Undercompressive shocks for nonstrictly hyperbolic conservation laws

We study 2×2 systems of hyperbolic conservation laws near an umbilic point. These systems have Undercompressive shock wave solutions, i.e., solutions whose viscous profiles are represented by saddle connections in an associated family of planar vector fields. Previous studies near umbilic points have assumed that the flux function is a quadratic polynomial, in which case saddle connections lie on invariant lines. We drop this assumption and study saddle connections using Golubitsky-Schaeffer equilibrium bifurcation theory and the Melnikov integral, which detects the breaking of heteroclinic orbits. The resulting information is used to construct solutions of Riemann problems.     

一个非线性方程转向点问题

本文讨论了一个非线性方程的转向点问题 .研究了转向点的所处位置 ,以及问题解的渐近性态 .     

Padé–Legendre approximants for uncertainty analysis with discontinuous response surfaces

A novel uncertainty propagation method for problems characterized by highly non-linear or discontinuous system responses is presented. The approach is based on a Padé–Legendre (PL) formalism which does not require modifications to existing computational tools (non-intrusive approach) and it is a global method. The paper presents a novel PL method for problems in multiple dimensions, which is non-trivial in the Padé literature. In addition, a filtering procedure is developed in order to minimize the errors introduced in the approximation close to the discontinuities. The numerical examples include fluid dynamic problems characterized by shock waves: a simple dual throat nozzle problem with uncertain initial state, and the turbulent transonic flow over a transonic airfoil where the flight conditions are assumed to be uncertain. Results are presented in terms of statistics of both shock position and strength and are compared to Monte Carlo simulations.     

摆锤式冲击试验机的加速度频率响应谱及基本参数计算式

本文导出了摆锤式冲击试验机的加速度频率响应诸方程和基本参数理论计算公式，这些公式与加速度频率响应谱对于我们设计、调试和标定摆锤式冲击试验机具有很大的实用价值．     

浅水运动方程的初等波解

浅水运动方程是2×2—阶拟线性双曲守恒律方程组。本文讨论了该方程组的初等波,即激波与疏散波,论证了它们怎样满足一些基本性质,从而得到了该方程组的黎曼问题的初等波解。     

“神光-Ⅱ”装置倍频激光直接驱动冲击波平面性的实验研究

 设计了3套针对“神光-Ⅱ”倍频激光直接驱动的透镜阵列均匀辐照系统，并对冲击波的平面性进行了实验研究。结果表明，冲击波的平面性与透镜阵列参数、平面靶厚度、靶面位置等有关，采用列阵元数为121的透镜阵列进行激光束匀滑驱动的冲击波平面性最好，间接说明它在靶面的激光辐照是最均匀的；另外，随着靶厚的增加，冲击波平面性变差，平面区变小；而且冲击波平面性随靶面离焦位置的变化成一定的周期性变化，第2套透镜阵列焦点处的冲击波平面性最好。     

小型化体外冲击波碎石机

本文介绍了一种新型的使用B型超声波检测仪定位的小型化体外冲击波碎石机。利用该机成功地进行了正规的动物实验,对184例泌尿系结石病人进行了治疗,成功率为97％,它可与大型碎石机相媲美,并且该机成本低,操作方便,受到了医生和病人的欢迎。     

Walker Bleakney and the development of the shock tube at Princeton

Recollections of activities in the Physics Department of Princeton University leading to the construction and use of the SHOCK TUBE are recorded. Walker Bleakney was the leader of these activities from 1940 to 1979, and his methods and attitude are described. Original interferograms made at Princeton show some results obtained.     

Visualization of shock-wave formation processes during shock reflection at obstacles with multiple steps

According to standard textbooks on compressible fluid dynamics, a shock wave is formed by an accumulation of compression waves. However, the process by which an accumulated compression wave grows into a shock wave has never been visualized. In the present paper, the authors tried to visualize this process using a model wedge with multiple steps. This model is useful for generating a series of compression waves and can simulate a compression process that occurs in a shock tube. By estimating the triple-point trajectory angle, we demonstrated visually that an accumulated compression wave grows into a shock wave. Further reflection experiments over a rough-surface wedge confirmed the tendency for the triple point trajectory angle to reach the asymptotic value _s in the end.This work was first presented at the Symposium on Shock Waves, Japan 2002