Discrete phase or two phase model in Fluent?
 

Good morning, I am a Ph.D.student working in the field of CFD, who used to code his own programs for CFD analysis, until now. I should model the flow of an ideal gas around and into an instrument for the measurement of dust properties (that is, a fairly complex 3D geometry), and the transportation of dust by the flow, as well as its interaction with the instrument. Ambient pressure is around 6 mbar and temperature is around -40 °K; the dust content is 1.8e-7 kg/m^3 (mass of dust per unit volume of gas). The dust radius is exceedingly small, e.g. of the order of microns: the characteristic length of the instrument may be taken to be 4-10 cm. I would like to use Fluent to simulate this problem: how can I choose between a two phase model and the discrete phase model? Any suggestions? Thanks,

Andrea Panizza

Re: Discrete phase or two phase model in Fluent?
 

As I understand you have only the gas and the dust, so a single flow solver and DPM should suffice.

Cheers

newbie

Re: Discrete phase or two phase model in Fluent?
 

And I think that you do not need to consider the 'interaction with continuous phase' because the mass flow rate of discrete phase is so small.

Sincerely, Jinwook

I have problems about CFD model of downdraft gasifier
 

Hello, Mr. Lee Jinwook,
I am a Master student study in biomass gasificaion in Korea. I am trying to make a CFD model of downdraft gasifier using FLUENT 6.3. I have a lot problems. I am not sure if you can see my message and give me some advise but I hope so.

I tried 2 ways to simulate this gasification process: one phase and multiphase.
In one phase case, wood determined as very small carbon particles. So the carbon particles and air determined as fluid phase. The details you can see in the fluent case file. The model was run in a computer which has 3G RAM and Q6600 cpu for more than 12 hours and iterated about 26,000 times.
The problem is:
1.The simulated result presented that nearly no reactions occurred in the gasifier.
2.If I use a injection of wood inlet, the injection rate will be very small because the wood is drop down very slowly, I cannot simulate the right case use a injection.

In 2 phase case, carbon determined as solid phase and details of model setting as below:
The problem is :
1.In the simulated result, temperature is too high (highest is 5000K), the temperature range in experiment is from 293K~1600K.
2.No reactions occurred in the gasifier as the simulated results.

**Setting of Multiphase (2 phase)
Slover
Slover -Pressure Based
Formulation -implicit
Space -3D
Velocity Formulation -Absolute
Gradient Option -Green-Gauss Cell Based
Porous Formulation -Superficial Velocity
Multiphase
Multiphase Model -Eulerian
Number of phase -2
Energy
-Energy Equation
Viscous Model
Model -k-epsilon (2 eqn)
k-epsilon Model -Realizable
Near-Wall Treatment -Standard Wall Functions
k-epsilon Multiphase Model -Mixture
Model Constants
C2-Epsilon: 1.9, TKE Prandtl Number: 1, TDR Prandtl Number: 1.2, Disperion Prandtl number: 0.75, Energy Prandtl Number: 0.85, Turb. Schmidt Number: 0.7,
Species Model
Model -Species Transport
Reactions -Volumetric & Particle Surface
Options -Inlet Diffusion & Diffusion Energy Source
Turbulent -Chemistry Interaction -Finite-Rate/Eddy-Dissipation
Operation Condition
Pressure: Operating Pressure(pascal)-101325
Gravity: Gravity- Gravitational Acceleration Z(m/s2)=-9.8
Boussinesq Parameters: Operating Temperature (k)=288.16

Fluent Vc++ Programer
 

is anyone have a software of Fluent Vc++ Programer?
can u share it for me
xjzzyan@sina.com or qq:349134327
thanks

use C++ builder its small program from C++ for making texts

Querries about Discrete phase model
 

Droplet evaporation;heat and mass transfer;two way interaction; coaxial fuel and air flow; known air velocity and fuel mass flow rate;
1) How can I model for a fuel which is not in the list of fluent (say, Iso-propyl alcohol [IPA])? If the fix is not regular.
2) I want to use UDF for heat and mass transfer. Can any one tell where to add udf. No option is available on my software or am I doing wrong?
3) Can I know the droplet phase velocity, diameter, temperature, etc., other than droplet trajectory. Also, droplet extinction time or evaporation rate. Then, How? I not able to get any DPM info other than droplet trajectory. Also the message from fluent was that Heat and mass transfer is incomplete.

another flow in mass flow inlet
 

dear all
hi
I am new in fluent
how i can define all of my mesh zone stagnation air
and mass flow inlet another flow like that fuel
then i have to the mixing rate of them
please help me?
thanks for your attention
amir mohebbi

Hi,Is a fixed bed of an adsorbent(with high surface area) for adsorption of air pollutants a Discrete Phase Model in fluent?
Our pollutants in air are vapors.

I Think, DPM model wouldn't be appropriate. You may also try COMSOL software, if needed.

droplet modeling
 

hi to all.
i want to modeling a liquid liquid direct contact heat exchanger and in this model i have 2 phases one of them is continuous phase and the other on disperes phase( group of droplet) and when i want to inject droplets from disperes surface all of the option related to particl type are off and i dont now why?somebody help me?tahnk u
fluent: define> model > disceret phase> injection >

I think, you should work with multiphases models and 'Solution initialization - volume fraction'.
But it depends what multiphase model is appropriate for you or/and what one you've chosen and what is you study purpose?.
Can you show picture of your model or explain your case of study in detail?

Check if species transport is ON.

Hi..I am Research Scholar and I am doing the CFD study of preparing an emulsion solution but I could not find it on FLUENT 6.3.26 can any one help me regarding this? I tried this on Discrete Phase Model but did not get it perfectly. So please help on this.

Hi. I want to simulate the dust explosion in a tube. the general picture of my work is as follow. we put some concentration of dust on a plate and air with high pressure(7 bar) enters the tube. so the particles of dust start to desperation. after a certain time spark ignition ignites and the reactants starts to burn. I want to know if should I consider DPM for dispersion of dust? if yes, which kind of the injection should I take into account?(surface, single, cone,...)?