Wu, Y.-T. and Hsiao, S.-C., 2013. Turbulence induced by a solitary wave propagating over a submerged object using particle image velocimetry.
We present an experimental study for solitary wave propagation over a submerged rectangular obstacle using the particle image velocimetry (PIV) technique. The PIV system, mainly consisting of a digital high-resolution camera and a dual-head pulse laser, is used to measure instantaneous free surface motion and corresponding velocity properties around the submerged object. Four fields of view (FOVs) are set in order to form a continuous flow fields around the structure. Quantitative mean properties are obtained by ensemble averaging 30 repeated measurements for each FOV. Therefore, the entire data of the time histories of the free surface elevation recorded by wave gauge is 120 sets, and the standard deviation (STD) for incident wave height is 0.61 mm or 1.3% of mean incident wave height. The experiments show high degree of repeatability. After gaining the mean velocity properties, the vorticity field can be calculated by taking curl of mean velocity field and the turbulent kinetic energy can be estimated from velocity fluctuations. It is found that the measured turbulence in the weather side is much larger than that in the lee side of object. A local maximum value of turbulent intensity in the weather side of object is about 63.4% of depth-averaged velocity as the crest of solitary wave approaches but not yet reaches the front edge of breakwater. On the other hand, a local maximum value of turbulent intensity in the trailing edge is around 37.1% of depth-averaged velocity.