Tech Briefs

Adaptive Meshing in CFD

In our January 15, 2009 News we focused on the ADINA algorithm that we developed to adapt meshes in the solution of fluid-structure interactions.

As we mentioned in that News, ADINA 8.6 offers the capability to adapt and repair CFD meshes so that appropriate mesh grading is used. The ADINA techniques operate on CFD solution gradients and involve refining and coarsening the mesh in the various regions of flow for adequate element sizes throughout the fluid region.

The ADINA capability operates on general free-form meshing and hence accommodates meshes from many pre-processors, and in particular also meshes prepared for Nastran (see our News ADINA Pre- and Post-processing Options and Using NASTRAN Models for 3D CFD and FSI Analyses).

In the present News we give the solution of a high-speed compressible flow problem, in order to illustrate that very strong gradients — shock fronts — can also be accurately resolved with the ADINA algorithm. We consider a 2D flow passing a circular cylinder with a free stream Mach number = 8, see Figure 1 below. This problem has been used widely to benchmark solution schemes.

The movie above shows the coarse starting mesh of 1,758 elements and 3 meshes, including the final mesh, of the 6 mesh adaptations used to reach the final mesh of 56,471 elements. The pressure solutions for these meshes are also shown in the movie. The final mesh resolves the shock front very accurately as shown in Figures 2 to 4.

Figure 1  Problem considered

Figure 2  Calculated velocities

Figure 3  Calculated pressure

Figure 4  Mach number along section A-A

This benchmark problem solution illustrates how ADINA can be used for high-speed compressible flows to accurately calculate solution quantities, including shock fronts.

CFD, compressible flows, high-speed, shock front, Mach number, adaptive mesh, solution gradients