Structure of space-time correlations of bursting phenomenon in an open-channel flow

The structure of space-time correlations of bursting motions, such as ejections and sweeps in an open-channel flow, is investigated by a conditional sampling method in which simultaneous measurements of the instantaneous Reynolds stress have been performed by two dual-hot-film probes. It is found that the spatial scale of the ejection motion extends more widely downstream than upstream, and vice versa for the sweep motion. In addition, the bursting motion is a kind of large-scale eddy structure, and its coherent structure is fairly inclined downstream toward the wall. Further, it is convected downstream with a longer life-time than the bursting passing-period, namely in the frozen-turbulence-like manner. Finally, a qualitative model is proposed which attempts to explain the space-time structures of the bursting phenomenon on the basis of the anemometry information and other visual information.