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The CfdOF workbench in FreeCAD includes the density-based compressible solver, HiSA, developed for transonic and supersonic flows. I am not experienced in compressible flow CFD, so I am learning as I go. The documentation discusses two validation test cases, the Army-Navy Basic Finner (ANF) and the Air Force Modified Finner (AFF). I built the ANF using the Rocket Workbench. The domain boundaries were prescribed as far-field with freestream conditions at 50 calibers away from the rocket body. I simulated a steady-state Mach 1.5 in this first go around. For y+=1 across the range of speeds I plan on testing, the first layer was 500 nm. Wow!
The initial mesh was about 1.7M cells. The meshing options include a shockwave adaptive refinement during the solve, which is way cool! After solution refinement, mesh size increased to 2.4M cells.
The solution is well-converged after 800 iterations or so. Wall time was about 8 hours on 4 cores. CD = 0.68, which is right in line with the wind tunnel and free flight data. Nice! I will do a complete speed sweep.
The compressible solver was no more difficult to set up in FreeCAD and seems just as robust as the incompressible. This really opens up CFD as an accurate hobby tool for drag, lift, center of pressure, etc. across all regimes of model rocketry. Really awesome freeware!
The initial mesh was about 1.7M cells. The meshing options include a shockwave adaptive refinement during the solve, which is way cool! After solution refinement, mesh size increased to 2.4M cells.
The solution is well-converged after 800 iterations or so. Wall time was about 8 hours on 4 cores. CD = 0.68, which is right in line with the wind tunnel and free flight data. Nice! I will do a complete speed sweep.
The compressible solver was no more difficult to set up in FreeCAD and seems just as robust as the incompressible. This really opens up CFD as an accurate hobby tool for drag, lift, center of pressure, etc. across all regimes of model rocketry. Really awesome freeware!
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