Experimental study on flow field induced by internal solitary wave and load characteristics on pile sections at different depth

Abstract

Internal solitary waves were generated in a density stratified two-layer fluid. A cylindrical pile composed of five sections was arranged throughout the water depth. The flow field induced by internal solitary wave was measured by applying PIV technique. The forces on three of the sections, which were in different layers or at different depth in the same layer, were obtained. Based on the experimental data of flow field and forces, the hydrodynamic coefficients of CD and CM were calculated for each cylinder section. The variation trend of the coefficients with Re and newly defined KC were obtained. The flow field information, load characteristics and hydrodynamic coefficients are greatly different between the upper and lower layers, and almost the same at different depth in the same layer. It is suggested to select different empirical coefficients when calculating internal solitary wave force on the structure parts in different layers. Besides, the variation trend of hydrodynamic coefficient under the condition of internal solitary wave has some similarities to that under the condition of combined wave-current flow.