Velocity measurements in the field of an internal gravity wave by means of speckle photography

Speckle velocimetry with forward scattering has been applied to measure and visualize the two-dimensional velocity field in an internal gravity wave. The wave was produced by towing a cylinder in vertical direction, normal to its axis, through stratified salt water. Neutrally buoyant tracer particles whose density was matched with the density distribution of the stratification were uniformly distributed in the test fluid. The experimental results verify the results of a linear theory in the far field of the wave.Most part of this work was performed when the three authors were with Institut für Thermo- und Fluiddynamik, Ruhr-Universität Bochum.