Structural Stability of Unsteadily Accelerated Liquid Pistons

The possibility of the fragmentation of a liquid piston moving with variable acceleration, due to air jets forming on its free surface and penetrating inward, is established experimentally. The liquid piston acceleration regimes in which air jets capable of penetrating into the liquid are formed from initial perturbations on its free surface are theoretically analyzed.     

Investigation of the rarefied gas flow around a circular cylinder in stationary and oscillatory regimes

Numerically, on the basis of the Krook kinetic equation, the rarefied gas flow around a circular cylinder is investigated in stationary and oscillatory regimes. The flows around a rotating cylinder and a cylinder with a nonuniformly heated surface are considered. The Knudsen numbers at which the lift force acting on the rotating cylinder changes sign are calculated. It is shown that at low Knudsen numbers a lift force acts on the nonuniformly heated cylinder.     

4:1椭球体分离流动湍流特性的试验研究

使用六线涡量探头,对α=30°条件下绕（4:1）椭球体分离流动的湍动能u’2,v’2,w’2,雷诺应力u’v’和涡量Ωx等进行了详尽的测量.应用频谱分析的方法揭示了绕（4:1）椭球体分离流内主附着涡外缘剪切层上的离散小涡的特性.     

圆柱形弹性贮液容器基频近似计算法

在工业和工程领域中,广泛地应用圆柱形弹性薄壁贮液容器。在冲击或地震地面运动激励下,此种容器的变形,严格地说就遵循薄壳结构动力学规律。考虑到在水平地震作用下短圆柱形容器的变形,剪切效应起主导作用,因而可用剪切梁变形理论来近似地代替。对于盛有液体的贮液容器,因为激励引起的振动是耦联的,即液体中产生的液动压力与结构的变形有关,而结构的变形又受到液动压力的很大影响。欲寻求此种耦联体系的动力响应,必须对其动力特性进行分析。为此,本文根据Fischer“冲击质量”理论,提出了对圆柱形弹性贮液容器基频的近似计算方法。此方法概念清晰,计算简便,很便于工程上应用。     

绕旋转圆柱流动涡尾流结构和临界状态特性

采用作者提出的基于区域分解，有限差分法与涡法杂交的数值方法，结合高阶隐式差分格式，和以修正的不完全ＬＵ分解为预处理器的共轭梯度法作求解器，系统地研究了雷诺数Ｒｅ＝１０００，旋转速度比α∈（０．５，３．２５）范围内，绕旋转圆柱从突然起到充分发展，长时间内尾流旋涡结构和阻力，升力系数的变化规律，计算所得流动图案与实验流场显示符合很好。数值试验证帝了临界状态的存在，并首次给出了临界状态时的旋涡结构特性。     

窄长方形贮箱中液体的强迫晃动

本文求解了窄长方形贮箱中液体的强迫晃动，给出激励中含恒定分量时的几种液面波高修正方法，并对它们作了比较．     

DNS of the Turbulent Channel Flow of a Dilute Polymer Solution

A direct numerical simulation of the turbulent channel flow of a dilute polymer solution has been performed in order to compare its turbulence statistics with those obtained in a Newtonian channel flow. The viscoelastic flow has been simulated by solving the whole set of continuity, momentum and constitutive equations for the six independent components of the extra-stress tensor induced by polymer addition. The Finitely Extensible Nonlinear Elastic dumbbell model was adopted in order to simulate a non-linear modulus of elasticity and a finite extendibility of the polymer macromolecules. Simulations were carried out under the narrow channel assumption at a Reynolds number of 169 based on the channel half height and on the friction velocity; they showed a significant reduction in drag, dependent on the influence of the elastic properties of the chains. A qualitative comparison with experiments at a higher Reynolds number has shown that the model here adopted is capable of reproducing all the main features of the polymer solution flow. Analysis of the turbulence statistics suggests that a dilute polymer solution can affect the intensity of the streamwise vortices, leading to an increase in the spacing between low speed streaks and eventually to a turbulent shear stress reduction.     

Steady ground-water flow through layered media

This paper deals with the flow through a layered medium that has alternate sand and clay strata. The solutions of plane, axisymmetric and spatial cases are given. Research results in this paper can be applied to seepage calculations and hydraulic engineering designs in flood areas and reclaimed marsh land.List of Symbols A _n Upward leakage factor of the nth sand stratum - A _n Downward leakage factor of the nth sand stratum - [B] Matrix of eigenvector - B _nm Element of [B] corresponding to the nth sand stratum and the mth eigenvalue - C _m , C _N+m Arbitrary constants belonging to the terms contained the mth eigenvalue - C_mj Arbitrary constant belonging to the term contained the mth eigenvalue due to a line source in the jth sand stratum - [D] Inverse matrix of [B] - d _f0 ^sup+ Additional length of the seepage path for ditches in symmetric flow - F, ^F _m Area and dimensionless area corresponding to the mth eigenvalue ( ^F _m = _fm ^sup2 F) - f ₀ Coefficient of additional resistance of partially penetrating well - H Total water head; upstream water head - h, h _n Water head and water head of the nth sand stratum - h _nj Water head of the nth sand stratum due to a line source in the jth sand stratum - h ₀ Surface water head - h/H × 100% Potential - i, j Number - k, k Permeability coefficient of the sand stratum and clay stratum, respectively - k _n , k _n Permeability coefficient of the nth sand stratum and the nth clay stratum, respectively - L Length - m Number - N Total number of sand or clay strata - n Number - Q _j Discharge of a line source distributed along a vertical line in the jth sand stratum - Q _ji The partial discharge of the ith well (or line source), which flows through the screen pipe penetrating the jth sand stratum - qj Discharge of a face source distributed on an area - unit breadth multiplied by the thickness of the jth sand stratum. The abbreviation is: unit discharge of a face source in the jth sand stratum - qji Unit discharge of a face source on the ith surface element in the jth sand stratum - R Constant radius - S Distance; length of a curve - ^S _m Dimensionless length of a curve corresponding to the mth eigenvalue ( ^S _m = _m S) - s Number - T _n , T _n Thickness of the nth sand stratum and the nth clay stratum, respectively - t Number; thickness - x, y, z Cartesian coordinates - y Polar coordinate; radius; distance - ^y _m Dimensionless distance corresponding to the mth eigenvalue ( ^y _m = _m y) - y ₀ Radius of well - y ₀ Radius of equivalent completely penetrating well - Infinitesimal half breadth - Infinitesimal area - Angle - Eigenvalue     

Stress amplification and plastic flow for spheroidal shells: Applications to myopia

Amplification of effective stress and plastic strain rates after yielding are derived for the anisotropic stress fields of the prolate and oblate spheroidal shells as models of the myopic and hyperopic eyes. Dimensionless closed-form results are presented for arbitrary axis ratio with both constant shell thickness and variable shell thickness, using the constant scleral mass assumption. The results show that the myopic and hyperopic eyes are susceptible to failure by plastic yielding at the equator and pole, respectively, for high intraocular pressures. Experimental data from the equatorial zone of rabbit sclera shows scleral yielding and plastic flow for intraocular pressures greater than 32 mm Hg. Practical applications include glaucoma and pathological myopia.     

A comprehensive experimental study of the rheological behaviour of HDPE.

Extensional properties of four high density polyethylenes with different molecular weights and molecular weight distributions are presented. The samples have already been well characterized in shear and non-isothermal extensional flow. The data were collected at 180 °C for elongational rates between 3 · 10^–1 and 10^–4s^–1. Some qualitative and quantitative generalizations of the results are given.