2D flow around a rectangle

Low resolution DNS using the projection method based on the “Stable Fluids“ algorithm of Jos Stam. Here I have improved it to be 4th order in space with a two-stage pressure correction, significantly reducing false diffusion. 10% vorticity confinement was used to energise the vorticity at all scales to simulate a higher Reynolds number “turbulent“ flow (recall there is no real turbulence in 2D due to the absence of vortex tube stretching and tilting since all vorticity vectors are in the same plane). Coded in VB from scratch, no external libraries. Colouring represents the concentration of a passive scalar continuously replenished on the surface of the object and advected with the local flow. Note the tilted large-scale structures moving along the plate, also note the backflow near the surface towards the leading edge. Further along the plate the surface flow goes forward again (on average), thus there is a separation bubble at the leading edge. Again, the large-scale outer motions are generated by the Kelvi