Ansys Learning Forum Forums Discuss Simulation Fluids Handling Solid Volume Fraction in Gas-Solid Reaction in ANSYS Fluent Reply To: Handling Solid Volume Fraction in Gas-Solid Reaction in ANSYS Fluent

Ahmed Hussien
Ansys Employee

When you use the Arrhenius equation for the reaction rate without including a UDF for the solid volume fraction (ϵs), Fluent does not automatically account for the solid volume fraction in the reaction rate unless it is explicitly defined in the reaction rate formula or through a UDF.

For specific reactions and rate equations that include the solid volume fraction as a variable, you would typically need to include this in your reaction rate definition, either directly in the rate formula or by using a UDF to define how the solid volume fraction affects the reaction rate.

Since you mentioned that your results are in good agreement with experimental observations, it suggests that your approach may be working for your specific case. However, for a more accurate representation and to ensure that the solid volume fraction is accounted for in the reaction rate, it would be advisable to include it through a UDF or directly in the reaction rate formula if the model requires it. 

You can use the DEFINE_HET_RXN_RATE macro to define the reaction rate. You may check the documentation for more information on the implementation and examples 2.4. Multiphase DEFINE Macros (ansys.com)