Numerical study of plane couette flow in a rotating framework

Summary A numerical study of laminar plane Couette flow subjected to a steady spanwise rotation is conducted. The full nonlinear Navier-Stokes equations in a steadily rotating framework are solved by a finite difference method for a long, large-aspect-ratio rectangular channel where the outer wall moves at a constant velocity. In this manner, nonlinear and wall end effects which are present in any real laboratory Couette flow experiment are taken into account. The computations demonstrate the existence of a roll instability, at intermediate rotation rates, when the Reynolds number exceeds a critical value of 42. The associated secondary flow in the form of longitudinal rolls is shown to have a severe distortional effect on the primary axial velocity in the interior of the channel which is not linear like its counterpart in an inertial framework. Comparisons are made with previously conducted linear stability analyses as well as with other analogous numerical and experimental studies.With 15 Figures     

Heat- and mass-transfer problem for plane couette flow in the sublimation of a moving plate

The problem of heat and mass transfer in a narrow slit channel with sublimation of a moving plate is solved in an approximate formulation. The influence of the velocity of plate motion on the efficiency of sublimational cooling is investigated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 46, No. 6, pp. 934–937, June, 1984.     

An Asymptotic Approach to Second-kind Similarity Solutions of the Modified Porous-medium Equation

The problem of a spreading ground-water mound of liquid in a porous medium, situated on an impermeable horizontal solid layer is revisited. The mathematical formulation for this problem is given by the modified porous medium equation. A global condition in form of an energy integral is derived, describing the loss of liquid in the porous medium. This yields the necessary condition that enables the aymptotic derivation of the similarity exponents for the similarity solution of second kind. The method developed here, is further applied to the corresponding dipole problem, when instead of an energy integral another conservation law, the first moment integral, is considered. I dedicate this article to the memory of Julian D. Cole, who has been a great inspiration to me and to the Applied Mathematics community in general for his profound impact on the development of Perturbation Methods.     

Modified smoothed particle hydrodynamics method and its application to transient problems

A modification to the smoothed particle hydrodynamics method is proposed that improves the accuracy of the approximation especially at points near the boundary of the domain. The modified method is used to study one-dimensional wave propagation and two-dimensional transient heat conduction problems.This work was supported by the ONR grant N00014-98-1-0300 and the ARO grant DAAD19-01-1-0657 to Virginia Polytechnic Institute and State University, and the AFOSR MURI grant to Georgia Tech that awarded a subcontract to Virginia Polytechnic Institute and State University. Opinions expressed in the paper are those of authors and not of the funding agencies.     

Conduit flow of a fluid through its solid phase and its application to intraglacial channel flow

The physics of water flow within glacier ice is closely examined with special reference to the unsteady flow through intraglacial channels. Starting from general global balance laws in 3-dimensional space 1-dimensional balance laws are derived which are valid for a curved and torded tube-like volume. Following the derivation of the general balance law 1-dimensional forms of the balance of mass, momentum, angular momentum and energy are presented. These laws are then simplified and compared with the theory of Nye. It is found that Nye's equations are strictly valid only for straight conduits with circular cross sections. To close the theory the genera] balance laws are then complemented by phenomenological assumptions. Finally, it is shown how this theory can be used to explain certain simple phenomena in unsteady intraglacial channels. A thorough exploitation of this theory is not attempted, however.     

Generalized couette flow with variable viscosity and dissipation of mechanical energy

We employ the method of a small parameter to solve the problem of a pressure-stabilized Couette flow in which we take into account dissipation of mechanical energy and an exponential temperature dependence of viscosity.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 20, No. 6, pp. 1042–1044, June, 1971.     

改性膨润土及其在环保方面的应用

本文综述了膨润土的改性及其近年来在环境保护方面的应用     

一种胶转磁设备的解决方案

一、概述 "胶转磁"技术足将胶片模拟图像信号转换为磁带录像电信号技术的简称.其基本原理是利用摄像器件的像素扫描与存贮功能把胶片图像转化产生视频电信号,使原本每秒24格播放的胶片图像被转换成每秒25帧的电子图像,最后记录到磁带或电子存储器上,以便用于后期进行非线性编辑制作等各种专业处理、播放.     

浅谈空分设备分析仪器应用及其误区

目前,空分设备运行企业对空分设备分析仪器的应用技术没有引起应有的重视,使购置的分析仪器没有充分发挥作用。简介分析仪器在保证产品质量和空分设备安全运行方面的作用,阐述分析仪器的选型和配置原则,叙述分析仪器的日常使用和维护措施以及应用中存在的误区。     

Full-field measurement technique and its application to the analysis of materials behaviour under plane strain mode

The purpose of the paper is to provide a comprehensive experimental and numerical analysis of one of the encountered and critical state modes in sheet metal forming processes. The study is carried out with the help of the full-field measurement techniques. In order to confer some generality to the proposed work, several materials and different specimen shapes are considered that exhibit more or less homogeneous strain field. The proposed experimental study of the plane strain test is completed by a preliminary identification of the material parameters for non-linear behaviour at finite strains, using heterogeneous strain field.     

气体多方指数的修正及其在声空化中的应用

为了对气体多方指数进行定量的描述,提出了一个随速度变化的气体多方指数的表达式;并以此表达式修正了Q-X方程,而后,以此方程对声空化进行了数值计算并与实验结果进行了比较。通过计算与比较,发现：不同的多方指数,对计算结果有较大影响;对不同实验条件,都有一个最优的多方指数;修正了多方指数的Q-X方程与不同实验条件下的数据都拟合得比较好。表明所提出的随速度变化的气体多方指数的表达式是合理的。     

Universal Crossover Approach to Equation of State for Fluids

It is well known that any classical equation of state fails to describe the properties of fluids in the critical region, where the behavior of fluids is strongly affected by density fluctuations. In the present work, a universal approach to incorporate the effects of density fluctuations in the global behavior of one-component fluids is proposed. As an illustration of our general approach, a crossover generalization of a four-parametric cubic equation of state, which can be useful for engineering applications, is demonstrated. The obtained crossover equation reproduces Ising-like singular scaling behavior in the critical region and reduces to the original cubic equation of state far away from the critical point. In addition, the crossover equation of state is applied to describe thermodynamic properties of methane, ethane, carbon dioxide, and water. It is shown that incorporation of critical fluctuations leads to a significant improvement in the ability of the cubic equation to represent thermodynamic properties and liquid–vapor equilibrium of one-component fluids.     

相干结构中特征值积分方程求解的一种新方法

相干结构在湍流研究中起着非常重要的作用。文中采用最优正交分解(POD)定义相干结构,将其表示为使得内能极大的空间变量的函数。将极大值问题转化求解特征值积分方程。利用变分原理和Galerkin方法的思想进行求解。文中的算例说明算法是有效可行的。算法可用于流体的优化控制和高效率算法的构造。     

Isochronous creep rupture loci on deviatoric plane and its application to P92 steel creep behaviour under multiaxial stress state

The transformation relationship of the coordinate variables between principal stress space and deviatoric stress plane has been deduced and the isochronous creep rupture loci of disparate criteria have been described on deviatoric stress plane so as to analyze the creep behaviour under multiaxial stress state. The creep experiments of P92 steel smooth and notched specimens subjected to various stresses at 650 °C have been conducted. A modified constitutive model for the creep of P92 steel has been proposed and used to simulate the creep of P92 steel notched specimens with FEA software. The FEA results were consistent with the experimental data and the fracture morphology observation. It was found that the Hayhurst criterion had the best correlation with the experimental results of P92 steel under multiaxial stress state than other criteria through the comparison of the isochronous creep rupture loci on deviatoric plane.     

Numerical solution of time dependent stratified two-phase flow of micropolar fluids and its application to flow of blood through fine capillaries

A numerical solution of the non-steady stratified two-phase flow of micropolar fluids in small diameter capillaries is given by using two different spin boundary conditions. Predictions of particle spin distributions using these two types of boundary conditions are compared. Numerical solutions of the start-up flows, as flow becomes steady, are in good agreement with the available exact solutions of steady flows. Results are analyzed with the view of applying micropolar fluids to describe the steady or non-steady flow of blood or particulate filled fluids in small diameter capillaries. The results are likely to be useful in mass transfer problems when the diffusion process is affected by the spin of the microstructure and by the presence of a particle-free region at the boundary.     

改进的光流法及其在云爆弹研究中的应用

在Hom-Schunck和N．Ohta的传统光流法的基础上，提出了用于抑制光线影响的改进的光流法，并将其用在云爆弹的爆炸过程分析研究中，得到云爆弹爆炸云雾扩散速度这一重要参数指标。改进的方法运用自适应高斯核平滑滤波器，对所拍摄的图像序列进行平滑滤波处理，以平滑图像和降低随机噪声对图像处理的干扰。利用脚彩色模型在白光照射下的不变性原理，将传统彩色图像光流法中的RGB彩色模型转换为rgb彩色模型，得到了一种新的可抑制光线变化影响光流场算法，以减少因光线变化而造成对目标的误检测的影响。以云爆弹为研究实例，采用改进的方法计算云爆弹爆炸云雾图片中各点光流，并提取了扩散云雾平均速度信息。实验所得图片中平均光流大小约2．5pixel／ms，经过参数换算得出云雾扩散速度为109．78m／s，取得了良好的效果。