{"id":370989,"date":"2024-07-08T16:17:33","date_gmt":"2024-07-08T16:17:33","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/high-mach-number-compressible-flow-3d-simulation-around-a-finned-projectile\/"},"modified":"2024-07-08T16:17:33","modified_gmt":"2024-07-08T16:17:33","slug":"high-mach-number-compressible-flow-3d-simulation-around-a-finned-projectile","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/high-mach-number-compressible-flow-3d-simulation-around-a-finned-projectile\/","title":{"rendered":"High Mach Number, Compressible Flow 3D Simulation around a Finned Projectile"},"content":{"rendered":"

Hello, I am currently working on a 3D simulation in Ansys Fluent that involves external flow over a finned projectile at high Mach Numbers (>5). I have several issues that I keep running into:<\/span><\/p>\n

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1. When I am constructing my mesh, I have my max element size set to 0.3m, I then input an element size face sizing feature for the projectile specifically and reduce the element size to 0.1m. I then input a body sizing (for an extruded box that was created in designmodeler in the wake) for wake refinement, also setting the element size to 0.1m. I then try to add an inflation feature for the projectile and every time I receive an error that says a stairstep mesh was created in some locations and this reduces my othogonal quality to extremely low, unacceptable, values. Do you know why this keep occurring or how I can fix it?<\/span><\/p>\n

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2. I have established my “setup” settings as density-based and transient, as I understand those are better for high mach number, compressible flow. Is this true? When I use pressure-based and steady, the simulation converges as opposed to density based where it typically does not. For my model I am currently using k-epsilon realizable, yet I have also used k-omega SST, do you know which may be better for my application?<\/span><\/p>\n

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3. For my boundary conditions, I have set up a fairly large enclosure around the projectile. Previously, I had several named selections, being inlet, outlet, walls, and projectile. Yet I read that for high mach number flows, it is better to define the entire enclosure as pressure far-field and enter in a mach number for the flow. I now have two named selections, being pressure far field for the entire enclosure, and the projectile. Is this correct? Is there a different way that I should be establishing my boundary conditions?<\/span><\/p>\n

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4. For most of the simulations I have run so far, my residuals have started low, and then increased largely to the point where most of the time, the calculations fail and a “floating point” error appears. Do you have any suggestions for how to go about defining specific mesh characteristics, or specific setup settings for my particular case? I previously tried running pressure-based, steady simulations on this same projectile and the contours that I obtained were not detailed at all and only appeared very close to the projectile surface.<\/p>\n

5. I am trying to determine center of pressure of the projectile that is oriented in the XY plane. I set Z = 0 yet the CP x value is no where near where the expected CP should be. Do you have any tips for how to go about this?<\/span><\/p>\n

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Any assistance that can be provided would be greatly appreciated.<\/span><\/p>\n

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Thank you.<\/span><\/p>\n","protected":false},"template":"","class_list":["post-370989","topic","type-topic","status-closed","hentry","topic-tag-fluent-cfd-ansys-1"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t