Experimental Rayleigh-Taylor instability in a circular tube

The Rayleigh-Taylor instability of an air-water system has been investigated experimentally. The instability was produced by accelerating a slug of water down a vertical circular tube of 6.25 in. inside diameter employing a pressure differential. Accelerations from 3 to 25 times gravitational acceleration with fluid depths from 5 to 20 centimeters were studied. The disturbances first observed were purely axisym-metric with wave numbers corresponding closely to the fastest growing values given by linear theory. Later stages of planform development were characterized by a series of transitions which cannot be predicted by linear theory. These transitions were correlated with disturbance height.