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Numerical simulations have been made on the three-dimensional laminar separations of the supersonic blunt cone at series of attack angles by solving the Navier-Stokes equations and using finite volume method. The purpose is to investigate the three-dimensional separation criteria through specific flow problem. In the first step, the detailed characteristics of the flow separation at different Mach numbers (1.8 and 10.6) are obtained. In order to make numerical analyses on the conditions of the three-dimensional separation, two vectors are constructed as ∂V/∂n - n(n ⋅ ∂V/∂n) and n ⋅ ∂²V/∂²n, which are used as the equivalent numerical expressions of the corresponding criteria of the separation and reattachment in reference [7] for investigations. Based on the outcomes and the numerical results obtained, numerical analyses are conducted on the separation criteria, and comparisons are made with the theoretical outcomes. The agreement has been obtained between the computation and theoretical analysis. [ABSTRACT FROM AUTHOR]

Through introducing a transformation for the density related velocity component wr=-1/ph1h2∫zoh1h2∂p/∂t dz on the direction normal to wall, the continuous equation of three dimensional unsteady compressible flow in physical space (ua, va, wa=u, v, w+wr) with no-slip wall condition can be trans- formed to an equation for the steady flow in the transformed velocity space (u,v,w) with no-slip wall. Then, using the same analysing method and corresponding result of the steady flow separation, the criteria for the compressible unsteady flow can be obtained after considering the contribution of wr. It is found that there is a case that flow separates on wall and reattaches off wall in both two dimensional and three dimensional flow. The analysing results have been proved by numerical simulation. [ABSTRACT FROM AUTHOR]

In order to make numerical simulations using Detached-Eddy Simulation (DES) hybrid method, a third-order hybrid scheme has been proposed on the basis of the traditional third-order upwind-biased scheme. The dissipation of the new hybrid scheme can be adjusted in moderate and higher band of the scaled wave number. Based on the aforementioned works, comparative numerical studies have been made on two RANS/LES hybrid methods, i. e., DES-SA based on the S-A turbulent model and DES-ML based on the mixing length model. The computations choose the low-speed flow around three-dimensional cylinder as an example, while using several difference schemes including the developed third-order scheme. Comparisons have been made between the obtained results and that from references, and discussions have been made about the new hybrid scheme and DES-ML method also. [ABSTRACT FROM AUTHOR]

Techniques are developed for the construction of difference schemes by analyzing their dissipation relations and using re-linearizing process; A center-typed third order nonlinear scheme is presented, which has the equivalent grid stencil as the NND scheme. Because the linear part of the scheme has well performance about the dissipative characteristics, and the linear form of it will be preferred as far as possible due to the re-linearizing technique, the improvement will be obtained theoretically on the resolution and maitainance ability about the vortices in computations; On the other hand, the scheme will change back into NND-like scheme by the nonlinear procedure when encountering non-smooth region, and the dissipation and stability mechanism will be brought into action. The validating computations show that, the scheme can be used in computations containing vortices and perturbations with viscosity, and the simple form of the algorithm makes it easily utilized in engineering purpose and extended to finite volume method. [ABSTRACT FROM AUTHOR]