The Numerical Simulation Of Frigate Surface Flow Field With DES Method

When the shipboard aircraft landing and taking off from the ship,it will be strongly affected by the air wake of the superstructure,and these vortices may cause severe accident.The traditional RANS method is inadequate to capture the small vortices,however,the DES method can effectively capture the key vortex structures with much less computational cost than the LES method.DES method is a three-dimensional unsteady numerical solution method with a single turbulence model,which combines the advantages of LES and RANS.It adopts the LES method in the separation area and use the RANS method as a supplement in other areas.In this study,a DES flow solver based on unstructured grids has been developed,which involves finite volume discretization with inviscid and viscous flux discretization,and the dual time-stepping with both explicit Runge-Kutta and implicit LU-SGS subiteration schemes,in which the inviscid flux is discretized by Roe flux difference splitting scheme.S-A model is adopted as a single turbulence model with wall distance modification for turbulent calculations.Solver parallelization has also been achieved to reduce the simulation time and to improve the efficiency,which involves many efforts of seeking well-balanced mesh partitioning and data communication strategies.Then a standard backward step flow case is used to perform the validation of the solver.By comparing the numerical simulation results with the experimental data,the correctness,feasibility and robustness of the flow solver are confirmed.Finally,the DES flow solver is applied to the numerical simulation of large separated flow of a frigate model,and compared with the results simulated by the mature RANS.The general physical phenomena,special flow structure and flow characteristics of ship surface are analyzed and discussed,which provides reliable and credible data for the later flight test on the flight deck.