Prediction Of Lock-exchange Turbidity Currents Use The Upwind Combined Compact Difference Scheme

Three-dimensional direct numerical simulation(DNS)with improved mul-ti-phase model for bi-dispersed turbidity over a flat terrain was presented and dis-cussed in this study.First,the advection term in sediment transport equation is solved by our improved algorithm-upwind dispersion relation preserving combined compact difference(UDRPCCD)scheme to preserve the dispersion well.Furthermore,the lev-e1 set method including concept of distance function is introduced to smooth the con-centration interface within multiphase flow and to solve the multi-phase model stably.In our work,mathematical analyses are conducted to testify the performance of this model,including the precision,dispersion and dissipation error,anisotropy and stabil-ity.Besides,visible characteristics of turbidity(e.g.the location of the front,the con-centration profile and the 3D details of the flow)and the inherent evolutions of the flow(e.g.the energy budget and the velocity distribution)are discussed.The front velocity of the turbidity experiences three stages,which are short ac-celeration,constant and deceleration periods as validated by previous experiments.The energy budget presents good agreement with Nasr-Azadani's DNS model,in-cluding transition of the kinetic energy,potential,dissipation in the flow and energy loss caused by sediment's settling.In addition,typical features such as higher current front location than the critical point are observed clearly in the numerical results,which also justify the rationality and feasibility of this model.At last,two kinds of ideal seafloor landforms-Gauss bump are considered in the model.The numerical results agree well with Nasr-Azadani's previous simulation and further validate the model's capability and applicability to simulate the turbidity currents in natural envi-ronments.