Combustion problem
 

I have solved a combustion problem using mixture fraction Pdf model without checking for damkohler number,...

Am having a problem with the solution,.. am getting negative pressures at nozzle throats,... is this bcoz i may have selected wrong model,..

i have even tried to solve the same problem with species transport model but i failed even to start the solution with that model,.....

what should i do,.. to get correct result,...