Numerical simulation in aerodynamics

For a long time now, aerodynamicists have been calculating the flows around a variety of moving objects, in order to improve their shape and thus their performance. The same applies to engines, whose power enables ever larger aircraft to fly. In recent years, the speed and memory capacity of today's computers have increased enormously, and new theoretical models and numerical methods have been developed to explain, understand and, if possible, control the turbulent flows that inexorably develop in the air.

Its behavior is fully predicted by the Navier-Stokes equations for a compressible fluid. Nowadays, these partial differential equations can be solved numerically. Air being the seat of turbulent phenomena, the solution sought can only be unsteady, but the scales of the vortex structures encountered are so numerous that theoretical and numerical models must be devised to capture these unsteady phenomena.

It is these new concepts that are now able to account for the complexity of flows. So, even before they actually exist, aircraft are virtually designed down to the smallest detail.

The aim of this article is to describe these recent developments, with a few illustrated examples.