Hi , I am trying supersonic combustion in cavity combustor..I am using Spalart Allmaras model ... The flow is with injection (h2 @ M=1.0)and main air flow at M=2.0..presently it is a non reacting case.. still mass is not getting conserved.inlet BCressure inlet fuel inlet :mass flow or pressure inlet.

What is the problem i am using 3rd order MUSCL scheme fro discretization. thanks in advance Sridhar

hi sridhar!

pr. inlet conditions are somevat rigid, if u r using them then start the simulation at low mach. nos and progressively increase them with unsteady set up, as the solution is about to coverge u can increase the flow velocities. and for bounded flows k-E models are appropriate ones,or the sst model, s-a is perfect for open flows.

hope this would help u. regards, raj

hi raj thanks for the advice ..i'll try that..but just one query...u said using pressure BC's is rigid .. what should it then be..i mean keeping them(BC) the same (for air and fuel) should I change the values of pressure (total) such that the velocities changes from subsonic to sonic..or should I change the BC's from inital Velocity inlet for Subsonic to Pressure inlet at supersonic. waiting for ur response,

thanks sridhar

Dear Sridhar!

As it is a combustor, we have no other way but to use the pressure inlet (we can use mass flow conditions but not preferred in this case), use the same conditions.but give the time step as low as possible, and as well the courant number too!

regards, raj....