Stabilization of tangential shear instability in shallow water with "supersonic" fluid flow

The experimental verification of the criterion of supersonic stabilization of a tangential shear instability in shallow water is addressed using the same setup employed as is used to study the Kelvin-Helmholtz instability of countermoving flows. The results showed that if the velocity of the countermoving flows exceeds some threshold, then an instability arises in the system leading to formation of vortices whose dimensions along the surface of the water always greatly exceed the depth of fluid and the width of the discontinuity. A typical flow instability is shown along with the dependence of the size of the vortices on the velocity of the countermoving flows. For countermoving flow velocities exceeding the threshold, the flows are laminar and the trajectories of test particles on the surface of the fluid look like concentric circles with centers on the axis of symmetry of the system.