Velocity Profile Optimization for the Riga Dynamo Experiment

The Riga dynamo experiment is an attempt to show the
self-excitation of a magnetic field in an electrically conducting fluid.
Due to the absence of any scale separation effects, the precise shape of
the velocity profile has a strong influence on the values
of the critical magnetic Reynolds numbers (Rm).
Several numerical codes have been developed and used for the determination
of these critical Rm for arbitrary velocity profiles.
Helicity maximizing
profiles are shown to provide smaller critical Rm than the
solid body rotation flow. We outline how the velocity profiles
have been optimized in an iterative process including flow measurements,
constructive improvements and numerical calculations.