超声速进气道可压及不可压流动数值模拟

采用Chio-Merkle预处理矩阵对可压NS(Navier-Stokes)方程组进行时间预处理,分析了预处理方法的物理和数学背景.用有限体积方法,结合LU-SGS(Lower-Upper-Symmetric-Gauss-Seidel)隐式时间积分和AUSM+(P)(Precondition Advection Upstream Splitting Method)格式、中心差分2种空间离散格式,求解该预处理NS方程组.通过圆弧凸包流动和二维方腔顶盖驱动流动的数值试验表明,该方法克服了传统时间迭代方法模拟低速流动时的刚性问题,加速了收敛过程,可以同时有效地模拟可压及不可压流动.用此方法与块结构化网格技术相结合,进行了在不同飞行马赫数、攻角和出口反压条件下,混压式轴对称超声速进气道三维流场数值模拟.计算结果表明:该方法能准确地捕获复杂激波系,清楚地揭示进气道三维流动现象;进气道性能随工作条件的变化规律,与理论分析一致.

Numerical simulation of compressible and incompressible flows in mix-compression axisymmetric supersonic inlet

A structure grid,multi-block computer code was developed for both compressible and incompressible flow simulations by solving the preconditioned NS(Navier-Stokes) equations with LU-SGS(lower-upper symmetric-Gauss-Seidel) implicit time integration method.The finite volume method was used to discrete the equations on the cell volume with AUSM (P)(precondition advection upstream splitting method) or central difference scheme.The Chio-Merkle precondition matrix was adopted.Physical and mathematical mechanism of precondition method was analyzed.Computational capabilities were demonstrated through a variety of computations of typical problems in CFD(computational fluid dynamics) area,including inviscid flows in a channel with a bump and driven flows in a two-dimensional square cavity.Results show that stiffness of conventional time iterative method to low speed flows is overcome,and convergence rate is speeded up.Three-dimensional calculations were made of mix-compressed supersonic inlet flows under different flight Mach numbers,attack angles and back pressures.Results indicate that the precondition method can capture shocks accurately,and inlet performance variations characteristics agree well with the theory results.