# Grabowski-Berger rotational flow

The geometry and boundary condition of this 3D flow have cylindrical symmetry. This symmetry breaks at a critical Reynolds number, with a production of helix branches. A regime with a double-helix is shown in this demo. The flow is visualized through injected passive tracer particles.

A detailed description of the problem and solutions obtained with other numerical tools are provided in *Ruith, Chen, Meiburg, Comp. Fluids 33 (2004) 1225–1250*.

## Simulation setup

The simulation is contained in a cylinder of radius 10 and length 20 (in dimensionless units). The axial direction in the following referred to as z-direction. The inlet (z=0) is defined through a rotating velocity profile with a core of radius 1. In cylindrical coordinates, the velocity takes the shape

Numerical Parameters

Reynolds number | 100 |

S | 1.5 |

1 |