三维复杂流动的间断有限元方法模拟

本文基于三维可压缩Euler方程,采用基于Runge-Kutta时间离散的间断有限元方法(RKDG方法),对三维前台阶、三维Riemann问题和球Riemann等问题进行了模拟。结果表明,本文的RKDG方法能够在很少的网格内清晰地捕捉到三维复杂流场中的激波和接触间断;同时,将球Riemann问题中z=0.4平面压强沿到对称轴距离的分布与文献中的近似精确解相比,吻合较好,这也验证了本文的RKDG方法不仅能够进行三维复杂流场的定性描述,也能够应用于三维复杂流场的定量计算。     

航行体通气空泡发射方式对出水过程的影响

潜射航行体自然空化情况下, 穿越水/气界面时会受到空泡溃灭的冲击载荷, 对空泡进行主动通气是一种有效的降载方法, 文章针对通气空泡的物理过程建立了一套完整的数值算法, 采用标准k-ε两方程湍流模型, VOF多相流模型, Zwart-Gerber-Belamri空化模型, 结合UDF自定义函数与动网格动态层技术, 开展了通气空泡整个出水过程的数值模拟工作, 研究了通气量通气时序通气方式等方面对空泡形态出水载荷等方面的影响, 获得了对工程设计有参考价值的基本结论.      

Shocklets in compressible flows

The mechanism of shocklets is studied theoretically and numerically for the stationary fluid, uniform compressible flow, and boundary layer flow. The conditions that trigger shock waves for sound wave, weak discontinuity, and Tollmien-Schlichting （T-S） wave in compressible flows are investigated. The relations between the three types of waves and shocklets are further analyzed and discussed. Different stages of the shocklet formation process are simulated. The results show that the three waves in compressible flows will transfer to shocklets only when the initial disturbance amplitudes are greater than the certain threshold values. In compressible boundary layers, the shocklets evolved from T-S wave exist only in a finite region near the surface instead of the whole wavefront.