Two Tandem Cylinders With Passive Turbulence Control in Flow Induced Vibration: Relation of Oscillation Patterns to Frequency Response

2017 ◽  
Author(s):  
Kai Lan ◽  
Hai Sun ◽  
Michael M. Bernitsas
Keyword(s):  
Frequency Response ◽  
Phase Difference ◽  
Volume Ratio ◽  
Flow Speed ◽  
Flow Induced Vibration ◽  
Frequency Spectra ◽  
Turbulence Control ◽  
Instantaneous Phase ◽  
Tandem Cylinders ◽  
Flow Induced Vibrations

Flow Induced Vibrations (FIV) are conventionally destructive and should be suppressed. Since 2006, the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan has been studying FIV of multiple cylinders to enhance their response for harnessing hydrokinetic power from ocean, river, and tidal currents. Interactions between multiple cylinders in FIV enable high power-to-volume ratio in a converter consisting of multiple oscillators of cylinders. This paper investigates experimentally the relation between oscillation patterns and frequency response of two cylinders in tandem. All experiments are conducted in the recirculating channel of the MRELab for 30,000<Re<120,000. Phase analysis reveals three dominant patterns of oscillation of two tandem cylinders by calculating the instantaneous phase difference between the two cylinders. This phase difference characterizes each major pattern. One is characterized by nearly 180° out of phase oscillations and one by small lead or lag of one cylinder over the other. In the third pattern, the instantaneous phase difference changes continuously from −180° to +180°. Using frequency spectra, oscillation characteristics of each cylinder are revealed in each flow speed range. Comparison of oscillation patterns and frequency spectra reveals that each oscillation pattern is related to a distinctly different frequency response.

Two Tandem Cylinders With Passive Turbulence Control in Flow-Induced Vibration: Relation of Oscillation Patterns to Frequency Response

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Kai Lan ◽  
Hai Sun ◽  
Michael M. Bernitsas
Keyword(s):  
Frequency Response ◽  
Phase Difference ◽  
Volume Ratio ◽  
Flow Induced Vibration ◽  
Frequency Spectra ◽  
Turbulence Control ◽  
Instantaneous Phase ◽  
Tandem Cylinders ◽  
Flow Induced Vibrations ◽  
The University

Flow-induced vibrations (FIV) are conventionally destructive and should be suppressed. Since 2006, the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan has been studying FIV of multiple cylinders to enhance their response for harnessing hydrokinetic power from ocean, river, and tidal currents. Interactions between multiple cylinders in FIV enable high power-to-volume ratio in a converter consisting of multiple oscillators. This paper investigates experimentally the relation between oscillation patterns and frequency response of two cylinders in tandem. All experiments are conducted in the recirculating channel of the MRELab for 30,000 < Re < 120,000. Phase analysis reveals three dominant patterns of oscillation of two tandem cylinders by calculating the instantaneous phase difference between the two cylinders. This phase difference characterizes each major pattern. Pattern A is characterized by small lead or lag of one cylinder over the other. In pattern B, there is nearly 180 deg out of phase oscillations between the cylinders. In pattern C, the instantaneous phase difference changes continuously from −180 deg to +180 deg. Using frequency spectra and amplitude response, oscillation characteristics of each cylinder are revealed in vortex-induced vibration (VIV) and galloping. Pattern A occurs mostly in galloping when the first cylinder has higher stiffness. Pattern B occurs seldom and typically in the initial VIV branch and transition from VIV to galloping. Pattern C occurs in the upper and lower VIV branches; and in galloping when the lead cylinder has lower stiffness.

Extraction of the Mayer wave component in blood pressure from the instantaneous phase difference between electrocardiograms and photoplethysmograms

2010 ◽  
Vol 15 (4) ◽  
pp. 522-525
Author(s):  
Norihiro Sugita ◽  
Makoto Yoshizawa ◽  
Masayuki Murakoshi ◽  
Makoto Abe ◽  
Noriyasu Homma ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Phase Difference ◽  
Wave Component ◽  
Instantaneous Phase ◽  
Mayer Wave

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.

Flow-Induced Vibrations in Bellows

1989 ◽  
Vol 111 (4) ◽  
pp. 402-406 ◽  
Author(s):  
D. S. Weaver ◽  
P. Ainsworth
Keyword(s):  
Flow Velocity ◽  
Steel Wire ◽  
Effective Means ◽  
Cooling Water ◽  
Wire Mesh ◽  
Mean Flow ◽  
Frequency Spectra ◽  
Inconel 600 ◽  
Flow Induced Vibrations ◽  
Steel Wire Mesh

Flow-induced vibrations have caused fatigue failures in a number of bellows units carrying cooling water flows. The bellows are made from Inconel 600 and have a nominal inside diameter of 20 mm. This paper presents the results of a project undertaken to study these vibrations and to develop a method for vibration alleviation. The experiments were conducted on prototype bellows with vibration amplitudes and frequency spectra being observed as a function of flow velocity. The bellows exhibit flow-induced resonant peaks with successively higher modes being excited by increasing flow velocities. The upstream flow geometry used in service conditions was found to reduce the mean flow velocity required to produce resonance. A fine stainless steel wire mesh was found to be the most effective means of eliminating the vibrations.

Flow Induced Vibrations of Pressure Let-Down Station in QATARGAS

2006 ◽  
Author(s):  
Mohammed Y. Qaradawi ◽  
Abdulaziz R. Moshaweh
Keyword(s):  
Flow Velocity ◽  
Oil And Gas ◽  
Fluid Pressure ◽  
Gas Pipeline ◽  
Fluid Type ◽  
Flow Induced Vibration ◽  
Type Flow ◽  
Flow Induced Vibrations ◽  
Common Application ◽  
Safety And Stability

The use of the pipes to transfer oil and gases from production to export places is a common application in oil and gas industries. The safety and stability of the pipelines are crucial to prevent human and equipment losses. One of the criteria that jeopardize safety and stability of the pipelines is the vibration, and especially flow-induced vibration. Flow induced vibration in pipes is affected by many factors such as fluid type, flow velocity, fluid and pipes densities and fluid pressure. This study considers the analysis and modification of an upstream gas pipeline in QATARGAS Company. The study proposes some solutions to the problem of flow-induced vibration in pipes and the platform supporting them.

scholarly journals A High-Fidelity Approach for the Simulation of Flow-Induced Vibration

2016 ◽  
Author(s):  
Elia Merzari ◽  
Jerome Solberg ◽  
Paul Fischer ◽  
Robert M. Ferencz
Keyword(s):  
Reactor Core ◽  
Spectral Element ◽  
Structural Mechanics ◽  
Nuclear Industry ◽  
High Fidelity ◽  
Flow Induced Vibration ◽  
Strong Basis ◽  
Flow Past A Cylinder ◽  
Flow Induced Vibrations ◽  
Computational Resources

Flow-induced vibration (FIV) is a widespread problem in energy systems because they rely on fluid movement for energy conversion. Vibrating structures may be damaged as fatigue or wear occur. Given the importance of reliable components in the nuclear industry, flow-induced vibrations have long been a major concern in the safety and operation of nuclear reactors. In particular, nuclear fuel and steam generators have been known to suffer from flow-induced vibrations and related failures. Over the past five years, the Nuclear Energy Advanced Modeling and Simulation program has developed the integrated multiphysics code suite SHARP. The goal of developing such a tool is to perform multiphysics modeling of the components inside a reactor core, the full reactor core or portions of it, and be able to achieve that with various levels of fidelity. This flexibility allows users to select the appropriate level of fidelity for their computational resources and design constraints. In particular SHARP contains high-fidelity single-physics codes for structural mechanics and fluid mechanics calculations: the structural mechanics implicit code Diablo and the computational fluid dynamics spectral element code Nek5000. Both codes are state-of-the-art. highly scalable (up to millions of processors in the case of Nek5000) tools that have been extensively validated. These tools form a strong basis on which to build an FIV modeling capability. This work discusses in detail the implementation of a fluid-structure interaction methodology in SHARP for simulating flow-induced viration based on the coupling between Diablo and Nek5000. Initial verification and validation efforts are also discussed, with a focus on standard benchmark cases: the flow past a cylinder, the Turek benchmark, and the flow in a Coriolis flow meter.

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