一种基于预估-修正策略的非定常流网格自适应加密/稀疏方法

给出一种非定常流动数值模拟的网格自适应处理方法.在"求解流动方程-自适应调整网格"的流程中,引入预估-修正步.根据自适应周期内每个时间步上的流场预估解,计算单元上的事后误差估算值.建立考虑解演变的网格自适应指示器,并进行多层次单元加密-稀疏的动态网格自适应处理.在自适应网格上重新计算流场.每个自适应周期中,流动演变区域的网格获得加密;而前一个周期中的特征现象已离开区域的网格被稀疏.应用边界非协调的当地DFD(Domain-Free Discretization)方法求解流动方程.为验证网格自适应处理方法,针对静止圆柱和自推进游鱼的流动进行了数值实验.

An Approach of Adaptive Mesh Refinement/Unrefinement Based on Prediction-Correction for Unsteady Flows

An approach for performing mesh adaptation in numerical simulation of two-dimensional unsteady flow is presented. A predictor-corrector step is introduced in the process of "solving flow equations-adjusting mesh". At first, flowfield during an adaptation period is precomputed to produce a posteriori error estimate. Then, an indicator for mesh adaptation in which solution progression is taken into account is constructed. Adaptive mesh is generated through multi-level reflnement/unrefinement. Finally, unsteady flow field is recomputed on the new adaptive mesh. In each adaptation period, mesh is refined in regions where solution evolves and is unrefined in regions where phenomena deviate since the last adaptation. A non-boundary-conforming method named local domain-free discretization is employed to solve flow equations. To validate the method, we simulated unsteady flows over a circular cylinder and a self-propelled swimming fish.