The Kolomogorov Flow and the Shear-Band Instability
In 1959, Kolomogorov proposed to use a 2D flow driven by space periodic force in one direction as an useful tool to study turbulence. The first experiment was realized in 1979 in a shallow layer by Bondarenko, Gaz And Dolhansky [Izv. Akad.Nauk 273 1017 (1979)]. They used an Electro-magnetic forcing to generate the periodic flow in an Salt water solution. We use the same technique (described hereafter) in our experiment.
At small intensity (I~ 10 mA) the following shear-band parallel Shear-Band flow is generated (top view):
where the velocity field is computed from particle tracking techniques.
But when the current is increased to 60 mA, the flow becomes instable and forms an array of vorticies:
(see a movie of the time dependent flow over 1 excitation period T~100 s)
We plan to characterize precisely these instablities in our device. Then we will add a convective flow.