Fluid Drag With and Without Vortex-Induced Vibrations

2020 ◽  
Author(s):  
Robert F. Zueck
Keyword(s):  
Maximum Amplitude ◽  
Dynamic Nature ◽  
Physical Relationship ◽  
Flowing Fluid ◽  
Vortex Induced Vibrations ◽  
Sustained Action ◽  
Fluid Drag ◽  
Slender Structure ◽  
Conservation Principles ◽  
Geometric Changes

Abstract Fluid drag is an integrated force that depends on the velocity of the fluid flow relative to the motion of a structure. In previous OMAE papers, we used nonlinear physics-based time-domain simulations to show how fluid drag evolves geometric changes in slender (long and thin) structures. We then showed how these changes physically determine the specific dynamic nature of the vibrations that the fluid can induce in the structure. Induced vibrations are four-dimensional oscillations in a marine riser, suspended pipe or other slender structure, whereby the maximum amplitude of deflection is generally perpendicular to the sustained action. The sustained action is often fluid drag. In this paper, we study the physical relationship between fluid drag and induced vibrations. By focusing on the nonlinear interaction between fluid and structure, we revisit a longstanding belief that vortex-induced vibrations amplify fluid drag. Using nonlinear physics-based simulations of a slender structure interacting with flowing fluid, we show how amplification depends on the type of vibration (imposed or free). In other words, drag amplification can occur when we impose a vibration on the structure, but does not occur when we allow sufficient geometric freedom so that the fluid merely induces the structure to vibrate. Using simple visual experiments, we confirm that Vortex-Induced Vibrations (VIV) do not amplify fluid drag. This result is consistent with basic energy conservation principles.

The Evolutionary Geometric Physics of Vortex-Induced Vibrations

2019 ◽  
Author(s):  
Robert F. Zueck
Keyword(s):  
Structural Changes ◽  
Maximum Amplitude ◽  
Marine Riser ◽  
Flowing Fluid ◽  
Vortex Induced Vibrations ◽  
Sustained Action ◽  
Fluid Drag ◽  
Simple Mass ◽  
Physical Changes ◽  
Slender Structures

Abstract Induced vibrations are multi-dimensional oscillations in a marine riser, suspended wire or other slender structures, whereby the maximum amplitude of deflection is generally perpendicular to the sustained action. In previous OMAE papers, we have shown how sustained actions evolve physical changes in slender structures. Using nonlinear physics-based simulations, we showed how these structural changes fundamentally determine the nature of the vibrations that any sustained action (including flowing fluid around the structure) can induce. In this paper, we step back to focus on a classical laboratory experiment, whereby the structure has been constrained to function as a simple mass-on-spring oscillator. In this unchanging structure, we show how the geometric physics of the fluid drag load induce Vortex-Induced Vibrations (VIV). We show how these vibrations naturally grow in time to maximum amplitude.

Insights of the Vortex-Induced Vibration Phenomenon: Ideal Models Versus Reality

2018 ◽  
Author(s):  
Robert F. Zueck
Keyword(s):  
Three Dimensional ◽  
Maximum Amplitude ◽  
Physical Nature ◽  
Dynamic Nature ◽  
Vortex Induced Vibration ◽  
Space And Time ◽  
Sustained Action ◽  
Fluid Drag ◽  
Slender Structures

Induced vibrations are three-dimensional oscillations in a structure, whereby maximum amplitude is mostly perpendicular to sustained action. In this paper, we discuss the specific physics for how induced-vibrations evolve with space and time in a few example structures. We demonstrate how a sustained action (particularly fluid drag and gravity loading) rotates and reshapes these slender structures. We demonstrate how this then shifts and expands the dynamic nature of the structure, making the structure more receptive to vibrational inducements of any kind. Contrary to historical focus, the structure (not the fluid) primarily determines the physical nature of any induced vibrations, including fluid-induced vibrations.

The Key Mechanics Principles for Vortex-Induced Vibrations

2014 ◽  
Author(s):  
Robert F. Zueck ◽  
Paul A. Palo
Keyword(s):  
Three Dimensional ◽  
Physical Nature ◽  
Dominant Factor ◽  
Actual Nature ◽  
Vortex Induced Vibrations ◽  
Fluid Drag ◽  
Slender Structure ◽  
Lock In ◽  
Geometric Changes ◽  
Amplitude Pattern

Vortex-Induced Vibrations (VIV) are cyclic motions in flexible slender structures that are induced by the shedding of vortices mostly transverse to the length of the structural member. The authors contend that the complete three-dimensional (3D) geometric changes that evolve in the structure are too often overlooked when investigating the basic physical nature of VIV. In this paper, we use a physics-based numerical model of a cable (a specific type of slender structure) to demonstrate the following mechanics principles: • Fluid drag (or other field loading) results in 3D geometric changes in a suspended cable. • Those changes necessarily include a lack of structural stiffness in the cable transverse to fluid flow. • In those instances, the structure will inevitably deflect to any kind of transverse action, particularly fluid vortices. • The nonlinear nature of this mechanism allows VIV to occur over a range of time periods, often called “lock-in.” Although the vortex shedding in the fluid provides the necessary repetitive inducement action, the evolving geometry of flexible slender structure appears to be the dominant factor concerning the actual nature (amplitude, pattern, etc.) of the resulting VIV behavior.

Vortex-Induced Vibrations of a Riser With Design Variations

2016 ◽  
Author(s):  
Robert F. Zueck
Keyword(s):  
Fluid Flow ◽  
Three Dimensional ◽  
Physical Effect ◽  
3D Shape ◽  
Vortex Induced Vibrations ◽  
Fluid Drag ◽  
End Conditions ◽  
Slender Structure ◽  
Physical Principles ◽  
Made In

As meta-stable motions transverse to fluid flow in slender bluff-bodied structures, Vortex-Induced Vibrations (VIV) are mostly determined by three-dimensional (3D) geometric and relativistic changes that evolve in the structure. Simplistic models of the structure ignore these key physical principles. In a 2014 OMAE paper, we introduced the key physical concepts for simulating VIV in a horizontal-oriented slender structure (pipeline). In a 2015 OMAE paper, we re-oriented the same structure vertically to simulate VIV in a vertical riser. In this paper, one or more of the following variations in the vertically-oriented riser will be made, in order to judge the physical effect each variation has on the character and distribution of VIV along the riser: • Cyclically move the upper end of the vertical riser • Change into an S-shaped riser by adding weight/buoyancy • Disconnect the lower end of the S-shaped riser The simulations help show and reinforce the following mechanical concepts of VIV • How gravity and fluid drag evolves a 3D shape in the riser • How this shape creates specific structural flexibilities • How these flexibilities set the stage for specific VIV • How tension and end conditions are vital to VIV behavior

scholarly journals Vibrations due to Flow-Driven Repeated Impacts

2013 ◽  
Vol 2013 ◽  
pp. 1-17 ◽  
Author(s):  
Sumin Jeong ◽  
Natalie Baddour
Keyword(s):  
Failure Mechanism ◽  
Resonance Condition ◽  
Coefficient Of Restitution ◽  
Flowing Fluid ◽  
Drag Forces ◽  
Fluid Drag ◽  
Repetitive Impact ◽  
Ice Failure ◽  
Two Degree Of Freedom ◽  
Good Agreement

We consider a two-degree-of-freedom model where the focus is on analyzing the vibrations of a fixed but flexible structure that is struck repeatedly by a second object. The repetitive impacts due to the second mass are driven by a flowing fluid. Morison’s equation is used to model the effect of the fluid on the properties of the structure. The model is developed based on both linearized and quadratic fluid drag forces, both of which are analyzed analytically and simulated numerically. Conservation of linear momentum and the coefficient of restitution are used to characterize the nature of the impacts between the two masses. A resonance condition of the model is analyzed with a Fourier transform. This model is proposed to explain the nature of ice-induced vibrations, without the need for a model of the ice-failure mechanism. The predictions of the model are compared to ice-induced vibrations data that are available in the open literature and found to be in good agreement. Therefore, the use of a repetitive impact model that does not require modeling the ice-failure mechanism can be used to explain some of the observed behavior of ice-induced vibrations.

Experimental Investigation of Vortex-Induced Vibration Responses of Tension Riser Transporting Fluid

2009 ◽  
Author(s):  
Yongbo Zhang ◽  
Fanshun Meng ◽  
Haiyan Guo
Keyword(s):  
Experimental Investigation ◽  
Frequency Spectrum ◽  
Cross Flow ◽  
Internal Flow ◽  
Strain Gauges ◽  
Test Results ◽  
Amplitude Response ◽  
Flowing Fluid ◽  
Vortex Induced Vibrations ◽  
Vibration Responses

This paper presents the test results of a vertically tensioned riser model under vortex-induced vibrations. The influence of internal flowing fluid and top tensions on the riser behavior is investigated. Twelve strain gauges were mounted on the riser and both the in-line and cross-flow responses at locations were measured. The frequency spectrum and amplitude response were derived from the strain date. The influences of internal flow and top tensions on two kinds of model risers are analyzed and some conclusions are drawn.

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.

Vortex-Induced Vibrations and Wake Structures of Isolated Plain and Straked Cylinders Mounted on a 2DOF Elastic Base

2010 ◽  
Author(s):  
Ivan Korkischko ◽  
Cesar M. Freire ◽  
Julio R. Meneghini ◽  
Ricardo Franciss
Keyword(s):  
Reynolds Number ◽  
Degrees Of Freedom ◽  
Particle Image ◽  
Maximum Amplitude ◽  
Elastic Base ◽  
Digital Particle Image Velocimetry ◽  
Circular Cylinders ◽  
Amplitude Response ◽  
Vortex Induced Vibrations ◽  
Image Velocimetry

This paper presents experimental results concerning the response of plain and straked circular cylinders. The isolated cylinders are mounted in a two degrees of freedom elastic base. Two straked cylinders are tested and they have the same pitch p = 10d and two different heights h = 0.1d and h = 0.2d. The longitudinal and transverse amplitude responses and wake structures of plain and helically straked cylinders are compared. The wake visualization uses the stereoscopic digital particle image velocimetry (SDPIV) technique. Comparing to the plain cylinder response, the p = 10d and h = 0.1d strakes moderately reduce the maximum amplitude response, while the p = 10d and h = 0.2d strakes suppress the vortex-induced vibrations. The strake effectiveness is directly related to the strake height. The Reynolds number varies from 1000 up to 7500 in the experiments.

scholarly journals Comparison of Two-Dimensional and Three- Dimensional Responses for Vortex-Induced Vibrations of a Rectangular Prism

2020 ◽  
Vol 10 (22) ◽  
pp. 7996
Author(s):  
Shuai Zhou ◽  
Yunfeng Zou ◽  
Xugang Hua ◽  
Zhipeng Liu
Keyword(s):  
Wind Tunnel ◽  
Scale Effects ◽  
Damping Ratio ◽  
Three Dimensional ◽  
Maximum Amplitude ◽  
Rectangular Prism ◽  
Two Dimensional ◽  
Modal Shape ◽  
Vortex Induced Vibrations ◽  
Section Model

The accurate prediction of the amplitudes of vortex-induced vibrations (VIV) is important in wind-resistant design. Wind tunnel tests of scaled section models have been commonly used. However, the amplitude prediction processes were usually inaccurate because of insufficient evaluations of three-dimensional (3D) effects. This study presents experimental measurements of VIV responses in a prototype rectangular prism and its 1:1 two-dimensional section model in smooth flow. The results show that the section model vibrates with the same Reynolds number, equivalent mass, frequency, and damping ratio as those of the prototype prism without scale effects. The VIV amplitudes can be qualitatively and quantitatively measured and analyzed. The measured VIV lock-ins of these two models agree with each other. However, the prototype prism produces a 20% higher maximum amplitude than the section model. Several classical VIV mathematical models are used to validate the wind tunnel test results. This confirms that the 3D coupling effects of the modal shape and the imperfect correlations of excitation forces positively contribute to the maximum amplitude. Based on the section model outcomes, the amplified factor of 1.2 is found to be appropriate for the amplitude prediction of VIV for the present prism, and it can also provide a reference for other structures.

scholarly journals High Order Accurate Numerical Simulation of Vortex-Induced Vibrations of a Cooled Circular Cylinder Case using Solution Dependent Weighted Least Square Gradient Calculations

2021 ◽  
Vol 321 ◽  
pp. 04005
Author(s):  
Chandrakant Sonawane ◽  
Priyambada Praharaj ◽  
Anand Pandey ◽  
Atul Kulkarni
Keyword(s):  
Circular Cylinder ◽  
Natural Frequencies ◽  
Flow Direction ◽  
Weighted Least Squares ◽  
Fluid Structure Interaction ◽  
Maximum Amplitude ◽  
Flowing Fluid ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Wide Range

In this paper, the fluid-structure interaction problem: vortex-induced vibration of a cooled circular cylinder involving thermal buoyancy is numerically investigated. The elastically mounted cylinder having a temperature lower than the flowing fluid is modelled using mass-spring-damper hence allowed to vibrate in the transverse direction to the flow direction. The gravity is acting opposite to the flow direction. In-house fluid-structure interaction solver is developed based on Harten Lax and van Leer with contact for artificial compressibility Riemann solver. The arbitrarily Lagrangian-Eulerian formulation is employed here, and the mesh is dynamically moved using radial basis function-based interpolation. The solution-dependent weighted least squares based gradient calculations are developed to achieve higher-order accuracy over unstructured meshes. The laminar incompressible flow at Reynolds number, Re = 200, and Prandtl number, Pr = 0.71, is simulated for the mass ratio of 1 and reduced damping coefficient of 0.001. The flow is investigated for Richardson number (-1, 0) and over a wide range of natural frequencies of the cylinder. The heat transfer characteristics from a cylinder are captured and compared with the existing literature results. From the study, it can be observed that in the presence of the thermal boundary layer, the oscillation of the cylinder increases to its maximum amplitude, particularly for values of natural frequencies (0.063 – 0.3).

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