矩形/非结构混合网格技术及在二维/三维复杂无粘流场数值模拟中的应用

建立了一套模拟复杂无粘流场的矩形／非结构混合网格技术，其中非结构网格仅限于物面附近，发挥非结构网格的几何灵活性，以少量的网格模拟复杂外形；同时在以外的区域采用矩形结构网格，发挥矩形网格计算简单快速的优势，有效地克服全非结构网格计算方法需要较大内存量和较长ＣＰＵ时间的不足。混合网格系统由修正的四分树（２Ｄ）／八分树（３Ｄ）方法生成。本文将ＮＮＤ有限差分与ＮＮＤ有限体积格式有机地融合于混合网格计算，消除了全矩形网格模拟曲面边界的台阶效应，同时保证了网格间的通量守恒。该算法被成功地运用于ＮＡＣＡ００１２翼型的跨、低超声速绕流，二维弯管内运动激波的非定常流，以及三维捆绑火箭的超声速绕流的数值模拟。计算结果表明本方法在模拟复杂无粘流场方面的灵活性和高效性。

A Cartesian/Unstructured Hybrid Grid Solver and Its Applications to 2D/3D Complex Inviscid Flow Fields

A Cartesian/unstructured hybrid grid solver is presented for numerical simulations of inviscid flows around complex geometries.The unstructured grids are applied only near complex configurations to simulate the realistic geometries,while the Cartesian grids are utilized to discretize almost entire area of outer flow fields.The present algorithm overcomes the disadvantages of requiring more memory storage and CPU time for the fully unstructured grid solvers,and solves the difficulty of describing curve boundaries for fully Cartesian grid methods.A simplified Quadtree(2D)/Octree(3D) method is introduced to generate 2D and 3D hybrid mesh.The node smoothing technique is applied to optimize the unstructured grid part.Based on the non oscillatory,non free parameter disspative finite difference (NND FD) scheme,a NND finite volume (NND FV) scheme is developed on unstructured grids and is coupled with NND FD scheme as a hybrid one to solve Euler equations.The numerical experiments demonstrate that the present scheme is quite accurate,efficient and robust.