3D hypersonic convergence problem

Fluidified · March 29, 2018, 20:48

Hello all

I am having serious issues with converging my 3D hypersonic case using FLUENT. I am simulating an air flow over a cone at Mach 10 and currently using a density based solver with an ideal gas model.
I’m using the k omega SST turb model with compressibility effects and a pressure far field as the boundary condition. In the solution methods I have it set to AUSM with a second order scheme with an under relaxation factor of 0.15. My courant number is set to 0.5.

When ran the residuals are very stiff, barely going below 1E-2 and/or the solution will diverge after 400 iterations.

I have tried changing the turbulence model, geometry, solution methods and controls and refining the mesh with no success. I’m currently running multiple cases with various inflation layer heights to see what effect that has.

If anyone could offer any suggestions to what the problem may be that would great!! I’m running out of ideas

AtoHM · March 31, 2018, 09:59

For such high residuals I would suggest refining the grid - I see you tried that. But where did you refine?
I am not a fluent user, but if possible, try to get the position of the high residuals and refine there.

March 29, 2018, 20:48	3D hypersonic convergence problem	#1
Fluidified New Member James Join Date: Mar 2018 Posts: 1 Rep Power: 0	Hello all I am having serious issues with converging my 3D hypersonic case using FLUENT. I am simulating an air flow over a cone at Mach 10 and currently using a density based solver with an ideal gas model. I’m using the k omega SST turb model with compressibility effects and a pressure far field as the boundary condition. In the solution methods I have it set to AUSM with a second order scheme with an under relaxation factor of 0.15. My courant number is set to 0.5. When ran the residuals are very stiff, barely going below 1E-2 and/or the solution will diverge after 400 iterations. I have tried changing the turbulence model, geometry, solution methods and controls and refining the mesh with no success. I’m currently running multiple cases with various inflation layer heights to see what effect that has. If anyone could offer any suggestions to what the problem may be that would great!! I’m running out of ideas

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March 31, 2018, 09:59		#2
AtoHM Senior Member M Join Date: Dec 2017 Posts: 642 Rep Power: 12	For such high residuals I would suggest refining the grid - I see you tried that. But where did you refine? I am not a fluent user, but if possible, try to get the position of the high residuals and refine there.