Study On Theory And Application Of Mathematical Model For Flow Around Structures

The existence of offshore pier-type wharf,pile-group foundation and large-scale vessels may bring complexity to the currents in the vicinity of the structures,causing velocity enhancement around the structures,and may thus impose adverse impact to the mooring condition of the berth.In application of numerical flow model to calculate current field,direct simulation of each pile of the pier-group is too time-consuming and may even be infeasible for the time being.Hence,reasonable simplification of the pile-group is of important significance in obtaining higher computational precision with smaller computing resources.The main achievements of the research are as follows.(1)A pile-group resistance effect simplification method is proposed by introducing an equivalent resistance term into the governing equation for the drag force for the group-pile,and by introducing the equivalent water depth to represent the sheltered area of the group pile,through which the 2D flow module of COASTALTOOL is improved.The flow model is not only of high accuracy,but also has good adaptability due to that the governing equations are solved by FVM,with numerical flux of the element interface being calculated by Osher scheme,the turbulence terms are calculated by the LES model,and calculation domain is discretized by triangular-quadrilateral unstructured hybrid grid.(2)Drag force coefficients of piles with circle and square transection are simulated respectively by using the laminar model and RNG k-? model.Variation of the drag force coefficients is investigated in terms of Reynolds number,different shape of pile transection,number of piles,array layout of pile-group,center distance as well as incident angle.(3)The RMA2 flow module of SMS and the 2D flow model of COASTALTOOL are chosen to calculate the typical example of flow field around a pile and the results show that the latter is superior to the former,the reason may be due to that the numerical scheme of the later has higher numerical accuracy.(4)Flow field of pile-group is studied by using the 2D flow module of COASTALTOOL.Velocity field and water surface elevation are investigated in terms of the effects by shape of pile transection,number of pile-group array,array layout of pile-group,center distance and incident angle;The model is validated by comparing the results of the fine mesh calculation and the simplified method;The resistance effect of various array layout form and shape pile transection.(5)The 2D flow module of COASTALTOOL is applied to the simulation of the flow field of a pile-support pier of Tangshan Port.The reason for the mooring line failure due to drive away events after its coming into service is analyzed.Study on the flow characteristics of several solutions of open type resistance pile-dyke is performed,which provides technique support for the solution optimization.(6)The instantaneous and mean flow field of logarithmic-law region in a turbulent boundary layer is measured by Tomo-TRPIV.The analysis method of the coherent flow structure and measurement method are investigated for further study of the 3D flow field around pile-group.