Different choices of outflow boundary conditions are discussed in this paper and a proper choice is used in a hybrid numerical simulation which produces data to investigate the effect of outflow boundary conditions The convective outflow boundary condition with the wave speed as predicted from linear stability theory is used. The non reflectiveness of this type is investigated and the reection or the lack of reection in a large decit plane wake ow simulation is studied The results of simulation reported in this paper indicate that the wave speed predicted from linear stability analysis is appropriate for the convective velocity at the outow boundary of the large decit plane wake ow On the other hand the use of the freestream velocity for the convective speed at the outow boundary of a large decit plane wake ow also generates a serious feedback problem

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