tailieunhanh - High Performance Computing on Vector Systems-P9

High Performance Computing on Vector Systems-P9: In March 2005 about 40 scientists from Europe, Japan and the US came together the second time to discuss ways to achieve sustained performance on supercomputers in the range of Teraflops. The workshop held at the High Performance Computing Center Stuttgart (HLRS) was the second of this kind. The first one had been held in May 2004. | Direct Numerical Simulation of Shear Flow Phenomena 241 u P Fig. 14. Initial condition of the primitive variables u v p and T at the inflow x0 30 The initial condition of the mixing layer is provided by solving the steady compressible two-dimensional boundary-layer equations. The initial coordinate x0 30 is chosen in a way that the vorticity thickness at the inflow is 1. By that length scales are made dimensionless with J. The spatial development of the vorticity thickness of the boundary layer solution is shown in Fig. 13. Velocities are normalized by UTO U1 and all other quantities by their values in the upper stream. Figure 14 shows the initial values at x0 30. A cartesian grid of 2300 x 850 points in x- and y-direction is used. In streamwise direction the grid is uniform with spacing Ax up to the sponge region where the grid is highly stretched. In normal direction the grid is continuously stretched with the smallest stepsize Ay inside the mixing layer y 0 and the largest spacing Ay at the upper and lower boundaries. In both directions smooth analytical functions are used to map the physical grid on the computational equidistant grid. The grid and its decomposition into 8 domains is illustrated in Fig. 15. Boundary Conditions Non-reflective boundary conditions as described by Giles 7 are implemented at the inflow and the freestream boundaries. To excite defined disturbances the flow is forced at the inflow using eigenfunctions from linear stability theory see Sect. in accordance with the characteristic boundary condition. Onedimensional characteristic boundary conditions posses low reflection coefficients for low-amplitude waves as long as they impinge normal to the boundary. To minimize reflections caused by oblique acoustic waves a damping zone is applied at the upper and lower boundary. It draws the flow variables Q to a steady state solution Qo by modifying the time derivative obtained from the Navier-Stokes Eqs. 3 dQ dQ - y Q - Qo .