Showing papers by "Kozo Fujii published in 1985"

Computation of Three-Dimensional Viscous Transonic Flows with the LU Factored Scheme

Abstract: The LU-ADI factored scheme has been successfully applied to solve the three-dimensional compressible “thin-layer” Navier-Stokes equations. The computations are carried out for the slightly supersonic flow over a hemisphere cylinder at high incidence and for the transonic flow over a swept wing. To simulate these complicated flow fields, fine grid distributions of up to about 200,000 points were used on a new Japanese supercomputer of 1 GFLOPS. The total cpu time for each case was less than two hours. The result for the flow over a hemisphere cylinder at high incidence revealed the existence of the shock wave and the detailed structure of the vortical flow field on the leeward side. The result for the flow over a swept wing shows that the three-dimensional shock-induced separation is well captured. These results indicate the capability of the present code to make three-dimensional complicated flow field simulations ; and the application of the present code to the more practical flow fields such as transonic flows over the wing or the wing-body combination of the transportation aircraft is very promising. Even simulation over the whole aircraft geometry may soon be possible.

Evaluation of euler and navier-stokes solutions for leading-edge and shock-induced separations.

Abstract: Simulations of vortical flow fields over conical delta wings are carried out, using Euler and ‘thin-layer’ Navier-Stokes equations to examine the reliability of the Euler separations.The computations over elliptic cones indicate that crossflow shock wave location is well predicted by the Navier-Stokes computations, but not well predicted by the Euler computations. The examinations of the time evolution of the leading-edge separation reveals that the origin of the separation in the Euler solution is the shock-induced separation. However, It is revealed that is not a physical shock-induced separation and the entropy production at the leading-edge due to numerical dissipation is an important factor through additional computations. The computations over circular-tip dalta wings reveal that the large leading-edge separation for the Euler solutions are actually induced by the shock wave near the leading-edge. The computed results, in general indicate that the numerical viscosity at the leading-edge induces the entropy gradient before the shock wave, and the separation occurs somewhere after the shock wave. That means both numerical dissipation and shock wave are responsible for Euler sepatations.