A Pressure-Based Unstructured Grid for Compressible Flow Calculation
|Keywords:||壓力修正法;可壓縮流;非結構性網格;Pressure Correction Method;Compressible Flow;Unstructured Grid|
In this thesis an extended pressured-correction method using SIMPLE algorithm is developed for the computations of two-dimensional steady compressible flow. The correction of pressure in pressure-correction equation is correlated to the density and velocity in terms of a “Mach control factor” so that it can automatically adopt elliptic or hyperbolic characteristics according to either subsonic or supersonic flow condition. An unstructured finite volume method with collocated variables arrangement is employed in space discretization where the diffusion fluxes are discretized using central difference scheme (CDS), and the convection terms are discretized using a blended central difference and upwind difference scheme (UDS). The blended scheme is so incorporated to increase the accuracy of the captured shock position and strength while eliminating the oscillations near shock wave. The method is verified by a series of test problems including invicid flows in a one-dimensional and a two-dimensional converging-diverging nozzle, viscous and invicid flows past a circular arc bump in a channel. Both quadrilateral and triangular cells are used in the computations to illustrate the unstructured capability and grid flexibility of the unstructured flow solver. Some effects of the “density-blending factor” to the numerical solutions are discussed and conclusions are drawn from the verification process. The accuracy and stability properties of the current method demonstrate its capability and potential in the computation of compressible flow past arbitrary body shapes at all flow speeds.
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