Dynamics of Flow Around a Cylinder Oscillating In-Line for Low Reynolds Numbers

Baranyi, László; Huynh, K.; Mureithi, Njuki W.

doi:10.1115/fedsm-icnmm2010-31183

Cited by 3 publications

(4 citation statements)

References 15 publications

(19 reference statements)

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“…Figure 14 shows the limit cycle curves (C D fb ,C L fb ) for the pre-and post-jump cases. Again, the very small difference in frequency ratio results in a drastic change in the shape of the two limit cycle curves, although here they are not mirror images of each other, as for the two sides of a jump for in-line cylinder oscillation (Baranyi, 2009;Baranyi et al, 2010). Figure 15 shows the vorticity contours for the pre-and post-jump frequency ratio values of ( f y /St 0 ) 1 =0.847 and (f y /St 0 ) 2 =0.848 belonging to the same cylinder positions (t=66T y where T y =1/f y is the period based of f y ) for Re=200.…”

Section: Results For Convex Cylinder Pathsmentioning

confidence: 77%

Computation of Low Reynolds Number Flow Around a Circular Cylinder Following a Horseshoe-Shaped Path

Baranyi

2011

Volume 4: Fluid-Structure Interaction

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Two-degree-of-freedom vortex-induced vibration investigations of low-mass ratio circular cylinders show that the streamwise frequency of oscillations is about twice that of the transverse oscillation. These cylinders have been observed to trace Lissajous-type trajectories. Depending on the phase difference between in-line and transverse motions paths, different shapes can be obtained, such as trajectories resembling a figure 8 or a horseshoe. In this study low Reynolds number flow is investigated numerically for a cylinder placed in a uniform stream and forced to follow a horseshoe-like path. Investigations were carried out using a thoroughly tested finite difference code developed by the present author. The mechanical energy transfer between the fluid and the cylinder, time-mean and rms values of force coefficients are investigated. Computations are carried out for Reynolds numbers of Re=140, 200 and 250 in the lock-in domain against the frequency ratio while other parameters are kept constant. All investigations were carried out at two phase difference values, resulting in convex and concave arc paths called horseshoe-shaped paths. The mechanical energy transfer and the time-mean and rms values of force coefficients show that a sudden jump in values is often observed, affecting flow features. Positive energy transfer after the jump is common.

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Section: Results For Convex Cylinder Pathsmentioning

confidence: 77%

Computation of Low Reynolds Number Flow Around a Circular Cylinder Following a Horseshoe-Shaped Path

Baranyi

2011

Volume 4: Fluid-Structure Interaction

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“…In equation ( 1) D is the diameter of the cylinder, is the fluid density, ∞ is the free-stream velocity, and and are the lift and drag per unit length of the cylinder, respectively. The torque coefficient is computed as [5]…”

Section: Methodsmentioning

confidence: 99%

“…Al-Mdallal et al [4] investigated a similar frequency ratio range numerically at Re=200 at oscillation amplitude A=0.1 and 0.3, finding abrupt changes in the vortex structure, or vortex switches. Baranyi et al [5] analyzed in-line cylinder oscillations at frequency ratios 0.8 and 0.9, where the oscillation amplitude was varied between 0.1 and 0.7. A large number of jumps were identified in the time-mean values of lift and torque coefficients, indicating vortex switches.…”

Section: Introductionmentioning

confidence: 99%

Effect of Frequency Ratio on Flow Around a Cylinder Oscillated In-line At Re=80-200

Baranyi¹,

Dorogi²

2016

The Publications of the MultiScience - XXX. MicroCAD International Scientific Conference

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This study deals with the numerical simulation of two-dimensional laminar incompressible Newtonian fluid flow past a circular cylinder forced to oscillate inline with the main stream. The effect of frequency ratio FR=f/St on the flow is investigated for Reynolds numbers Re=80, 120, 160 and 200 at a dimensionless oscillation amplitude 0.5. Computations were carried out using a thoroughly tested finite-difference code developed by the authors. Lift, drag and torque coefficients are investigated. When the time-mean values of lift and torque coefficients are plotted against frequency ratio, abrupt changes can be found in the curves, suggesting the presence of switches in the vortex structure. No jumps were observed in the time-mean of drag and rms values of lift, drag and torque coefficients plotted against the frequency ratio. Both rms and time-mean values of force coefficients revealed a shift toward lower frequency ratio with higher Re. Where vortex switches occur, a pre-and post-jump analysis is carried out.

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“…These results are unexpected, since in earlier investigations it has generally been found that the time-mean of the torque coeffi cient behaves similarly to the lift coeffi cient; see e.g. [28][29][30]. Further investigations are needed in this area.…”

Section: Effect Of In-line Amplitude For Clockwise Orbit In the Upper Loopmentioning

confidence: 95%

Simulation of a low-reynolds number flow around a cylinder following a figure-8-path

Baranyi

2012

IRASE

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This numerical study investigates a circular cylinder placed in a uniform stream and moving along a slender figure-8-path, using a 2D computational method based on the finite difference method. The effects of in-line amplitude of oscillation and of frequency ratio are investigated. Computations for varying amplitude values were carried out at Re = 150, 200 and 250 for a clockwise orbit (in the upper loop). Time-mean and rms values of force coefficients yielded smooth curves and tended to increase with amplitude. The effect of frequency ratio was investigated at Re = 200, 250 and 300 in the lock-in domain for both clockwise (CW) and anticlockwise (ACW) orientation. Results differ substantially depending on the direction of orientation. Mechanical energy transfer was always positive in ACW direction, which may lead to vortex-induced vibration, and always negative for CW orientation. The time-mean of drag was much lower for CW over the whole frequency ratio domain investigated. For the CW orbit vortex switches were found at specific frequency ratios at Re = 250 and 300. Limit cycle curves for the CW orbit before and after a jump were symmetric, mirror images, and quite complex, while vorticity contours were close to symmetry. These results indicate the possibility of symmetry-breaking bifurcation.

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Dynamics of Flow Around a Cylinder Oscillating In-Line for Low Reynolds Numbers

Cited by 3 publications

References 15 publications

Computation of Low Reynolds Number Flow Around a Circular Cylinder Following a Horseshoe-Shaped Path

Computation of Low Reynolds Number Flow Around a Circular Cylinder Following a Horseshoe-Shaped Path

Effect of Frequency Ratio on Flow Around a Cylinder Oscillated In-line At Re=80-200

Simulation of a low-reynolds number flow around a cylinder following a figure-8-path

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