Head on collision of a planar shock wave with a dusty gas layer

The head-on collision of a planar shock wave with a dust-air suspension is studied numerically. In this study the suspension is placed inside a conduit adjacent to its rigid end-wall. It is shown that as a result of this collision two different types of transmitted shock waves are possible, depending on the strength of the incident shock wave and the dust loading ratio in the suspension. One possibility is a partially dispersed shock wave, the other is a compression wave. The flow fields resulting in these two options are investigated. It is shown that in both cases, at late times after the head-on reflection of the transmitted shock wave from the conduit end-wall a negative flow (away from the end-wall) is evident. The observed flow behavior may suggest a kind of dust particle lifting mechanism that could shed new light on the complex phenomenon of dust entrainment behind sliding shock waves.      

扭动微动的模拟及其试验研究

在CETR UMT-2型多功能摩擦磨损试验机上配置高精度低速往复转动台,构成新型试验装置并成功实现了球/平面接触条件下的扭动微动;在低速往复转动台上进行了GCr15钢球(直径10 mm)与LZ50钢在扭动角位移幅值为3°～20°和法向载荷10 N时的扭动微动试验,并在分析其摩擦动力学行为的基础上对LZ50钢的扭动微动损伤特征进行探讨.结果表明:角位移幅值和循环次数对扭动微动行为影响很大;可以通过摩擦力矩-角位移(T-θ)曲线表征扭动微动行为;随着循环次数变化,T-θ曲线呈3种基本类型,即平行四边形状、椭圆状和直线状.扭动微动损伤在低角位移幅值时较轻微,随着角位移幅值增加,出现塑性流动、氧化磨损和剥层.     

精确制导炸弹坐标转换技术

将制导炸弹的SINS/GPS组合导航系统输出的导航信息进行坐标转换,产生制导控制系统所需要的发射坐标系下的信息,以实现制导炸弹的制导与控制功能.针对某型制导炸弹的工程化研制,研究了制导炸弹在飞行过程中不同坐标系间的转换关系,分析了方位角误差对制导炸弹坐标转换精度的影响,推导了一个新的方位角计算方法.提出了一种递推的坐标转换方法,并与传统的坐标转换方法和基于迭代的坐标转换方法进行了比较.仿真结果表明,该方法可对坐标转换过程中产生的误差进行相应的修正,并且误差不会积累,该方法的转换精度最高.仿真结果验证了该方法的正确性和可行性.     

Hyperbolicity singularities in Rarefaction Waves

For mixed-type systems of conservation laws, rarefaction waves may contain states at the boundary of the elliptic region, where two characteristic speeds coincide, and the Lax family of the wave changes. Such contiguous rarefaction waves form a single fan with a continuous profile. Different pairs of families may appear in such rarefactions, giving rise to novel Riemann solution structures. We study the structure of such rarefaction waves near regular and exceptional points of the elliptic boundary and describe their effect on Riemann solutions.     

Fully Quantized Theory of Six-Wave Mixing with Matter Waves

We show that Wu-Yang theory of fully quantized four-wave mixing can be generalized to the six-wave mixing and derive the analytical solution of the coupled equations describing the quantum dynamics of six-wave mixing.     

Existing Regions of Either Rarefactive or Compressive Solitary Waves for Particular Dusty Plasma

By deriving a Korteweg-de Vries (KdV) equation for particular dusty plasma, we find the existing regions of solitary waves. The regions of both rarefactive and compressive solitary waves have also been given in this paper for a two-temperature ions and a hot adiabatic dusty fluid, where the dust charges can vary.     

Self-organized Criticality Model for Ocean Internal Waves

In this paper, we present a simple spring-block model for ocean internal waves based on the self-organized criticality （SOC）. The oscillations of the water blocks in the model display power-law behavior with an exponent of -2 in the frequency domain, which is similar to the current and sea water temperature spectra in the actual ocean and the universal Garrett and Munk deep ocean internal wave model [Geophysical Fluid Dynamics 2 （1972） 225; J. Geophys. Res. 80 （1975） 291]. The influence of the ratio of the driving force to the spring coefficient to SOC behaviors in the model is also discussed.     

Exploring Solutions of Nonlinear Rossby Waves with Complete Coriolis Force

Nonlinear Rossby waves in a Boussinesq fluid model which includes both the vertical and horizontal components of Coriolis force are studied by using the semi-geostrophic approximation and the method of travelling-wave solution. Taylor series expansion has been employed to isolate the characteristics of the linear Rossby waves and identify the Rossby cnoidal and solitary waves. Qualitative analysis indicates that if the disturbances are independent of latitude, the effect of horizontal components of Coriolis force disappears.     

Wave interaction with multiple articulated floating elastic plates

Flexural gravity wave scattering by multiple articulated floating elastic plates is investigated in the three cases for water of finite depth, infinite depth and shallow water approximation under the assumptions of two-dimensional linearized theory of water waves. The elastic plates are joined through connectors, which act as articulated joints. In the case when two semi-infinite plates are connected through a single articulation, using the symmetric characteristic of the plate geometry and the expansion formulae for wave-structure interaction problem, the velocity potentials are obtained in closed forms in the case of finite and infinite water depths. On the other hand, in the case of shallow water approximation, the continuity of energy and mass flux are used to obtain a system of equations for the determination of the full velocity potentials for wave scattering by multiple articulations. Further, using the results for single articulation and assuming that the articulated joints are wide apart, the wide-spacing approximation method is used to obtain the reflection coefficient for wave scattering due to multiple articulated floating elastic plates. The effects of the stiffness of the connectors, length of the elastic plates and water depth on the propagation of flexural gravity waves are investigated by analysing the reflection coefficient.     

New Exact Solutions and Evolution of Solitons in Background Waves for (2+1)-Dimensional Modified Dispersive Water-Wave System

With the help of the conditional similarity reduction method, some new exact solutions of the (2+1)-dimensional modified dispersive water-wave system (MDWW) are obtained. Based on the derived solution, we investigate the evolution of solitons in the background waves.