CFD

CFD (Computational Fluid Dynamics) deals with the numerical solution of the equations of hydrodynamics. Throughout its roughly 50 years spanning history many methods have been developed and later improved; progress however still relies heavily on the computational resources, which so far have become more for same price every year.

I have been writing two-dimensional grid based codes using finite differencing and finite volume schemes, inspired by what is done in computational astrophysics. At some point I became interested in high order codes that are possible with WENO methods. Here are some nice images produced with a such. (For the experts I must admit that the obstacle has been implemented in a non-conservative manner.)

In all cases we have a flow around an obstacle (a circle). The fluid is let in from the left and disappears on the right. Here is a supersonic result (you see a pseudo-schlieren image of the fluid state, when the shock has not yet reached stationarity):
bow shock around an obstacle


When we make the flow less quick, a Karman vortex street develops on the downwind side.

karman vortex street
And all of this in motion:
karman vortex street animated

karman vortex street animated

You can see the influence of the resolution by comparing these 4 images:
karman vortex street animatedkarman vortex street animated

karman vortex street animatedkarman vortex street animated

The supersonic and subsonic flow around a sphere is a fascinating problem showing a huge variety of different flow states, from creeping (or creepy ;) ) flow at low Reynolds numbers and the incompressible flow at low Mach numbers to the development of a bow shock and further supersonic features, all this with a nice colorful garnish of a turbulent wake.

Last modified: Tue Apr 21 11:40:03 CEST 2015