The structure of the head of an inertial gravity current determined by particle-tracking velocimetry

Abstract

Digital particle-tracking velocimetry is used to obtain the two-dimensional structure of the head of inertial gravity currents propagating along a no-slip boundary. The early stage of development of lock-release gravity current experiments is recorded in the laboratory frame of reference and subsequently transformed by software to a frame moving with the current head. Time averages of these statistically stationary flows are computed, with the technique providing not only the mean two-dimensional velocity field but also the vorticity, shear stress and divergence fields, and streamlines of the flows. The distributions of the magnitude of the fluid velocity fluctuation and Reynolds stress complete the picture of the flow. Key features of the flow are broadly in line with earlier qualitative and quantitative investigations, and the detailed measurements presented here confirm some of the most recent findings from numerical simulations.