# Domain Reference Pressure and mass flow inlet boundary

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 January 19, 2010, 19:29 Domain Reference Pressure and mass flow inlet boundary #1 Member     Mauricio Caamaño Flores Join Date: May 2009 Location: Punta Arenas, Chile Posts: 62 Rep Power: 16 hello everyone, im very stuck with the settings of my boundary condition and specially with the referente pressure: im modelling combustion with flamelet, and i want to use mass flow for all the inlet (air and fuel), the air enters to the chamber with 6.4bar and the fuel with 14.31bar, my question is: how can i set the mass flow boundary for a specific pressure? when i set this boundary, i just set the temperature, but the density depends on pressure and temperature, how can i set this two different mass flow? another thing its, the domain reference pressure affect to the whole domain, so, if a set the boundary of fuel (mass flow) this mas flow will be affected for this pressure, so im not sure to what refference pressure set.(i was using the pressure of the inlet air, becuase in a chamber its relleativy constant). well, please helpe im vvvvvvvvvery stuck with this thanks ver much

 January 20, 2010, 16:07 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143 If you know both the mass flow rates and pressures of the input gases then I would use a mass flow rate boundary for the inlets and a pressure boundary at the outlet (I assume you know the exit pressure - it is probably just atmospheric pressure with a small allowance for exhaust pipe losses). Then you can check the input gas pressure as a check of the accuracy of your simulation. The reference pressure is purely a numerical thing. You set the reference pressure so the numerical accuracy of the pressure field is higher as the solver works on the pressure relative to the reference pressure. Set the reference pressure to be the outlet pressure (if you are using a pressure outlet) or the average pressure in the chamber. The exact value you use is not really important, but you do need to make sure all pressures you specify are correct relative to the reference pressure. Milan2013 and hogsonik like this.

 January 20, 2010, 22:15 #3 Member     Mauricio Caamaño Flores Join Date: May 2009 Location: Punta Arenas, Chile Posts: 62 Rep Power: 16 Thanks very much for your time: First: im trying to use inlets mass flow boundary because i read in some pdf, that's is a better choice for compressible flows instead of velocity im a right?. second: in a firts time i was using the tutorial of combustion, for the setting of the reference pressure (1atm) and pressure boundary outlet (0Pa). but this is correct? 0Pa to the outlet its a very very low pressure?, in my case i dont have any information of the pressure outelet, so im using this configuration: 6.40(bar)-->reference pressure (this value its the pressure of the inlet of air) 6(bar)--> to the oulet boundary condition (because in a combustion chamber of a turbine, generally the losses are of arround a 6%). but im not sure if this its right?, in this moment, i just want to make an a firts aproximation of this simulation, and im wondering who value is the better choice, the values of the tutorial (for reference 1atm and outlet pressure 0Pa),or mines =/. another things its, when i run the simulation with velocitys, the flow field(temperature,radiation) are not homogeneous, and all the boundary has the same value, like this image (when i try with randoms values of mass flow rate boundary, this not happend)the first image its the good one =) ) sorry for all the inappropriate question but im working by myself in CFD, and i dont have anyone to ask about the settings of the software =/. thanks very much for your time best regards Mauricio

January 21, 2010, 00:15
#4
Member

Mauricio Caamaño Flores
Join Date: May 2009
Location: Punta Arenas, Chile
Posts: 62
Rep Power: 16
Quote:
 If you know both the mass flow rates and pressures of the input gases then I would use a mass flow rate boundary for the inlets and a pressure boundary at the outlet
i really know the mass flow rate, im ok with that, but, how can i set the pressure inlets for that mass flow rate? in the setting of the inlet boundary mass flow rate just ask for the temperature. how can i set for inlet boundary mass flow rate with pressure?

ohh and i forgot,my values of mas flow rate are in the ISO CONDITION (15ºc and 1atm)(from the documentation of the turbine), but in the operation of the turbine i have other values for temp and pressure, what can i do?

 January 21, 2010, 16:42 #5 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143 You cannot set both the flow rate and pressure at the same boundary. It is a numerical impossibility. Do some reading on "well posed boundary conditions" for CFD simulations. It should be a trivial matter for you to convert the flow rates at ISO conditions to any other temperature and pressure. If you can't do this then why are you doing CFD? .......and anyway, if you know the mass flow rate it does not matter what temperature and pressure you are at!

 January 21, 2010, 18:57 #6 Member     Mauricio Caamaño Flores Join Date: May 2009 Location: Punta Arenas, Chile Posts: 62 Rep Power: 16 you have rigth, im gona check if this boundary conditions are correct. thanks

 January 22, 2010, 03:00 #7 Senior Member     Attesz Join Date: Mar 2009 Location: Munich Posts: 368 Rep Power: 17 if you know the inlet mass flow rate and pressure value, you are lucky, because if you set the mass flow after the simulation you can check the pressure at the inlet, and you can validate! setting both value means an overconstrainted boundary contition, where you set two quantities wich depend on each other.

 January 23, 2010, 00:20 #8 Member     Mauricio Caamaño Flores Join Date: May 2009 Location: Punta Arenas, Chile Posts: 62 Rep Power: 16 Attesz: thanks very much for your reply, im working wiht approximate mass flow rate for the inlet boundary, what do you recommend me for the outlet? pressure o mass flow rate? (the pressure outlet its an aproximation to, i dont have the exact value). thanks

 January 23, 2010, 01:07 #9 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143 As I said, it looks like you need to do some reading into well posed boundary conditions. Some combinations of boundary conditions are not possible and will never converge. Mass flow rate inlet and mass flow rate outlet on a steady state simulation is an example of an impossible boundary condition. The documentation has some basic information about this, I think under choice of boundary conditions.

 January 23, 2010, 01:54 #10 Member     Mauricio Caamaño Flores Join Date: May 2009 Location: Punta Arenas, Chile Posts: 62 Rep Power: 16 yeah, you have all right, in the documentation said: best robustness: mass flow rate or velocity (inlet) and for oultetressure im using for the outlet static average pressure. but its true that for compressible flows (combustion case) its better use mass flow rate for inlet boundary instead velocity?. thanks

 January 23, 2010, 04:12 #11 Senior Member     Attesz Join Date: Mar 2009 Location: Munich Posts: 368 Rep Power: 17 mass flow rate or velocity inlet are good, static pressure outlet also. i recommend not to use averaging, because the solver use that value for the whole area, and can give bad results. i dont know, how disturbed is the flow at inlet and at the outlet. if the inlet flow is consistent, and the outlet not, maybe inlet total pressure and outlet mass flow is better, because the pressure at outlet is very uneven. you must set boundary conditions taking into account the real phenomenons...

 January 23, 2010, 05:00 #12 Member     Mauricio Caamaño Flores Join Date: May 2009 Location: Punta Arenas, Chile Posts: 62 Rep Power: 16 thanks very much for your reply yeah one of my difficults its the exact value for the inlet or outlet boundary, because this turbine(hitachi ge frame V 1974) its very old and dont have measure instrument in the places that i need ( mass flow of air, temperature of combustor) so im using aproximation based on tables parameter of the turbine. it was very helpful, im gonna use your advice for the outlet pressure, im gona use just static pressure and not the average static pressure. thanks very much

 February 11, 2010, 20:28 #13 Member     Mauricio Caamaño Flores Join Date: May 2009 Location: Punta Arenas, Chile Posts: 62 Rep Power: 16 ghorrocks; sorry for that stupid question about the mass flow rate boundary! i really dont know what i was thinking. my simulation finally walk well. when i use 0bar for reference pressure and some static pressure for the outlet everything works fine, and the results inlete velocity correct. thanks very much again, and sorry for that stupid question , the first think that imgona do finishing this work, its sleep long time! best regards

March 1, 2017, 13:51
#14
Member

Ftab
Join Date: Sep 2011
Posts: 87
Rep Power: 14
Quote:
 Originally Posted by ghorrocks Some combinations of boundary conditions are not possible and will never converge. Mass flow rate inlet and mass flow rate outlet on a steady state simulation is an example of an impossible boundary condition.
Hi Glenn,
Could you please explain why do you say that?
I am confused. If you have a pipe which branches into two. I set a mass flow inlet and then put say 30% of mass flow outlet in one branch and 70% in another. For incompressible steady simulation, why is this wrong?

 March 1, 2017, 16:53 #15 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143 It cannot work because there is nothing to define the pressure.

March 6, 2017, 16:20
#16
Member

Ftab
Join Date: Sep 2011
Posts: 87
Rep Power: 14
Quote:
 Originally Posted by ghorrocks It cannot work because there is nothing to define the pressure.
Thanks for the reply Glenn. CFX actually puts the Node 1 pressure equal to zero to start the simulation. As this Dirichlet value is sufficient to solve the problem and for incompressible steady flow it is not the value of pressure but the gradient which plays a role; could we say that it is ok to put all BC as mass flow? I mean now it is possible in CFX to do all mass flow BC, keeping in mind that the solver itself will give P=0 to Node 1?
I still agree that theoretically only one node pressure value is sufficient to solve all mass flow BC case.

 March 6, 2017, 17:10 #17 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143 You are correct. It does mean the absolute value of the pressure is arbitrary. So I move onto the second problem.... If you define the mass flow rate in and out of a domain in a steady state simulation, then it is not possible to achieve imbalances convergence. All floating point numbers are approximate in a computer, meaning that after floating point approximation your inlet flow will not balance your outlet flow. This small imbalance in flow rates cannot be removed as there is nothing the solver can adjust to balance it. This means you cannot converge the imbalances in this approach. This imbalance may be small or large depending on your simulation setup. More completely: Your simulation is not well posed. Wikipedia's definition of well posed (https://en.wikipedia.org/wiki/Well-posed_problem) states that the solution has to be unique. Your condition with the boundary conditions only is not unique as the pressure level is not set, and therefore is badly posed. You have to make an additional assumption of the pressure at a point to make it solvable. Here is another reference which dives into more mathematical rigour on the definition of well posed: http://liu.diva-portal.org/smash/get...FULLTEXT01.pdf phPatras, ftab and hogsonik like this.

 July 31, 2018, 09:16 #18 Senior Member   Join Date: Mar 2011 Location: Germany Posts: 552 Rep Power: 20 Hi Glenn, does the Total Pressure at Inlet in a domain with No Outlet is a well-posed problem or ill-posed problem? Can I study the pressure drops in the system with Total Pressure at Inlet. It's a high pressure hydraulic system where hydraulic oil enters from one inlet. Pressure and Mass flow rate are known at Inlet. The pipes diameters are of the order of milimeters and even at some places microns. Pressure at Inlet is about 100 bars. I cannot made the simulation to run as it is very unstable. I tried many things like refining the mesh, decreasing the physical time step very very low (like 10e-20), used ramping function to ramp the pressure at Inlet and even i extented the inlet 10 times upstream to allow the flow to develop but unfortunately Nothing helped. I am not sure if the domain with No Outlet is an unusual problem for CFX to solve OR the system of the orders of millimeters with very high pressure is a difficult for CFX to solve OR using Total pressure boundary condition at Inlet without any Outlet in the domain is a problem for CFX? Any suggestions are welcomed. Thanks in advance. Regards

 July 31, 2018, 18:39 #19 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143 To answer that question I would have to see what you are modelling and how you are modelling it. Please attach some images which show what boundary conditions you apply and your CCL. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

August 1, 2018, 03:36
#20
Senior Member

Join Date: Mar 2011
Location: Germany
Posts: 552
Rep Power: 20
Hello Glenn,

thanks for your reply. I have attached the image with the message. As mentioned previously the purpose of the simulation is to study the pressure drops in the system.

CCL:

LIBRARY:
CEL:
EXPRESSIONS:
Flow000 = 0 [bar]
Flow999 = 109 [bar]
Iter = 4000
flowapplied = Flow000 + \
Flow999*aitern/Iter*step(Iter-aitern)+Flow999*step(aitern-Iter)
END
END
MATERIAL GROUP: Air Data
Group Description = Ideal gas and constant property air. Constant \
properties are for dry air at STP (0 C, 1 atm) and 25 C, 1 atm.
END
MATERIAL GROUP: CHT Solids
Group Description = Pure solid substances that can be used for conjugate \
heat transfer.
END
MATERIAL GROUP: Calorically Perfect Ideal Gases
Group Description = Ideal gases with constant specific heat capacity. \
Specific heat is evaluated at STP.
END
MATERIAL GROUP: Constant Property Gases
Group Description = Gaseous substances with constant properties. \
Properties are calculated at STP (0C and 1 atm). Can be combined with \
NASA SP-273 materials for combustion modelling.
END
MATERIAL GROUP: Constant Property Liquids
Group Description = Liquid substances with constant properties.
END
MATERIAL GROUP: Dry Peng Robinson
Group Description = Materials with properties specified using the built \
in Peng Robinson equation of state. Suitable for dry real gas modelling.
END
MATERIAL GROUP: Dry Redlich Kwong
Group Description = Materials with properties specified using the built \
in Redlich Kwong equation of state. Suitable for dry real gas modelling.
END
MATERIAL GROUP: Dry Soave Redlich Kwong
Group Description = Materials with properties specified using the built \
in Soave Redlich Kwong equation of state. Suitable for dry real gas \
modelling.
END
MATERIAL GROUP: Dry Steam
Group Description = Materials with properties specified using the IAPWS \
equation of state. Suitable for dry steam modelling.
END
MATERIAL GROUP: Gas Phase Combustion
Group Description = Ideal gas materials which can be use for gas phase \
combustion. Ideal gas specific heat coefficients are specified using \
the NASA SP-273 format.
END
MATERIAL GROUP: IAPWS IF97
Group Description = Liquid, vapour and binary mixture materials which use \
the IAPWS IF-97 equation of state. Materials are suitable for \
compressible liquids, phase change calculations and dry steam flows.
END
MATERIAL GROUP: Interphase Mass Transfer
Group Description = Materials with reference properties suitable for \
performing either Eulerian or Lagrangian multiphase mass transfer \
problems. Examples include cavitation, evaporation or condensation.
END
MATERIAL GROUP: Liquid Phase Combustion
Group Description = Liquid and homogenous binary mixture materials which \
can be included with Gas Phase Combustion materials if combustion \
modelling also requires phase change (eg: evaporation) for certain \
components.
END
MATERIAL GROUP: Particle Solids
Group Description = Pure solid substances that can be used for particle \
tracking
END
MATERIAL GROUP: Peng Robinson Dry Hydrocarbons
Group Description = Common hydrocarbons which use the Peng Robinson \
equation of state. Suitable for dry real gas models.
END
MATERIAL GROUP: Peng Robinson Dry Refrigerants
Group Description = Common refrigerants which use the Peng Robinson \
equation of state. Suitable for dry real gas models.
END
MATERIAL GROUP: Peng Robinson Dry Steam
Group Description = Water materials which use the Peng Robinson equation \
of state. Suitable for dry steam modelling.
END
MATERIAL GROUP: Peng Robinson Wet Hydrocarbons
Group Description = Common hydrocarbons which use the Peng Robinson \
equation of state. Suitable for condensing real gas models.
END
MATERIAL GROUP: Peng Robinson Wet Refrigerants
Group Description = Common refrigerants which use the Peng Robinson \
equation of state. Suitable for condensing real gas models.
END
MATERIAL GROUP: Peng Robinson Wet Steam
Group Description = Water materials which use the Peng Robinson equation \
of state. Suitable for condensing steam modelling.
END
MATERIAL GROUP: Real Gas Combustion
Group Description = Real gas materials which can be use for gas phase \
combustion. Ideal gas specific heat coefficients are specified using \
the NASA SP-273 format.
END
MATERIAL GROUP: Redlich Kwong Dry Hydrocarbons
Group Description = Common hydrocarbons which use the Redlich Kwong \
equation of state. Suitable for dry real gas models.
END
MATERIAL GROUP: Redlich Kwong Dry Refrigerants
Group Description = Common refrigerants which use the Redlich Kwong \
equation of state. Suitable for dry real gas models.
END
MATERIAL GROUP: Redlich Kwong Dry Steam
Group Description = Water materials which use the Redlich Kwong equation \
of state. Suitable for dry steam modelling.
END
MATERIAL GROUP: Redlich Kwong Wet Hydrocarbons
Group Description = Common hydrocarbons which use the Redlich Kwong \
equation of state. Suitable for condensing real gas models.
END
MATERIAL GROUP: Redlich Kwong Wet Refrigerants
Group Description = Common refrigerants which use the Redlich Kwong \
equation of state. Suitable for condensing real gas models.
END
MATERIAL GROUP: Redlich Kwong Wet Steam
Group Description = Water materials which use the Redlich Kwong equation \
of state. Suitable for condensing steam modelling.
END
MATERIAL GROUP: Soave Redlich Kwong Dry Hydrocarbons
Group Description = Common hydrocarbons which use the Soave Redlich Kwong \
equation of state. Suitable for dry real gas models.
END
MATERIAL GROUP: Soave Redlich Kwong Dry Refrigerants
Group Description = Common refrigerants which use the Soave Redlich Kwong \
equation of state. Suitable for dry real gas models.
END
MATERIAL GROUP: Soave Redlich Kwong Dry Steam
Group Description = Water materials which use the Soave Redlich Kwong \
equation of state. Suitable for dry steam modelling.
END
MATERIAL GROUP: Soave Redlich Kwong Wet Hydrocarbons
Group Description = Common hydrocarbons which use the Soave Redlich Kwong \
equation of state. Suitable for condensing real gas models.
END
MATERIAL GROUP: Soave Redlich Kwong Wet Refrigerants
Group Description = Common refrigerants which use the Soave Redlich Kwong \
equation of state. Suitable for condensing real gas models.
END
MATERIAL GROUP: Soave Redlich Kwong Wet Steam
Group Description = Water materials which use the Soave Redlich Kwong \
equation of state. Suitable for condensing steam modelling.
END
MATERIAL GROUP: Soot
Group Description = Solid substances that can be used when performing \
soot modelling
END
MATERIAL GROUP: User
Group Description = Materials that are defined by the user
END
MATERIAL GROUP: Water Data
Group Description = Liquid and vapour water materials with constant \
properties. Can be combined with NASA SP-273 materials for combustion \
modelling.
END
MATERIAL GROUP: Wet Peng Robinson
Group Description = Materials with properties specified using the built \
in Peng Robinson equation of state. Suitable for wet real gas modelling.
END
MATERIAL GROUP: Wet Redlich Kwong
Group Description = Materials with properties specified using the built \
in Redlich Kwong equation of state. Suitable for wet real gas modelling.
END
MATERIAL GROUP: Wet Soave Redlich Kwong
Group Description = Materials with properties specified using the built \
in Soave Redlich Kwong equation of state. Suitable for wet real gas \
modelling.
END
MATERIAL GROUP: Wet Steam
Group Description = Materials with properties specified using the IAPWS \
equation of state. Suitable for wet steam modelling.
END
MATERIAL: Air Ideal Gas
Material Description = Air Ideal Gas (constant Cp)
Material Group = Air Data, Calorically Perfect Ideal Gases
Option = Pure Substance
Thermodynamic State = Gas
PROPERTIES:
Option = General Material
EQUATION OF STATE:
Molar Mass = 28.96 [kg kmol^-1]
Option = Ideal Gas
END
SPECIFIC HEAT CAPACITY:
Option = Value
Specific Heat Capacity = 1.0044E+03 [J kg^-1 K^-1]
Specific Heat Type = Constant Pressure
END
REFERENCE STATE:
Option = Specified Point
Reference Pressure = 1 [atm]
Reference Specific Enthalpy = 0. [J/kg]
Reference Specific Entropy = 0. [J/kg/K]
Reference Temperature = 25 [C]
END
DYNAMIC VISCOSITY:
Dynamic Viscosity = 1.831E-05 [kg m^-1 s^-1]
Option = Value
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 2.61E-2 [W m^-1 K^-1]
END
ABSORPTION COEFFICIENT:
Absorption Coefficient = 0.01 [m^-1]
Option = Value
END
SCATTERING COEFFICIENT:
Option = Value
Scattering Coefficient = 0.0 [m^-1]
END
REFRACTIVE INDEX:
Option = Value
Refractive Index = 1.0 [m m^-1]
END
END
END
MATERIAL: Air at 25 C
Material Description = Air at 25 C and 1 atm (dry)
Material Group = Air Data, Constant Property Gases
Option = Pure Substance
Thermodynamic State = Gas
PROPERTIES:
Option = General Material
EQUATION OF STATE:
Density = 1.185 [kg m^-3]
Molar Mass = 28.96 [kg kmol^-1]
Option = Value
END
SPECIFIC HEAT CAPACITY:
Option = Value
Specific Heat Capacity = 1.0044E+03 [J kg^-1 K^-1]
Specific Heat Type = Constant Pressure
END
REFERENCE STATE:
Option = Specified Point
Reference Pressure = 1 [atm]
Reference Specific Enthalpy = 0. [J/kg]
Reference Specific Entropy = 0. [J/kg/K]
Reference Temperature = 25 [C]
END
DYNAMIC VISCOSITY:
Dynamic Viscosity = 1.831E-05 [kg m^-1 s^-1]
Option = Value
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 2.61E-02 [W m^-1 K^-1]
END
ABSORPTION COEFFICIENT:
Absorption Coefficient = 0.01 [m^-1]
Option = Value
END
SCATTERING COEFFICIENT:
Option = Value
Scattering Coefficient = 0.0 [m^-1]
END
REFRACTIVE INDEX:
Option = Value
Refractive Index = 1.0 [m m^-1]
END
THERMAL EXPANSIVITY:
Option = Value
Thermal Expansivity = 0.003356 [K^-1]
END
END
END
MATERIAL: Aluminium
Material Group = CHT Solids, Particle Solids
Option = Pure Substance
Thermodynamic State = Solid
PROPERTIES:
Option = General Material
EQUATION OF STATE:
Density = 2702 [kg m^-3]
Molar Mass = 26.98 [kg kmol^-1]
Option = Value
END
SPECIFIC HEAT CAPACITY:
Option = Value
Specific Heat Capacity = 9.03E+02 [J kg^-1 K^-1]
END
REFERENCE STATE:
Option = Specified Point
Reference Specific Enthalpy = 0 [J/kg]
Reference Specific Entropy = 0 [J/kg/K]
Reference Temperature = 25 [C]
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 237 [W m^-1 K^-1]
END
END
END
MATERIAL: Copper
Material Group = CHT Solids, Particle Solids
Option = Pure Substance
Thermodynamic State = Solid
PROPERTIES:
Option = General Material
EQUATION OF STATE:
Density = 8933 [kg m^-3]
Molar Mass = 63.55 [kg kmol^-1]
Option = Value
END
SPECIFIC HEAT CAPACITY:
Option = Value
Specific Heat Capacity = 3.85E+02 [J kg^-1 K^-1]
END
REFERENCE STATE:
Option = Specified Point
Reference Specific Enthalpy = 0 [J/kg]
Reference Specific Entropy = 0 [J/kg/K]
Reference Temperature = 25 [C]
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 401.0 [W m^-1 K^-1]
END
END
END
MATERIAL: Oil
Material Group = User
Option = Pure Substance
Thermodynamic State = Liquid
PROPERTIES:
Option = General Material
EQUATION OF STATE:
Density = 881 [kg m^-3]
Molar Mass = 1.0 [kg kmol^-1]
Option = Value
END
SPECIFIC HEAT CAPACITY:
Option = Value
Specific Heat Capacity = 1861 [J kg^-1 K^-1]
Specific Heat Type = Constant Pressure
END
DYNAMIC VISCOSITY:
Dynamic Viscosity = 0.029073 [kg m^-1 s^-1]
Option = Value
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 0.14 [W m^-1 K^-1]
END
END
END
MATERIAL: Soot
Material Group = Soot
Option = Pure Substance
Thermodynamic State = Solid
PROPERTIES:
Option = General Material
EQUATION OF STATE:
Density = 2000 [kg m^-3]
Molar Mass = 12 [kg kmol^-1]
Option = Value
END
REFERENCE STATE:
Option = Automatic
END
ABSORPTION COEFFICIENT:
Absorption Coefficient = 0 [m^-1]
Option = Value
END
END
END
MATERIAL: Steel
Material Group = CHT Solids, Particle Solids
Option = Pure Substance
Thermodynamic State = Solid
PROPERTIES:
Option = General Material
EQUATION OF STATE:
Density = 7854 [kg m^-3]
Molar Mass = 55.85 [kg kmol^-1]
Option = Value
END
SPECIFIC HEAT CAPACITY:
Option = Value
Specific Heat Capacity = 4.34E+02 [J kg^-1 K^-1]
END
REFERENCE STATE:
Option = Specified Point
Reference Specific Enthalpy = 0 [J/kg]
Reference Specific Entropy = 0 [J/kg/K]
Reference Temperature = 25 [C]
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 60.5 [W m^-1 K^-1]
END
END
END
MATERIAL: Water
Material Description = Water (liquid)
Material Group = Water Data, Constant Property Liquids
Option = Pure Substance
Thermodynamic State = Liquid
PROPERTIES:
Option = General Material
EQUATION OF STATE:
Density = 997.0 [kg m^-3]
Molar Mass = 18.02 [kg kmol^-1]
Option = Value
END
SPECIFIC HEAT CAPACITY:
Option = Value
Specific Heat Capacity = 4181.7 [J kg^-1 K^-1]
Specific Heat Type = Constant Pressure
END
REFERENCE STATE:
Option = Specified Point
Reference Pressure = 1 [atm]
Reference Specific Enthalpy = 0.0 [J/kg]
Reference Specific Entropy = 0.0 [J/kg/K]
Reference Temperature = 25 [C]
END
DYNAMIC VISCOSITY:
Dynamic Viscosity = 8.899E-4 [kg m^-1 s^-1]
Option = Value
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 0.6069 [W m^-1 K^-1]
END
ABSORPTION COEFFICIENT:
Absorption Coefficient = 1.0 [m^-1]
Option = Value
END
SCATTERING COEFFICIENT:
Option = Value
Scattering Coefficient = 0.0 [m^-1]
END
REFRACTIVE INDEX:
Option = Value
Refractive Index = 1.0 [m m^-1]
END
THERMAL EXPANSIVITY:
Option = Value
Thermal Expansivity = 2.57E-04 [K^-1]
END
END
END
MATERIAL: Water Ideal Gas
Material Description = Water Vapour Ideal Gas (100 C and 1 atm)
Material Group = Calorically Perfect Ideal Gases, Water Data
Option = Pure Substance
Thermodynamic State = Gas
PROPERTIES:
Option = General Material
EQUATION OF STATE:
Molar Mass = 18.02 [kg kmol^-1]
Option = Ideal Gas
END
SPECIFIC HEAT CAPACITY:
Option = Value
Specific Heat Capacity = 2080.1 [J kg^-1 K^-1]
Specific Heat Type = Constant Pressure
END
REFERENCE STATE:
Option = Specified Point
Reference Pressure = 1.014 [bar]
Reference Specific Enthalpy = 0. [J/kg]
Reference Specific Entropy = 0. [J/kg/K]
Reference Temperature = 100 [C]
END
DYNAMIC VISCOSITY:
Dynamic Viscosity = 9.4E-06 [kg m^-1 s^-1]
Option = Value
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 193E-04 [W m^-1 K^-1]
END
ABSORPTION COEFFICIENT:
Absorption Coefficient = 1.0 [m^-1]
Option = Value
END
SCATTERING COEFFICIENT:
Option = Value
Scattering Coefficient = 0.0 [m^-1]
END
REFRACTIVE INDEX:
Option = Value
Refractive Index = 1.0 [m m^-1]
END
END
END
END
FLOW: Flow Analysis 1
SOLUTION UNITS:
Length Units = [m]
Mass Units = [kg]
Solid Angle Units = [sr]
Temperature Units = [K]
Time Units = [s]
END
ANALYSIS TYPE:
EXTERNAL SOLVER COUPLING:
Option = None
END
END
DOMAIN: Default Domain
Coord Frame = Coord 0
Domain Type = Fluid
Location = FLUID
BOUNDARY: Inlet
Boundary Type = INLET
Location = INLET
BOUNDARY CONDITIONS:
FLOW DIRECTION:
Option = Normal to Boundary Condition
END
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Option = Total Pressure
Relative Pressure = flowapplied
END
TURBULENCE:
Option = Medium Intensity and Eddy Viscosity Ratio
END
END
END
BOUNDARY: Symmetry
Boundary Type = SYMMETRY
Location = Primitive 2D A,Primitive 2D B
END
BOUNDARY: Walls
Boundary Type = WALL
Location = GEOM_1 GEOM_OBERFL_CHE_1
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = No Slip Wall
END
WALL ROUGHNESS:
Option = Smooth Wall
END
END
END
DOMAIN MODELS:
BUOYANCY MODEL:
Option = Non Buoyant
END
DOMAIN MOTION:
Option = Stationary
END
MESH DEFORMATION:
Option = None
END
REFERENCE PRESSURE:
Reference Pressure = 1 [bar]
END
END
FLUID DEFINITION: Fluid 1
Material = Oil
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID MODELS:
COMBUSTION MODEL:
Option = None
END
HEAT TRANSFER MODEL:
Fluid Temperature = 25 [C]
Option = Isothermal
END
Option = None
END
TURBULENCE MODEL:
Option = SST
END
TURBULENT WALL FUNCTIONS:
Option = Automatic
END
END
END
OUTPUT CONTROL:
BACKUP DATA RETENTION:
Option = Delete Old Files
END
BACKUP RESULTS: Backup Results 1
File Compression Level = Default
Option = Standard
OUTPUT FREQUENCY:
Iteration Interval = 100
Option = Iteration Interval
END
END
RESULTS:
File Compression Level = Default
Option = Standard
END
END
SOLVER CONTROL:
Turbulence Numerics = High Resolution
Option = High Resolution
END
CONVERGENCE CONTROL:
Maximum Number of Iterations = 8000
Minimum Number of Iterations = 1
Physical Timescale = 1e-20 [s]
Timescale Control = Physical Timescale
END
CONVERGENCE CRITERIA:
Residual Target = 1e-010
Residual Type = MAX
END
DYNAMIC MODEL CONTROL:
Global Dynamic Model Control = On
END
END
END
COMMAND FILE:
Version = 19.1
END
Attached Images
 CFX_Model.jpg (38.0 KB, 20 views)