large (flame-holder wakes, walls ...). In those regions a positive reaction rate occurs and an artificial flame can be observed.<br />
CFD codes usually has some remedies to overcome this problem.<br />
<br />
This model largely over-predicts temperatures and concentrations of species like <i>CO</i> and other species. Still this model is quite popular for its simplicity and relatively easy convergence and implementation.<br />
<br />
==== Bray-Moss-Libby Model ====<br />
<br />
=== Non premixed combustion ===<br />
<br />
==== Conserved scalar equilibrium models ====<br />
<br />
== Finite rate chemistry ==<br />
<br />
=== Premixed Combustion ===<br />
<br />
==== Coherent Flame Model ====<br />
<br />
==== Flamelets based on G equation ====<br />
<br />
=== Non-premixed Combustion ===<br />
<br />
==== Flamelets based on conserved scalar ====<br />
<br />
==== Conditional Moment Closure (CMC)====<br />
<br />
==== Multiple Mapping Closure (MMC) ====<br />
<br />
=== Linear Eddy Model ===<br />
<br />
=== PDF transport models ===<br />
<br />
==== Lagrangian ====<br />
<br />
==== Eulerian ====<br />
<br />
== References ==<br />
<br />
*{{reference-paper|author=Griffiths J.F.|year=1994|title=Reduced Kinetic Models and Their Application to Practical Combustion Systems |rest=Prog. in Energy and Combustion Science,Vol. 21, pp. 25-107}} <br />
*{{reference-paper|author=Westbrook, Ch.K., Dryer,F.L.,|year=1984|title=Chemical Kinetic Modeling of Hydrocarbon Combustion |rest=Prog. in Energy and Combustion Science,Vol. 10, pp. 1-57}}<br />
<br />
== External links and sources ==</div>ForMathttp://www.cfd-online.com/Wiki/CombustionCombustion2005-10-02T14:31:36Z<p>ForMat: /* Infinitely fast chemistry */</p>
<hr />
<div>== What is combustion -- Physics versus modelling ==<br />
<br />
Combustion phenomena consists of many physical and chemical processes with <br />
broad range of time scales. Mathematical description of combustion is not <br />
always trivial. Analytical solutions exists only for basic situations of <br />
laminar flame and <br />
because of its assumptions it is often restricted to few problems solved <br />
usually in zero or one-dimensional space. <br />
<br />
Problems solved today concern mainly turbulent flows, gas as well as liquid <br />
fuels, pollution issues (products of combustion as well as for example noise <br />
pollution). These problems require not only extensive experimental <br />
work, but also numerical modelling. All combustion models must be validated <br />
against the experiments as each one has its own drawbacks and limits. However here <br />
the modelling part will be mainly addressed.<br />
<br />
<br />
== Reaction mechanisms ==<br />
<br />
The combustion is mainly chemical process and although we can, to some extend, <br />
describe flame without any chemistry informations, for modelling of flame <br />
propagation we need to know the speed of reactions, product concentrations, <br />
temperature and other parameters. <br />
Therefore more or less detailed information about reaction kinetics is <br />
essential for any combustion model. <br />
Mixture will generally combust, if the reaction of fuel and oxidiser is fast enough to <br />
maintain until all of the mixture is burned into products. If the reaction <br />
is too slow, the flame will extinguish, if too fast, explosion or even <br />
detonation will occur. The reaction rate of typical combustion reaction <br />
is influenced mainly by concentration of reactants, temperature and pressure. <br />
<br />
A stoichiometric equation of an arbitrary equation can be written as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\sum_{j=1}^{n}\nu' (M_j) = \sum_{j=1}^{n}\nu'' (M_j),<br />
</math></td></tr></table><br />
<br />
where $\nu$ is the stoichiometric coefficient, <math>M_j</math> is arbitrary species. One <br />
prime specifies the reactants and double prime products of the reaction. <br />
<br />
Reaction rate, expressing the rate of disappearance of reactant <b>i</b><br />
of such a reaction, is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
RR_i = k \, \prod_{j=1}^{n}(M_j)^{\nu'},<br />
</math></td></tr></table><br />
<br />
in which <b>k</b> is the specific reaction rate constant. Arrhenius found that this <br />
constant is a function only of temperature and this function is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
k= A T^{\beta} \, exp \left( \frac{-E}{RT}\right)<br />
</math></td></table><br />
<br />
where <b>A</b> is pre--exponential factor, <b>E</b> is activation energy and <math>\beta</math> is <br />
temperature exponent. <br />
These constants for given reactions can be found in literature. <br />
The reaction mechanism can be given from experiments for every reaction <br />
resolved, it could be also constructed numerically by automatic generation <br />
method (see [Griffiths (1994)] for review on reaction mechanisms).<br />
For simple hydrocarbon tens to hundreds of reactions are involved. <br />
By analysis and systematic reduction of reaction mechanisms global reaction <br />
(from one to five step reactions) can be found (see [Westbrook (1984)]).<br />
<br />
== Governing Equations ==<br />
<br />
The mass fraction transport equation for <i>k-th</i> species <math> Y_k </math> <br />
<br />
<table width="100%"><br />
:<math><br />
\frac{\partial}{\partial t} \left( \rho Y_k \right) +<br />
\frac{\partial}{\partial x_j} \left( \rho u_j Y_k\right) = <br />
\frac{\partial}{\partial x_j} \left( \rho D_k \frac{\partial Y_k}{\partial x_j}\right)+ w_k<br />
</math><br />
</td><td>(1)</td></tr><br />
<tr><td><br />
</table><br />
<br />
where Ficks law is assumed for scalar diffusion and <br />
<math> w_k </math> is the species reaction rate.<br />
<br />
== Infinitely fast chemistry ==<br />
All combustion models can be divided into two main groups according to the <br />
assumptions on the reaction kinetics.<br />
We can either assume the reactions to be infinitely fast - compared to <br />
e.g. mixing of the species, or of the comparable time scale of the mixing <br />
process. The simpler approach assuming chemistry fast enough, that the limiting <br />
process is mixing of the species is historically older approach and even today can<br />
be appropriate approach. It is simpler to solve then [[#Finite rate chemistry models]], <br />
but introduces errors to the solution which may or may not be important. <br />
<br />
=== Premixed Combustion ===<br />
Premixed flame occurs in mixtures of fuel and oxidiser,<br />
homogeneously premixed prior to the flame. These flames are not <br />
limited only to gas fuels, but also to the pre-vaporised fuels.<br />
Typical example of premixed laminar flame is bunsen burner, where <br />
the air enters the fuel stream. The mixture burns in the wake of the <br />
riser tube walls forming nice stable flame.<br />
The premixed flames has many advantages in terms of control of temperature and <br />
products and pollution concentration, but introduce also some dangers like the autoignition (in the supply system).<br />
<br />
==== Turbulent flame speed model ====<br />
<br />
==== Eddy Break-Up model ====<br />
<br />
The Eddy Break-Up model is the typical example of mixed-is-burnt combustion model. <br />
It is based on the work of Magnussen and Hjertager, <br />
and Spalding and can be found in all CFD packages. <br />
The model assumes the reactions to be completed in the moment of mixing, so that the reaction rate is completely controlled by turbulent mixing. <br />
The combustion is described by a single step global chemical reaction:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
F + \nu_s O \rightarrow (1+\nu_s) P<br />
</math></td><td width="5%"></td></tr></table><br />
<br />
in which <b>F</b> stands for fuel, <b>O</b> for oxidiser and <b>P</b> for products of the reaction. Alternativelly we can have multistep scheme, where each reaction has its own mean reaction rate.<br />
The mean reaction rate is given by:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\bar{\dot\omega}_F=A_{EB} \frac{\epsilon}{k} <br />
min\left[\bar{C}_F,\frac{\bar{C}_O}{\nu},<br />
B_{EB}\frac{\bar{C}_P}{(1+\nu)}\right]<br />
</math></td><td width="5%"></td></tr></table><br />
<br />
<br />
<math>\bar{C}</math> denotes mean concentrations for fuel, oxidiser and products <br />
respectively, <b>A</b> and <b>B</b> are model constants with typical values of 0.5 <br />
and 4.0 respectively. The values of these constants are fitted according <br />
to the experimental results and they are suitable for most of the general cases. <br />
Still they are just constants based on experimental fitting and they need not <br />
be suitable for <b>all</b> the situations. <br />
Care must be taken especially in highly strained regions, where the ratio of <math>k</math> <br />
to <math>\epsilon</math> is large (flame-holder wakes, walls ...). In those regions a positive reaction rate occurs and an artificial flame can be observed.<br />
CFD codes usually has some remedies to overcome this problem.<br />
<br />
This model largely over-predicts temperatures and concentrations of species like <i>CO</i> and other species. Still this model is quite popular for its simplicity and relatively easy convergence and implementation.<br />
<br />
==== Bray-Moss-Libby Model ====<br />
<br />
=== Non premixed combustion ===<br />
<br />
==== Conserved scalar equilibrium models ====<br />
<br />
== Finite rate chemistry ==<br />
<br />
=== Premixed Combustion ===<br />
<br />
==== Coherent Flame Model ====<br />
<br />
==== Flamelets based on G equation ====<br />
<br />
=== Non-premixed Combustion ===<br />
<br />
==== Flamelets based on conserved scalar ====<br />
<br />
==== Conditional Moment Closure (CMC)====<br />
<br />
==== Multiple Mapping Closure (MMC) ====<br />
<br />
=== Linear Eddy Model ===<br />
<br />
=== PDF transport models ===<br />
<br />
==== Lagrangian ====<br />
<br />
==== Eulerian ====<br />
<br />
== References ==<br />
<br />
*{{reference-paper|author=Griffiths J.F.|year=1994|title=Reduced Kinetic Models and Their Application to Practical Combustion Systems |rest=Prog. in Energy and Combustion Science,Vol. 21, pp. 25-107}} <br />
*{{reference-paper|author=Westbrook, Ch.K., Dryer,F.L.,|year=1984|title=Chemical Kinetic Modeling of Hydrocarbon Combustion |rest=Prog. in Energy and Combustion Science,Vol. 10, pp. 1-57}}<br />
<br />
== External links and sources ==</div>ForMathttp://www.cfd-online.com/Wiki/CombustionCombustion2005-10-02T14:25:08Z<p>ForMat: /* Eddy Break-Up model */</p>
<hr />
<div>== What is combustion -- Physics versus modelling ==<br />
<br />
Combustion phenomena consists of many physical and chemical processes with <br />
broad range of time scales. Mathematical description of combustion is not <br />
always trivial. Analytical solutions exists only for basic situations of <br />
laminar flame and <br />
because of its assumptions it is often restricted to few problems solved <br />
usually in zero or one-dimensional space. <br />
<br />
Problems solved today concern mainly turbulent flows, gas as well as liquid <br />
fuels, pollution issues (products of combustion as well as for example noise <br />
pollution). These problems require not only extensive experimental <br />
work, but also numerical modelling. All combustion models must be validated <br />
against the experiments as each one has its own drawbacks and limits. However here <br />
the modelling part will be mainly addressed.<br />
<br />
<br />
== Reaction mechanisms ==<br />
<br />
The combustion is mainly chemical process and although we can, to some extend, <br />
describe flame without any chemistry informations, for modelling of flame <br />
propagation we need to know the speed of reactions, product concentrations, <br />
temperature and other parameters. <br />
Therefore more or less detailed information about reaction kinetics is <br />
essential for any combustion model. <br />
Mixture will generally combust, if the reaction of fuel and oxidiser is fast enough to <br />
maintain until all of the mixture is burned into products. If the reaction <br />
is too slow, the flame will extinguish, if too fast, explosion or even <br />
detonation will occur. The reaction rate of typical combustion reaction <br />
is influenced mainly by concentration of reactants, temperature and pressure. <br />
<br />
A stoichiometric equation of an arbitrary equation can be written as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\sum_{j=1}^{n}\nu' (M_j) = \sum_{j=1}^{n}\nu'' (M_j),<br />
</math></td></tr></table><br />
<br />
where $\nu$ is the stoichiometric coefficient, <math>M_j</math> is arbitrary species. One <br />
prime specifies the reactants and double prime products of the reaction. <br />
<br />
Reaction rate, expressing the rate of disappearance of reactant <b>i</b><br />
of such a reaction, is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
RR_i = k \, \prod_{j=1}^{n}(M_j)^{\nu'},<br />
</math></td></tr></table><br />
<br />
in which <b>k</b> is the specific reaction rate constant. Arrhenius found that this <br />
constant is a function only of temperature and this function is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
k= A T^{\beta} \, exp \left( \frac{-E}{RT}\right)<br />
</math></td></table><br />
<br />
where <b>A</b> is pre--exponential factor, <b>E</b> is activation energy and <math>\beta</math> is <br />
temperature exponent. <br />
These constants for given reactions can be found in literature. <br />
The reaction mechanism can be given from experiments for every reaction <br />
resolved, it could be also constructed numerically by automatic generation <br />
method (see [Griffiths (1994)] for review on reaction mechanisms).<br />
For simple hydrocarbon tens to hundreds of reactions are involved. <br />
By analysis and systematic reduction of reaction mechanisms global reaction <br />
(from one to five step reactions) can be found (see [Westbrook (1984)]).<br />
<br />
== Governing Equations ==<br />
<br />
The mass fraction transport equation for <i>k-th</i> species <math> Y_k </math> <br />
<br />
<table width="100%"><br />
:<math><br />
\frac{\partial}{\partial t} \left( \rho Y_k \right) +<br />
\frac{\partial}{\partial x_j} \left( \rho u_j Y_k\right) = <br />
\frac{\partial}{\partial x_j} \left( \rho D_k \frac{\partial Y_k}{\partial x_j}\right)+ w_k<br />
</math><br />
</td><td>(1)</td></tr><br />
<tr><td><br />
</table><br />
<br />
where Ficks law is assumed for scalar diffusion and <br />
<math> w_k </math> is the species reaction rate.<br />
<br />
== Infinitely fast chemistry ==<br />
<br />
=== Premixed Combustion ===<br />
Premixed flame occurs in mixtures of fuel and oxidiser,<br />
homogeneously premixed prior to the flame. These flames are not <br />
limited only to gas fuels, but also to the pre-vaporised fuels.<br />
Typical example of premixed laminar flame is bunsen burner, where <br />
the air enters the fuel stream. The mixture burns in the wake of the <br />
riser tube walls forming nice stable flame.<br />
The premixed flames has many advantages in terms of control of temperature and <br />
products and pollution concentration, but introduce also some dangers like the autoignition (in the supply system).<br />
<br />
==== Turbulent flame speed model ====<br />
<br />
==== Eddy Break-Up model ====<br />
<br />
The Eddy Break-Up model is the typical example of mixed-is-burnt combustion model. <br />
It is based on the work of Magnussen and Hjertager, <br />
and Spalding and can be found in all CFD packages. <br />
The model assumes the reactions to be completed in the moment of mixing, so that the reaction rate is completely controlled by turbulent mixing. <br />
The combustion is described by a single step global chemical reaction:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
F + \nu_s O \rightarrow (1+\nu_s) P<br />
</math></td><td width="5%"></td></tr></table><br />
<br />
in which <b>F</b> stands for fuel, <b>O</b> for oxidiser and <b>P</b> for products of the reaction. Alternativelly we can have multistep scheme, where each reaction has its own mean reaction rate.<br />
The mean reaction rate is given by:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\bar{\dot\omega}_F=A_{EB} \frac{\epsilon}{k} <br />
min\left[\bar{C}_F,\frac{\bar{C}_O}{\nu},<br />
B_{EB}\frac{\bar{C}_P}{(1+\nu)}\right]<br />
</math></td><td width="5%"></td></tr></table><br />
<br />
<br />
<math>\bar{C}</math> denotes mean concentrations for fuel, oxidiser and products <br />
respectively, <b>A</b> and <b>B</b> are model constants with typical values of 0.5 <br />
and 4.0 respectively. The values of these constants are fitted according <br />
to the experimental results and they are suitable for most of the general cases. <br />
Still they are just constants based on experimental fitting and they need not <br />
be suitable for <b>all</b> the situations. <br />
Care must be taken especially in highly strained regions, where the ratio of <math>k</math> <br />
to <math>\epsilon</math> is large (flame-holder wakes, walls ...). In those regions a positive reaction rate occurs and an artificial flame can be observed.<br />
CFD codes usually has some remedies to overcome this problem.<br />
<br />
This model largely over-predicts temperatures and concentrations of species like <i>CO</i> and other species. Still this model is quite popular for its simplicity and relatively easy convergence and implementation.<br />
<br />
==== Bray-Moss-Libby Model ====<br />
<br />
=== Non premixed combustion ===<br />
<br />
==== Conserved scalar equilibrium models ====<br />
<br />
== Finite rate chemistry ==<br />
<br />
=== Premixed Combustion ===<br />
<br />
==== Coherent Flame Model ====<br />
<br />
==== Flamelets based on G equation ====<br />
<br />
=== Non-premixed Combustion ===<br />
<br />
==== Flamelets based on conserved scalar ====<br />
<br />
==== Conditional Moment Closure (CMC)====<br />
<br />
==== Multiple Mapping Closure (MMC) ====<br />
<br />
=== Linear Eddy Model ===<br />
<br />
=== PDF transport models ===<br />
<br />
==== Lagrangian ====<br />
<br />
==== Eulerian ====<br />
<br />
== References ==<br />
<br />
*{{reference-paper|author=Griffiths J.F.|year=1994|title=Reduced Kinetic Models and Their Application to Practical Combustion Systems |rest=Prog. in Energy and Combustion Science,Vol. 21, pp. 25-107}} <br />
*{{reference-paper|author=Westbrook, Ch.K., Dryer,F.L.,|year=1984|title=Chemical Kinetic Modeling of Hydrocarbon Combustion |rest=Prog. in Energy and Combustion Science,Vol. 10, pp. 1-57}}<br />
<br />
== External links and sources ==</div>ForMathttp://www.cfd-online.com/Wiki/CombustionCombustion2005-10-02T14:12:37Z<p>ForMat: /* Premixed Combustion */</p>
<hr />
<div>== What is combustion -- Physics versus modelling ==<br />
<br />
Combustion phenomena consists of many physical and chemical processes with <br />
broad range of time scales. Mathematical description of combustion is not <br />
always trivial. Analytical solutions exists only for basic situations of <br />
laminar flame and <br />
because of its assumptions it is often restricted to few problems solved <br />
usually in zero or one-dimensional space. <br />
<br />
Problems solved today concern mainly turbulent flows, gas as well as liquid <br />
fuels, pollution issues (products of combustion as well as for example noise <br />
pollution). These problems require not only extensive experimental <br />
work, but also numerical modelling. All combustion models must be validated <br />
against the experiments as each one has its own drawbacks and limits. However here <br />
the modelling part will be mainly addressed.<br />
<br />
<br />
== Reaction mechanisms ==<br />
<br />
The combustion is mainly chemical process and although we can, to some extend, <br />
describe flame without any chemistry informations, for modelling of flame <br />
propagation we need to know the speed of reactions, product concentrations, <br />
temperature and other parameters. <br />
Therefore more or less detailed information about reaction kinetics is <br />
essential for any combustion model. <br />
Mixture will generally combust, if the reaction of fuel and oxidiser is fast enough to <br />
maintain until all of the mixture is burned into products. If the reaction <br />
is too slow, the flame will extinguish, if too fast, explosion or even <br />
detonation will occur. The reaction rate of typical combustion reaction <br />
is influenced mainly by concentration of reactants, temperature and pressure. <br />
<br />
A stoichiometric equation of an arbitrary equation can be written as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\sum_{j=1}^{n}\nu' (M_j) = \sum_{j=1}^{n}\nu'' (M_j),<br />
</math></td></tr></table><br />
<br />
where $\nu$ is the stoichiometric coefficient, <math>M_j</math> is arbitrary species. One <br />
prime specifies the reactants and double prime products of the reaction. <br />
<br />
Reaction rate, expressing the rate of disappearance of reactant <b>i</b><br />
of such a reaction, is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
RR_i = k \, \prod_{j=1}^{n}(M_j)^{\nu'},<br />
</math></td></tr></table><br />
<br />
in which <b>k</b> is the specific reaction rate constant. Arrhenius found that this <br />
constant is a function only of temperature and this function is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
k= A T^{\beta} \, exp \left( \frac{-E}{RT}\right)<br />
</math></td></table><br />
<br />
where <b>A</b> is pre--exponential factor, <b>E</b> is activation energy and <math>\beta</math> is <br />
temperature exponent. <br />
These constants for given reactions can be found in literature. <br />
The reaction mechanism can be given from experiments for every reaction <br />
resolved, it could be also constructed numerically by automatic generation <br />
method (see [Griffiths (1994)] for review on reaction mechanisms).<br />
For simple hydrocarbon tens to hundreds of reactions are involved. <br />
By analysis and systematic reduction of reaction mechanisms global reaction <br />
(from one to five step reactions) can be found (see [Westbrook (1984)]).<br />
<br />
== Governing Equations ==<br />
<br />
The mass fraction transport equation for <i>k-th</i> species <math> Y_k </math> <br />
<br />
<table width="100%"><br />
:<math><br />
\frac{\partial}{\partial t} \left( \rho Y_k \right) +<br />
\frac{\partial}{\partial x_j} \left( \rho u_j Y_k\right) = <br />
\frac{\partial}{\partial x_j} \left( \rho D_k \frac{\partial Y_k}{\partial x_j}\right)+ w_k<br />
</math><br />
</td><td>(1)</td></tr><br />
<tr><td><br />
</table><br />
<br />
where Ficks law is assumed for scalar diffusion and <br />
<math> w_k </math> is the species reaction rate.<br />
<br />
== Infinitely fast chemistry ==<br />
<br />
=== Premixed Combustion ===<br />
Premixed flame occurs in mixtures of fuel and oxidiser,<br />
homogeneously premixed prior to the flame. These flames are not <br />
limited only to gas fuels, but also to the pre-vaporised fuels.<br />
Typical example of premixed laminar flame is bunsen burner, where <br />
the air enters the fuel stream. The mixture burns in the wake of the <br />
riser tube walls forming nice stable flame.<br />
The premixed flames has many advantages in terms of control of temperature and <br />
products and pollution concentration, but introduce also some dangers like the autoignition (in the supply system).<br />
<br />
==== Turbulent flame speed model ====<br />
<br />
==== Eddy Break-Up model ====<br />
<br />
The Eddy Break-Up model is the typical example of mixed-is-burnt combustion model. <br />
It is based on the work of Magnussen and Hjertager, <br />
and Spalding and can be found in all CFD packages. <br />
The model assumes the reactions to be completed in the moment of mixing, so that the reaction rate is completely controlled by turbulent mixing. <br />
The combustion is described by a single step global chemical reaction:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
F + \nu_s O \rightarrow (1+\nu_s) P<br />
</math></td><td width="5%"></td></tr></table><br />
<br />
in which <b>F</b> stands for fuel, <b>O</b> for oxidiser and <b>P</b> for products of the reaction. Alternativelly we can have multistep scheme, where each reaction has its own mean reaction rate.<br />
The mean reaction rate is given by:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\bar{\dot\omega}_F=A_{EB} \frac{\varepsilon}{k} <br />
min\left[\bar{C}_F,\frac{\bar{C}_O}{\nu},<br />
B_{EB}\frac{\bar{C}_P}{(1+\nu)}\right]<br />
</math></td><td width="5%"></td></tr></table><br />
<br />
<br />
<math>\bar{C}</math> denotes mean concentrations for fuel, oxidiser and products <br />
respectively, <b>A</b> and <b>B</b> are model constants with typical values of 0.5 <br />
and 4.0 respectively. The values of these constants are fitted according <br />
to the experimental results and they are suitable for most of the general cases. <br />
Still they are just constants based on experimental fitting and they need not <br />
be suitable for <b>all</b> the situations. <br />
Care must be taken especially in highly strained regions, where the ratio of <math>k</math> <br />
to <math>\varepsilon</math> is large (flame-holder wakes, walls ...). In those regions a positive reaction rate occurs and an artificial flame can be observed.<br />
CFD codes usually has some remedies to overcome this problem.<br />
<br />
This model largely over-predicts temperatures and concentrations of species like <i>CO</i> and other species. Still this model is quite popular for its simplicity and relatively easy convergence and implementation.<br />
<br />
==== Bray-Moss-Libby Model ====<br />
<br />
=== Non premixed combustion ===<br />
<br />
==== Conserved scalar equilibrium models ====<br />
<br />
== Finite rate chemistry ==<br />
<br />
=== Premixed Combustion ===<br />
<br />
==== Coherent Flame Model ====<br />
<br />
==== Flamelets based on G equation ====<br />
<br />
=== Non-premixed Combustion ===<br />
<br />
==== Flamelets based on conserved scalar ====<br />
<br />
==== Conditional Moment Closure (CMC)====<br />
<br />
==== Multiple Mapping Closure (MMC) ====<br />
<br />
=== Linear Eddy Model ===<br />
<br />
=== PDF transport models ===<br />
<br />
==== Lagrangian ====<br />
<br />
==== Eulerian ====<br />
<br />
== References ==<br />
<br />
*{{reference-paper|author=Griffiths J.F.|year=1994|title=Reduced Kinetic Models and Their Application to Practical Combustion Systems |rest=Prog. in Energy and Combustion Science,Vol. 21, pp. 25-107}} <br />
*{{reference-paper|author=Westbrook, Ch.K., Dryer,F.L.,|year=1984|title=Chemical Kinetic Modeling of Hydrocarbon Combustion |rest=Prog. in Energy and Combustion Science,Vol. 10, pp. 1-57}}<br />
<br />
== External links and sources ==</div>ForMathttp://www.cfd-online.com/Wiki/CombustionCombustion2005-10-02T14:01:20Z<p>ForMat: /* Eddy Break-Up model */ first edit</p>
<hr />
<div>== What is combustion -- Physics versus modelling ==<br />
<br />
Combustion phenomena consists of many physical and chemical processes with <br />
broad range of time scales. Mathematical description of combustion is not <br />
always trivial. Analytical solutions exists only for basic situations of <br />
laminar flame and <br />
because of its assumptions it is often restricted to few problems solved <br />
usually in zero or one-dimensional space. <br />
<br />
Problems solved today concern mainly turbulent flows, gas as well as liquid <br />
fuels, pollution issues (products of combustion as well as for example noise <br />
pollution). These problems require not only extensive experimental <br />
work, but also numerical modelling. All combustion models must be validated <br />
against the experiments as each one has its own drawbacks and limits. However here <br />
the modelling part will be mainly addressed.<br />
<br />
<br />
== Reaction mechanisms ==<br />
<br />
The combustion is mainly chemical process and although we can, to some extend, <br />
describe flame without any chemistry informations, for modelling of flame <br />
propagation we need to know the speed of reactions, product concentrations, <br />
temperature and other parameters. <br />
Therefore more or less detailed information about reaction kinetics is <br />
essential for any combustion model. <br />
Mixture will generally combust, if the reaction of fuel and oxidiser is fast enough to <br />
maintain until all of the mixture is burned into products. If the reaction <br />
is too slow, the flame will extinguish, if too fast, explosion or even <br />
detonation will occur. The reaction rate of typical combustion reaction <br />
is influenced mainly by concentration of reactants, temperature and pressure. <br />
<br />
A stoichiometric equation of an arbitrary equation can be written as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\sum_{j=1}^{n}\nu' (M_j) = \sum_{j=1}^{n}\nu'' (M_j),<br />
</math></td></tr></table><br />
<br />
where $\nu$ is the stoichiometric coefficient, <math>M_j</math> is arbitrary species. One <br />
prime specifies the reactants and double prime products of the reaction. <br />
<br />
Reaction rate, expressing the rate of disappearance of reactant <b>i</b><br />
of such a reaction, is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
RR_i = k \, \prod_{j=1}^{n}(M_j)^{\nu'},<br />
</math></td></tr></table><br />
<br />
in which <b>k</b> is the specific reaction rate constant. Arrhenius found that this <br />
constant is a function only of temperature and this function is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
k= A T^{\beta} \, exp \left( \frac{-E}{RT}\right)<br />
</math></td></table><br />
<br />
where <b>A</b> is pre--exponential factor, <b>E</b> is activation energy and <math>\beta</math> is <br />
temperature exponent. <br />
These constants for given reactions can be found in literature. <br />
The reaction mechanism can be given from experiments for every reaction <br />
resolved, it could be also constructed numerically by automatic generation <br />
method (see [Griffiths (1994)] for review on reaction mechanisms).<br />
For simple hydrocarbon tens to hundreds of reactions are involved. <br />
By analysis and systematic reduction of reaction mechanisms global reaction <br />
(from one to five step reactions) can be found (see [Westbrook (1984)]).<br />
<br />
== Governing Equations ==<br />
<br />
The mass fraction transport equation for <i>k-th</i> species <math> Y_k </math> <br />
<br />
<table width="100%"><br />
:<math><br />
\frac{\partial}{\partial t} \left( \rho Y_k \right) +<br />
\frac{\partial}{\partial x_j} \left( \rho u_j Y_k\right) = <br />
\frac{\partial}{\partial x_j} \left( \rho D_k \frac{\partial Y_k}{\partial x_j}\right)+ w_k<br />
</math><br />
</td><td>(1)</td></tr><br />
<tr><td><br />
</table><br />
<br />
where Ficks law is assumed for scalar diffusion and <br />
<math> w_k </math> is the species reaction rate.<br />
<br />
== Infinitely fast chemistry ==<br />
<br />
=== Premixed Combustion ===<br />
<br />
==== Turbulent flame speed model ====<br />
<br />
==== Eddy Break-Up model ====<br />
<br />
The Eddy Break-Up model is the typical example of mixed-is-burnt combustion model. <br />
It is based on the work of Magnussen and Hjertager, <br />
and Spalding and can be found in all CFD packages. <br />
The model assumes the reactions to be completed in the moment of mixing, so that the reaction rate is completely controlled by turbulent mixing. <br />
The combustion is described by a single step global chemical reaction:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
F + \nu_s O \rightarrow (1+\nu_s) P<br />
</math></td><td width="5%"></td></tr></table><br />
<br />
in which <b>F</b> stands for fuel, <b>O</b> for oxidiser and <b>P</b> for products of the reaction. Alternativelly we can have multistep scheme, where each reaction has its own mean reaction rate.<br />
The mean reaction rate is given by:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\bar{\dot\omega}_F=A_{EB} \frac{\varepsilon}{k} <br />
min\left[\bar{C}_F,\frac{\bar{C}_O}{\nu},<br />
B_{EB}\frac{\bar{C}_P}{(1+\nu)}\right]<br />
</math></td><td width="5%"></td></tr></table><br />
<br />
<br />
<math>\bar{C}</math> denotes mean concentrations for fuel, oxidiser and products <br />
respectively, <b>A</b> and <b>B</b> are model constants with typical values of 0.5 <br />
and 4.0 respectively. The values of these constants are fitted according <br />
to the experimental results and they are suitable for most of the general cases. <br />
Still they are just constants based on experimental fitting and they need not <br />
be suitable for <b>all</b> the situations. <br />
Care must be taken especially in highly strained regions, where the ratio of <math>k</math> <br />
to <math>\varepsilon</math> is large (flame-holder wakes, walls ...). In those regions a positive reaction rate occurs and an artificial flame can be observed.<br />
CFD codes usually has some remedies to overcome this problem.<br />
<br />
This model largely over-predicts temperatures and concentrations of species like <i>CO</i> and other species. Still this model is quite popular for its simplicity and relatively easy convergence and implementation.<br />
<br />
==== Bray-Moss-Libby Model ====<br />
<br />
=== Non premixed combustion ===<br />
<br />
==== Conserved scalar equilibrium models ====<br />
<br />
== Finite rate chemistry ==<br />
<br />
=== Premixed Combustion ===<br />
<br />
==== Coherent Flame Model ====<br />
<br />
==== Flamelets based on G equation ====<br />
<br />
=== Non-premixed Combustion ===<br />
<br />
==== Flamelets based on conserved scalar ====<br />
<br />
==== Conditional Moment Closure (CMC)====<br />
<br />
==== Multiple Mapping Closure (MMC) ====<br />
<br />
=== Linear Eddy Model ===<br />
<br />
=== PDF transport models ===<br />
<br />
==== Lagrangian ====<br />
<br />
==== Eulerian ====<br />
<br />
== References ==<br />
<br />
*{{reference-paper|author=Griffiths J.F.|year=1994|title=Reduced Kinetic Models and Their Application to Practical Combustion Systems |rest=Prog. in Energy and Combustion Science,Vol. 21, pp. 25-107}} <br />
*{{reference-paper|author=Westbrook, Ch.K., Dryer,F.L.,|year=1984|title=Chemical Kinetic Modeling of Hydrocarbon Combustion |rest=Prog. in Energy and Combustion Science,Vol. 10, pp. 1-57}}<br />
<br />
== External links and sources ==</div>ForMathttp://www.cfd-online.com/Wiki/CombustionCombustion2005-09-18T10:55:34Z<p>ForMat: /* References */</p>
<hr />
<div>== What is combustion -- Physics versus modelling ==<br />
<br />
Combustion phenomena consists of many physical and chemical processes with <br />
broad range of time scales. Mathematical description of combustion is not <br />
always trivial. Analytical solutions exists only for basic situations of <br />
laminar flame and <br />
because of its assumptions it is often restricted to few problems solved <br />
usually in zero or one-dimensional space. <br />
<br />
Problems solved today concern mainly turbulent flows, gas as well as liquid <br />
fuels, pollution issues (products of combustion as well as for example noise <br />
pollution). These problems require not only extensive experimental <br />
work, but also numerical modelling. All combustion models must be validated <br />
against the experiments as each one has its own drawbacks and limits. However here <br />
the modelling part will be mainly addressed.<br />
<br />
<br />
== Reaction mechanisms ==<br />
<br />
The combustion is mainly chemical process and although we can, to some extend, <br />
describe flame without any chemistry informations, for modelling of flame <br />
propagation we need to know the speed of reactions, product concentrations, <br />
temperature and other parameters. <br />
Therefore more or less detailed information about reaction kinetics is <br />
essential for any combustion model. <br />
Mixture will generally combust, if the reaction of fuel and oxidiser is fast enough to <br />
maintain until all of the mixture is burned into products. If the reaction <br />
is too slow, the flame will extinguish, if too fast, explosion or even <br />
detonation will occur. The reaction rate of typical combustion reaction <br />
is influenced mainly by concentration of reactants, temperature and pressure. <br />
<br />
A stoichiometric equation of an arbitrary equation can be written as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\sum_{j=1}^{n}\nu' (M_j) = \sum_{j=1}^{n}\nu'' (M_j),<br />
</math></td></tr></table><br />
<br />
where $\nu$ is the stoichiometric coefficient, <math>M_j</math> is arbitrary species. One <br />
prime specifies the reactants and double prime products of the reaction. <br />
<br />
Reaction rate, expressing the rate of disappearance of reactant <b>i</b><br />
of such a reaction, is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
RR_i = k \, \prod_{j=1}^{n}(M_j)^{\nu'},<br />
</math></td></tr></table><br />
<br />
in which <b>k</b> is the specific reaction rate constant. Arrhenius found that this <br />
constant is a function only of temperature and this function is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
k= A T^{\beta} \, exp \left( \frac{-E}{RT}\right)<br />
</math></td></table><br />
<br />
where <b>A</b> is pre--exponential factor, <b>E</b> is activation energy and <math>\beta</math> is <br />
temperature exponent. <br />
These constants for given reactions can be found in literature. <br />
The reaction mechanism can be given from experiments for every reaction <br />
resolved, it could be also constructed numerically by automatic generation <br />
method (see [Griffiths (1994)] for review on reaction mechanisms).<br />
For simple hydrocarbon tens to hundreds of reactions are involved. <br />
By analysis and systematic reduction of reaction mechanisms global reaction <br />
(from one to five step reactions) can be found (see [Westbrook (1984)]).<br />
<br />
== Infinitely fast chemistry ==<br />
<br />
=== Turbulent flame speed model ===<br />
<br />
=== Eddy Break-Up model ===<br />
<br />
=== Equilibrium chemistry models ===<br />
<br />
<br />
<br />
== Finite chemistry ==<br />
<br />
=== Full reaction mechanism model ===<br />
<br />
=== Reduced scheme models ===<br />
<br />
# Flamelet model<br />
<br />
# Other reaction progress variable models<br />
<br />
== References ==<br />
<br />
*{{reference-paper|author=Griffiths J.F.|year=1994|title=Reduced Kinetic Models and Their Application to Practical Combustion Systems |rest=Prog. in Energy and Combustion Science,Vol. 21, pp. 25-107}} <br />
*{{reference-paper|author=Westbrook, Ch.K., Dryer,F.L.,|year=1984|title=Chemical Kinetic Modeling of Hydrocarbon Combustion |rest=Prog. in Energy and Combustion Science,Vol. 10, pp. 1-57}}<br />
<br />
== External links and sources ==</div>ForMathttp://www.cfd-online.com/Wiki/CombustionCombustion2005-09-18T10:54:20Z<p>ForMat: /* Reaction mechanisms */ references style change</p>
<hr />
<div>== What is combustion -- Physics versus modelling ==<br />
<br />
Combustion phenomena consists of many physical and chemical processes with <br />
broad range of time scales. Mathematical description of combustion is not <br />
always trivial. Analytical solutions exists only for basic situations of <br />
laminar flame and <br />
because of its assumptions it is often restricted to few problems solved <br />
usually in zero or one-dimensional space. <br />
<br />
Problems solved today concern mainly turbulent flows, gas as well as liquid <br />
fuels, pollution issues (products of combustion as well as for example noise <br />
pollution). These problems require not only extensive experimental <br />
work, but also numerical modelling. All combustion models must be validated <br />
against the experiments as each one has its own drawbacks and limits. However here <br />
the modelling part will be mainly addressed.<br />
<br />
<br />
== Reaction mechanisms ==<br />
<br />
The combustion is mainly chemical process and although we can, to some extend, <br />
describe flame without any chemistry informations, for modelling of flame <br />
propagation we need to know the speed of reactions, product concentrations, <br />
temperature and other parameters. <br />
Therefore more or less detailed information about reaction kinetics is <br />
essential for any combustion model. <br />
Mixture will generally combust, if the reaction of fuel and oxidiser is fast enough to <br />
maintain until all of the mixture is burned into products. If the reaction <br />
is too slow, the flame will extinguish, if too fast, explosion or even <br />
detonation will occur. The reaction rate of typical combustion reaction <br />
is influenced mainly by concentration of reactants, temperature and pressure. <br />
<br />
A stoichiometric equation of an arbitrary equation can be written as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\sum_{j=1}^{n}\nu' (M_j) = \sum_{j=1}^{n}\nu'' (M_j),<br />
</math></td></tr></table><br />
<br />
where $\nu$ is the stoichiometric coefficient, <math>M_j</math> is arbitrary species. One <br />
prime specifies the reactants and double prime products of the reaction. <br />
<br />
Reaction rate, expressing the rate of disappearance of reactant <b>i</b><br />
of such a reaction, is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
RR_i = k \, \prod_{j=1}^{n}(M_j)^{\nu'},<br />
</math></td></tr></table><br />
<br />
in which <b>k</b> is the specific reaction rate constant. Arrhenius found that this <br />
constant is a function only of temperature and this function is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
k= A T^{\beta} \, exp \left( \frac{-E}{RT}\right)<br />
</math></td></table><br />
<br />
where <b>A</b> is pre--exponential factor, <b>E</b> is activation energy and <math>\beta</math> is <br />
temperature exponent. <br />
These constants for given reactions can be found in literature. <br />
The reaction mechanism can be given from experiments for every reaction <br />
resolved, it could be also constructed numerically by automatic generation <br />
method (see [Griffiths (1994)] for review on reaction mechanisms).<br />
For simple hydrocarbon tens to hundreds of reactions are involved. <br />
By analysis and systematic reduction of reaction mechanisms global reaction <br />
(from one to five step reactions) can be found (see [Westbrook (1984)]).<br />
<br />
== Infinitely fast chemistry ==<br />
<br />
=== Turbulent flame speed model ===<br />
<br />
=== Eddy Break-Up model ===<br />
<br />
=== Equilibrium chemistry models ===<br />
<br />
<br />
<br />
== Finite chemistry ==<br />
<br />
=== Full reaction mechanism model ===<br />
<br />
=== Reduced scheme models ===<br />
<br />
# Flamelet model<br />
<br />
# Other reaction progress variable models<br />
<br />
== References ==<br />
<br />
<div id="Griffiths"><br />
{{reference-paper|author=Griffiths J.F.|year=1994|title=Reduced Kinetic Models and Their Application to Practical Combustion Systems |rest=Prog. in Energy and Combustion Science,Vol. 21, pp. 25-107}} <br />
</div><br />
<div id="Westbrook"><br />
{{reference-paper|author=Westbrook, Ch.K., Dryer,F.L.,|year=1984|title=Chemical Kinetic Modeling of Hydrocarbon Combustion |rest=Prog. in Energy and Combustion Science,Vol. 10, pp. 1-57}} <br />
</div><br />
<br />
== External links and sources ==</div>ForMathttp://www.cfd-online.com/Wiki/CombustionCombustion2005-09-18T10:38:12Z<p>ForMat: /* Reaction mechanisms */</p>
<hr />
<div>== What is combustion -- Physics versus modelling ==<br />
<br />
Combustion phenomena consists of many physical and chemical processes with <br />
broad range of time scales. Mathematical description of combustion is not <br />
always trivial. Analytical solutions exists only for basic situations of <br />
laminar flame and <br />
because of its assumptions it is often restricted to few problems solved <br />
usually in zero or one-dimensional space. <br />
<br />
Problems solved today concern mainly turbulent flows, gas as well as liquid <br />
fuels, pollution issues (products of combustion as well as for example noise <br />
pollution). These problems require not only extensive experimental <br />
work, but also numerical modelling. All combustion models must be validated <br />
against the experiments as each one has its own drawbacks and limits. However here <br />
the modelling part will be mainly addressed.<br />
<br />
<br />
== Reaction mechanisms ==<br />
<br />
The combustion is mainly chemical process and although we can, to some extend, <br />
describe flame without any chemistry informations, for modelling of flame <br />
propagation we need to know the speed of reactions, product concentrations, <br />
temperature and other parameters. <br />
Therefore more or less detailed information about reaction kinetics is <br />
essential for any combustion model. <br />
Mixture will generally combust, if the reaction of fuel and oxidiser is fast enough to <br />
maintain until all of the mixture is burned into products. If the reaction <br />
is too slow, the flame will extinguish, if too fast, explosion or even <br />
detonation will occur. The reaction rate of typical combustion reaction <br />
is influenced mainly by concentration of reactants, temperature and pressure. <br />
<br />
A stoichiometric equation of an arbitrary equation can be written as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\sum_{j=1}^{n}\nu' (M_j) = \sum_{j=1}^{n}\nu'' (M_j),<br />
</math></td><td width="5%">(2.1)</td></tr></table><br />
<br />
where $\nu$ is the stoichiometric coefficient, <math>M_j</math> is arbitrary species. One <br />
prime specifies the reactants and double prime products of the reaction. <br />
<br />
Reaction rate, expressing the rate of disappearance of reactant <b>i</b><br />
of such a reaction, is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
RR_i = k \, \prod_{j=1}^{n}(M_j)^{\nu'},<br />
</math></td><td width="5%">(2.2)</td></tr></table><br />
<br />
in which <b>k</b> is the specific reaction rate constant. Arrhenius found that this <br />
constant is a function only of temperature and this function is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
k= A T^{\beta} \, exp \left( \frac{-E}{RT}\right)<br />
</math></td><td width="5%">(2.3)</td></tr></table><br />
<br />
where <b>A</b> is pre--exponential factor, <b>E</b> is activation energy and <math>\beta</math> is <br />
temperature exponent. <br />
These constants for given reactions can be found in literature. <br />
The reaction mechanism can be given from experiments for every reaction <br />
resolved, it could be also constructed numerically by automatic generation <br />
method (see article of [[#Griffiths]] for review on reaction mechanisms).<br />
For simple hydrocarbon tens to hundreds of reactions are involved. <br />
By analysis and systematic reduction of reaction mechanisms global reaction <br />
(from one to five step reactions) can be found (see [[#Westbrook]]).<br />
<br />
== Infinitely fast chemistry ==<br />
<br />
=== Turbulent flame speed model ===<br />
<br />
=== Eddy Break-Up model ===<br />
<br />
=== Equilibrium chemistry models ===<br />
<br />
<br />
<br />
== Finite chemistry ==<br />
<br />
=== Full reaction mechanism model ===<br />
<br />
=== Reduced scheme models ===<br />
<br />
# Flamelet model<br />
<br />
# Other reaction progress variable models<br />
<br />
== References ==<br />
<br />
<div id="Griffiths"><br />
{{reference-paper|author=Griffiths J.F.|year=1994|title=Reduced Kinetic Models and Their Application to Practical Combustion Systems |rest=Prog. in Energy and Combustion Science,Vol. 21, pp. 25-107}} <br />
</div><br />
<div id="Westbrook"><br />
{{reference-paper|author=Westbrook, Ch.K., Dryer,F.L.,|year=1984|title=Chemical Kinetic Modeling of Hydrocarbon Combustion |rest=Prog. in Energy and Combustion Science,Vol. 10, pp. 1-57}} <br />
</div><br />
<br />
== External links and sources ==</div>ForMathttp://www.cfd-online.com/Wiki/CombustionCombustion2005-09-18T10:32:26Z<p>ForMat: /* References */</p>
<hr />
<div>== What is combustion -- Physics versus modelling ==<br />
<br />
Combustion phenomena consists of many physical and chemical processes with <br />
broad range of time scales. Mathematical description of combustion is not <br />
always trivial. Analytical solutions exists only for basic situations of <br />
laminar flame and <br />
because of its assumptions it is often restricted to few problems solved <br />
usually in zero or one-dimensional space. <br />
<br />
Problems solved today concern mainly turbulent flows, gas as well as liquid <br />
fuels, pollution issues (products of combustion as well as for example noise <br />
pollution). These problems require not only extensive experimental <br />
work, but also numerical modelling. All combustion models must be validated <br />
against the experiments as each one has its own drawbacks and limits. However here <br />
the modelling part will be mainly addressed.<br />
<br />
<br />
== Reaction mechanisms ==<br />
<br />
The combustion is mainly chemical process and although we can, to some extend, <br />
describe flame without any chemistry informations, for modelling of flame <br />
propagation we need to know the speed of reactions, product concentrations, <br />
temperature and other parameters. <br />
Therefore more or less detailed information about reaction kinetics is <br />
essential for any combustion model. \par<br />
Mixture will generally combust, if the reaction of fuel and oxidiser is fast enough to <br />
maintain until all of the mixture is burned into products. If the reaction <br />
is too slow, the flame will extinguish, if too fast, explosion or even <br />
detonation will occur. The reaction rate of typical combustion reaction <br />
is influenced mainly by concentration of reactants, temperature and pressure. <br />
<br />
A stoichiometric equation of an arbitrary equation can be written as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\sum_{j=1}^{n}\nu' (M_j) = \sum_{j=1}^{n}\nu'' (M_j),<br />
</math></td><td width="5%">(2.1)</td></tr></table><br />
<br />
where $\nu$ is the stoichiometric coefficient, <math>M_j</math> is arbitrary species. One <br />
prime specifies the reactants and double prime products of the reaction. <br />
<br />
Reaction rate, expressing the rate of disappearance of reactant <b>i</b><br />
of such a reaction, is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
RR_i = k \, \prod_{j=1}^{n}(M_j)^{\nu'},<br />
</math></td><td width="5%">(2.2)</td></tr></table><br />
<br />
in which <b>k</b> is the specific reaction rate constant. Arrhenius found that this <br />
constant is a function only of temperature and this function is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
k= A T^{\beta} \, exp \left( \frac{-E}{RT}\right)<br />
</math></td><td width="5%">(2.3)</td></tr></table><br />
<br />
where <b>A</b> is pre--exponential factor, <b>E</b> is activation energy and <math>\beta</math> is <br />
temperature exponent. <br />
These constants for given reactions can be found in literature. <br />
The reaction mechanism can be given from experiments for every reaction <br />
resolved, it could be also constructed numerically by automatic generation <br />
method (see article of [[#Griffiths]] for review on reaction mechanisms).<br />
For simple hydrocarbon tens to hundreds of reactions are involved. <br />
By analysis and systematic reduction of reaction mechanisms global reaction <br />
(from one to five step reactions) can be found (see [[#Westbrook]]).<br />
<br />
== Infinitely fast chemistry ==<br />
<br />
=== Turbulent flame speed model ===<br />
<br />
=== Eddy Break-Up model ===<br />
<br />
=== Equilibrium chemistry models ===<br />
<br />
<br />
<br />
== Finite chemistry ==<br />
<br />
=== Full reaction mechanism model ===<br />
<br />
=== Reduced scheme models ===<br />
<br />
# Flamelet model<br />
<br />
# Other reaction progress variable models<br />
<br />
== References ==<br />
<br />
<div id="Griffiths"><br />
{{reference-paper|author=Griffiths J.F.|year=1994|title=Reduced Kinetic Models and Their Application to Practical Combustion Systems |rest=Prog. in Energy and Combustion Science,Vol. 21, pp. 25-107}} <br />
</div><br />
<div id="Westbrook"><br />
{{reference-paper|author=Westbrook, Ch.K., Dryer,F.L.,|year=1984|title=Chemical Kinetic Modeling of Hydrocarbon Combustion |rest=Prog. in Energy and Combustion Science,Vol. 10, pp. 1-57}} <br />
</div><br />
<br />
== External links and sources ==</div>ForMathttp://www.cfd-online.com/Wiki/CombustionCombustion2005-09-18T10:29:00Z<p>ForMat: /* Reaction mechanisms */</p>
<hr />
<div>== What is combustion -- Physics versus modelling ==<br />
<br />
Combustion phenomena consists of many physical and chemical processes with <br />
broad range of time scales. Mathematical description of combustion is not <br />
always trivial. Analytical solutions exists only for basic situations of <br />
laminar flame and <br />
because of its assumptions it is often restricted to few problems solved <br />
usually in zero or one-dimensional space. <br />
<br />
Problems solved today concern mainly turbulent flows, gas as well as liquid <br />
fuels, pollution issues (products of combustion as well as for example noise <br />
pollution). These problems require not only extensive experimental <br />
work, but also numerical modelling. All combustion models must be validated <br />
against the experiments as each one has its own drawbacks and limits. However here <br />
the modelling part will be mainly addressed.<br />
<br />
<br />
== Reaction mechanisms ==<br />
<br />
The combustion is mainly chemical process and although we can, to some extend, <br />
describe flame without any chemistry informations, for modelling of flame <br />
propagation we need to know the speed of reactions, product concentrations, <br />
temperature and other parameters. <br />
Therefore more or less detailed information about reaction kinetics is <br />
essential for any combustion model. \par<br />
Mixture will generally combust, if the reaction of fuel and oxidiser is fast enough to <br />
maintain until all of the mixture is burned into products. If the reaction <br />
is too slow, the flame will extinguish, if too fast, explosion or even <br />
detonation will occur. The reaction rate of typical combustion reaction <br />
is influenced mainly by concentration of reactants, temperature and pressure. <br />
<br />
A stoichiometric equation of an arbitrary equation can be written as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
\sum_{j=1}^{n}\nu' (M_j) = \sum_{j=1}^{n}\nu'' (M_j),<br />
</math></td><td width="5%">(2.1)</td></tr></table><br />
<br />
where $\nu$ is the stoichiometric coefficient, <math>M_j</math> is arbitrary species. One <br />
prime specifies the reactants and double prime products of the reaction. <br />
<br />
Reaction rate, expressing the rate of disappearance of reactant <b>i</b><br />
of such a reaction, is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
RR_i = k \, \prod_{j=1}^{n}(M_j)^{\nu'},<br />
</math></td><td width="5%">(2.2)</td></tr></table><br />
<br />
in which <b>k</b> is the specific reaction rate constant. Arrhenius found that this <br />
constant is a function only of temperature and this function is defined as:<br />
<br />
<table width="100%"><br />
<tr><td><br />
:<math><br />
k= A T^{\beta} \, exp \left( \frac{-E}{RT}\right)<br />
</math></td><td width="5%">(2.3)</td></tr></table><br />
<br />
where <b>A</b> is pre--exponential factor, <b>E</b> is activation energy and <math>\beta</math> is <br />
temperature exponent. <br />
These constants for given reactions can be found in literature. <br />
The reaction mechanism can be given from experiments for every reaction <br />
resolved, it could be also constructed numerically by automatic generation <br />
method (see article of [[#Griffiths]] for review on reaction mechanisms).<br />
For simple hydrocarbon tens to hundreds of reactions are involved. <br />
By analysis and systematic reduction of reaction mechanisms global reaction <br />
(from one to five step reactions) can be found (see [[#Westbrook]]).<br />
<br />
== Infinitely fast chemistry ==<br />
<br />
=== Turbulent flame speed model ===<br />
<br />
=== Eddy Break-Up model ===<br />
<br />
=== Equilibrium chemistry models ===<br />
<br />
<br />
<br />
== Finite chemistry ==<br />
<br />
=== Full reaction mechanism model ===<br />
<br />
=== Reduced scheme models ===<br />
<br />
# Flamelet model<br />
<br />
# Other reaction progress variable models<br />
<br />
== References ==<br />
== External links and sources ==</div>ForMathttp://www.cfd-online.com/Wiki/CombustionCombustion2005-09-18T09:37:14Z<p>ForMat: </p>
<hr />
<div>== What is combustion -- Physics versus modelling ==<br />
<br />
Combustion phenomena consists of many physical and chemical processes with <br />
broad range of time scales. Mathematical description of combustion is not <br />
always trivial. Analytical solutions exists only for basic situations of <br />
laminar flame and <br />
because of its assumptions it is often restricted to few problems solved <br />
usually in zero or one-dimensional space. <br />
<br />
Problems solved today concern mainly turbulent flows, gas as well as liquid <br />
fuels, pollution issues (products of combustion as well as for example noise <br />
pollution). These problems require not only extensive experimental <br />
work, but also numerical modelling. All combustion models must be validated <br />
against the experiments as each one has its own drawbacks and limits. However here <br />
the modelling part will be mainly addressed.<br />
<br />
<br />
== Reaction mechanisms ==<br />
<br />
<br />
== Infinitely fast chemistry ==<br />
<br />
=== Turbulent flame speed model ===<br />
<br />
=== Eddy Break-Up model ===<br />
<br />
=== Equilibrium chemistry models ===<br />
<br />
<br />
<br />
== Finite chemistry ==<br />
<br />
=== Full reaction mechanism model ===<br />
<br />
=== Reduced scheme models ===<br />
<br />
# Flamelet model<br />
<br />
# Other reaction progress variable models<br />
<br />
== References ==<br />
== External links and sources ==</div>ForMathttp://www.cfd-online.com/Wiki/CombustionCombustion2005-09-18T09:36:57Z<p>ForMat: /* What is combustion */</p>
<hr />
<div>== What is combustion -- Physics versus modelling ==<br />
<br />
Combustion phenomena consists of many physical and chemical processes with <br />
broad range of time scales. Mathematical description of combustion is not <br />
always trivial. Analytical solutions exists only for basic situations of <br />
laminar flame and <br />
because of its assumptions it is often restricted to few problems solved <br />
usually in zero or one-dimensional space. <br />
<br />
Problems solved today concern mainly turbulent flows, gas as well as liquid <br />
fuels, pollution issues (products of combustion as well as for example noise <br />
pollution). These problems require not only extensive experimental <br />
work, but also numerical modelling. All combustion models must be validated <br />
against the experiments as each one has its own drawbacks and limits. However here <br />
the modelling part will be mainly addressed.<br />
<br />
== Physics versus modelling ==<br />
<br />
== Reaction mechanisms ==<br />
<br />
<br />
== Infinitely fast chemistry ==<br />
<br />
=== Turbulent flame speed model ===<br />
<br />
=== Eddy Break-Up model ===<br />
<br />
=== Equilibrium chemistry models ===<br />
<br />
<br />
<br />
== Finite chemistry ==<br />
<br />
=== Full reaction mechanism model ===<br />
<br />
=== Reduced scheme models ===<br />
<br />
# Flamelet model<br />
<br />
# Other reaction progress variable models<br />
<br />
== References ==<br />
== External links and sources ==</div>ForMathttp://www.cfd-online.com/Wiki/CombustionCombustion2005-09-18T08:43:50Z<p>ForMat: </p>
<hr />
<div>== What is combustion ==<br />
<br />
== Physics versus modelling ==<br />
<br />
== Reaction mechanisms ==<br />
<br />
<br />
== Infinitely fast chemistry ==<br />
<br />
=== Turbulent flame speed model ===<br />
<br />
=== Eddy Break-Up model ===<br />
<br />
=== Equilibrium chemistry models ===<br />
<br />
<br />
<br />
== Finite chemistry ==<br />
<br />
=== Full reaction mechanism model ===<br />
<br />
=== Reduced scheme models ===<br />
<br />
# Flamelet model<br />
<br />
# Other reaction progress variable models<br />
<br />
== References ==<br />
== External links and sources ==</div>ForMathttp://www.cfd-online.com/Wiki/CFD-Wiki:Community_portalCFD-Wiki:Community portal2005-09-18T08:06:02Z<p>ForMat: </p>
<hr />
<div>Here you can find an overview over what is happening with this Wiki. For help with technical details and guidelines for how to contribute material to the Wiki read the [[Help:Contents]] page. We also have a [http://www.cfd-online.com/Forum/wiki.cgi discussion forum] for people that edit or add material to the Wiki. Both of these can also be reached via the links in the navigation section to the left.<br />
<br />
'''We should be focusing on two things right now:'''<br />
<br />
*Create a basic structure for the Wiki, with "stubs" (short articles which invite people to add more to them) for sections/pages where we still lack any significant content.<br />
<br />
*Finish a few high-quality sections/pages which other contributors can be inspired by and copy. This is important since we need to develop some form of common standard and understanding of how this Wiki should "look and feel", how we write references, equations, links etc. I have started to summarize a few guidelines [[Help:Contents | here]].<br />
<br />
The intention is that we should launch the Wiki publicly by the end of October (which year depends on us ;-)<br />
<br />
== What's in the works ==<br />
<br />
You who do significant additions to the Wiki, please add some information about your work, plans and progress here so that others can see what you are working on and perhaps help, monitor, come with suggestions and most importantly, be inspired by.<br />
<br />
* I've started work on creating a first best-practise guide. I think we need some sort of first example for how one of these should look. Writing this type of guide is not easy though. I chose to start with a guide for [[Best practise guidelines for turbomachinery CFD | turbomachinery CFD]] since that is the application area that I know most about. So far I've only created a table of contents and written a few sections. What do you think about it? --[[User:Jola|Jola]] 08:09, 8 September 2005 (MDT)<br />
<br />
* I have written a fairly comprehensive description of a turbulence model - see the [[Baldwin-Lomax model]] page. I think that this is a fairly good example of how we should write this type of page about a certain model. Or what do you think? --[[User:Jola|Jola]] 08:09, 8 September 2005 (MDT)<br />
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* A few people have started work on the numerics section. It now has a basic structure and I think it will get significantly more content within the next few days. --[[User:Jola|Jola]] 17:02, 12 September 2005 (MDT)<br />
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* We have been allowed to base the turbulence section on an excellent intro book on turbulence written by Professor William K. George. So expect to see significant additions in this section soon. --[[User:Jola|Jola]] 17:02, 12 September 2005 (MDT)<br />
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* We need to coordinate our style and structure. I've started to write some guidlines on the Help page and have also emailed a few of you trying to get things a bit more organized. --[[User:Jola|Jola]] 17:02, 12 September 2005 (MDT)<br />
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* I'm trying to engage editors to write FAQ's for the largest codes (Fluent, CFX and STAR-CD) and have posted messages to the code forums here at CFD Online inviting people to contribute to these FAQ's. I'm also in direct contact with a couple of support managers at CFD companies who are wondering how they can or if they should support this FAQ initiative. We'll see what happens. --[[User:Jola|Jola]] 17:02, 12 September 2005 (MDT)<br />
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== What needs to be done ==<br />
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* We have many turbulence models listed in the [[turbulence modeling]] section which still lack any description. Feel free to pick a model that you are familiar with and write a description of it. --[[User:Jola|Jola]] 01:50, 13 September 2005 (MDT)<br />
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* The [[FAQ's | FAQ]] section is still very thin. If you are familiar with one of the larger CFD codes please consider adding a few questions and answers to the FAQ. --[[User:Jola|Jola]] 08:28, 13 September 2005 (MDT)<br />
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== Wiki editors - Who we are ==<br />
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Add your name here if you make contributions to the wiki. The order is alphabetical based on the last name.<br />
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* [[User:praveen]] - Praveen. C<br />
* [[User:jasond]] - Jason D.<br />
* [[User:Pavitran]] - Pavitran. D<br />
* [[User:ForMat]] - Matej Forman<br />
* [[User:Michail]] - Michail Kirichkov<br />
* [[User:jola]] - Jonas Larsson<br />
* [[User:zxaar]] - Arjun Yadav</div>ForMathttp://www.cfd-online.com/Wiki/User:ForMatUser:ForMat2005-09-18T06:44:37Z<p>ForMat: </p>
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<div>== Matej Forman ==<br />
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I'm finishing my PhD at Technical University of Brno,Czech Republic and Twente University, The Netherlands.<br />
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I work in the field of turbulent combustion and two-phase flow.</div>ForMat