The Nature of Self-Excitation in the Flow-Induced Vibration of Flat Plates

1964 ◽  
Vol 86 (3) ◽  
pp. 599-606 ◽  
Author(s):  
P. S. Eagleson ◽  
G. K. Noutsopoulos ◽  
J. W. Daily
Keyword(s):  
Bluff Body ◽  
Body Motion ◽  
Vibrational Amplitude ◽  
Flat Plates ◽  
Flow Induced Vibration ◽  
Trailing Edges ◽  
Flow Induced Vibrations ◽  
Plate Spring ◽  
Spring System ◽  
Bluff Body Wake

Flow-induced vibrations of flat plates are studied in water. An equation of motion of the plate-spring system is formulated incorporating the hydrodynamic loads given by the linearized potential theory, and the unknown, vortex-induced, forcing moments. Considerations of bluff-body wake dynamics show the coefficient of this forcing moment to be a function of the steady-body Strouhal number, the chord-to-thickness ratio, and a self-excitation parameter which contains the transverse body motion. This function is evaluated for plates with different trailing edges using experimental measurements of vibrational amplitude and frequency, and the nature of its dependence on vibration is shown to be equivalent to a negative damping. The poles of the amplitude-response relation are shown to predict the bounds of the zone in which large vibrational (“singing”) motion occurs. Criteria are offered for the design of systems to avoid these self-excited vibrations.

Numerical Simulation of Flow-Induced Vibration of a Rectangular Cylinder

2003 ◽  
Author(s):  
Atsushi Enya ◽  
Atsushi Okajima
Keyword(s):  
Bluff Body ◽  
Cross Flow ◽  
Uniform Flow ◽  
Low Velocity ◽  
Flow Induced Vibration ◽  
Eddy Simulation ◽  
Rectangular Cylinder ◽  
Flow Induced Vibrations ◽  
High Reynolds ◽  
Elastically Supported

It is important for industrial purposes to predict flow-induced vibration of a bluff body elastically supported in an uniform flow. In this paper, the free oscillation of a rectangular cylinder with two-degree of freedom in the streamwise (in-line) and cross-flow (transverse) directions in a uniform flow, was computed by the Large Eddy Simulation (LES) method at high Reynolds number of 2.2 × 104. The Smagorinsky model was used as a subgrid scale (SGS) model. The main objectives of this work were to predict and estimate characteristics of flows around a free-oscillating cylinder. The present computations successfully reproduce various types of flow-induced vibrations of a free-oscillating rectangular cylinder as found by experiments; in-line oscillation, eddy-excitation and low-velocity galloping.

Tailored Bluff Body Motion for Generating Desired Wake Structures

2020 ◽  
Author(s):  
Punnag Chatterjee ◽  
Michael Jenkins ◽  
Arun Vishnu Suresh Babu ◽  
Albert Medina ◽  
Ashok Gopalarathnam ◽  
...  
Keyword(s):  
Bluff Body ◽  
Body Motion

Open Loop Transient Forcing of an Axisymmetric Bluff Body Wake

2008 ◽  
Author(s):  
Stefan Siegel ◽  
Jürgen Seidel ◽  
Kelly Cohen ◽  
Selin Aradag ◽  
Thomas McLaughlin
Keyword(s):  
Bluff Body ◽  
Open Loop ◽  
Transient Forcing ◽  
Bluff Body Wake

Towards Understanding Two-Phase Flow Induced Vibration of Piping Structure With a U-Bend

2019 ◽  
Author(s):  
Olufemi E. Bamidele ◽  
Wael H. Ahmed ◽  
Marwan Hassan
Keyword(s):  
Void Fraction ◽  
Vibration Amplitude ◽  
Two Phase Flow ◽  
Bubbly Flow ◽  
Phase Flow ◽  
Flow Conditions ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Void Fractions ◽  
Flow Induced Vibrations

Abstract The current work investigates two-phase flow induced vibrations in 90° U-bend. The two-phase induced vibration of the structure was investigated in the vertical, horizontal and axial directions for various flow patterns from bubbly flow to wavy and annular-dispersed flow. The void fractions at various locations along the piping including the fully developed void fraction and the void fraction at the entrance of the U-bend were fully investigated and correlated with the vibration amplitude. The results show that the excitation forces of the two-phase flow in a piping structure are highly dependent on the flow pattern and the flow conditions upstream of the bend. The fully developed void fraction and slip between phases are important in modelling of forces in U-bends and elbows.

Boundary Backstepping Control of Flow-Induced Vibrations of a Membrane at High Mach Numbers

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Aziz Sezgin ◽  
Miroslav Krstic
Keyword(s):  
Wave Equation ◽  
Original System ◽  
Target System ◽  
Spanwise Direction ◽  
Infinite Length ◽  
Flow Induced Vibration ◽  
Trailing Edge ◽  
Flow Induced Vibrations ◽  
Mach Numbers ◽  
High Mach

We design a controller for flow-induced vibrations of an infinite-band membrane, with flow running across the band and only above it, and with actuation only on the trailing edge of the membrane. Due to the infinite length of the membrane, the dynamics of the membrane in the spanwise direction are neglected, namely, we employ a one-dimensional (1D) model that focuses on streamwise vibrations. This framework is inspired by a flow along an airplane wing with actuation on the trailing edge. The model of the flow-induced vibration is given by a wave partial differential equation (PDE) with an antidamping term throughout the 1D domain. Such a model is based on linear aeroelastic theory for Mach numbers above 0.8. To design a controller, we introduce a three-stage backstepping transformation. The first stage gets the system to a critically antidamped wave equation, changing the stiffness coefficient's value but not its sign. The second stage changes the system from a critically antidamped to a critically damped equation with an arbitrary damping coefficient. The third stage adjusts stiffness arbitrarily. The controller and backstepping transformation map the original system into a target system given by a wave equation with arbitrary positive damping and stiffness.

Experimental Study on Flow-Induced Vibration of Floating Squared Section Cylinders With Low Aspect Ratio: Part II — Effects of Rounded Edges

2016 ◽  
Author(s):  
Rodolfo T. Gonçalves ◽  
Dennis M. Gambarine ◽  
Aline M. Momenti ◽  
Felipe P. Figueiredo ◽  
André L. C. Fujarra
Keyword(s):  
Aspect Ratio ◽  
Reynolds Numbers ◽  
Ocean Basin ◽  
Separation Point ◽  
Flow Induced Vibration ◽  
Low Aspect Ratio ◽  
Aspect Ratios ◽  
Significant Difference ◽  
Flow Induced Vibrations ◽  
Elastically Supported

Experiments regarding flow-induced vibration on floating rounded squared section cylinders with low aspect ratio were carried out in an ocean basin equipped with a rotating-arm apparatus. Floating squared section cylinders with rounded edges and aspect ratios of L/D = 2.0 were elastically supported by a set of linear springs in order to provide low structural damping to the system. Two different incidence angles were tested, namely 0 and 45 degrees. The Reynolds numbers covered the range from 2,000 to 30,000. The aim was to understand the flow-induced vibrations around single columns, gathering information for further understanding the causes for the Vortex-Induced Motions in semi-submersible and TLP platforms. Experiments on circular and squared sections cylinders (without rounded edges) were also carried out to compare the results with the rounded square section cylinders (with rounded edges). The amplitude results for in-line, transverse and yaw amplitude for 0-degree models showed to be higher for squared section cylinders compared to those for the rounded square section cylinders. No significant difference between the 45-degree models was observed. The results of ratio between frequency of motion in the transverse direction and natural frequency in still water confirmed the vortex-induced vibration behavior for the squared and rounded square section cylinders for 45-degree incidence; and also the galloping characteristics for 0-degree incidence cases. The rounded effect on the square section cylinders showed to be important only for reduced velocity larger than 8, which is probably related to the position of the separation point that changes around the rounded edge, behavior that did not occurr for the squared edge that fixed the separation point for any reduced velocity.

Control of vortex shedding in an axisymmetric bluff body wake

2000 ◽  
Vol 19 (5) ◽  
pp. 789-812 ◽  
Author(s):  
Ansgar Weickgenannt ◽  
Peter A. Monkewitz
Keyword(s):  
Vortex Shedding ◽  
Bluff Body ◽  
Bluff Body Wake
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