Abstract
In this paper, we experimentally investigate hydromechanical behavior of water surface ripples by using the simultaneous image measurements of an open-channel turbulent flow and the free surface. We also try evaluating the performance of the water surface ripples as a visualization tracer quantitatively for the local remote sensing technology for river flows. It is found out that the behavior of the water surface ripples can be explained very much well by using the theory of wave-current interactions in which the propagation velocity of water surface ripples is treated as the group velocity of waves propagating upstream in the open channel flow. An equation that estimates the mean bulk velocity through using the representative wave number is derived by taking the wave energy conservation into account, and its validity is confirmed by the experimental data. It can be expected from the obtained results that the performance of the water surface ripples as a passive visualization tracer in a river flow is limited since the water surface ripple has its own propagation velocity, and a correction based on the wave theory as treated in this paper should be needed for accurate river velocity measurements.
