Surface wave observations in 60% Umf fluidised granular current

High speed video frames taken at 500 fps, looking down at the upper surface of a granular flow being supplied with 60% of the minimum fluidisation velocity (Umf). Shows development and evolution of surface waves as the current propagates and comes to a halt. Flume base is 15 cm wide. Current is comprised of 45-90 micron soda lime ballotini.