Rotating elliptic cylinders in a viscous fluid at rest or in a parallel stream

Lugt, Hans J.; Ohring, Samuel

doi:10.1017/s002211207700007x

Cited by 23 publications

(8 citation statements)

References 10 publications

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“…In their experiment, the non-dimensional rotation speed * ω was set to be 0.417, 0.833, 1.667, and 2.5, and the Reynolds number Re was 200 and 1000, respectively. When * 0.417 ω = , the measurement result of Lua et al (2010) is similar to the computation by Lugt and Ohring (1977), in that a pair of counter-rotating vortices shed during every half-rotation period, and the center and orientation between adjacent vortex pairs changes alternately. At * 0.833 ω = , vortex pair shedding was still observed, but a neighboring advancing vortex may merge.…”

Section: Introductionsupporting

confidence: 53%

“…As in figure 4, periodic vortex shedding patterns are observed for the wings of all three aspect ratios. The vortex ring is formed and shed during every half-rotation ( t* 0.5 δ = ) from the leading and trailing edges of the wing, which corresponds to a pair of counter-rotating vortices in two dimensions, as observed by Lugt and Ohring (1977) and Lua et al (2010). If we define the start and the end of every half-rotation by 0 α = and α π = (α is the angle of attack), the vortex ring is composed of the leading edge vortex in the previous half-rotation, and the trailing vortex in the following half-rotation.…”

Section: Effect Of Aspect Ratiomentioning

confidence: 81%

“…For simplification, one can study the problem of the flow past a rotating body about a fixed axis with prescribed angular velocity in a first stage. Lugt and Ohring (1977) studied a two-dimensional (2D) flow past a rotating elliptic cylinder numerically. In their study, the Reynolds number (Re U c ν = ∞ , where c is the chord length of the foil, U ∞ is the freestream velocity, and ν is the kinematic viscosity of the fluid) was 200, and the non-dimensional rotating speed ( c U *…”

Section: Introductionmentioning

confidence: 99%

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Three-dimensional flow past rotating wing at low Reynolds number: a computational study

2015

Fluid Dyn. Res.

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In this work, we performed a computational study on the three-dimensional (3D) flow past a rotating wing at a low Reynolds number (Re = 200). The 3D vortical structures and aerodynamic performances of the rotating wing with different aspect ratios and rotating speeds are computed and analyzed. A quasi-steady model is adopted for prediction of aerodynamic performances of the wing, and its applicability is evaluated by the computation. It is found that there exists a periodic vortex shedding pattern at a low rotating speed, while vortices may cluster near the wing when rotating speed is high enough. The wake vortex topology is also affected by the aspect ratio. The current quasisteady aerodynamic model could only be used for rotating wing aerodynamics at a low rotating speed when regularly periodic vortex shedding exists.

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Section: Introductionsupporting

confidence: 53%

Section: Effect Of Aspect Ratiomentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

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Three-dimensional flow past rotating wing at low Reynolds number: a computational study

2015

Fluid Dyn. Res.

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“…We begin by writing the solution to equation (2). This equation is nothing more than that given by o=curlV.…”

Section: Vorticity-velocity Formulationmentioning

confidence: 98%

Unsteady viscous flow over a grooved wall: A comparison of two numerical methods

Hung

Kinney

1988

Numerical Methods in Fluids

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SUMMARYA numerical study is made of the unsteady two-dimensional laminar flow of an incompressible fluid over a periodically grooved wall. Two independent finite difference techniques are employed. One is based on the vorticity-stream function and the other on the vorticity-velocity (i.e. induction law) formulation. The fluid motion is initiated impulsively from rest and is assumed to be spatially periodic in the streamwise direction. The numerical formulations are derived in detail. The generation of vorticity at the solid surface is modelled differently in the two approaches, and this is found to play an important role in determining the surface pressure distribution and the drag coefficient. The flow field is examined during the early transient phase of development, during which the greatest changes occur. Results are presented for a moderate Reynolds number (based on groove depth) equal to 100. It is found that the vorticity-stream function approach does not produce a spatially periodic wall pressure distribution, and therefore global conservation of total vorticity is not achieved. This results in substantial errors in the predictions for the drag coefficient. These deficiencies are not found in the results obtained by the vorticity-velocity formulation.

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“…For instance, even for a twodimensional rotating plates, both computational study by Lugt & Ohring (1977) and W. B. Wang, R. F. Hu, S. J. Xu and Z. N. Wu experimental study by Lua, Lim & Yeo (2010) show that a pair of spanwise advancing vortex and retreating vortex is shed from the leading and trailing edges of the plate during every half rotation.…”

Section: Force and Torque Expressions By Correction Due To Trailing Amentioning

confidence: 99%

Influence of aspect ratio on tumbling plates

Wang

et al. 2013

J. Fluid Mech.

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The tumbling motion of freely falling plates with aspect ratio ranging from 2 to 10 is studied using both experimental measurement and simplified lifting line theory. The trajectories of plates are recorded by high-speed video camera and analysed to obtain instantaneous and average kinematic and aerodynamic parameters, including the descent angle, rotating speed, descent velocities, lift and drag coefficients, and their fluctuation spectrums. A double period rotation with period doubling is observed here for some range of aspect ratio and the double frequency is determined from a Fourier analysis. By adding a correction from the inducing effect of trailing vortices and wing-tip vortices to the corresponding two-dimensional force and torque expressions, a simplified kinematic model is obtained which successfully predicts the qualitative influence of aspect ratio on the averaged kinematics, that the descent angle and the vertical descent velocity component are decreasing functions of the aspect ratio, while the rotation speed and horizontal velocity component are increasing functions of the aspect ratio. For decreasing aspect ratio, the induced drag due to the trailing and tip vortices reduces the lift to drag ratio and thus increases the descent angle, while the dissipative torque due to translational induced drag decreases the rotation speed.

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Rotating elliptic cylinders in a viscous fluid at rest or in a parallel stream

Cited by 23 publications

References 10 publications

Three-dimensional flow past rotating wing at low Reynolds number: a computational study

Three-dimensional flow past rotating wing at low Reynolds number: a computational study

Unsteady viscous flow over a grooved wall: A comparison of two numerical methods

Influence of aspect ratio on tumbling plates

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