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Modes of vortex shedding from a rotary oscillating plate

Acta Mechanica Sinica 2022年第5期38卷 42-60,I0002页

作者： Liangliang Yan Jiawei Pan Chuanping Shao Institute of Flow Measurement and Simulation China Jiliang UniversityHangzhou 310018China

The wake of a two-dimensional rotary oscillating plate of chord to thickness ratio B/H=3.0 was investigated by smoke wire visualization and hot-wire measurement in a wind tunnel at Re=1500 and oscillation amplitudes and reduced frequencies in the ranges ofα=2.5°-50°and f_(e)H/V_(∞)=0.02-0.25,respectively,where fe is oscillation frequency,V_(∞) is on-coming wind *** are six modes of synchronized vortex shedding observed,including three new modes,i.e.,3P—three vortex pairs shed in one period,2S_(2)—two pairs of vortex twins shed in one period,and T—three vortices shed in one period of plate *** zone of every mode was found out and drawn on the amplitude-reduced frequency *** simulation was carried out,and the simulated vorticity field,velocity profiles,and wake width were verified by experiment at typical oscillation *** higher oscillation frequencies,the linear local unsteady term of inertial force dominates,and the simulated moment is an accurate linear function of rotary displacement and angular *** lower frequencies,where 2T,3P,and 2S_(2) modes of vortex shedding occur,however,the nonlinear convective term of inertial force dominates,and the simulated fluctuating moment deviates from Scanlan’s *** results of numerical data show that the root-mean-square(r.m.s)value of fluctuating moment is an exponential function of single parameter η=αf_(e)H/V_(∞).

关键词： Rotary oscillation Vortex shedding Mode Lift Moment

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Deformation and Vibration of a Platanus Acerifolia Tree Leaf in Wind

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AIP Conference Proceedings 2011年第1期1376卷 495-497页

作者： C. P. Shao Y.J. Chen Institute of Fluid Flow Measurement and Simulation China Jiliang University Hangzhou 310018 China

The behavior of a twig‐connected leaf in wind was investigated. With the variation of wind speed in the range of 0.7‐11.5 m/s, the leaf experienced different patterns of deformation or vibration, and abrupt changes from one pattern to another occurred at critical wind speeds. For the case of the back side facing high speed wind stream, the leaf rolled up into conical shapes to reduce resistance and vibration. When the front side facing high wind, however, the leaf vibrated fiercely and no “reconfiguration” phenomenon observed.

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Suppression of Downstream Vortex‐Street of an Oscillating Cylinder by a Splitter Plate

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AIP Conference Proceedings 2011年第1期1376卷 299-301页

作者： S Wang C. P. Shao Institute of Fluid Flow Measurement and Simulation China Jiliang University Hangzhou 310018 China

A splitter plate was used and set along the centerline of the wake to suppress vortex shedding from a stream‐wisely oscillating cylinder of diameter D at Reynolds numbers Re = V∞D/n = 1.05×103 and 2.05×104, feD/V∞ = 0.165 and 0.323, and A/D = 0.2. The control parameters were L/D and G/D, where L was the length of plate and G was the distance between central position of cylinder oscillation and leading edge of plate. Results of PIV measurement showed that vortex shedding could be efficiently inhibited in certain regions of control parameters.

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Control of Vortex Shedding From an Oscillating Cylinder

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AIP Conference Proceedings 2011年第1期1376卷 305-307页

作者： Y. J. Chen C. P. Shao Institute of Fluid Flow Measurement and Simulation China Jiling University Hangzhou 310018 China

A strip of width b/D = 0.2, thickness h/D = 0.05 was used as an element to suppress vortex street downstream of an stream‐wisely oscillating circular cylinder at Re = V∞D/n = 2 400, 5 700, 9 500; feD/V∞ = 0–0.43, and A/D = 0.2, where fe and A are respectively the frequency and amplitude of the cylinder oscillation. The wide side of the strip was perpendicular to the oncoming stream, and the control parameter is the element position. Results of Hot‐Wire and PIV measurements in wind tunnel show that vortex shedding from both sides of the oscillating cylinder is suppressed if the element is applied in effective zones.

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simulation of gas flows in micro/nano systems using the Burnett equations

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Journal of Physics: Conference Series 2012年第1期362卷

作者： Fubing Bao Xia Yu Jianzhong Lin Institute of Flow Measurement and Simulation China Jiliang University Hangzhou 310018 China Department of Mechanics State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China

The gaseous flow characteristics in micro/nano systems are studied using the Burnett equations. The Burnett equations are the second-order approximation of the Chapman–Enskog solution to the Boltzmann equation. This set of equation is appropriate to describe the rarefied gas flows. Velocity slip and temperature jump boundary conditions are applied on solid surface. Several techniques, including the usage of relaxation method on slip values and Burnett terms, are introduced to increase the stability of the Burnett equations. Hence, convergent results at Knudsen number up to 0.5 are achieved for the first time. The results of the Burnett equations are first verified using the corresponding experimental and the DSMC data. The Navier-Stokes and the Burnett equations give almost the same result when the flow is in slip regime (Kn<0.0l). But when the flow is in transition regime (0.1flows in micro/nano systems. The pressure driven plane Poiseuille and the backward-facing step flows, the flows through micro filters are then studied. Different inlet to outlet pressure ratios, size effects, shape effects and boundary conditions are analyzed. The competitive relations of rarefied and compressible effects in micro gas flows are discussed.

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