Vortex Induced Vibration Attenuation Of Circular Cylinders With Low Mass And Damping
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Vortex Induced Vibration Attenuation Of Circular Cylinders With Low Mass And Damping
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Author : Mas̆a Branković
language : en
Publisher:
Release Date : 2004
Vortex Induced Vibration Attenuation Of Circular Cylinders With Low Mass And Damping written by Mas̆a Branković and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with Artificial islands categories.
Vortex Induced Vibration Attenuation Of Circular Cylinders With Low Mass And Damping
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Author :
language : en
Publisher:
Release Date : 2004
Vortex Induced Vibration Attenuation Of Circular Cylinders With Low Mass And Damping written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.
Flow Induced Vibration Of Circular And Square Cylinder With Low Mass And Damping
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Author : Jisheng Zhao
language : en
Publisher:
Release Date : 2012
Flow Induced Vibration Of Circular And Square Cylinder With Low Mass And Damping written by Jisheng Zhao and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
This thesis investigates cross-flow flow-induced vibration of elastically mounted rigid circular and square cylinders with low mass and damping ratio over a range of low and vibration parameters. In particular, two typical body oscillator phenomena of flow-induced vibration, vortex-induced vibration and galloping, are studied experimentally. Thus, the study consists of two main parts. The first part, using simultaneous displacement, force and vorticity measurements, investigates the dynamic response of a circular cylinder undergoing transverse free vortex-induced vibrations and controlled trajectory-following vibrations. The second part characterises the amplitude and frequency responses of a square cylinder with angle of attack variation. Despite extensive work has been undertaken to understand the fundamental characteristics of free and forced vibrations of a circular cylinder, there are still a number of unresolved questions in the literature concerning the similarities and differences between the free and forced vibration cases. In order to directly compare these two vibration cases, a low-friction air-bearing rig and a real-time feedback control system were therefore designed and implemented in experiments. The major results obtained show that the transverse lift force and the decomposed vortex force experienced by a cylinder forced to follow the trajectory of free VIV are identical to the free vibration case, when both the total phase and the vortex phase relative to the body motion are constantly stable. However, significant differences between the two vibration cases are found at a reduced velocity located in the middle upper branch of VIV where largest-scale body vibration occur with complex switching phenomena in the total phase and the vortex phase. The results from the second part, flow-induced vibration of a square cylinder with angle of attack variation, show that the cylinder, as expected, experiences galloping at the zero angle of attack orientation (0 degree) and vortex-induced vibration at the diamond orientation (45 degree). As the angle of attack is varied from 45 degree to 0 degree, the body can undergo combinations of both vortex-induced vibration and galloping in a mixed response region. In this region, the oscillation amplitude response exhibits a new branch that exceeds the responses resulting from the two body-oscillator phenomena independently. For velocities above this resonant region, the body oscillation frequency splits into two diverging branches. Further, analysis of the amplitude reveals that the transition between galloping and vortex-induced vibrations occurs over a narrow range of angle of incidence. Despite the rich set of states found in the parameter space the vortex shedding modes remain very similar to those found previously in vortex-induced vibration.
Vortex Induced Vibration On A Two Dimensional Circular Cylinder With Low Reynolds Number And Low Mass Damping Parameter
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Author :
language : en
Publisher:
Release Date : 2015
Vortex Induced Vibration On A Two Dimensional Circular Cylinder With Low Reynolds Number And Low Mass Damping Parameter written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Modelling And Analysis Of Vortex Induced Vibrations Of Rigid And Flexible Cylinders
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Author : Hossein Zanganeh
language : en
Publisher:
Release Date : 2014
Modelling And Analysis Of Vortex Induced Vibrations Of Rigid And Flexible Cylinders written by Hossein Zanganeh and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
Vortex-induced vibration (VIV) is a fundamental phenomenon commonly encountered in various practical engineering. Owing to the complexities associated with this phenomenon, modelling and prediction of VIV is a challenging task. In this research, a new predictive phenomenological model is developed for VIV of an elastically mounted rigid cylinder subjected to a fluid flow and free to vibrate in both cross-flow (CF) and in-line (IL) directions. The ensuing dynamical system is based on double Duffing-van der Pol (structural-wake) oscillators with the two structural equations containing both cubic and quadratic nonlinear terms. The cubic nonlinearities capture the geometrical coupling of CF/IL displacements excited by hydrodynamic lift/drag forces whereas the quadratic nonlinearities allow the fluid-structure interactions. The model predictions are extensively compared with published and in-house experimental results. Experiments are carried out at the Department's towing tank to calibrate and validate numerical prediction results. Comparisons illustrate the qualitative resemblance between experimental and prediction results, highlighting how the new model can capture several important VIV characteristics including a two-dimensional lock-in, jump and hysteresis phenomenon, and figure-of-eight trajectory tracing the periodically coupled CF/IL oscillations. Moreover, the parametric studies reveal the important effect of geometrical nonlinearities, mass ratio, damping ratio and natural frequency ratio. Insights into hydrodynamic properties such as VIV-induced mean drag, added mass and damping are drawn based on the newly proposed model via analytical-numerical approaches and comparisons with published literature. Consequently, the new prediction model is applied to the VIV analysis of flexible circular cylinders subjected to uniform and linearly sheared currents. To capture a three-dimensional aspect of the flexible cylinder experiencing VIV, nonlinear equations of CF, IL and axial structural oscillations are considered to be coupled with the distributed van der Pol wake-oscillators. Governing equations are numerically solved via a space-time finite difference scheme, and the obtained numerical results highlight several aspects of VIV of elastic cylinders along with the axial motion effects. Apart from the validation of the numerical model with published experimental results, this study reveals how the effect of axial motion and its nonlinear coupling with the two transverse CF/IL motions can be very important. These depend on the reduced velocity, the fluid-structure parameters, the single or multi-mode lock-in condition, and the standing-wave versus travelling-wave features.
Vortex Induced Vibration And Forced Oscillation Motion Of A Circular Cylinder Fitted With A Single Spanwise Tripwire
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Author : Ehsan Vaziri
language : en
Publisher:
Release Date : 2021
Vortex Induced Vibration And Forced Oscillation Motion Of A Circular Cylinder Fitted With A Single Spanwise Tripwire written by Ehsan Vaziri and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
This experimental study consisted of two main parts. The first part investigated the control induced by a spanwise tripwire on a circular cylinder undergoing one-degree-of-freedom vortex-induced vibration (VIV). The cylinder vibrates in the cross-stream direction as a result of the fluid forcing in a recirculating water tunnel. Changing mass and damping ratios in the test rig allowed the investigation at different VIV response branches. The tripwire diameter was 6.25% of the cylinder diameter. Experimental research was conducted by attaching the large-scale tripwire along the span of the cylinder at various angular positions ranging from 0° to 180° (with respect to the most upstream point of the cylinder). Along with measuring the trajectory of the cylinder motion, the instantaneous velocity field in the near wake of the cylinder was obtained simultaneously at a fixed Reynolds number of 10,000 (based on the cylinder diameter) using a Particle Image Velocimetry (PIV) system. Various vortex-formation modes induced by the tripwire were observed. It was shown that the oscillation pattern, frequency, and amplitude of the cylinder can be altered significantly depending on the angular position of the tripwire and the VIV response branch. For specific tripwire positions, increases of up to 52 times and decreases of up to 98% were identified in the oscillation amplitude of the tripped cylinder compared to the amplitude of the clean cylinder.The second part of the study investigated the effects of the tripwire on the flow structure behind a circular cylinder forced to oscillate harmonically at prescribed amplitudes and frequencies in the cross-stream direction. Oscillation amplitudes are 0.05, 0.3 and 0.6 times the cylinder diameter, and oscillation frequencies are 0.61, 0.8, and 1 times the vortex shedding frequency of the stationary clean cylinder counterpart. For a fixed oscillation amplitude and frequency, the tripwire can either induce intermittent switching between various vortex shedding modes or cause a wake mode to be dominant during the entire observed oscillation motion by altering the vortex shedding mechanism. The wake of the tripped cylinder undergoing the lowest amplitude forced oscillation motion showed resemblance to the wake of the stationary tripped cylinder.
Vortex Induced Vibrations Of A Pivoted Circular Cylinder And Their Control Using A Tuned Mass Damper
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Author : Sina Kheirkhah
language : en
Publisher:
Release Date : 2011
Vortex Induced Vibrations Of A Pivoted Circular Cylinder And Their Control Using A Tuned Mass Damper written by Sina Kheirkhah and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Vortex-induced vibrations of a pivoted circular cylinder and control of these vibrations were investigated experimentally.
Vortex Induced Vibration Of Circular Cylinders
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Author : Indranil Goswami
language : en
Publisher:
Release Date : 1992
Vortex Induced Vibration Of Circular Cylinders written by Indranil Goswami and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1992 with categories.
On Vortex Shedding And Prediction Of Vortex Induced Vibrations Of Circular Cylinders
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Author : Karl Henning Halse
language : en
Publisher:
Release Date : 1997
On Vortex Shedding And Prediction Of Vortex Induced Vibrations Of Circular Cylinders written by Karl Henning Halse and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1997 with Vortex-motion categories.
Vortex Induced Vibration Of A Circular Cylinder
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Author : 朱執均
language : en
Publisher:
Release Date : 2011
Vortex Induced Vibration Of A Circular Cylinder written by 朱執均 and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.