Vortex-induced Response Research Articles

Effects of turbulent flows on vortex-induced oscillation of bridge girders with basic sections

This paper investigates the effects of turbulence characteristics such as turbulence intensity and scale on vortex-induced oscillation of bridge girders with basic sections. The basic sections are selected taking into account of various effects of turbulences on vortex-induced oscillation such as ; the maximum amplitude of vortex-induced oscillation is 1) reduced, 2) enlarged in some cases or 3) not changed by the existence of wind velocity fluctuations, which are referred from literature review. The vortex-induced responses of models are examined not only in grid-generated turbulent flows but also in actively simulated turbulences with large scale through an active gust generator. The effects of turbulence properties on vortex-induced response are evaluated in terms of the ratio of the maximum amplitude in turbulent flows to that in a smooth flow.

Vortex‐Induced Vibration of Circular Cylinders. I: Experimental Data

Vortexinduced response of a springmounted circular cylinder was observed in a lowspeed wind tunnel. Vertical (lift) displacement of the cylinder and velocity fluctuations in the near wake region of...

Vortex shedding from circular cylinders: Experimental data and a new model

Vortex-induced response of a spring-mounted circular cylinder was observed in the wind tunnel. Vertical displacement of cylinder and velocity fluctuations in the near wake were measured. The ‘lock-in’ or synchronization phenomenon, and its dependence on mechanical damping, were observed in detail. An analyical model with linear and nonlinear aerodynamic damping and linear parametric coupling was analyzed and compared with Experimental dta. with experimental data.

Effects of turbulence characteristics on vortex-induced oscillation of rectangular cylinders

This paper investigates the effects of turbulence properties such as turbulent intensity and scale on the vortex-induced oscillation of two-dimensional rectangular cylinders with aspect ratio of 2 and 5. An active gust generator consisted of two arrays of plates and airfoils is developed to produced the turbulent flows similar to natural wind in a wind tunnel. The power spectra of a generated turbulence successfully agree with the target ones in wide range of frequency, and the turbulence characteristics of generated flows approximately cover those of natural wind. The vortex-induced oscillation of rectangular cylinders are more strongly affected by the turbulence intensity than the turbulence scale. There is a slight tendency that the maximum amplitude of the vortex-induced response of the rectangular cylinder with aspect ratio of 5 reduces as the turbulence scale decreases.

Modeling spanwise correlation effects in the vortex-induced response of flexible bridges

Two methods for modeling the effect of imperfect spanwise correlation of aerodynamic forces on the vortex-induced response of long-span flexible bridges are described. These methods are based on a semi-empirical non-linear mathematical model for the vortex-induced response of bluff bodies and results of wind-tunnel tests on bridge-deck section models. Application of these methods requires the knowledge of the spanwise behavior of aerodynamic forces on a prototype bridge undergoing vortex-induced oscillation. A method of approximating this behavior using measured spanwise correlation of forces on a two-dimensional, rigid section model is described. Examples of the application of the proposed methods are provided.

Modeling spanwise correlation effects in the vortex-induced response of flexible bridges

Two methods for modeling the effect of imperfect spanwise correlation of aerodynamic forces on the vortex-induced response of long-span flexible bridges are described. These methods are based on a semi-empirical non-linear mathematical model for the vortex-induced response of bluff bodies and results of wind-tunnel tests on bridge-deck section models. Application of these methods requires the knowledge of the spanwise behavior of aerodynamic forces on a prototype bridge undergoing vortex-induced oscillation. A method of approximating this behavior using measured spanwise correlation of forces on a two-dimensional, rigid section model is described. Examples of the application of the proposed methods are provided.

Application of a General Technique for Prediction of Riser Vortex-Induced Response in Waves and Current

Abstract This paper describes applications of an extension to a recently developed calculation method for vortex-induced response of risers and tethers. The vortex-induced vibration response for the excited modes is generated using a semi-empirical formulation which is applied within a time domain calculation. This makes it possible to take account of the variation of flow properties along the riser length, as well as in time. The calculation method has been verified by comparison with model test data for vortex-induced response to surface vessel motions in still water. This paper presents applications of the technique for vortex shedding due to the combined action of current, surface vessel motions and waves. The mathematics of the extended prediction technique is described and results are illustrated by presenting typical vortex-induced responses for single-tube risers. The results of the prediction method are used to highlight the relative magnitudes and nature of vortex-induced response excited by currents, surface vessel motions and waves.

Mechanism of vortex-excited oscillations of a bridge deck

The results of a wind-tunnel study of vortex-induced response of a cable-stayed bridge deck are presented. A bridge section model was employed in smooth flow. The experiments included measurement of the model aerodynamic response and flow visualization. The results indicated existence of two mechanisms causing the vortex-induced model response. One is related to the Kármán voritces shed in the wake. The other mechanism is associated with occurrence of the motion-induced vortices.

Wind-tunnel study of effects of geometry modification on aerodynamics of a cable-stayed bridge deck

The results of a wind-tunnel study of the aerodynamic response and stability of a cable-stayed bridge deck are presented. A bridge section model was employed in smooth flow and the effects of modifying the bridge geometry were investigated. The results showed that the original bridge deck was unstable in torsion and exhibited high, vertex-induced, vertical oscillation. Streamlining of the deck resulted in improved aerodynamic performance, with an increase in the critical wind speed for torsional flutter and decrease in the vortex-induced response.

Wind-tunnel study of aerodynamic stability and response of a cable-stayed bridge deck

The results of a wind-tunnel study of the aerodynamic response and stability of a cable-stayed bridge deck are presented. A bridge section model was employed in smooth flow and the effects of relaxing the Froude number similarity and modifying the bridge geometry by the removal of traffic barriers were investigated. It was verified that the Froude number similarity can be relaxed. The results showed that the bridge deck was unstable in torsion. Removal of the traffic barriers resulted in improved bridge deck aerodynamic behavior, i.e. an increase in the critical wind speed for torsional flutter and a decrease in the vortex-induced response.

Vortex-Induced Response of a Flexible Cylinder in a Sheared Current

In this paper we outline a method for the approximate prediction of the static and lift responses of a flexible cylinder in a unidirectional variable stream. Our prediction is based on information derived from experimental results involving rigid cylinders forced to oscillate sinusoidally orthogonally to a uniform stream. Our approach represents the multifrequency lift response of a flexible cylinder in a sheared current by predicting a number of independently determined, monochromatic, multimode dynamic solutions. For each such multimode solution, our procedure allows the simultaneous evaluation of lift response frequency, amplitude, and phase between modes. A numerical example assuming bimodal solutions is included to illustrate our method for the geometry of a single-tube marine riser.

Vortex-Induced Response of a Flexible Cylinder in a Constant Current

In this paper we develop a method for the theoretical prediction of the static and lift responses of a flexible cylinder in a unidirectional constant current. Our theoretical prediction is based on information derived from experimental results involving rigid cylinders forced to oscillate sinusoidally orthogonally to a uniform stream. Our approach allows the prediction of a number of, independently determined, monochromatic, and multimode dynamic solutions. For each such multimode solution our procedure allows the simultaneous evaluation of lift response frequency, amplitude and phase between modes. Numerical examples assuming monomodal solutions are included to allow comparison of our theoretical predictions with experimental and other published theoretical results.

On the critical reduced velocity and the response characteristics of vortex-induced oscillations of bluff structural sections

This paper presents an investigation on vortex-induced deflectional oscillations of various bluff structural sections.With aid of a number of formerly reported works, it is noted that the onset critical reduced velocity Vcr, 0 of vortex-induced oscillations is characterized by slenderness ratio B/D where B and D signify projection of chord length to mean flow and that of height to the plane normal to mean flow.Experimental results indicate that critical reduced velocity of vortex-induced oscillations can be classified into four types. In the onset reduced critical velocity and slenderness ratio diagram, the two of four types show that Vcr, 0 increases linearly with slenderness ratio B/D, to which a majority of road bridge deck sections belongs, while other types show that the onset reduced velocity Vcr, 0 tends to be controlled by the Strouhal number. It should be-however noted that the equivalent lift farce coefficient CL or the maximum amplitude of vortex-induced responses relates dispersedly with geometrical shape of cross sections.