Different behavior using UDF vs constant value
 

Hi there!

I want to simulate fast combustion of air-methane mixture in FLUENT and I use methane-air-2step as material. Giving to this mixture a constant value for specific heat and the same value by meaning of DEFINE_SPECIFIC_HEAT, the results are very different (for example, in the first case the temperatures start from 300K, as I set for initial conditions, and the second case has temperatures start from 2400K). The interpreted and compiled UDFs give identical results.
Can you explain the different behavior between usage of constant value and same value in an UDF?
Thank you!

Could you supply the UDF you are using? Compare the results between using the UDF and not using the UDF; are these results different? Ensure that Fluent is hooking the UDF you intend and not an old copy.

Thank you for reply, 'e'. Meanwhile, I solved the problem. The different between cases is that, using constant value, Fluent takes into account a reference temperature of 298.15K, and in case of using the same value in an UDF, the reference value is that you specified for initial conditions.