The Estimation Of Scour Induced By Wave And Tide In The East China Sea Based On DRAMBUIE Model

The scour induced by wave and tide in the East China Sea is simulated usingDRAMBUIE model in this paper. The DRAMBUIE model was designed in atime-step fashion, and was used to calculate the extent of scour after8–daycombined impact of wave and tide. Because of nonlinear effects, the orbitalvelocity above the wave boundary layer, propagating direction of wave and theperiod of wave above the wave boundary layer were simulated by the SWANmodel. Tidal current is simulated by the ECOM model.Results show that the tide is the most important input that influences theprocess of scour, and the followers are the mean size of sediment, water depth andwave-induced orbital velocity above the boundary layer. Factors affecting the processof scour are examined in terms of three aspects: DRAMBUIE itself, data andtime-step fashion. The data especially orbital velocity above the wave boundarylayer and tidal current come from models completely, and thus they are affected bythe setting and input files. For example, the orbital velocity above the waveboundary layer is sensitive to the wind field. The time-step fashion plays animportant role in DRAMBUIE model, and the size of time-step determines theinputs of wave parameters and tidal current, besides the time-step fashion is themain source of model errors in this paper. The biggest problem using theDRAMBUIE model is how to represent the infilling process, however, there hasn’tany is no reliable explanation about how it would happen and change with time bynow.This paper also separately simulated scour processes induced by combinedeffects of tide and wave under extreme weather (take typhoon for example with aspeed of35m/s in the central wind field and a speed of25m/s in the peripherywind field) and normal strong wind condition (winter monsoon with a speed of10m/s). It is indicated that the wave-induced orbital velocity above the boundary layer caused by typhoon is much more obvious than that caused by normal wind field inmagnitude，so the scour in shallow water region(<30m) induced by typhoon isobviously stronger than by winter monsoon, the scour processes are different whenthe grain size is different even if the depth and wind field are the same.