可压缩轴对称冲击射流流场的数值模拟

数值模拟一种可压缩轴对称冲击射流。所构造的数值模拟方法是:直接求解柱坐标系下的二维可压缩Navier-Stokes方程的差分离散方程,其中对流项采用基于非等距网格上的五阶精度迎风紧致型差分格式,黏性项采用基于非等距网格上的六阶精度对称紧致型差分格式,时间项采用3步三阶精度Runge-Kutta方法。模拟不同雷诺数、马赫数条件下冲击射流大尺度涡结构的演化过程。结果表明:流体从喷嘴射出后卷起形成一个独立的大尺度负涡,即初生漩涡,它会在壁面处逐渐激发出一个具有正涡量的壁面二次生成涡;初生漩涡和二次生成涡互相旋转挤压,壁面二次生成涡的力量很快占优势,带动初生漩涡向流场内部发展;随马赫数的增大,初生漩涡具有更强的力量,抑制了壁面二次生成涡和其他小尺度负涡的发展;随雷诺数的增大,初生漩涡的力量有所减弱,促进了壁面二次生成涡和其他小尺度负涡的发展。

Numerical simulation of compressible axisymmetric impinging jet

Numerical simulation for a compressible axisymmetric impinging jet was completed.The constructed numerical simulation method was to directly solve the discrete difference equations of the 2-D compressible Navier-Stokes equations under cylindrical coordinate system.The five-order accurate upwind compact difference scheme based on non-uniform meshes was used to discrete the convection terms.The six-order accurate symmetric compact difference scheme based on non-uniform meshes was used to discrete the viscous terms.The three steps and three-order accurate Runge-Kutta method was used to discrete the time terms.The large-size eddy structure evolution process was simulated with different Reynolds and Mach number.The results show that the fluid is ejected from the nozzle exit,and then rolls up to form a separate large scale negative vorticity which is called the primary vortex.It will arise gradually a wall second generation vortex with positive vorticity.Those two vortexes mutually rotate and extrude.The wall second generation vortex gains quickly,and leads the primary vortex to the inner flow field development.With the Mach number increasing,the primary vortex has a stronger power,which inhibits the development of the wall second generation vortex and other small scale negative vortexes.With the Reynolds number increasing,the primary vortex power is weakened,which promotes the development of the wall second generation vortex and other small scale negative vortexes.