scholarly journals Application of SPOD analysis to PIV data obtained in the wake of a circular cylinder undergoing vortex induced vibrations

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Christopher Mark O'Neill ◽  
Yannick Schubert ◽  
Moritz Sieber ◽  
Robert Martinuzzi ◽  
Chris Morton
Keyword(s):  
Circular Cylinder ◽  
Lower Branch ◽  
Dynamical Models ◽  
Vortex Induced Vibrations ◽  
Mode Pair ◽  
Low Mass ◽  
Distinct Frequency ◽  
Low Mass Ratio ◽  
Proper Orthogonal ◽  
Modal Dynamics

Vortex induced vibrations (VIV) of a circular cylinder have been investigated experimentally using a cyberphysical apparatus with m∗ = 8, ζ = 0.005, and Re = 4000. This study considers the application of proper orthogonal decomposition (POD) and spectral POD (SPOD) analysis to the wake dynamics of the low-mass-ratio VIV of a circular cylinder in the lower branch at U∗ = 7.5. SPOD has been previously shown to better separate frequency-centered modal dynamics, compared to POD. Coherent POD and SPOD modes were compared and the newly separated third SPOD mode pair was found to have a periodicity characteristic of vortex shedding and a peak in the temporal coefficient spectra at St = f D/U∞ = 0.2248. The literature has identified that the wake dynamics within the lower branch are synchronized to the cylinder motion; however the present study suggests that some hidden dynamics persist at the Strouhal frequency. Low order models based on the first eight POD and SPOD modes were compared, and it was found that the filtering operation in SPOD removes the uncorrelated stochastic energy component of the POD modes while producing a comparable representation of the coherent deterministic part of the wake dynamics. Using SPOD to separate the distinct frequency-centered dynamics into unique, interpretable mode pairs will simplify future efforts to develop sparse dynamical models of the flow.

Numerical Simulation of the Multiple Branch Transverse Response of a Low Mass Ratio Elastically Supported Circular Cylinder

2006 ◽  
Author(s):  
Richard H. J. Willden
Keyword(s):  
Circular Cylinder ◽  
Maximum Amplitude ◽  
Mass Ratio ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Vortex Induced Vibrations ◽  
Low Mass ◽  
Low Mass Ratio ◽  
Elastically Supported ◽  
High Degree

The paper presents the results of a numerical investigation of the transverse Vortex-Induced Vibrations of an undamped, low mass ratio elastically supported circular cylinder that was subjected to a uniform flow that resulted in a Reynolds number of 104. The numerical simulations were performed using a two-dimensional Large Eddy Simulation model. The computed cylinder response exhibits three branches; the initial, upper and lower branches. The computed initial and lower branches, which exhibit 2S and 2P modes of shedding respectively, show many similarities to those reported from experiments. However, the computed upper branch, on which a maximum amplitude of response of 0.83D was achieved, shows some dissimilarities to those reported from experiments. The failure to correctly simulate the upper branch response is thought to be due to the high degree of flow three-dimensionality that has been reported to exist on the upper branch.

CFD-FSI simulation of vortex-induced vibrations of a circular cylinder with low mass-damping

2013 ◽  
Vol 16 (5) ◽  
pp. 411-431 ◽  
Author(s):  
Amir Borna ◽  
Wagdi G. Habashi ◽  
Ghyslaine McClure ◽  
Siva K. Nadarajah
Keyword(s):  
Circular Cylinder ◽  
Vortex Induced Vibrations ◽  
Low Mass

VIV Control and Drag Reduction Using the Guided Porosity Concept

2008 ◽  
Author(s):  
Antonio C. Fernandes ◽  
Fabio M. Coelho ◽  
Ricardo Franciss ◽  
Severino F. S. Neto
Keyword(s):  
Drag Reduction ◽  
Potential Theory ◽  
Experimental Tests ◽  
Experimental Results ◽  
Mass Ratio ◽  
Vortex Induced Vibrations ◽  
Low Mass ◽  
Low Mass Ratio ◽  
Moving Parts

This paper aims to discuss the effectiveness of a new passive kind of VIV (Vortex Induced Vibrations) suppression. Moreover, the proposed solutions leads to a significant drag reduction when compared with conventional proposals (strakes for instance). The concept of guided porosity is applied in experimental tests conducted with low mass ratio cylindrical models. The works also shows that the job (VIV control and drag reduction) is achieved without moving parts, in contrast with segmented fairings. It also advances in terms of the omnidirectional solution. Initially, the concept is discussed in terms of the potential theory. Then experimental results are presented in terms of displacements and forces.

POD Analysis of the Wake Development of a Pivoted Circular Cylinder Undergoing Vortex Induced Vibrations

2017 ◽  
Author(s):  
E. Marble ◽  
C. Morton ◽  
S. Yarusevych
Keyword(s):  
Circular Cylinder ◽  
Degrees Of Freedom ◽  
Structural Response ◽  
Cylinder Wake ◽  
Time Resolved ◽  
Vortex Induced Vibrations ◽  
Image Velocimetry ◽  
Pod Analysis ◽  
Component Particle ◽  
Proper Orthogonal

Vortex Induced Vibrations (VIV) of a pivoted circular cylinder with two degrees of freedom are investigated experimentally, focusing on quantifying the wake topology. Experiments are performed in a water tunnel for a pivoted cylinder with a fixed mass ratio of 10.8, moment of inertia ratio of 87.0–109.5, and a diameter-based Reynolds number of 3100. The reduced velocity was varied from 4.42 to 9.05 by varying the natural frequency of the structure. Velocity measurements were performed via time-resolved, two-component Particle Image Velocimetry (PIV), synchronized with cylinder displacement measurements. Time and phase-averaging are employed to analyze the wake development and relate it to the structural response. Proper Orthogonal Decomposition (POD) is utilized to gain insight into the development of coherent structures in the cylinder wake. The observed shedding patterns agree well with the Morse & Williamson [1] shedding map except for the cases at the boundary between 2P and non-synchronized shedding. The results show that the cylinder follows an elliptical trajectory with equal frequency of oscillation in streamwise and transverse directions. For the 2P regime, the tilt and direction of trajectory affect the formation and development of vortices in the wake. This results in a distinct asymmetry about the wake centerline in time-averaged statistics.

Numerical Simulations of Riser Vortex-Induced Vibrations

2005 ◽  
Author(s):  
Juan P. Pontaza ◽  
Hamn-Ching Chen ◽  
Chia-Rong Chen
Keyword(s):  
Stokes Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Reynolds Number Flow ◽  
Vortex Induced Vibrations ◽  
Number Flow ◽  
Low Mass ◽  
High Reynolds ◽  
Low Mass Ratio ◽  
Important Design

Vortex-induced vibrations (VIV) is an important design consideration for marine risers in offshore drilling and production. In an effort to better understand the VIV phenomena, we present numerical simulation results for two-dimensional incompressible flow past freely vibrating multi-cylinder configurations found in offshore engineering. Of interest is the response of the structure for low mass ratio, low damping, and high Reynolds number flow conditions. The governing incompressible Navier-Stokes equations are numerically solved and time-integrated using a local-analytic-based discretization procedure, implemented in conjunction with overset (Chimera) grid capabilities for zonal-based resolution of the flow field.

The Effect of Rotational Friction on the Stability of Short-Tailed Fairings Suppressing Vortex-Induced Vibrations

2011 ◽  
Author(s):  
Gustavo R. S. Assi ◽  
Peter W. Bearman ◽  
Michael A. Tognarelli ◽  
Julia R. H. Rodrigues
Keyword(s):  
Circular Cylinder ◽  
Lift Force ◽  
Flow Direction ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Critical Limit ◽  
Vortex Induced Vibrations ◽  
Equivalent Length ◽  
Low Mass ◽  
The Stability

Experiments have been carried out on a free-to-rotate short-tail fairing fitted to a rigid length of circular cylinder to investigate the effect of rotational friction on the stability of this type of VIV suppressor. Measurements of the dynamic response are presented for models with low mass and damping which are free to respond in the cross-flow and streamwise directions. It is shown how VIV can be reduced if the fairing presents a rotational friction above a critical limit. In this configuration the fairing finds a stable position deflected from the flow direction and a steady lift force appears towards the side the fairing has deflected. The fluid-dynamic mechanism is very similar to that observed for a free-to-rotate splitter plate of equivalent length.

An Experimental Study on Flow Induced Vibration of a Circular Cylinder in Shear Flow

2010 ◽  
Author(s):  
Ming Huei Yu ◽  
Yi-hsin Wu
Keyword(s):  
Circular Cylinder ◽  
Shear Flow ◽  
Test Section ◽  
Unit Length ◽  
Large Mass ◽  
Elastic Vibration ◽  
Mass Ratio ◽  
Flow Induced Vibration ◽  
Low Mass ◽  
Low Mass Ratio

The vibrations of a circular cylinder in both uniform and shear flows are investigated experimentally. For the experimental investigation, a low speed water tunnel was designed and built to provide either uniform or shear flow in the test section, depending on the upstream flow management. In the test section, a circular tube of various materials can be flexibly mounted for vibration testing. Two accelerators were carefully installed inside the tube so that one accelerator is sensitive to the cylinder vibration in the streamwise direction only, and the other in the cross-stream direction. The vibration amplitudes of the cylinder in the streamwise and cross-stream directions were simultaneously measured by the two accelerators, and recorded by a two-channel data acquisition system. The orbits of the cylinder motion can be drawn from the data. Experiments were conduced at various mass ratios (the ratio of the cylinder mass per unit length to its buoyancy force) and shear parameters (the non-dimensional velocity gradient of the approaching fluid flow to the cylinder). By analyzing the orbits and amplitude diagrams, it is found that both the shear parameter and mass ratio have profound effects on the cylinder vibration. The orbits of the cylinder in uniform flow are symmetric while they are asymmetric in shear flow. Vibration amplitude as a function of reduced velocity illustrates that the cylinder in uniform or shear flow does not vibrate at low reduced velocities but vibrate significantly beginning at the reduced velocity around 5, initiated by vortex-induced instability. At high reduced velocity, the circular cylinder in shear flow still vibrates at significant amplitude, an evidence of fluid elastic vibration. It is also shown by the amplitude diagrams that low mass ratio promotes the cylinder’s vibration while large mass ratio reduces the vibration.

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