Study On Hydrodynamic Characteristics Of Solitary Wave Transformation And Evaluation Over Reef Profiles

Tsunami is usually generated by earthquakes,volcanic eruptions,landslide and other earth activities.It contains huge energy and is a natural disaster with great destructive power.Solitary wave has always employed in laboratory research and numerical simulation,which can represent many important properties of the leading wave of tsunami.Reef topography is a typical nearshore topography.It is of great significance to study the propagation characteristics of solitary waves on this topography to prevent tsunami disasters.In this paper,by combining experiments with numerical simulation,the propagation of solitary waves on the reefs and the hydrodynamic characteristics of run-up are studied,and the pressure distribution characteristics of the straight wall behind the reef flat are analyzed,so as to provide technical support for disaster prevention and mitigation projects in tsunami waves.Firstly,laboratory experiment of solitary wave propagation on the reef topography is carried out in a wave flume.The generation of solitary wave takes the third-order solution as the target profile,and adopts the improved goring method which considers the effects of the unsteady wave profile near the wave generating zone.The generated solitary wave profile is in good agreement with the analytical solution.The results show that with the decrease of the wave height of the solitary wave,the location of the wave breaking gradually moves backward,the run-up and the maximum pressure gradually decreases.The maximum pressure appears near the still water level.When the wave height is very small,the solitary wave does not break on the reef flat and totally reflects on the straight wall.In addition,the reef crest plays a significant role in protecting the reef flat.Then,the OpenFOAM numerical model is utilized in this study.After comparing with the experimental data in detail,it can be find that OpenFOAM numerical model can accurately simulate the propagation of solitary waves on the reef,and especially can accurately simulate the run-up before the straight wall and the pressure on it.The hydrodynamic characteristics in the propagation process are also analyzed in detail according to the numerical simulation results.Finally,the effects of solitary wave height and the topographic characteristic parameters of the reefs on the hydrodynamic characteristics on reefs are studied through numerical simulation.The results show that: with the increase of solitary wave height and reef flat water depth and the decrease of reef flat length,the run-up and pressure before the straight wall will incease gradually.The existence of reef crest will affect the propagation of solitary wave on the reef flat and cause the decrease of the run-up and pressure of the straight wall.