Experimental Investigation on the Stability of Parallel and Oblique Plates as Suppressors of Vortex-Induced Vibration

2013 ◽  
Author(s):  
Gustavo R. S. Assi ◽  
Guilherme S. Franco
Keyword(s):  
Cross Flow ◽  
Lateral Force ◽  
High Amplitude ◽  
Parallel Plates ◽  
Number Range ◽  
Vortex Induced Vibration ◽  
Plate Length ◽  
Low Mass ◽  
The Stability ◽  
Vibration Suppressor

Experiments have been carried out on models of free-to-rotate parallel and oblique plates fitted to a rigid section of circular cylinder to investigate the effect of plate length and oblique angle on the stability of this type of VIV (vortex-induced vibration) suppressor. Measurements of the dynamic response and trajectories of motion are presented for models with low mass and damping which are free to respond in the cross-flow and streamwise directions. It is shown that, depending on a combination of geometric parameters — such as plate length, plate angle and gap between plates and cylinder — devices might not be able to completely suppress VIV for the whole range of reduced velocities investigated. Plates with larger oblique angles turned to be less stable than parallel plates and induced high-amplitude vibrations for some specific reduced velocities. An undesirable steady lateral force was also observed to occur for all configurations and might be related to the existence of a large gap and oblique angles. Systems may present streamwise vibration due to strong flow separation and reattachment on the outer surface of plates with large oblique angles. Large angles may also increase drag. Experiments with a plain cylinder in the Reynolds number range from 3,000 to 20,000 have been performed to serve as reference. Reduced velocity was varied between 2 and 13.

The Effect of Plate Length on the Behaviour of Free-to-Rotate VIV Suppressors With Parallel Plates

2012 ◽  
Author(s):  
Gustavo R. S. Assi ◽  
Julia R. H. Rodrigues ◽  
Cesar M. Freire
Keyword(s):  
Reynolds Number ◽  
Cross Flow ◽  
Lateral Force ◽  
High Amplitude ◽  
Parallel Plates ◽  
Number Range ◽  
Plate Length ◽  
Low Mass ◽  
The Stability ◽  
Vibration Suppressor

Experiments have been carried out on free-to-rotate parallel plates fitted to a rigid section of circular cylinder to investigate the effect of plate length on the stability of this type of VIV (vortex-induced vibration) suppressor. Measurements of the dynamic response and trajectories are presented for models with low mass and damping which are free to respond in the cross-flow and streamwise directions. It is shown that, depending on a combination of geometric and strucutral parameters, parallel plates might not be able to completely suppress VIV for the whole range of reduced velocities investigated. Plates with length between 1.0 and 2.0 diameters showed instabilities and induced high-amplitude vibrations for some specific reduced velocities. Rotational friction was increased for a second run and all plates stabilised and suppressed VIV for the whole range of reduced velocities tested. An undesirable steady lateral force was also observed to occur for all configurations. Experiments with a plain cylinder in the Reynolds number range from 1,000 to 20,000 have been performed to serve as reference.

Investigation on the Stability of Parallel and Oblique Plates as Suppressors of Vortex-Induced Vibration of a Circular Cylinder

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Gustavo R. S. Assi ◽  
Guilherme S. Franco ◽  
Michaelli S. Vestri
Keyword(s):  
Circular Cylinder ◽  
Structural Parameters ◽  
Cross Flow ◽  
Separated Flow ◽  
High Amplitude ◽  
Parallel Plates ◽  
Number Range ◽  
Vortex Induced Vibration ◽  
Plate Length ◽  
The Stability

Experiments have been carried out with models of free-to-rotate parallel and oblique plates fitted to a rigid section of circular cylinder to investigate the effect of plate length and oblique angle on the stability of this type of vortex-induced vibration (VIV) suppressor. Measurements of the dynamic response and trajectories of motion are presented for models with low mass and damping which are free to respond in the cross-flow and streamwise directions. It is shown that, depending on a combination of some geometric parameters, the devices might not be able to completely suppress VIV for the whole range of reduced velocities investigated. Plates with larger oblique angles turned to be less stable than parallel plates and induced high-amplitude vibrations for specific reduced velocities. Systems may present streamwise vibration due to strong flow separation and reattachment on the outer surface of plates with large oblique angles. Large angles may also increase drag. Experiments with a plain cylinder in the Reynolds number range from 3000 to 20,000 have been performed to serve as reference. Reduced velocity was varied between 2 and 13. Two-dimensional numerical simulation of static systems at Re = 10,000 revealed that complex and fully separated flow regimes exist for almost all investigated cases. There is a good chance that systems with such geometric characteristics will be unstable unless other structural parameters are positively verified.

Experimental Evaluation of Pure In-Line Vortex Induced Vibration (VIVx) of Low Mass-Damping Ratio Cylinder

2016 ◽  
Author(s):  
Mohammad Mobasher Amini ◽  
Antonio Carlos Fernandes
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Damping Ratio ◽  
Cross Flow ◽  
Current Channel ◽  
Number Range ◽  
Vortex Induced Vibration ◽  
Numerical Studies ◽  
Lower Amplitude ◽  
Low Mass

Numerous experimental and numerical studies have been carried out to better understand and to improve prediction of cylinder VIV (vortex Induced Vibration) phenomenon. The behavior of cylinder due to in-line vibration (VIVx) has been neglected in the earlier studies because of its lower amplitude in comparison with cross flow vibration (VIVy). However, some researchers have studied VIVx in 2DOF along with VIVy. Recent investigations show that response amplitude of structure caused by VIVx is large enough to bring it to consideration. This study focuses on understanding the origin and prediction of VIVx amplitude exclusively in 1DOF and subcritical flow regime. The experiments were performed in current channel on bare circular cylinder with low mass-damping ratio in Reynolds number range Re = 10000 ∼ 45000.

Steering and Stability of Single-track Vehicles

1951 ◽  
Vol 5 (1) ◽  
pp. 191-213 ◽  
Author(s):  
R. A. Wilson-Jones
Keyword(s):  
Lateral Force ◽  
Front Wheel ◽  
Slip Angle ◽  
Single Track ◽  
Motor Cycle ◽  
Low Mass ◽  
Low Speeds ◽  
The Stability ◽  
Straight Ahead

The author briefly states the elementary principles of equilibrium and claims that the stability of the conventional bicycle or motor cycle is automatic except at very low speeds. This is because the steering automatically turns in the direction in which the machine is leaning and returns to the straight ahead position when the machine is restored to the vertical. The achievement of these effects is largely due to the “trail” of the front wheel. The causes of “steering roll” and “steering wobble” and the purpose of the inclination of the steering head, are examined, as are the effects of high and low mass centres and of the rider leaning with and against the machine. It is shown how the elementary principles of steering apply to various types of vehicle, including single-track vehicles in which the necessary lateral force comes mainly from camber thrust rather than slip angle. The results are given of experiments on varying amounts of “trail”, and a method of measuring slip angles is described which is applicable to motor cycles. Finally, a method of indicating the direction of the torque applied to the handlebars when entering, holding, and leaving a bend is described.

Wake-Induced Vibration (WIV) of Two Tandem Pre-Tensioned Flexible Cylinders

2013 ◽  
Author(s):  
Bijan Sanaati ◽  
Naomi Kato
Keyword(s):  
Amplitude Ratio ◽  
Cross Flow ◽  
Dynamic Responses ◽  
Flexible Cylinder ◽  
Number Range ◽  
Frequency Responses ◽  
Aspect Ratios ◽  
Tandem Cylinders ◽  
Low Mass ◽  
Lock In

It is believed that investigations on flow around pairs of cylinders can provide a better understanding of the interference effects than the cases involving larger numbers of cylinders. Studies that deal with the dynamic responses of multiple flexible cylinders with low mass ratios and high aspect ratios are few because of the complexities in the responses. In this paper, the effects of wake interference on the dynamic responses of two pre-tensioned flexible cylinders in tandem arrangement subjected to uniform cross-flow are investigated. The analysis results of the tandem cylinders are presented and compared with an isolated flexible cylinder. Two flexible cylinders of the same size, properties, and pretensions were tested at four different centre-to-centre separation distances, namely, 2.75, 5.5, 8.25 and 11 diameters. Reynolds number range is from 1400 to 20000 (subcritical regime). The aspect ratio of the cylinders is 162 (length over diameter). Mass ratio (cylinders mass over displaced water) is 1.17. The amplitude ratio of the CF vibration of the downstream cylinder, IL deflections of both cylinders, frequency responses in both CF and inline (IL) directions were analyzed. For all the examined separation distances, the downstream cylinder does not show build-up of upper branch (within the lock-in region of the classical VIV of the isolated cylinder). The initial distance between the tandem cylinders cannot remain constant. The distance decreases with reduced velocity because of the unequal IL deflection of tandem cylinders. From the CF frequency response of the lift (transverse) force of downstream cylinder, the highest vibration amplitude at all the separation distances occurs whenever their frequencies transitioned into second modal value. The frequency responses of the upstream cylinder cannot be greatly affected by the downstream cylinder even for small separations in contrast to the downstream cylinder.

Reynolds Number Effect on Vortex-Induced Vibration on a Two-Dimensional Circular Cylinder With Low Mass-Damping Parameter

2011 ◽  
Author(s):  
Juan B. V. Wanderley ◽  
Luiz F. Soares ◽  
Marcelo Vitola ◽  
Sergio H. Sphaier ◽  
Carlos Levi
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Lift Coefficient ◽  
The Body ◽  
Response Amplitude ◽  
Curvilinear Coordinates ◽  
Number Range ◽  
Vortex Induced Vibration ◽  
Damping Parameter ◽  
Low Mass

The vortex induced vibration (VIV) on a circular cylinder with low mass-damping parameter and low Reynolds number is investigated numerically as basis for applications on dynamics of risers used in the offshore oil and gas industry and as a first step before tackling the harder high Reynolds number problem. The cylinder is supported by a spring and a damper and free to vibrate in the transverse direction. The numerical solution of the Reynolds average Navier-Stokes equations written in curvilinear coordinates is obtained using an upwind and Total Variation Diminishing conservative scheme and the k-ε turbulence model is used to simulate the turbulent flow in the wake of the body. Results were obtained for the phase angle, response amplitude, frequency, and lift coefficient for a variation of reduced velocity from 2 to 12 and three different proportional variations of Reynolds number, 2000–6000, 2000–12000, and 2000–24000. The numerical results indicate the strong effect of the Reynolds number range on the response amplitude, lift coefficient, and frequency of oscillation for a low mass-damping parameter.

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.

Vortex-Induced Vibration Experiment Research of Two Cylinders in Tandem Arrangement

2013 ◽  
Author(s):  
Zhuang Kang ◽  
Weixing Liu ◽  
Wei Qin
Keyword(s):  
Degrees Of Freedom ◽  
Flow Direction ◽  
Cross Flow ◽  
Near Wake ◽  
Tandem Arrangement ◽  
Vortex Induced Vibration ◽  
Wake Interference ◽  
Vibration Experiment ◽  
Low Mass ◽  
Far Wake

The vortex-induced vibration of tandem arrangement of two cylinders compared with the single cylinder is more complicated, The double cylinder arranged in tandem, which is free to move in two degrees of freedom respectively, and which has low mass and damping. The present study shows that a critical centre-to-centre spacing can be used to distinguish the far and near wake interference. The streams in this test were uniform flow, ranging from 0.2m/s to 0.8m/s with the interval of 0.1m/s. The Re numbers are ranging from 22000 to 88000. The mass ratio of cylinder is low. For far wake interference, the downstream cylinder shows large amplitudes of response, therefore the wake induced vibration (WIV) is found. For near wake interference, both the upstream cylinder and downstream cylinder are exposed to an evident phenomenon of VIV, but the amplitude of upstream and downstream are less than that of single cylinders in cross-flow direction and in-line direction. We found the critical spacing to be 3.4 to 4.9.

Study on the Test Results of Cross-Flow Vortex-Induced Vibration of a Towed Circular Cylinder

2014 ◽  
Author(s):  
Wei-Wu Wu ◽  
Quan-Ming Miao ◽  
Yan-Xia Wang
Keyword(s):  
Circular Cylinder ◽  
Natural Frequency ◽  
Cross Flow ◽  
Test Cases ◽  
Test Results ◽  
Vortex Induced Vibration ◽  
Low Mass ◽  
Low Mass Ratio ◽  
Flow Vortex ◽  
Lock In

This paper gives a review on VIV experimental research. A detailed introduction of the experimental study on the cross-flow vortex-induced vibration of a towed circular cylinder in CSSRC’s towing tank is presented and classical VIV phenomena are explained and analyzed in this study. However, some results which are much different from those in the classical literatures in the past few decades are observed at the same time. For example, instead of reduced velocity Ur from 5 to 8, the “lock-in” region happened in the reduced velocity ranged from 10 to 14 in our tests, where the reduced velocity is calculated by the natural frequency. The non-dimensional frequency (oscillation frequency over natural frequency) of about 1.8 in the “lock-in” region is also different from that of 1.0 in the classical literatures. Interestingly, the author found that some of the results given by Moe and Wu (1990), Sarpkaya (1995), Govardhan and Williamson (2000), Pan zhiyuan (2005) and so on, reported the similar phenomenon. Since above listed papers have the same points of view, whether can we say that the results in this paper are possible for the case of low mass ratio. To conclude that, however, many questions need to be answered. In an effort to gain a better understanding of VIV phenomenon, this paper presents results of further analysis on the test cases and parameters.

An experimental investigation of vortex-induced vibration of a curved flexible cylinder

2021 ◽  
Vol 927 ◽  
Author(s):  
Banafsheh Seyed-Aghazadeh ◽  
Bridget Benner ◽  
Xhino Gjokollari ◽  
Yahya Modarres-Sadeghi
Keyword(s):  
Vortex Shedding ◽  
Flow Direction ◽  
Cross Flow ◽  
Mode Number ◽  
Radius Of Curvature ◽  
Mode Transition ◽  
Flexible Cylinder ◽  
Number Range ◽  
Vortex Induced Vibration ◽  
The Cross

Vortex-induced vibration of a curved flexible cylinder placed in the test section of a recirculating water tunnel and fixed at both ends is studied experimentally. Both the concave and the convex orientations (with respect to the incoming flow direction) are considered. The cylinder was hung by its own weight with a dimensionless radius of curvature of $R/D=66$ , and a low mass ratio of $m^{*} = 3.6$ . A high-speed imaging technique was employed to record the oscillations of the cylinder in the cross-flow direction for a reduced velocity range of $U^{*} = 3.7 - 48.4$ , corresponding to a Reynolds number range of $Re= 165 - 2146$ . Mono- and multi-frequency responses as well as transition from low-mode-number to high-mode-number oscillations were observed. Regardless of the type of curvature, both odd and even mode shapes were excited in the cross-flow directions. However, the response of the system, in terms of the excited modes, amplitudes and frequencies of the oscillations, was observed to be sensitive to the direction of the curvature (i.e. concave vs convex), in particular at higher reduced velocities, where mode transition occurred. Hydrogen bubble flow visualization exhibited highly three-dimensional vortex shedding patterns in the wake of the cylinder, where there existed spatial and temporal evolution of the vortex shedding modes along the length of the cylinder. The time-varying intermittent vortex shedding in the wake of the cylinder was linked to the spanwise travelling wave behaviour of the vortex-induced vibration response. The observed spatially altering wake corresponded to the multi-modal excitation and mode transition along the length of the cylinder.

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