[weiyi]

Hi, there

I want to define the turbulent flame speed using a UDF as follows: turb_flamespeed = laminar_flamespeed + laminar_flamespeed * A * pow(uprime / laminar_flamespeed, 5 / 6), where A is a constant. But when I change A to any value, the pressure inside the cylinder remains consistent.
May I ask if this is a compilation failure or is there some other reason?

[ksrivast]

Hello Wei,

Could you confirm you are recompiling the UDFs when you make changes to your turbulent flamespeed calculation formula? And you are using the newly compiled libconverge_udf.so file with your simulations?
It would also be helpful if you can let us know :
1. What flags in udf.in you have active.
2. Which one of our sample UDFs you have modified to define your custom turbulent flamespeed?

It might also be helpful to add print/log messages in your UDFs to ensure the approriate routines are correctly called during the simulation.

Sincerely,

[weiyi]

Hello, I have modified the turbulent flame speed in g_eqn_unburned.c, but the compilation in g-equation in combustion chemistry does not include this modification. How can I implement the modification of the turbulent flame speed?

[ksrivast]

Hello Wei,

Are you facing issues with UDF compilation or with your CONVERGE simulations which do not show the effect of the modified flame speed?

Sincerely,

[weiyi]

Originally Posted by ksrivast

Hello Wei,

Are you facing issues with UDF compilation or with your CONVERGE simulations which do not show the effect of the modified flame speed?

Sincerely,

Hello,
The issue of flame speed has been resolved. I now want to consider the impact of thermal diffusion instability in hydrogen flames. I saw relevant content in the CONVERGE CFD reference, ADVANCED G-EQUATION MODELING FRAMEWORK FOR HYDROGEN-FUELED SI ENGINE COMBUSTION SYSTEMS. It involves laminar flame speed, and I need to modify and rework the equation for laminar flame speed?