Flow Past a Cylinder

The following model examines unsteady, incompressible flow past a long cylinder placed in a channel at right angle to the oncoming fluid. The cylinder is offset somewhat from the center of the flow to make the steady-state symmetrical flow unstable.

The simulation time necessary for a periodic flow pattern to appear is difficult to predict. A key predictor is the Reynolds number, which is based on cylinder diameter. For low values—below 100—the flow is steady.

In this simulation the Reynolds number equals 100, which gives a developed Karman vortex street; but the flow is still not fully turbulent.

The plot shows the velocity field of a flow past a long cylinder, the von Karman path is clearly visible.