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Role of Viscosity Stratification and Insoluble Surfactant in Instability of Two-Layer Channel Flow

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Chinese physics Letters 2010年第4期27卷 175-177页

作者：彭杰朱克勤 Department of Engineering Mechanics Tsinghua University Beijing 100084

We study, for the case of the two layer plane Poiseuille flow, the effect of viscosity stratification and interracial surfactant on the flow instability. Considering a normal mode of the streamwise wave number α, both the linear and energy analyses are presented. The expressions of perturbation energy supplied at the interface are derived. The result demonstrates that the jumps of horizontal velocity and tangential stress of the perturbed flow across the interface could be induced by the presence of viscosity stratification and surfactant. This is expected to be responsible for the Yih and Marangoni instability.

关键词： fluid dynamics mathematical physics

Local Heating Effect of Flow Past a Circular Cylinder

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Chinese physics Letters 2010年第4期27卷 167-170页

作者：辛晓峰陈诚王伯福马东军孙德军 Department of Modern Mechanics University of Science and Technology of China Hefei 230027

Heating effects of air flows past a two-dimensional circular cylinder at low Reynolds numbers and low Mach numbers are investigated by numerical simulation. The cylinder wall is heated partially rather than heated on the whole surface as with previous researches. The heating effects are completely different for various heating locations on the cylinder surface. Heating either windward or leeward side stabilizes the flow and reduces or completely suppresses vortex shedding from the cylinder at supercritical Reynolds numbers, which is consistent with previous results of heating on the whole surface of the cylinder. However, as the lateral sides of the cylinder （perpendicular to the stream-wise direction） are heated, an adverse effect is found for the first time in that the flow is destabilized and vortex shedding can be excited at subcritical Reynolds numbers. As the lateral sides of the cylinder are cooled, the flow is stabilized.

关键词： fluid dynamics mathematical physics

Stretching a Curved Surface in a Viscous fluid

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Chinese physics Letters 2010年第2期27卷 149-152页

作者： M. Sajid N. Ali T. Javed Z. Abbas Theoretical Plasma physics Division PINSTECH P.O. Nilore Islamabad 44000 Pakistan Faculty of Basic and Applied Sciences International Islamic University Islamabad 44000 Pakistan

This work is concerned with the viscous flow due to a curved stretching sheet. The similarity solution of the problem is obtained numerically by a shooting method using the Runge-Kutta algorithm. The physical quantities of interest like the fluid velocity and skin friction coefficient are obtained and discussed under the influence of dimensionless curvature. It is evident from the results that dimensionless curvature causes an increase in boundary layer thickness and a decrease in the skin friction coefficient.

关键词： fluid dynamics mathematical physics

Mechanism Responsible for the Complete Suppression of Kármán Vortex in Flows Past a Wavy Square-Section Cylinder

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Chinese physics Letters 2010年第3期27卷 204-207页

作者：林黎明凌国灿吴应湘 The Division of Engineering Sciences Institute of Mechanics Chinese Academy of Sciences Beijing 100190 The Stake Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100190

The Kármán vortex shedding is totally suppressed in flows past a wavy square-section cylinder at a Reynolds number of 100 and the wave steepness of 0.025. Such a phenomenon is illuminated by the numerical simulations. In the present study, the mechanism responsible for it is mainly attributed to the vertical vorticity. The geometric disturbance on the rear surface leads to the appearance of spanwise flow near the base. The specific vertical vorticity is generated on the rear surface and convecting into the near wake. The wake flow is recirculated with the appearance of the pair of recirculating cells. The interaction between the upper and lower shear layers is weakened by such cells, so that the vortex rolls could not be formed and the near wake flow becomes stable.

关键词： fluid dynamics mathematical physics