The Study On Moving Patterns Of Density Flow Under Waves In Estuary

Density flow is the phenomenon of a mixing motion between two or more fluids that a fluid moves along the interface surface due to the difference of fluid densities.And density flow is a common phenomenon in nature.It has been widely studied and used in meteorology,geology and petroleum science.Density flow is also a key issue in sediment research.Studying the transport mechanism of density flow under wave actions is great importance to understand the movement law of density current.In addition,it is of significant engineering applications for preventing and curbing siltation in estuary area,maintaining the safety of coastal engineering,as well as site selection of port engineering,dredging of waterways and the control of pollutants.In order to study the effect of wave disturbance on density current,the method of combining theoretical analysis with numerical calculation is used in this paper,and the motion patterns of density current in estuary is studied.Based on Eulerian coordinate system,a double-layer fluid model is established.It's assumed that the two layers of fluids are incompressible and non-mixing,as well as the micro-amplitude waves are generated on the free surface and the interface surface under wave disturbance.The upper layer is modeled by a Newton's model,and the lower layer is descried by a power-law model.The motion equation of fluids is simplified,and the velocity and pressure fields of the two-layer fluid as well as the wave parameters of the interface surface wave are solved by the finite difference method.Compared with the previous experiments,the results show good coincide with the test dates.Based on the numerical results,the effects of mud density,wave frequency and power-law flow index of lower layer on flow fields and interfacial wave are analyzed.In addition,the sediment concentration of density flow is calculated and the formation conditions of density flow are studied preliminarily.