An automated multi-grid Chimera method based on the implicit hole technique

An automated multi-grid overset grid algorithm is presented for accurate simulation of viscous flows around complex configurations. The algorithm is based on the implicit hole cutting technique optimized with an overset grid construction strategy, a grid cutting criterion and a multi-level overset grid cutting method. The enhanced method is more general than the original method, while preserving the high degree of automation of the implicit hole cutting algorithm. Moreover, a mesh sequencing and multi-grid Chimera strategy is proposed to achieve convergence acceleration of the flow calculations. The present Chimera algorithm is demonstrated through the solution of the flows over the NASA Common Research Model configurations. The results show that the present mesh sequencing and multi-grid strategy in the overset grid framework are very effective in increasing convergence of solution in comparison with the standard three-level multi-grid. Wing pressure comparisons indicate the pressure distribution varies with grid solution at the shock, and a higher grid resolution improves shock definition. Abrupt reductions in lift and drag coefficients are correlated with the side-of-body separation bubble as angle of attack is increased. And various modeling and grid resolution have a strong impact on predicting the side-of-body separation. The side-of-body separation decreases with grid refinement. And the bubble size from spalart-allmaras (SA) modeling is larger than that from shear stress transport model.