Flamelet Parameters
 

I'm starting to make reactive simulations using Steady Flamelet models. My objective is to simulate a hydrogen flame in air in a tipical bluff-body configuration. I'm using the Burke 2011 kinetic model (8 species + inerts and 19 reactions).

There is any golden rule to determine the following parameters to calculate the flamelet and generate the pdf table?

• Number of Grid Points in Flamelet
  
• Maximum Number of Flamelets
  
  
• Number of Mean Mixture Fraction Points
  
  
  
• Number of Mixture Fraction Variance Points
  
  
  
  

hi every body
is there anyone here to answer the question?
It's mine too!
Also I want to know if there's any optimum under-relaxations?
My model convergence has many fluctuations.

Hi all ,
As far as i know there isn't any golden rule , however you can validate your results by looking to the Flamelet shape, species , scalar dissipation and mixture fractions .
I am always using the automated refinement with 8 to 40 points /20 flamelets and it gives good results . Check also the time vs . residuels while creating flamletes ,if it is smooth then you are good to go , if on the other hand it takes long time , try to redude the fourrier no. to 1 .

Hi Kingpots,

thank you very much for your response, it was really helpful. :):D

Could you shade some light in solving my simulation, please?? :(

I am doing a non-premixed Methane-air combustion which has swirling air-flow involved. I am using both GRI-mech 3.0 and GRI-mech 2.11 chemical kinetics mechanism and using Steady Diffusion Flamelet chemistry model in Fluent non-premixed combustion. Standard k-epsilon Turbulence model and P-1 radiation model is used.

Simulation Results of Velocity and Gas mass-fraction are matching the experimental data in all locations except gas mass-fraction data in two initial upstream locations. In order to get better gas mass-fraction data, I was trying to figure out a way.

I also always used Automated Grid Refinement.

Now the question is, changing (increasing/decreasing) following default values will give better result ??

1) Maximum number of flamelets (default value: 8)

2) How about Initial Scalar Dissipation (default: 0.01)
and Scalar Dissipation Step (default: 5)?

3) Initial number of Grid points in Flamelet- 8 and
Maximum number of Grid points in Flamelet- 64

4) Maximum Change in Value Ratio- 0.5

5) Maximum Change in Slope Ratio- 0.5

I'm attaching the Fluent Flamelet window screenshot as well.

Could you please help me out??

Hi all,
Error while creating flamelet.
Anyone can explain how to use steady diffusion flamelet non-premixed model.

Thanks in advance.