Finally, a tetrahedral mesh is created to efficiently fill the remaining volume. Also effective are non-equilibrium wall functions, which are sensitized to the local pressure gradient. First-order convective differences are useful at the start of a calculation because they increase numerical stability when the initialized flow field is a poor approximation to the converged result. Afterwards, second-order differences should be employed so that the physically realistic gradients emerge. Adequate spatial resolution is another requirement for error minimization.
Spatial resolution is improved through solution-adaptive mesh refinement.
A small series of strategic adaptions usually is sufficient to yield wind tunnel accuracy with only a modest increase in cell count and total CPU-time. While the basic building blocks of a successful methodology can be summarized as above, Fluent staff have expended considerable effort to define and refine what constitutes best-practice for automotive external aerodynamics.