Measurements of the dynamic lift force acting on a circular cylinder in cross-flow and exposed to acoustic resonance

2011 ◽  
Vol 27 (8) ◽  
pp. 1149-1164 ◽  
Author(s):  
A. Mohany ◽  
S. Ziada
Keyword(s):  
Circular Cylinder ◽  
Lift Force ◽  
Cross Flow ◽  
Acoustic Resonance

The Numerical Simulation of Two-Degrees-of-Freedom Vortex-Induced Vibrations of Circular Cylinder with High Mass-Ratio

2013 ◽  
Vol 284-287 ◽  
pp. 557-561
Author(s):  
Jie Li Fan ◽  
Wei Ping Huang
Keyword(s):  
Circular Cylinder ◽  
Drag Force ◽  
Frequency Ratio ◽  
Lift Force ◽  
Degrees Of Freedom ◽  
Cross Flow ◽  
High Mass ◽  
Mass Ratio ◽  
Main Frequency ◽  
Line Amplitude

The two-degrees-of-freedom VIV of the circular cylinder with high mass-ratio is numerically simulated with the software ANSYS/CFX. The VIV characteristic is analyzed in the different conditions (Ur=3, 5, 6, 8, 10). When Ur is 5, 6, 8 and 10, the conclusion which is different from the cylinder with low mass-ratio can be obtained. When Ur is 3, the frequency of in-line VIV is twice of that of cross-flow VIV which is equal to the frequency ratio between drag force and lift force, and the in-line amplitude is much smaller than the cross-flow amplitude. The motion trace is the crescent. When Ur is 5 and 6, the frequency ratio between the drag force and lift force is still 2, but the main frequency of in-line VIV is mainly the same as that of cross-flow VIV and the secondary frequency of in-line VIV is equal to the frequency of the drag force. The in-line amplitude is still very small compared with the cross-flow amplitude. When Ur is up to 8 and 10, the frequency of in-line VIV is the same as the main frequency of cross-flow VIV which is close to the inherent frequency of the cylinder and is different from the frequency of drag force or lift force. But the secondary frequency of cross-flow VIV is equal to the frequency of the lift force. The amplitude ratio of the VIV between in-line and cross-flow direction is about 0.5. When Ur is 5, 6, 8 and 10, the motion trace is mainly the oval.

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.

The Effect of Rotational Friction on the Stability of Short-Tailed Fairings Suppressing Vortex-Induced Vibrations

2011 ◽  
Author(s):  
Gustavo R. S. Assi ◽  
Peter W. Bearman ◽  
Michael A. Tognarelli ◽  
Julia R. H. Rodrigues
Keyword(s):  
Circular Cylinder ◽  
Lift Force ◽  
Flow Direction ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Critical Limit ◽  
Vortex Induced Vibrations ◽  
Equivalent Length ◽  
Low Mass ◽  
The Stability

Experiments have been carried out on a free-to-rotate short-tail fairing fitted to a rigid length of circular cylinder to investigate the effect of rotational friction on the stability of this type of VIV suppressor. Measurements of the dynamic response are presented for models with low mass and damping which are free to respond in the cross-flow and streamwise directions. It is shown how VIV can be reduced if the fairing presents a rotational friction above a critical limit. In this configuration the fairing finds a stable position deflected from the flow direction and a steady lift force appears towards the side the fairing has deflected. The fluid-dynamic mechanism is very similar to that observed for a free-to-rotate splitter plate of equivalent length.

Effect of Acoustic Resonance on the Dynamic Lift Forces Acting on Two Tandem Cylinders in Cross-Flow

2006 ◽  
Author(s):  
Atef Mohany ◽  
Samir Ziada
Keyword(s):  
Lift Force ◽  
Lift Coefficient ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Transverse Modes ◽  
Tandem Cylinders ◽  
Abrupt Changes ◽  
Drastic Increase ◽  
Lift Forces ◽  
Force Components

Direct measurement of the dynamic lift force for the case of two tandem cylinders in cross-flow during acoustic resonance is performed. Two spacing ratios inside the proximity interference region, L/D = 2.5 and 3, are considered. During the tests, the acoustic transverse-modes of the duct housing the cylinder are self-excited. In the absence of acoustic resonance, the measured dynamic lift coefficient agrees well with those reported in the literature. When the acoustic resonance is initiated, a drastic increase in the dynamic lift coefficient is observed, especially on the downstream cylinder. This is associated with abrupt changes in the phase between the lift forces and the acoustic pressure. The dynamic lift forces on both cylinders are also decomposed into in-phase and out-of-phase components, with respect to the resonant sound pressure. The lift force components for the downstream cylinder are found to be dominant. Moreover, the out-of-phase component of the lift force on the downstream cylinder is found to become negative over two different ranges of flow velocity and to virtually vanish between these two ranges. Acoustic resonance is therefore generated over two ranges of reduced velocity separated by a non-resonant range near the velocity of frequency coincidence. The out-of-phase lift component of the downstream cylinder is found to control the occurrence of acoustic resonance, whereas the in-phase lift component seems to cause slight variations in the acoustic resonance frequency.

The Aeroacoustic Response of a Single Square Cylinder in Confined Cross Flow

2021 ◽  
Author(s):  
Mahmoud Shaaban ◽  
Atef Mohany
Keyword(s):  
Circular Cylinder ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Acoustic Mode ◽  
Edge Length ◽  
Bluff Bodies ◽  
Square Cylinder ◽  
Unstable Flow ◽  
Response Characteristics ◽  
Flow Fluctuations

Abstract Unstable flow patterns around arrangements of bluff bodies in different engineering applications can give rise to pressure oscillations, leading to excitation of strong acoustic resonance that can interrupt operation. In certain conditions, flow fluctuations arising from vortex shedding downstream of a circular cylinder are reported to excite severe acoustic resonance. On the other hand, cylinders of a square cross section are known to be particularly susceptible to mechanisms that involve coupling between the flow and a structural mode. It is not documented, however, if such coupling would occur between an acoustic mode and flow fluctuations downstream of a square cylinder. In this work, the possibility of excitation of acoustic resonance due to coupling between unsteady flow downstream of a single square cylinder with an acoustic cross mode of a rectangular duct is experimentally investigated. During the experiments, acoustic resonance was self-excited. Measurements of the acoustic pressure and the flow velocity are carried out for a single square cylinder of an edge length of 25.4 mm. Results show that aeroacoustic response characteristics for this configuration are not completely analogous to the case of a circular cylinder, with a number of features not reported before. A brief summary of the results is presented in this work.

TRANSONIC CROSS FLOW (M∞ = 0.8) OVER A CIRCULAR CYLINDER AT HIGH REYNOLDS NUMBERS

2012 ◽  
Vol 43 (5) ◽  
pp. 589-613
Author(s):  
Vyacheslav Antonovich Bashkin ◽  
Ivan Vladimirovich Egorov ◽  
Ivan Valeryevich Ezhov ◽  
Sergey Vladimirovich Utyuzhnikov
Keyword(s):  
Circular Cylinder ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds

scholarly journals LAMINAR FLOW PAST AN OSCILLATING CIRCULAR CYLINDER IN CROSS FLOW

2010 ◽  
Vol 18 (3) ◽  
Author(s):  
Pham Anh-Hung ◽  
Lee Chang-Yeol ◽  
Seo Jang-Hoon ◽  
Chun Ho-Hwan ◽  
Kim Hee-Jung ◽  
...  
Keyword(s):  
Laminar Flow ◽  
Circular Cylinder ◽  
Cross Flow ◽  
Flow Past
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