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INVESTIGATION ON THE flow stability OF NEWTONIAN FLUID IN ECCENTRIC ANNULUS VIA THE AXIAL RECIPROCATION OF THE INNER TUBE

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Journal of Hydrodynamics 2007年第6期19卷 671-676页

作者： YUAN Ai-wu CUI Hai-qing GAO Tao Management Institute Tianjin University Tianjin 300072 China Department of Petroleum Engineering Daqing Petroleum Institute Daqing 163318 China Daqing Exploration and Development Institute Daqing 163712 China

The governing equation, together with the formulas of the averaged flux and the stability parameter for Newtonian fluid flowing in eccentric annulus via the axial reciprocation of the inner tube was established in the bipolar coordinate system. Numerical calculation was conducted for the measurement of water flow using the formulas above, of which the results agree well with the experimental data. It is shown that the flow instability can be induced by the increase of the stroke, the frequency, and the eccentricity of annulus, making the sucker rod more susceptible to partial abrasion. Some protecting methods, including adding centralizers, adjusting the stroke and frequency, are proposed to protect the sucker rod from the partial abrasion, and satisfactory results have been achieved in the oilfields.

关键词： eccentric annulus axial reciprocation flow stability partial abrasion

ANALYSIS OF EDL EFFECTS ON THE flow AND flow stability IN MICROCHANNELS

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Journal of Hydrodynamics 2010年第5期22卷 725-731页

作者： YOU Xue-yi GUO Li-xiang School of Environmental Science and Engineering Tianjin University 300072 Tianjin China

The effects of the Electrical Double Layer （EDL） on the liquid mean flow and the flow stability in microchannels are investigated by solving the Poisson-Boltzmann equation. The models of the traditional streaming Electrical Current Balance （ECB） and the newly introduced streaming Electrical Current Density Balance （ECDB） are applied to determine the electrical streaming current. The numerical results show that the electrical streaming current backflow in the ECB model near the wall can be removed by using the ECDB model, which is suitable to study the effects of the EDL on the mean flow and the flow stability in microchannels. The flow is found more unstable if the ECDB model is applied.

关键词： electrical double layer Poisson-Boltzmann equation electrical streaming current balance flow stability microchan

SIDEWALL flow stability IN THE MHD CHANNEL flowS

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Acta Mechanica Sinica 1996年第2期12卷 97-103页

作者：徐复 Institute of Mechanics Chinese Academy of SciencesBeijing 100080China

The velocity distribution between two sidewalls is; M-shaped for the MHD channel flows with rectangular cross section and thin conducting walls in a strong transverse magnetic field. Assume that the dimensionless numbers R(m) much less than 1, M, N much greater than 1, and sigma* much less than 1 and that the distance between two perpendicular walls is very long in comparison with the distance between two sidewalls. First, the equation for steady flow is established, and the solution of M-shaped velocity distribution is given. Then, an equation for stability of small disturbances is derived based on the velocity distribution obtained. Finally, it is proved that the stability equation for sidewall how can be transformed into the famous Orr-Sommerfeld equation, in addition, the following theorems are also proved, namely, the analogy theorem, the generalized Rayleigh's theorem, the generalized Fjortoft's theorem and the generalized Joseph's theorems.

关键词： MHD channel flow sidewall flow flow stability

stability IN THE CIRCULAR PIPE flow OF FIBER SUSPENSIONS

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Journal of Hydrodynamics 2003年第2期15卷 12-18页

作者： You Zhen jiang, Lin Jian zhong Department of Mechanics, State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou 310027, China Lab. of Fluid Power Transmission Dept. of Mech. Zhejiang Univ. Hangzhou 310027 China

A linear stability analysis on the circular pipe flow of fiber suspensions ispresented. The fiber orientation tensors are used to describe the characteristics of theorientation dislribution of fibers. The constitutive equation for the fiber suspensions is set upand the modified Orr-Sommerfeld stability equation is derived. An improved finite difference methodwith high order accuracy is employed to solve the e-quation. The Newtonian pipe Poiseuille flowcorresponding to H = 0 is also analyzed for comparison. The results reveal that the fiber additiveswill enhance the flow stability, the degree of enhancement becomes high with the increases of theparameter H which accounts for the fiber resistance to the stretching along its axis. Fibersuspensions with large H can suppress the influence of high Reynolds number on the flow stability.Particularly, fibers give a higher attenuation of the short waves of disturbance.

关键词： flow stability circular pipe flow fiber suspensions numerical simulation

stability ANALYSIS IN SPATIAL MODE FOR CHANNEL flow OF FIBER SUSPENSIONS

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Applied Mathematics and Mechanics(English Edition) 2003年第8期24卷 871-879页

作者：林建忠游振江 Department of Mechanics State Key Laboratory of Fluid Power Transmission and ControlZhejiang University Hangzhou 310027 P.R.China Department of Mechanics State Key Laboratory of Fluid Power Transmission and ControlZhejiang University Hangzhou 310027 P.R.Chinaifferent from previous temporal evolution assumption the spatially growing mode was employed to analyze the linear stability for the channel flow of fiber suspensions. The stability equation applicable to fiber suspensions was established and solutions for a wide range of Reynolds number and angular frequency were given numerically . The results show that the flow instability is governed by a parameter H which represents a ratio between the axial stretching resistance of fiber and the inertial force of the fluid. An increase of H leads to a raise of the critical Reynolds number a decrease of corresponding wave number a slowdown of the decreasing of phase velocity a growth of the spatial attenuation rate and a diminishment of the peak value of disturbance velocity. Although the unstable region is reduced on the whole long wave disturbances are susceptible to fibers.

Different from previous temporal evolution assumption, the spatially growing mode was employed to analyze the linear stability for the channel flow of fiber suspensions. The stability equation applicable to fiber suspensions was established and solutions for a wide range of Reynolds number and angular frequency were given numerically . The results show that, the flow instability is governed by a parameter H which represents a ratio between the axial stretching resistance of fiber and the inertial force of the fluid. An increase of H leads to a raise of the critical Reynolds number, a decrease of corresponding wave number, a slowdown of the decreasing of phase velocity , a growth of the spatial attenuation rate and a diminishment of the peak value of disturbance velocity. Although the unstable region is reduced on the whole, long wave disturbances are susceptible to fibers.

关键词： flow stability spatial mode fiber suspensions channel flow

Discussion on stability Criterion of Inviscid Compressible Swirling flow

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Advances in Manufacturing 1999年第1期3卷 4-6页

作者： Xia Nan (Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University) Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

The stability condition for compressible and incompressible swirling flow is discussed and compared. It is found that Eckhoff and Storesletten's necessary condition for stability of inviscid compressible swirling flow... 详细信息

关键词： flow stability Vortex flow Swirling flow

Numerical study of flow fluctuation attenuation performance of a surge tank

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Journal of Hydrodynamics 2013年第6期25卷 938-943页

作者：郭兰兰刘正刚耿介李东杜广生 School of Energy and Power Engineering Shandong University College of Mechanical and Electronic Engineering Shandong University of Science and Technology

The surge tank plays an important role in ensuring the stability of a water flow standard device. To study the influence of the structure and the working conditions on the regulator performance of a surge tank, a three-dimensional model, including a surge tank, the pipeline and the water tank is built, and the VOF model in the Fluent software is used to simulate the two-phase pulsatile flow in the surge tank. The inlet flow pulsation is defined by the User Defined Functions （UDF）, and the outlet flow is set to be a free jet. By calculating the flow fluctuation coefficient of the variation uader different flow conditions, the influences of the pulse frequency, the initial water level height and the baffle plate structure on the flow stability are analyzed. It is shown that the surge tank has a good attenuation effect on high-frequency pulsations, there is an optimal initial water level to suppress the fluctuations, the round holes of the baffle should ensure a certain circulation area with the bore diameter small enough to have the necessary damping effect.

关键词： surge tank numerical simulation VOF flow stability

Lane changing analysis for two-lane traffic flow

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Acta Mechanica Sinica 2007年第1期23卷 49-54页

作者： Tieqiao Tang Haijun Huang S. C. Wong Rui Jiang Department of Automobile Engineering Beihang University Beijing 100083 China School of Management Beihang University Beijing 100083 China Department of Civil Engineering The University of Hong Kong Pokfulam Road Hong Kong China School of Engineering Science University of Science and Technology of China Hefei 230026 China

In this paper, the two-lane traffic are studied by using the lane-changing rules in the car-following models. The simulation show that the frequent lane changing occurs when the lateral distance in car following activities is considered and it gives rise to oscillating waves. In contrast, if the lateral distance is not considered （or considered occasionally）, the lane changing appears infrequently and soliton waves occurs. This implies that the stabilization mechanism no longer functions when the lane changing is permitted. Since the oscillating and soliton waves correspond to the unstable and metastable flow regimes, respectively, our study verifies that a phase transition may occur as a result of the lane changing.

关键词： Traffic flow Lane-changing rules Car-following models flow stability

Micro-flow calibration system based on a new diverter valve design

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Micro-flow calibration system based on a new diverter valve ...