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Old   April 19, 2013, 15:41
Unhappy Hypersonic flow over double wedge
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Hi! I want to analyze the shock interactions in a hypersonic flow over a double wedge. My Mach number is 9. I generated an unstructured mesh with about 2lakh elements. I chose such a large number because my instructor says that the mesh has to be very refined for such flows.I am new to CFD and Fluent and I am not sure in how many iterations my solution should converge. I set the residuals to 1e-5. Even after about 80000 iterations, the residual was still at 1e-2. Is this natural or am I doing something wrong? Also, how long do these computations usually take? Please help. Thanks a lot.
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Old   April 19, 2013, 15:55
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A not converged solution can be caused by various setting ? probably your mesh, probably you boundary conditions. have you followed any tutorial before ?
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Old   April 19, 2013, 16:34
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Quote:
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A not converged solution can be caused by various setting ? probably your mesh, probably you boundary conditions. have you followed any tutorial before ?
I could not get any tutorial specific to double wedge flow problems. But, I followed a tutorial on supersonic flow over a wedge. I think my boundary conditions are also right. I have set the wedges to wall boundary condition, otlet to pressure outlet and the farfield boundary to pressure farfield. As far as the mesh is concerned, I perform the grid check operation whenever I start the simulation. It has never shown any error.
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Old   April 19, 2013, 16:50
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good, how about your mesh ? are working in 3d or 2D ?? structured or unstructured ? i have work with supersonic flow, they are very very difficult to converge, did you run the simulation with 1st order then switched to second ?
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Old   April 19, 2013, 16:56
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Quote:
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good, how about your mesh ? are working in 3d or 2D ?? structured or unstructured ? i have work with supersonic flow, they are very very difficult to converge, did you run the simulation with 1st order then switched to second ?
It is a 2D mesh. and a very simple geometry. It is an unstructured mesh with local refining around a vertex. I directly ran it in the second order.

Last edited by marilyn; April 19, 2013 at 17:05. Reason: more info
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Old   April 19, 2013, 17:04
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deciding what order should depend on the nature of the flow, and not the simplicity of the geometry. hypersonic should be difficult to predict. i suggest you start with a density based, first order see what you get...
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Old   April 19, 2013, 17:07
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deciding what order should depend on the nature of the flow, and not the simplicity of the geometry. hypersonic should be difficult to predict. i suggest you start with a density based, first order see what you get...
shall try doing that and see what happens. thanks a lot for your help
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Old   April 20, 2013, 14:26
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