Study on the Suppression of Vortex Induced Oscillation of Cylinder by Forward Jets

2020 ◽  
Author(s):  
S. S. Dai ◽  
D. Tang ◽  
B. A. Younis ◽  
G. Q. Fu
Keyword(s):  
Cross Flow ◽  
Critical Value ◽  
Practical Application ◽  
Ocean Engineering ◽  
Saturation Regime ◽  
Cylindrical Structures ◽  
Suppression Effect ◽  
Flow Displacement ◽  
Flow Variables ◽  
Forward Jets

Abstract Oscillation induced by vortex shedding often causes fatigue damage of slender cylindrical structures in many engineering fields, so it is significant to study the suppression of vortex induced oscillation. We focus on the methods of experimental test to study on the suppression effect of vortex induced oscillation of cylinder with single freedom at Reynolds number of 2.4 × 104. We designed a set of device with forward water jet to suppress vortex induced oscillation. We found the most notable observation from a serials of experiments: reduction of displacement of cylinder exhibits two distinct modes separated by a sudden and very pronounced decrease in the extent of cross-flow displacement at a critical value of the geometric and flow variables followed by what appears to be a saturation regime where no further decrease is observed. These results will provide some meaningful and evaluable references for practical application in ocean engineering.

Flow-induced Instabilities of Cylindrical Structures

1987 ◽  
Vol 40 (2) ◽  
pp. 163-175 ◽  
Author(s):  
Michael P. Paidoussis
Keyword(s):  
Annular Flow ◽  
Dynamical Behavior ◽  
Cross Flow ◽  
Axial Flow ◽  
Internal Flow ◽  
Internal Flows ◽  
Cylindrical Structures ◽  
Curved Pipes ◽  
The Stability ◽  
The Many

A kaleidoscopic view of the many diverse and interesting instabilities are presented, to which cylindrical structures are susceptible when in contact with flowing fluids. The physical mechanisms involved are discussed in each case, to the extent that they are understood, and the degree of success of available mathematical models is assessed. Four classes of problems are dealt with, according to the disposition of the flow vis-a`-vis the cylindrical structures: (a) instabilities induced by internal flows in tubular structures; (b) instabilities of solitary or clustered cylinders due to external axial flow; (c) annular-flow-induced instabilities of coaxial beams and shells; (d) instabilities of arrays of cylinders subject to cross-flow. In the first class of problems, the stability of straight tubular beams and cylindrical shells conveying fluid is discussed first, followed by the stability of curved pipes containing flow. In the second class of problems, the instabilities of solitary and clustered cylinders subjected to an external axial flow are treated, and their dynamical behavior is compared to that of systems with internal flow. The third class of problems involves annular flow in coaxial systems of beams and/or shells. Cross-flow-induced instabilities of clustered cylinders, in the form of arrays of different geometrical patterns, are the last class of problems considered; they are fundamentally distinct from the foregoing in terms of the fluid mechanics of the problem, for in this case the flow field is not irrotational—not even approximately.

Interference Effect of Wake Body on the Cross Flow Oscillation of a Square Cylinder in Uniform Flow

2009 ◽  
Author(s):  
Yusuke Kawabata ◽  
Takeshi Haginoya ◽  
Mizuyasu Koide ◽  
Tsutomu Takahashi ◽  
Masataka Shirakashi
Keyword(s):  
Interference Effect ◽  
Cross Flow ◽  
Elastic Vibration ◽  
Uniform Flow ◽  
Longitudinal Vortex ◽  
Square Cylinder ◽  
Suppression Effect ◽  
Strip Plate ◽  
Karman Vortex ◽  
Viv Suppression

Wind tunnel experiments are carried out to investigate interference effect of wake body on cross flow vibration of a square cylinder in uniform flow. The side length d of the square cylinder is 26∼40 mm and the length le = 315 mm. As the wake body, a strip-plate of width w = d is set downstream the square cylinder with a gap s in cruciform arrangement. The length of the plate ld is varied from infinity, i.e. full measuring section height, to ld/d = 1. Both the Karman vortex excitation (K-VIV) and the galloping are suppressed by the ld/d = ∞ plate in the non-dimensional gap range of 1.6<s/d ≦ 4, although the mechanisms are completely different between the two oscillations. The longitudinal vortex excitation (L-VIV) found in the previous work is confirmed to be induced by the plate at around s/d = 1.4 for the systems with various dimensions and structure parameters. The K-VIV suppression effect is virtually the same for the wake plates with ld/d≧10, and becomes less definite for shorter plates when ld/d ≦ 6. The galloping suppression effect persists up to the shortest wake plate of ld/d = 1 at s/d<2. The L-VIV is observed for plates of ld/d≧6, with weaker degree for shorter plates. The K-VIV seems to be enhanced by ld/d = 2, 4, 6 plates at 1≦s/d≦2 (EK-VIV). By setting the wake plate with ld/d = 1 or 2 at s/d around 0.3, a new type of fluid-elastic vibration is induced as an interference effect of wake body (WBI-FEV). A method is presented to predict fluid-elastic vibrations to which the Van der Pol equation does not apply. The prediction by this method agrees well with measured WBI-FEV for the ld/d = 2 plate.

The Application of Computational Fluid Dynamics to Railway Aerodynamics

1993 ◽  
Vol 207 (2) ◽  
pp. 133-141 ◽  
Author(s):  
A P Gaylard
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Cross Flow ◽  
Practical Application ◽  
High Speed Rail ◽  
Promising Strategy ◽  
Temperature Environment ◽  
Computational Work ◽  
Computational Fluid Dynamics Cfd

The growing application of computational fluid dynamics (CFD) to railway aerodynamics is described. After cautioning against overselling the capabilities of CFD codes, a review is presented of the more significant computational work undertaken in this field. Three recent applications of CFD are examined: (a) a high-speed rail vehicle in a cross-wind; (b) cross-flow impingement on a freight vehicle in the Channel Tunnel; (c) the temperature environment in a stationary passenger train. Comparative experimental data are offered for each of the above. An analysis of these applications is used to derive a promising strategy for the practical application of CFD.

Resonance in Flow-Induced Cable Vibration: Analytical Prediction and Numerical Simulation

2005 ◽  
Author(s):  
M. K. Kwan ◽  
R. R. Hwang ◽  
C. T. Hsu
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Cross Section ◽  
Flow Direction ◽  
Cross Flow ◽  
Transverse Cross Section ◽  
Analytical Prediction ◽  
Water Flows ◽  
Flow Displacement ◽  
The Cross

Flow-induced resonance for a two-end hinged cable under uniform incoming flows is investigated using analytical prediction and numerical simulation. In this study, the fundamental mode is analyzed for simplicity. First, based on a series of physical judgments, the approximate cable trajectory is predicted — the whole cable vibrates as a standing wave, with its locus on the transverse cross-section having a convex “8”-like shape. To find the exact path, however, experiment or numerical simulation is necessary. Hence, a bronze cable at aspect ratio (length/diameter) of 100 under water flows at Reynolds number (based on cable diameter and incoming velocity) of 200 is computed. The result confirms our predictions. Moreover, it is found that the amplitude of the cross-flow displacement is much higher than that of the streamwise displacement, despite the higher streamwise fluid force. As a consequence, energy transfer from fluid to solid is maximized in the cross-flow direction.

scholarly journals On the Beltramian motion of the bidirectional vortex in a conical cyclone

2017 ◽  
Vol 828 ◽  
pp. 708-732
Author(s):  
Timothy A. Barber ◽  
Joseph Majdalani
Keyword(s):  
Cross Sections ◽  
Accurate Determination ◽  
Cross Flow ◽  
Numerical Data ◽  
Divergence Angle ◽  
Rocket Engines ◽  
Bulk Motion ◽  
Half Angle ◽  
Liquid Rocket ◽  
Flow Variables

In this work, an exact Eulerian model is used to describe the steady-state motion of a bidirectional vortex in a conical chamber. This particular model is applicable to idealized representations of cyclone separators and liquid rocket engines with slowly expanding chamber cross-sections. The corresponding bulk motion is assumed to be non-reactive, rotational, inviscid and incompressible. Then, following Bloor & Ingham (J. Fluid Mech., vol. 178, 1987, pp. 507–519), the spherical Bragg–Hawthorne equation is used to construct a mathematical model that connects the solution to the swirl number and the cone divergence angle. Consequently, a self-similar formulation is obtained independently of the cone’s finite body length. This enables us to characterize the problem using closed-form approximations of the principal flow variables. Among the cyclonic parameters of interest, the mantle divergence angle and the maximum cross-flow velocity are obtained explicitly. The mantle consists of a spinning cone that separates the circumferential inflow region from the central outflow. This interfacial layer bisects the fluid domain at approximately 60 per cent of the cone’s divergence half-angle. Its accurate determination is proven asymptotically using two different criteria, one being preferred by experimentalists. Finally, recognizing that the flow in question is of the Beltramian type, results are systematically described over a range of cone angles and spatial locations in both spherical and cylindrical coordinates; they are also compared to available experimental and numerical data.

Vortex-Induced In-Line Vibration and Random Vibration of a Circular Cylinder Under Various Inflow Conditions

2010 ◽  
Author(s):  
Takashi Nishihara ◽  
Yuzuru Eguchi
Keyword(s):  
Circular Cylinder ◽  
Random Vibration ◽  
Practical Importance ◽  
Cross Flow ◽  
Cylindrical Structures ◽  
Response Characteristics ◽  
Inflow Turbulence ◽  
Flow Induced Vibrations ◽  
Yaw Angle ◽  
Inflow Conditions

The flow-induced vibrations (FIV) of cylindrical structures subjected to a cross flow have been investigated in a number of studies owing to their practical importance. The results of these studies have been compiled into guidelines for the evaluation of FIV of cylindrical structures. However, the applicability of the guidelines to cases with upstream structures and with an oblique inflow has not been fully examined. In this paper, we describe the response characteristics of vortex-induced in-line vibration and random vibration of a circular cylinder under various inflow conditions. Water tunnel tests were conducted on a circular cylinder in a cross flow at three yaw angles of 0, 30 and 45 degrees to clarify the effects of the yaw angle on vortex-induced in-line vibration and random vibration. The vibration amplitudes of a circular cylinder downstream of another circular cylinder of five times larger diameter were also measured to investigate the effects of inflow turbulence generated by an upstream cylinder. The tests were conducted for two different relative locations of the upstream cylinder in the same reduced-velocity range as that of the single-cylinder tests. The response amplitudes and onset flow velocities obtained by the tests were compared with values predicted using the cosine law and the guidelines to verify the evaluation methods in the guidelines.

Vortex-Shedding Response of Long Cylindrical Structures in Shear Flow

1988 ◽  
Vol 110 (1) ◽  
pp. 24-31 ◽  
Author(s):  
E. Wang ◽  
A. K. Whitney ◽  
K. G. Nikkel
Keyword(s):  
Shear Flow ◽  
Vortex Shedding ◽  
Solution Method ◽  
Lift Coefficient ◽  
Cross Flow ◽  
Quantitative Agreement ◽  
Cylindrical Structures ◽  
Fluid Damping ◽  
Energy Dissipated ◽  
Random Vibration Analysis

The response of cylindrical structures to vortex shedding in a vertically sheared cross flow is analyzed. In contrast to the uniform cross-flow case, shear flow can excite more than one modal frequency at a time. Thus, the net response of the structure is a superposition of several vibration modes. The amplitude of each mode is determined by a balance between energy fed into the structure over a “locked-on” region of the structure and energy dissipated by fluid damping over the remainder of the structure. A solution method based on random vibration analysis is developed that uses an empirically derived lift coefficient and correlation length models. The technique is capable of handling both uniform and sheared (depth-varying) current profiles. Good quantitative agreement is found between the present method and the very limited field data available for shear flows, although it is concluded that the shear conditions in the tests were not sufficiently strong to validate the theory conclusively. The results show how using uniform-flow approximations to treat shear flow cases can significantly overpredict vibration amplitudes caused by vortex shedding.

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