Velocity measurements in dry granular avalanches using particle image velocimetry technique and comparison with theoretical predictions

Velocity and depth are crucial field variables to describe the dynamics of avalanches of sand or soil or snow and to draw conclusions about their flow behavior. In this paper we present new results about velocity measurements in granular laboratory avalanches and their comparison with theoretical predictions. Particle image velocimetry measurement technique is introduced and used to measure the dynamics of the velocity distribution of free surface and unsteady flows of avalanches of non-transparent quartz particles down a curved chute merging into a horizontal plane from initiation to the runout zone. Velocity distributions at the free surface are determined and in one case also at the bottom from below. Also measured is the settlement of the avalanche in the deposit. For the theoretical prediction we consider the model equations proposed by Pudasaini and Hutter [J. Fluid Mech. 495, 193 (2003)]. A nonoscillatory central differencing total variation diminishing scheme is implemented to integrate these model equations. It is demonstrated that the theory, numerics, and experimental observations are in excellent agreement. These results can be applied to estimate impact pressures exerted by avalanches on defence structures and infrastructures along the channel and in runout zones.