Abstract
In high-Reynolds number viscous aircraft flows, very fine and stretched grids are generally required to resolve accurately thin boundary layers developed along the body surface. An application of tetrahedral single unstructured grids has several difficulties in computational efficiency and solution accuracy and so a hybrid unstructured grid technique is incorporated into a CFD-based design system, CASPER. To validate the present code, we carried out hybrid unstructured Navier-Stokes computations of transonic and high Reynolds number flows around a typical transport aircraft, ONERA Model M5 configuration. With respect to wing surface pressure distributions, forces and moment coefficients and boundary layer transition lines, the present computed results are quantitatively compared with the other computed results and wind-tunnel testing data. Especially, the drag prediction is remarkably improved by the following three strategies: i) high resolution of chord surface grids around each leading edge, ii) extension of Shima’s Normalized Unstructured Mesh method, and iii) modification of transition parameters in Spalart-Allmaras one-equation turbulence model.
