Regarding UDF for Fuel Inlet Boundary condition
 

Hi guys,
I have a fuel inlet which is set to be interface Boundary Condition and mass flow rate is required to be calculated from the mass balance equation i.e.

m[dot[]= rho_s*regression_rate_solid=-rho_fluid*velocity_fluid

I am new to Fluent UDF. Can anyone suggest which Macro can be used for such an operation or provide me with the code.

Thanx for precious time. :)