Secondary inlet

Martin_D · May 6, 2011, 01:28

Grettings,
I'm simulating a flow over an airfoil that has a secondary inlet so the flow from the secondary inlet exits at the trailing edge of the airfoil. The problem is that when airflow is coming in the domain from both inlets the solver either crashes or the solution does not converge. Simulations have been made with only the primary inlet and were good but as soon as the secondary inlet becomes involved I can't seem to get any kind of solution. The boundary conditions at both inlets are defined as mass flow. Outlet is defined as static pressure imposed.

Can anyone hep me with this matter or give me an advice?

Martin_D · May 9, 2011, 05:39

After changing the boundary conditions of the main inlet and outlet to EXTERNAL (secondary inlet stay the same- mass flow imposed) I got a converged solution for a steady simulation but I'm still not able to get an unsteady solution.

Hamidzoka · May 15, 2011, 00:00

Dear Martin
what is your initial solution when you solving unsteady model?
did you check the delta t? maybe it needs to be reduced.

Martin_D · May 16, 2011, 03:39

My initial solution was a steady Spalart-Almaras solution and then a SST steady solution.
I have tried changing the physical timestep, at first it was 0.001 and when I changed it at 0.005 it actually worked but the convergence was poor. It's is a bit confussing.
I've noticed that the solver is very sensitive when applying different initial solutions and boundary conditions.

Martin_D · May 23, 2011, 08:33

When I run an unsteady SST simulation with a timestep of 0.006 the solver does the job but when I lower the timestep to 0.001 or 0.0001 seconds then the solver calculates a negative pressure and crashes. Can anyone help me with this matter?

May 6, 2011, 01:28	Secondary inlet	#1
Martin_D New Member Martin Join Date: Jul 2010 Posts: 20 Rep Power: 16	Grettings, I'm simulating a flow over an airfoil that has a secondary inlet so the flow from the secondary inlet exits at the trailing edge of the airfoil. The problem is that when airflow is coming in the domain from both inlets the solver either crashes or the solution does not converge. Simulations have been made with only the primary inlet and were good but as soon as the secondary inlet becomes involved I can't seem to get any kind of solution. The boundary conditions at both inlets are defined as mass flow. Outlet is defined as static pressure imposed. Can anyone hep me with this matter or give me an advice?

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May 9, 2011, 05:39		#2
Martin_D New Member Martin Join Date: Jul 2010 Posts: 20 Rep Power: 16	After changing the boundary conditions of the main inlet and outlet to EXTERNAL (secondary inlet stay the same- mass flow imposed) I got a converged solution for a steady simulation but I'm still not able to get an unsteady solution.

May 15, 2011, 00:00		#3
Hamidzoka Senior Member Hamid Zoka Join Date: Nov 2009 Posts: 293 Rep Power: 19	Dear Martin what is your initial solution when you solving unsteady model? did you check the delta t? maybe it needs to be reduced.

May 16, 2011, 03:39		#4
Martin_D New Member Martin Join Date: Jul 2010 Posts: 20 Rep Power: 16	My initial solution was a steady Spalart-Almaras solution and then a SST steady solution. I have tried changing the physical timestep, at first it was 0.001 and when I changed it at 0.005 it actually worked but the convergence was poor. It's is a bit confussing. I've noticed that the solver is very sensitive when applying different initial solutions and boundary conditions.

May 23, 2011, 08:33		#5
Martin_D New Member Martin Join Date: Jul 2010 Posts: 20 Rep Power: 16	When I run an unsteady SST simulation with a timestep of 0.006 the solver does the job but when I lower the timestep to 0.001 or 0.0001 seconds then the solver calculates a negative pressure and crashes. Can anyone help me with this matter?