微重力气液两相环状流界面波特性分析

本文利用双重小波包分解算法,对微重力气液两相环状流界面波特性进行了分析,将实验测量到的环状液膜厚度信号分解成相干分量和非相干分量,并对相干信号与非相干信号的特征进行了分析,提出了一个新的描述微重力气液两相环状流界面波特性参数。     

Numerical analysis of the method of fundamental solution for harmonic problems in annular domains

In this study, we investigate the application of the method of fundamental solutions (MFS) to the Dirichlet problem for Laplace's equation in an annular domain. We examine the properties of the resulting coefficient matrix and its eigenvalues. The convergence of the method is proved for analytic boundary data. An efficient matrix decomposition algorithm using fast Fourier transforms (FFTs) is developed for the computation of the MFS approximation. We also tested the algorithm numerically on several problems confirming the theoretical predictions. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2005     

圆环旋转液体射流稳定性的研究

本文详细研究了圆环旋转非粘液体射流在静止的非粘不可压缩气体介质中的不稳定性问题，给出了描述射流稳定性的色散方程，证明了圆环旋转液体射流失稳的主导模式是准非对称模式，最后讨论了射流稳定性的影响参数．     

On the role of droplets in cocurrent annular and churn-annular pipe flow

Decreasing the gas flow-rate in an initially vertical upward annular dispersed pipe-flow, will eventually lead to a down-flow of liquid. The onset of this down-flow has been related in the literature to the presence of the dispersed phase and the instability of the liquid film. Here we investigate how the dispersed-phase may influence the down-flow, performing detailed PDA-measurements in a 5 cm vertical air–water annular-flow. It is shown that the dispersed-phase does not cause the liquid down-flow, but that it delays the onset of liquid down-flow. In cocurrent annular flow the dispersed phase seems to stabilise the film flow, whereas in churn-annular flow the opposite seems to be true.     

Magnetohydrodynamic pipe flow in ducts with partial circular ring cross section and annular cross section

In this paper we use the Green function method to solve the problem of steady one dimensional flow of an incompressible viscous, electrically conducting fluid through a pipe with partial circular ring cross section and one with annular cross section, in the presence of an applied transverse uniform magnetic field. We obtain analytic solutions and carry out some numerical calculations of the velocity distribution and induced magnetic field.     

用奇异函数法简化计算具有悬臂端环板的极限荷载

本文应用奇异函数简化计算具有悬臂端环板的极限荷载.文中分别以具有内悬臂或外悬臂的环板的塑性极限分析为例,给出简化计算的方法及结果.算例表明了本文方法的可行性及简便性.     

Numerical Investigation of the Flows in Cumulative Short-Plug Nozzles within the Framework of the Reynolds Equations

Numerical simulation is used to study the gasdynamics of annular cumulative nozzles. The class of nozzles considered includes those with a flat-ended plug and plugs of different length. The thrust performance of cumulative nozzles is determined over wide ranges of the nozzle pressure ratio and the specific heat ratio and the ranges on which the self-adjustment effect takes place are established. It is found that for low nozzle pressure ratios the cumulative nozzle with a flat-ended plug provides greater thrust than a finite-length plug nozzle optimal for operation in a vacuum.     

Study on steady surge pressure for Yield-Pseudoplastic fluid in a concentric annulus

Surge pressure caused by pipe moving through the wellbore full of drilling fluid is the main factor affecting wellbore stability, on which the additional mud density is designed. Thus it is desired to predict the surge pressure with high accuracy. While this is closely related with the selection of mud rheological models. Yield-Pseudoplastic model which has three parameters and is famous for its higher accuracy has been used to describe the mud rheological properties in recent years. Based on this model the paper presents a new theoretical model for calculating surge pressure caused by mud viscosity during tripping or casing in a concentric annulus of directional wells under steady laminar situation. For convenience, the paper plots the distribution of the coefficients of surge pressure for different conditions. An example is given. These results provide the basis for controlling pressure surges and tripping velocity.     

不同构型和多点喷射对短环型燃烧室燃烧性能的影响

对短环形流燃烧室内有较强回流的湍流旋流流动进行了模拟,并从两个方面(燃烧室构型和多点喷射)对燃烧室性能的影响进行了分析。计算中采用Reynoldes应力湍流模型(RSM)、EBU-Arrheniue湍流燃烧模型和离散坐标辐射模型描述其燃烧流动,液相采用Lagrange法处理,气相采用SIMPLE法求解。研究表明:在燃料和空气总流量不变的情况下,燃烧室构型对燃烧室出口平均温度影响不大,对出口温度分布、燃烧室内空气流场有比较大的影响。喷嘴数目的改变对出口处的平均温度和平均速度影响不大,但是对出口截面处的温度分布影响比较大,在局部范围可能产生温度比较高的热斑。     

Axial annular flow of plastic fluids: dead zones and plug-free flow

In axial annular flow, the shear stress decreases from its value τ(κR) at the inner cylinder to 0 at r = λR and increases from then on to τ(R) at the outer cylinder. For plastic fluids with a yield stress τ _c, λ will be such that flow commences when τ(κR) = τ(R) = τ _c. For fluids with position-dependent yield stresses (electro- and magnetorheological fluids are examples), the situation is more complex. While it is possible that yielding and flow occur everywhere, it is also possible that flow occurs only in parts of the fluid-filled space, and a dead zone (region in which the fluid is at rest) close to one of the walls exists. In that case, the fluid will flow no matter how small the applied pressure difference is. If P is large enough, the dead zone ceases to exist and flow without any plug is possible. The fluid flows as if no yield stress exists.