| Budget Amount *help |
¥2,800,000 (Direct Cost : ¥2,800,000)
Fiscal Year 2003 : ¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 2002 : ¥700,000 (Direct Cost : ¥700,000)
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| Research Abstract |
In this research project, the computational codes were developed in order to simulate atmospheric flow problems with density stratification. The governing equations are the incompressible and compressible Navier-Stokes equations. The method of lines (MOL) approach is adopted in both equations. The MOL approach is constructed by the spatial discretization and time integration. In the spatial discretization, the variable order proper convective scheme and the modified differential quadrature method are used for the convection and diffusion terms, respectively. Both discretization techniques give the arbitrary order of spatial accuracy by changing only 1 parameter. And the resulting system of ordinary differential equations in time is integrated by the Runge-Kutta type scheme. In this project, the order of spatial accuracy is fixed by the second order. Also, the virtual boundary method is incorporated into the method. Usually, the flows with complicated. geometry are computed on the bound
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ary fitted coordinate (BFC) system. However, the BFC system has the lack of efficiency. Instead of the BFC, in the virtual boundary method, the computation is carried out on the Cartesian grid. Moreover, the local mesh refinement technique is used for obtaining the high resolution.
The present method is applied to flows around a circular cylinder and the results are in very good agreement with other computational results. The computational time is 2/3 times the uniform Cartesian grid. Then, the flows around a sphere are simulated up to Reynolds number Re=1000. In Re=1000, the transition from laminar to turbulent flow can be reappeared. The flow around multi-spheres is simulated and the results show that the released vortices are interacted each other. Also, the flows over an isolated mountain is simulated in order to investigate the effect of density stratification. The results show clearly that the vortex structure behind of the mountain is different by the density stratification.
These results are opened by the international conferences. Then, it is concluded that the present method is very promising for the environmental simulations. Less
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