Flow Simulations by Enhanced Implicit-Hole-Cutting Method on Overset Grids

Abstract

Based on a hierarchical overset-grid strategy, enhanced implicit-hole-cutting method has been applied to the study of viscous flows around 30P30N multi-element airfoil and the wing–body configuration of the NASA common research model. Numerical simulations were performed on overlapping grids by an in-house computational fluid dynamics solver called Exstream. The present paper conducted the grid-convergence and buffet study of the NASA common research model, which was used in the Fifth AIAA Computational Fluid Dynamics Drag Prediction Workshop. The result of the 30P30N multi-element airfoil proves that the enhanced implicit-hole-cutting method and Exstream solver could obtain great robustness and accurateness. From the result of the grid-convergence study, the value of total drag follows a nearly linear trend and seems to converge to a given value under different grid refinements. Moreover, grid density has a nonnegligible impact on the skin-friction drag component. The consequence of buffet study reveals that there is a very interesting variation of lift coefficient that it decreases from 0.599 to 0.587 when the angle of attack increases from 3.00 to 3.25 deg. The streamlines and surface-pressure contours show that a flow separation bubble appears near the trailing edge of the wing–fuselage junction. Extrafine overlapping grid, matched structured grid, and different turbulence models have been tested for the flow separation bubble.