Feedback control of vortex shedding from a circular cylinder by cross-flow cylinder oscillations

1996 ◽  
Vol 21 (1) ◽  
pp. 49-56 ◽  
Author(s):  
H. M. Warui ◽  
N. Fujisawa
Keyword(s):  
Feedback Control ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Cross Flow

Numerical Simulation of Vortex Shedding Past a Circular Cylinder in a Cross-Flow at Low Reynolds Number With Finite Volume-Technique: Part 1 — Forced Oscillations

2007 ◽  
Author(s):  
Antoine Placzek ◽  
Jean-Franc¸ois Sigrist ◽  
Aziz Hamdouni
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Finite Volume ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Cross Flow ◽  
Forced Oscillations ◽  
Lift And Drag ◽  
Wake Characteristics

The numerical simulation of the flow past a circular cylinder forced to oscillate transversely to the incident stream is presented here for a fixed Reynolds number equal to 100. The 2D Navier-Stokes equations are solved with a classical Finite Volume Method with an industrial CFD code which has been coupled with a user subroutine to obtain an explicit staggered procedure providing the cylinder displacement. A preliminary work is conducted in order to check the computation of the wake characteristics for Reynolds numbers smaller than 150. The Strouhal frequency fS, the lift and drag coefficients CL and CD are thus controlled among other parameters. The simulations are then performed with forced oscillations f0 for different frequency rations F = f0/fS in [0.50–1.50] and an amplitude A varying between 0.25 and 1.25. The wake characteristics are analysed using the time series of the fluctuating aerodynamic coefficients and their FFT. The frequency content is then linked to the shape of the phase portrait and to the vortex shedding mode. By choosing interesting couples (A,F), different vortex shedding modes have been observed, which are similar to those of the Williamson-Roshko map.

Feedback control of vortex shedding from a circular cylinder

1996 ◽  
Vol 20 (3) ◽  
pp. 218-224 ◽  
Author(s):  
X. Y. Huang
Keyword(s):  
Feedback Control ◽  
Circular Cylinder ◽  
Vortex Shedding

814 Effect of fin around a circular cylinder on Karman vortex shedding in cross flow

2007 ◽  
Vol 2007 (0) ◽  
pp. _814-1_-_814-4_
Author(s):  
Hiromitsu HAMAKAWA ◽  
Tomohiro KUDO ◽  
Eiichi NISHIDA ◽  
Tohru FUKANO
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Karman Vortex

1125 VORTEX SHEDDING NOISE GENERATED FROM A CIRCULAR CYLINDER WITH SPIRAL FIN IN CROSS FLOW

2013 ◽  
Vol 2013.4 (0) ◽  
pp. _1125-1_-_1125-6_
Author(s):  
Hamakawa Hiromitsu ◽  
Adachi Takaaki ◽  
Asakura Kenta ◽  
Hosokai Kazuki ◽  
Nishida Eiichi ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Vortex Shedding Noise

Vortex Shedding Suppression for a Circular Cylinder by Attaching Cylindrical Rings (A Consideration of the Mechanism)

2011 ◽  
Author(s):  
Hajime Nakamura
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Lift Force ◽  
Cross Flow ◽  
Piv Measurements ◽  
Ring Configuration ◽  
Turbulent Transition ◽  
Through Flow ◽  
Flow Visualizations ◽  
Spanwise Flow

Omnidirectional reductions in drag and fluctuating forces can be achieved for a circular cylinder subjected to cross-flow by attaching cylindrical rings along its span at an interval of several diameters. In this work, the effects of ring configuration, the diameter D, spanwise width W, and spanwise pitch P, on the vortex shedding suppression was investigated. As a result, it was found that the periodicity in the pressure fluctuation on the sides of the cylinder disappeared for Red ≥ 20000 at ring configurations of D/d = 1.3, W/d = 1 and P/d ≈ 3. At this configuration, the fluctuating lift force reduced markedly to about 1/30 of a 2D cylinder due to the suppression of the periodic shedding together with the weakening of the spanwise correlation. The mechanism of this was explored through flow visualizations and PIV measurements, which was considered as follows: A spanwise pressure gradient originated from a stepwise change in the diameter induces a spanwise flow, which brings the corner vortex to the side of the ring. This promotes the turbulent transition in the shear layer separated from the ring for Red ≥ 20000. As a result, the wake behind the ring markedly shrinks, which induces a pair of large transverse circulations just behind the ring edges. Consequently, two-dimensional spanwise vortices are obstructed to form, resulting in the suppression of the periodicity in the vortex shedding.

Synchronized Vibrations of a Circular Cylinder in Cross Flow at Supercritical Reynolds Numbers1

2003 ◽  
Vol 125 (1) ◽  
pp. 97-108 ◽  
Author(s):  
Tsutomu Kawamura ◽  
Toshitsugu Nakao ◽  
Masanori Takahashi ◽  
Masaaki Hayashi ◽  
Kouichi Murayama ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Excited Vibration ◽  
Karman Vortex ◽  
Lock In

Synchronized vibrations of a circular cylinder in a water cross flow at supercritical Reynolds numbers were measured. Turbulence intensities were varied to investigate the effect of the Strouhal number on the synchronization range. Self-excited vibration in the drag direction due to symmetrical vortex shedding began only when the Strouhal number was about 0.29, at a reduced velocity of 1.1. The reduced velocities at the beginning of lock-in vibrations caused by Karman vortex shedding decreased from 1.5 to 1.1 in the drag direction and from 2.7 to 2.2 in the lift direction, as the Strouhal number increased from 0.29 to 0.48.

Influence of Thermal Buoyancy on Vortex Shedding Behind a Rotating Circular Cylinder in Cross Flow at Subcritical Reynolds Numbers

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Dipankar Chatterjee ◽  
Chiranjit Sinha
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Thermal Instability ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Forced Flow ◽  
Thermal Buoyancy ◽  
Thermal Fields ◽  
Rotating Circular Cylinder ◽  
Unbounded Medium

The vortex shedding (VS) behind stationary bluff obstacles in cross-flow can be initiated by imposing thermal instability at subcritical Reynolds numbers (Re). We demonstrate here that additional thermal instability is required to be imparted in the form of heating for destabilizing the flow around a rotating bluff obstacle. A two-dimensional numerical simulation is performed in this regard to investigate the influences of cross buoyancy on the VS process behind a heated and rotating circular cylinder at subcritical Re. The flow is considered in an unbounded medium. The range of Re is chosen to be 5–45 with a dimensionless rotational speed (Ω) ranging between 0 and 4. At this subcritical range of Reynolds number the flow and thermal fields are found to be steady without the superimposed thermal buoyancy (i.e., for pure forced flow). However, as the buoyancy parameter (Richardson number, Ri) increases flow becomes unstable and subsequently, at some critical value of Ri, periodic VS is observed to characterize the flow and thermal fields. The rotation of the cylinder is found to have a stabilizing effect and as Ω increases more heating is observed to be required to destabilize the flow.

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