Computational Mesh Options are Plentiful for Wind-US

Like most CFD codes, Wind-US requires a sufficiently detailed computational mesh (a.k.a. a “grid”) which describes the volume in which you want to compute the flow. Any experienced CFD practitioner will tell you that it usually takes a lot longer to create a good grid than to run the code, so it is notable that with the Wind-US solver, you have a lot of flexibility in building computational mesh.

If you are unfamiliar with some of the terminology used here, brush up with this overview of computational mesh types.

Model Flows Using Structured or Unstructured Meshes

With Wind-US, both structured and unstructured grids can be used. Unlike some other codes I have encountered which claim this capability, the structured grids are actually solved with a true structured grid solver for maximum efficiency. You can even combine structured and unstructured grids in the same problem.

Some of the grid coupling methods supported by Wind-US

On the structured grid side, the code can run 2-D grids (i.e. just a single plane of points), 2-D axi-symmetric, and full 3-D. Multi-block grids are supported, with blocks both abutting each other (point-matched or not) or overlapping each other CHIMERA fashion.

The figure above shows a slice of a sample grid which uses several of the available options (point-matched abutting, non-point-matched overlapping, and boundaries in the interior of a grid). A CHIMERA-type grid, where the smaller grid cuts a hole in the larger, is illustrated below.

Example of a CHIMERA grid system

With Wind-US version 1.0, the NPARC Alliance began adding the capability to use unstructured grids. The unstructured grid solver requires a 3-D grid consisting of tetrahedra, prisms, and/or hexahedra. 2-D simulations can be handled using a couple planes of cells. While the unstructured solver is much less mature than the structured algorithms, it is improving with each release.

A sample unstructured grid used with Wind-US is shown below. This plot shows part of a cross-section of the mesh for a rocket nozzle. As is recommended for many different unstructured CFD solvers, hexahedral cells are used near solid surfaces. Away from walls, the grid transitions (generally using layers of prisms) to a tetrahedral grid in the core regions.

Example unstructured grid


Choose the Right Grid for the Job

The ability of Wind-US to handle many different classes of computational mesh gives you, the user, the ability to use the right grid topology for each different configuration you simulate. You are not forced to take a one-size-fits-all approach.

When figuring out which approach to use, it is important to weigh the strengths and weaknesses of each and balance that against your requirements. Obviously, this page only scratches the surface of this subject. If you would like to know more about the various grid topologies or the capabilities of the Wind-US code contact me.

Ready to move on? The next page covers the various options for parallel processing supported by Wind-US.

Or, you can return to the introduction page for this CFD analysis software review.

Alternatively, go back to the free CFD solvers page or the Innovative CFD home page

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