What is CFD?

Imagine carrying out pressure and flow analyses to test existing structures or prototypes in a windless, simulated wind tunnel on your desktop computer. The technique is called computational fluid dynamics (CFD).

The technology was pioneered in the UK in the 1970s by CHAM (CHAM Ltd) of Wimbledon which for many years was the only company offering commercial products. It is still one of a handful of leaders in the field.

CFD is dedicated to solving fundamental non-linear differential equations that describe fluid flow, heat transfer, and turbulence on a computer. The process depends on the ability of high powered computers to solve millions of mathematical expressions per second in a similar way that computer-aided design and finite element analysis operate, using computational grids.
Grids or meshes are constructed on the computer to simulate finite blocks of physical space. The grids break up the real fluid space around an object into small imaginary computational elements. These shapes may be quadrilateral, triangular, hexahedral, tetrahedral or even composed of mixed elements.

Computer analysis provides a grid cell by grid cell prediction of local fluid velocities, pressures and temperatures to simulate wind tunnel or water model flow around a solid body.

Two forms of mesh are used, structured and unstructured. Structured meshes have the same number of cells across and along the grid, although they may be non-uniform in shape. Unstructured meshes may have varying numbers of cells joined in several different ways and need more computer power to run but offer advantages for complex shapes.

The results of this analysis are used to predict how changes in these parameters affect the behaviour of the fluids and the mechanical pieces of equipment they interact with.