Effects of Free-End Condition on End-Cell-Induced Vibration

Kitagawa, Tetsuya; Fujino, Yozo; Kimura, Kichiro

doi:10.1006/jfls.1999.0214

Cited by 35 publications

(25 citation statements)

References 14 publications

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“…where f is the vortex-shedding frequency calculated from the vertical interval of vortexes and the vertical time-averaged velocity, was approximately 0.06, which is close to St of trailing vortex shown in Kitagawa et al [6]. From this result, it is deduced that the vortex associated with recirculation is separated periodically by the trailing vortex.…”

Section: Resultssupporting

confidence: 84%

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The effects of free surface and end cell on flow around a finite circular cylinder with low aspect ratio

2015

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Vortex-induced motion is an oscillatory phenomenon which occurs to a floating body with low aspect ratio. The basic phenomenological study about the effects of free surface and end cell on flow around a finite fixed circular cylinder was investigated in this study using particle image velocimetry and hydrodynamic force measurement. It was found from the former experiment that the wake of the cylinder is influenced by the both end cell and free surface. Blowup and back flow are generated from the end cell, and their effects are suspended by free surface. The result of hydrodynamic force measurement showed the effect of Reynolds number, Froude number, and the aspect ratio of the floating body on the hydrodynamic force. Fluctuating components of hydrodynamic coefficients decrease for increasing Reynolds number, Froude number, and the aspect ratio. On the other hand, the mean drag coefficient increases as Froude number increases and decreases as the aspect ratio increases. The interpretation to these results was discussed in comparison with flow structures observed in the experiment. In addition, it was found that the effect of Reynolds number on the mean drag coefficient changes at different aspect ratios. A possible interpretation to this phenomenon was proposed.

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Section: Resultssupporting

confidence: 84%

“…1. The phenomenon called end-cell-induced vibration (ECIV) was discovered by Kitagawa et al [6]. ECIV is the strong oscillation which occurs at one-third of flow velocity of VIV and it is caused by tip-associated vortex.…”

Section: Introductionmentioning

confidence: 99%

The effects of free surface and end cell on flow around a finite circular cylinder with low aspect ratio

2015

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“…A lower frequency at St % 0:07 was found in Kitagawa et al (1999) and was ascribed to the dynamics of the tip-vortices generated over the free-end of a model with h/d ¼25. In Kitagawa et al (2002) it was then highlighted that this spectral component was due to a non-alternate oscillation of the axial vorticity structures generated by the flow passing over the free-end, even if this motion was found to be highly irregular.…”

Section: Introductionmentioning

confidence: 83%

Experimental investigation on the aerodynamic loads and wake flow features of a low aspect-ratio circular cylinder

Iungo

Pii

Buresti

2012

Journal of Fluids and Structures

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a b s t r a c tAn experimental investigation on the flow features of the wake generated from a circular cylinder with finite height and placed vertically on a plane is presented. Through force measurements the mean drag coefficient is found to be roughly invariant by varying Reynolds number in a range between 6 Â 10 4 and 11 Â 10 4 . As for the fluctuating forces, a dominant spectral component is clearly detected for the signals of the cross-flow force. A spectral contribution with roughly the same Strouhal number is detected from velocity signals acquired, through hot-wire anemometry, in proximity to the lateral wake boundary; its energy is found to decrease by moving the probe away from the wake and upwards. Simultaneous velocity measurements showed that these fluctuations can confidently be ascribed to an alternate vortex shedding. Subsequently, dynamic measurements of the pressure field over the lateral surface and the free-end of the model were carried out, which highlight that the spectral component connected to vortex shedding is found over the lateral surface, with maximum energy at an azimuthal position just before the separation of the shear layers. The fluctuating energy connected to vortex shedding decreases by moving towards regions immersed in the separated wake, and with increasing vertical coordinate; as a matter of fact, above about half model height an evident energy peak cannot be detected anymore. This feature highlights that a regular alternate vortex shedding occurs only for the lower half-span of the model and that the remaining part is dominated by the upwash generated by the flow passing over the free-end. From the spectral analysis of the pressure measurements carried out over the model free-end no evidence of the presence of the spectral component connected to the alternate vortex shedding is found, as expected. However, a significant fluctuating energy is observed at lower dominating frequencies.

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“…On the other hand, an interesting large-amplitude response mode is found at higher reduced velocities outside the principal synchronization range [14,15], resulting in a large amplification of the drag coefficient. This vibration mode is due to a coupled streamwise-transverse motion, where the streamwise amplitude becomes non-negligible.…”

Section: Lock-in and Drag Amplification Phenomenonmentioning

confidence: 99%

Simplified numerical method for understanding the aeroelastic response of line slender structures under vortex shedding action

Vasallo¹,

Lorenzana²,

Foces³

et al. 2009

WIT Transactions on the Built Environment

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The lock-in and drag amplification phenomenon is studied in a flexible cantilever using a simplified fluid-structure interaction (FSI) algorithm. NavierStokes equations for incompressible flow have been solved in 2D in several transverse planes of the line-like structure. A fractional step scheme has been used to solve the fluid field. In each fluid plane, the displacements have been taken into account considering an Arbitrary Lagrangian Eulerian (ALE) approach. The stabilization of convection and diffusion terms has been achieved by means of orthogonal quasi-static subscales. No turbulence model has been included. In order to solve the structural problem, a monodimensional element for thin walled cross-section beams has been considered. The standard second order Newmark method has been used to include the dynamical behaviour equations. The wind has been considered to be an incompressible fluid acting on the structure in a series of planes that are independent among them, and transverse to the structure. For each period of time, the fluid problem was solved, the aeroelastic analysis was carried out, and the geometry of the mesh of each fluid plane was updated according to the structure displacements.

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Effects of Free-End Condition on End-Cell-Induced Vibration

Cited by 35 publications

References 14 publications

The effects of free surface and end cell on flow around a finite circular cylinder with low aspect ratio

The effects of free surface and end cell on flow around a finite circular cylinder with low aspect ratio

Experimental investigation on the aerodynamic loads and wake flow features of a low aspect-ratio circular cylinder

Simplified numerical method for understanding the aeroelastic response of line slender structures under vortex shedding action

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