This is the second blog of the Blog Series: Learning CFD in Aerospace Engineering.
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Supersonic flow around a three-dimensional sphere
Students simulate the supersonic flow around a three dimensional sphere in a laboratory work of 90 minutes with FINE™/Open with OpenLabs™.
Objective: As the introductory laboratory work, students learn to create the solution domain, generate the mesh, set up solver parameters and post-process the results. Calculations are carried out for a sphere of one-meter in diameter with an oncoming speed of 640 m/s directed in the X direction.
In HEXPRESS™ the geometry of the sphere is subtracted from a cuboidal box to represent the domain. The surface of the sphere is refined with Surface Refinement to ensure that the curvature of the sphere is captured smoothly. The region around and downstream of the sphere are refined additionally with Box Refinement to capture the wake. The meshing step is completed by inserting viscous layers on the sphere with a dimensionless wall distance (y+) of 30.
In the FINE™/Open solver, the simulation is set up with:
- the fluid type: air (calorically perfect gas),
- the turbulence model: k-ε (extended wall function),
- the boundary conditions:
- the sphere is set as a Navier-Stokes (no-slip) wall,
- all 6 faces of the external box are set with the far-field boundary condition (with a velocity of 640 m/s in the X-direction),
- a CFL number of 2.
The students also compare the simulations between 1st and 2nd* order discretization schemes. The students observe that the differences relate not only to aerodynamic coefficients (of the order of 10%), but also to the flow structure.
*It may be necessary to deactivate residual smoothing while using the 2nd order discretization scheme
Students of Prof. Malashin learning with FINE™/Open with OpenLabs™ at MSTU