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Showing papers on "Vortex-induced vibration published in 1992"


Journal ArticleDOI
TL;DR: In this paper, the flow patterns and the corresponding Strouhal number of four circular cylinders subjected to a cross-flow were analyzed at a subcritical Reynolds number of 2100, at a rotated square position, the wake of the frontmost cylinder shrinks significantly, yet maintains vortex shedding at a very small spacing ratio.

66 citations


Journal ArticleDOI
TL;DR: For a tall building of which aspect ratio is larger than 8, the resonant velocity of vortex induced vibration or the onset velocity of galloping can be within the design wind velocity as discussed by the authors.

60 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of wind-induced response of the plane shape of a super high-rise building with an assumed height of 600m, as well as the dynamic effects of the vibration were studied.

20 citations


Journal ArticleDOI
TL;DR: In this article, a theoretical analysis of the flow-induced flexural vibration of long-span gates at small openings is presented, which is based on a potential theory developed by Rayleigh for dissipative-wave radiation problems.

14 citations


Journal ArticleDOI
TL;DR: In this paper, a two-dimensional model study of a shell-type long-span gate under small gate opening was performed to measure the vibration frequency, the excitation ratio, and the trajectories of gate motion.

14 citations


Proceedings ArticleDOI
01 Jan 1992
TL;DR: In this article, a series of design observations were made concerning the importance of various vortex generator design parameters in minimizing engine face circumferential distortion, and the installed vortex generator performance was found to be a function of three categories of variables: the inflow conditions, the aerodynamic characteristics associated with the inlet duct, and design parameters related to the geometry, arrangement and placement of the vortex generators within the outlet duct itself.
Abstract: Computational fluid dynamics was used to investigate the management of inlet distortion by the introduction of discrete vorticity sources at selected locations in the inlet for the purpose of controlling secondary flow. These sources of vorticity were introduced by means of vortex generators. A series of design observations were made concerning the importance of various vortex generator design parameters in minimizing engine face circumferential distortion. The study showed that vortex strength, generator scale, and secondary flow field structure have a complicated and interrelated influence on the engine face distortion, over and above the initial geometry and arrangement of the generators. The installed vortex generator performance was found to be a function of three categories of variables: the inflow conditions, the aerodynamic characteristics associated with the inlet duct, and the design parameters related to the geometry, arrangement, and placement of the vortex generators within the outlet duct itself.

11 citations


Journal ArticleDOI
T. Nakamura1, K. Fujita1, K. Kawanishi1, N. Yamaguchi1, A. Tsuge1 
TL;DR: In this paper, the experimental results on turbulent buffeting forces generated both by air-water flow and by steam-water two-phase flow for the extreme pressure conditions up to 5.8 MPa and temperatures reaching 272oC were presented.
Abstract: This paper presents the experimental results on turbulent buffeting forces generated both by air-water flow and by steam-water two-phase flow for the extreme pressure conditions up to 5.8 MPa and temperatures reaching 272oC, the explanation of the mechanism producing these forces, and a method for evaluating tube response caused by two-phase flow. The main source of the buffeting forces in slug or froth two-phase flow is recognized to be the impact forces caused by the intermittently rising water slugs. The slug speed and the fluid forces acting on a tube are estimated, together with an estimation of the period of the occurrence of the rising water slug. The accuracy of this estimation method is proved by comparing the theoretical response with the measured one.

8 citations


Journal ArticleDOI
TL;DR: In this article, the authors present flow-induced vibration characteristics which were obtained in a model gate test and show that these properties are well predicted by dimensionless parameters, such as the reduced gate opening and the reduced velocity.
Abstract: Submerged long-span gates which dam wide rivers can undergo violent streamwise vibrations caused by vortex shedding beneath the gate. This study presents flow-induced vibration characteristics which were obtained in a model gate test. From the measured vibration frequencies and damping ratios in air and water, the level of fluid excitation and the added mass for small-amplitude gate vibrations are calculated and reduced to a dimensionless form. Thus, the vibration criteria are obtained. In addition, the average values of the maximum amplitudes of gate vibration were measured. The results of these experiments, taken as a whole, suggest that the flow-induced vibration characteristics of the long-span gates are well predicted by dimensionless parameters, such as the reduced gate opening and the reduced velocity.

5 citations


Proceedings ArticleDOI
01 Jan 1992

3 citations


01 Jan 1992
TL;DR: In this article, it was shown that with complete riser coverage the strake would achieve a vibration suppression level of 75% and that the vibration amplitude of the bare cylinder was reduced in critical flow regime.
Abstract: During the planning for an exploration well, a possible problem due to vortex induced vibration was highlighted. It was therefore decided to fit a suppression device to the conductor to control the level of structural vibration. Helival Strakes were chosen because of their proven track record in this type of application, and because of their low cost and east of fitment. It was not possible to predict the performance of the strake using analytical or empirical methods because of the nature of the coverage and the flow regimes present. A model test programme was therefore undertaken to determine the strakes performance in terms of its capacity to reduce the level of vibration and hydrodynamic drag. Results showed that with complete riser coverage the strake would achieve a vibration suppression level of 75% and that the vibration amplitude of the bare cylinder was reduced in the critical flow regime. Further work demonstrated that impressive levels of vibration suppression could be achieved with a reduced amount of strake coverage, provided that the strake was correctly positioned. Reducing the strake coverage also had a beneficial effect on the overall level of drag on the conductor. Both these effects were predicted by a recently developed mathematical model and details of this model are included in the paper.

2 citations



Journal ArticleDOI
TL;DR: In this article, the authors investigated flow-induced streamwise vibrations of elastically mounted rectangular cylinders and cut-out square cylinders in the reduced velocity range 1 U ND′ (where D′ is the dimension of the model perpendicular to the flow) at angles of incidence, α, in the range from 0 to 90°.

01 Jan 1992
TL;DR: In this paper, a semi-empirical vortex induced vibration model has been used to investigate the effects of spatial variation of wave and sheared current with increasing water depth in a realistic tensioned riser of fixed section.
Abstract: A semi-empirical vortex induced vibration model which has been validated against experimental tests is the subject of this paper investigating the effects of spatial variation of wave and sheared current with increasing water depth. A realistic tensioned riser of fixed section is extended into increasingly deep water to examine the variation of multi-modal vortex induced vibration. Some surprises arise in respect of the occasions when vibrations become of concern. This results from the localised nature of the regions of excitation for any mode of interest, when of course all modes which might possibly be excited are of interest. The interactive effects of wave frequencies with vortex shedding frequencies and riser natural frequencies are shown to be important in determining the likelihood and level of vibrations. The components of the model explain why the sometimes high levels of vibration predicted by less comprehensive models are not found in practice. The implications for case study investigations in respect of fatigue are highlighted to show the importance of an adequately detailed range of flow conditions. This is so since small variations can have a significant impact on the fatigue lives.

01 Jan 1992
TL;DR: In this article, the authors describe a new method for reducing vortex induced vibrations of structures, by introducing a second phase (air) in the vicinity of the structure. But the air was released from manifolds attached to the structure and the amplitude of vibrations and the forces on the structure were measured.
Abstract: Vortex shedding induced oscillations of marine structures such as, risers platform members and cold water pipes is an important fluid-structure interaction phenomenon since it can lead to structural damage and even sometimes to destructive failures. To avoid failures of cylindrical structures in uniform or sheared flows one has to use means of suppressing or decorrelating the vortices shed behind it. In this paper we describe a new method for reducing vortex induced vibrations of structures, by introducing a second phase (air) in the vicinity of the structure. Laboratory experiments were carried out in 1 m deep water flume for three current speeds (u) of 0.25 m/s, 0.45 m/s and 0.8 m/s. The air was released from manifolds attached to the structure. The amplitude of vibrations and the forces on the structure were measured. It was found that the amplitude of vibration was reduced by 82% when air was released at 0.5L and 0.4L (L being the cylinder length) simultaneously. Furthermore, the mean drag force on the structure is reduced by 13% as compared to a bare cylinder. A semi-empirical equation relating the amplitude reduction to the air flow required has been derived.


Journal ArticleDOI
TL;DR: In this paper, the authors considered the possibility of intense mixing of a viscous fluid in the gap between two quasiconcentric cylinders, with one of the cylinders performing high-frequency vibrations about its axis.
Abstract: We consider the possibility of intense mixing of a viscous fluid in the gap between two quasiconcentric cylinders, with one of the cylinders performing high-frequency vibrations about its axis. The motion of the fluid is described by Navier-Stokes equations for the axisymmetric case. The stream function is represented by a generalized Fourier series. The small parameter is the ratio of the vibration amplitude to the radius of the external cylinder. Calculations carried out in the zeroth approximation produced the pattern of stream lines for various Reynolds numbers, vibration amplitudes, and ratios of external and internal radii. The mixing intensity was found to increase substantially with the reduction of the gap between the cylinders, whereas variation of the ratio of the vibration amplitude to the Reynolds number did not produce marked qualitative changes. The fluid flow in this system generates a contraction semigroup, which makes it possible to derive the ergodicity criterion for the stream function.

Journal ArticleDOI
TL;DR: In this paper, a cantilever is mounted across a mainstream flow while subjected to another jet injected parallel to the test cylinder, and the dimensionless vibration displacement amplitude was measured in the transverse direction (lift force direction) as well as in the streamwise direction (drag force direction).
Abstract: Some of the experimental features of the dynamic response of a cantilever subjected to two streams of air at right angles to each other are reported. The cantilever is mounted across a mainstream flow while subjected to another jet injected parallel to the test cylinder. The dimensionless vibration displacement amplitude was measured in the transverse direction (lift force direction) as well as in the streamwise direction (drag force direction) while varying the secondary jet flow velocity. It was found that in the vicinity of the cylinder a secondary jet can be used to reduce the dimensionless transverse vibration displacement amplitude in the lock-in region and increase it outside the lock-in region. The effect of jet injection on the streamwise direction vibration is to increase it for all reduced velocities considered.