Reduction of internal-solitary-wave-induced forces on a circular cylinder with a splitter plate

Internal solitary wave (ISW) of depression type widely exists in stratified water, with upper layer having a lower density caused by salinity or temperature. The ISW-induced force on the pile is different from that induced by pure current due to the feature of different flow directions between these two layers. The question remains whether the method commonly used for reduction of forces acting on a pile under pure current can still be applied in case of ISW propagation. In this study, a splitter plate deployed upstream of the pile with its frontal face normal to the wave propagation is used to explore the reduction of forces on an erected cylindrical pile. The ISWs-induced forces acting on a pile with different splitter plates are simulated by means of the large eddy numerical simulation. Extra laboratory experiments on the propagation of the ISWs around an erected cylindrical pile without a splitter plate are carried out for verifying the numerical models. It is found that the splitter plate has prominent influences on the force distribution of the pile in the upper layer. However, it hardly has an effect on the counterpart in the lower layer during the propagation of the ISWs of depression type. In addition, the pattern of vortex structures existing behind the splitter plate does play an important role in reducing the forces on the frontal side of the pile. Numerical results also reveal that the length of the splitter plate and the distance between the splitter plate and the frontal side of the pile characterize the feature of vortex structures around the pile. It is important to restrain the parameters of splitter plates at an appropriate level. Otherwise, over-reduction would occur and the ISWs-induced forces acting on a pile with the splitter plate would be unexpectedly larger than forces on the single pile without a splitter plate.