3. Two-dimensional flow in a channel

Each consists in simulating flow in a channel disturbed by a horizontal row of circular obstacles. This is a very good approximation of water flow around pillars, assumed to be cylindrical (a bridge, for example). These experiments are shown in figure 4 . The length of the channel, noted Ω, is four times greater than its width L. The Reynolds number for both simulations, based on the diameter of the obstacles (equal to 0.1 × L) is Re = 50,000.

The first simulation is based on the numerical solution of the Navier-Stokes equations whose rectangular domain Ω is composed of Ω _s for the obstacles (5 disks), and Ω _...