TILT TANK : DEMONSTRATE KELVIN HELMHOLTZ INSTABILITY AND WAVE BREAKING IN A STRATIFIED SHEAR FLOW.
This is a one or two shot experiment, best performed out of the class (i.e. in the preparation lab). It uses a long 8 foot plexiglass tank. Fill the tank have way with water. Then fill it from the bottom the rest of the way with a 2% salt solution dyed dark blue with food coloring. Filling can be accomplished by using a Carboy and adjusting the outlet valve. This creates a two layer system with a slight diffused interface.
After the interface is established tilt the tank up on a support. A good slope is 1.5/8. The salt water runs down and the fresh water runs up. The stratified shear flow is unstable. You can see dramatic instability, nonlinear spatial doubling of period, convective overturning and turbulence bursting.
Setup after tilting showing typical angle. Use a video camera to record the event on a VCR.
This shows a close up of the filling tube. Attach with hose to a large container with a valve. The tank holds about 4 liters of water/saltwater in each layer.
QT MOVIE OF THE BIG EVENT: FORMATION AND BREAKING OF KELVIN HELMHOLTZ INSTABILITY (2% SALTY LOWER LAYER, TILT SLOPE ~ 1.5/8)