CFD - A Primer
CFD works by dividing the region of interest, the inside of a mixing vessel or the air around the outside of a car for example, into a large number of cells or control volumes (the mesh or grid). In each of these cells, the partial differential equations describing the fluid flow (the Navier-Stokes equations) are rewritten as algebraic equations that relate the pressure, velocity, temperature and other variables, such as species concentrations, to the values in the neighboring cells. These equations are then solved numerically yielding a complete picture of the flow down to the resolution of the grid.
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| The first stage in any CFD model is to create a geometry which represents the object being modeled. From this point, a mesh is generated (shown right) which creates the cells or control volumes. Advanced CFD software can automatically optimize the mesh to concentrate analysis on points of interest. |  |
| Once the mesh is complete, the model input values are specified and the software then solves the equations of state for each cell until an acceptable convergence is achieved. This can be a time consuming process, but fast optimized codes can exploit parallel processing (as shown right where the mesh has been automatically divided up between several processors) |  |
| When the model has been solved, the results can be analyzed both numerically and graphically. ANSYS CFD software provides a powerful, comprehensive set of post-processing tools to create visualization ranging from simple 2-D graphs to 3-D representations of particle tracks, vectors and gradients as well as animations. |  |