PIV analysis on turbulent flows in current-wave interactions

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732Particle image velocimetry (PIV) was used to measure velocity vectors in a wave-current coexistence flow field in a laboratory experiment in order to investigate effects of turbulence and waves on flow structures in, for example, tsunamis at estuaries and river mouths of coastal areas. In the PIV procedure, we introduced a simultaneous image measurement method to quantify instantaneous velocity vectors and the corresponding wave profile in a vertical cross section of the flow field. We firstly examined the instantaneous velocity fields. The velocity distributions indicated that the instantaneous velocity structures were considerably modified by adding the wave component as well as the velocity shear had maximal and minimal values at the wave trough and crest near free surface region, respectively. The mean velocity profile, on the other hand, was approximately the same as the velocity profile of the simple open-channel turbulent flow without waves. As for the phase-averaged wave component, effects of the turbulent flows appeared at both the near bed and free surface regions where the wave component tended to increase. Moreover, the profiles of the turbulent intensities indicated that their values became considerably larger near the free surface region as the wave component increased