| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2005: ¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 2004: ¥700,000 (Direct Cost: ¥700,000)
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| Research Abstract |
In this research, the compressible Navier-Stokes equations are developed into the incompressible environmental flow simulations. First, it is shown that the compressible solutions with low Mach number are in very good agreement with the incompressible solutions in the test problem. And the present approach is applied to two and three dimensional homogeneous isotropic turbulence. In order to ensure the higher order spatial and time accuracy, the spatial derivatives are discretized by the modified differential quadrature (MDQ) method and the resulting system of ordinary differential equations in time is integrated by the 4th order Runge-Kutta scheme. In these cases, the unphysical oscillations appear in the flow field. Then, the shifted flux technique is adopted, so that the very smooth flow field without unphysical oscillations can be obtained. In comparison with the incompressible solutions based on higher order finite difference and spectral method, the present results show the excell
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ent flow field and statistical quantities, i.e., total energy, energy dissipation, enstrophy dissipation and energy spectra.
Next, the incompressible flows over a hill are considered as the fundamental environmental simulation with density stratification. In the laminar flow region, the present solutions with weak density stratification are in very good agreement with the corresponding incompressible solution. However, in the strong density stratification, the present approach gives the solutions with only qualitative agreement. Then, we introduce the Mach uniform pressure correction method and the validations are performed in the two dimensional channel flow with circular bump. In comparison with the usual compressible solutions based on the density, the very good agreement can be obtained in the range from supersonic flow to subsonic flow. In the quasi-incompressible regime, Ma<0.01, the usual compressible solutions are different from the present solutions. However, the present solutions are almost the same as the incompressible solutions. Therefore, it is concluded that the present Mach uniform pressure correction approach is very promising for numerical simulation of incompressible flows. Less
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