scholarly journals Kill Line Model Cross Flow Inline Coupled Vortex-Induced Vibration

2017 ◽  
Author(s):  
Baiheng Wu ◽  
Jorlyn Le Garrec ◽  
Dixia Fan ◽  
Michael S. Triantafyllou
Keyword(s):  
Bluff Body ◽  
Oil And Gas ◽  
Cross Flow ◽  
The Body ◽  
Bluff Bodies ◽  
Structural Vibrations ◽  
Vortex Induced Vibrations ◽  
Series Of Experiments ◽  
Central Pipe ◽  
Semi Empirical

Currents and waves cause flow-structure interaction problems in systems installed in the ocean. Particularly for bluff bodies, vortices form in the body wake, which can cause strong structural vibrations (Vortex-Induced Vibrations, VIV). The magnitude and frequency content of VIV is determined by the shape, material properties, and size of the bluff body, and the nature and velocity of the oncoming flow. Riser systems are extensively used in the ocean to drill for oil wells, or produce oil and gas from the bottom of the ocean. Risers often consist of a central pipe, surrounded by several smaller cylinders, including the kill and choke lines. We present a series of experiments involving forced in-line and cross flow motions of short rigid sections of a riser containing 6 symmetrically arranged kill and choke lines. The experiments were carried out at the MIT Towing Tank. We present a systematic database of the hydrodynamic coefficients, consisting of the forces in phase with velocity and the added mass coefficients that are also suitable to be used with semi-empirical VIV predicting codes.

scholarly journals Fluid-Structure Energy Transfer of a Tensioned Beam Subject to Vortex-Induced Vibrations in Shear Flow

2011 ◽  
Author(s):  
Remi Bourguet ◽  
Michael S. Triantafyllou ◽  
Michael Tognarelli ◽  
Pierre Beynet
Keyword(s):  
Energy Transfer ◽  
Shear Flow ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Structural Vibrations ◽  
Fluid Structure ◽  
Vortex Induced Vibrations ◽  
Linear Shear ◽  
Structural Responses ◽  
Lock In

The fluid-structure energy transfer of a tensioned beam of length to diameter ratio 200, subject to vortex-induced vibrations in linear shear flow, is investigated by means of direct numerical simulation at three Reynolds numbers, from 110 to 1,100. In both the in-line and cross-flow directions, the high-wavenumber structural responses are characterized by mixed standing-traveling wave patterns. The spanwise zones where the flow provides energy to excite the structural vibrations are located mainly within the region of high current where the lock-in condition is established, i.e. where vortex shedding and cross-flow vibration frequencies coincide. However, the energy input is not uniform across the entire lock-in region. This can be related to observed changes from counterclockwise to clockwise structural orbits. The energy transfer is also impacted by the possible occurrence of multi-frequency vibrations.

Fatigue Analysis of Free Spanning Pipelines Subjected to Vortex Induced Vibrations

2013 ◽  
Author(s):  
F. Van den Abeele ◽  
F. Boël ◽  
M. Hill
Keyword(s):  
Fatigue Damage ◽  
Oil And Gas ◽  
Flow Direction ◽  
Cross Flow ◽  
Fatigue Analysis ◽  
Sensitivity Analyses ◽  
Vortex Induced Vibration ◽  
Vortex Induced Vibrations ◽  
Offshore Industry ◽  
Girth Welds

Vortex induced vibration is a major cause of fatigue failure in submarine oil and gas pipelines and steel catenary risers. Even moderate currents can induce vortex shedding, alternately at the top and bottom of the pipeline, at a rate determined by the flow velocity. Each time a vortex sheds, a force is generated in both the in-line and cross-flow direction, causing an oscillatory multi-mode vibration. This vortex induced vibration can give rise to fatigue damage of submarine pipeline spans, especially in the vicinity of the girth welds. In this paper, an integrated numerical framework is presented to predict and identify free spans that may be vulnerable to fatigue damage caused by vortex induced vibrations (VIV). An elegant and efficient algorithm is introduced to simulate offshore pipeline installation on an uneven seabed. Once the laydown simulation has been completed, the free spans can be automatically detected. When the fatigue screening for both inline and cross-flow VIV indicates that a particular span may be prone to vortex induced vibrations, a detailed fatigue analysis is required. Amplitude response models are constructed to predict the maximum steady state VIV amplitudes for a given pipeline configuration (mechanical properties) and sea state (hydrodynamic parameters). The vibration amplitudes are translated into corresponding stress ranges, which then provide an input for the fatigue analysis. A case study from the offshore industry is presented, and sensitivity analyses are performed to study the influence of the seabed conditions, where special emphasis is devoted on the selection of pipe soil interaction parameters.

Improved In-Line Vortex-Induced Vibrations Prediction for Combined In-Line and Cross-Flow Vortex-Induced Vibrations Responses

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Decao Yin ◽  
Elizabeth Passano ◽  
Carl M. Larsen
Keyword(s):  
Cross Flow ◽  
Hydrodynamic Coefficients ◽  
Marine Structures ◽  
Flexible Pipe ◽  
Flexible Beams ◽  
Forced Motion ◽  
Pipe Model ◽  
Vortex Induced Vibrations ◽  
Flow Vortex ◽  
Semi Empirical

Slender marine structures are subjected to ocean currents, which can cause vortex-induced vibrations (VIV). Accumulated damage due to VIV can shorten the fatigue life of marine structures, so it needs to be considered in the design and operation phase. Semi-empirical VIV prediction tools are based on hydrodynamic coefficients. The hydrodynamic coefficients can either be calculated from experiments on flexible beams by using inverse analysis or theoretical methods, or obtained from forced motion experiments on a circular cylinder. Most of the forced motion experiments apply harmonic motions in either in-line (IL) or crossflow (CF) direction. Combined IL and CF forced motion experiments are also reported. However, measured motions from flexible pipe VIV tests contain higher order harmonic components, which have not yet been extensively studied. This paper presents results from conventional forced motion VIV experiments, but using measured motions taken from a flexible pipe undergoing VIV. The IL excitation coefficients were used by semi-empirical VIV prediction software vivana to perform combined IL and CF VIV calculation. The key IL results are compared with Norwegian Deepwater Programme (NDP) flexible pipe model test results. By using present IL excitation coefficients, the prediction of IL responses for combined IL and CF VIV responses is improved.

Numerical and Experimental Evaluation of Lift Forces in Flows Around Surface-Mounted Bluff Bodies

2002 ◽  
Author(s):  
T. Stengel ◽  
F. Ebert ◽  
M. Fallen
Keyword(s):  
Velocity Field ◽  
Bluff Body ◽  
Recirculation Zone ◽  
Separation Zone ◽  
Laser Doppler Anemometry ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
The Body ◽  
Bluff Bodies ◽  
Large Eddy

The flow around a surface-mounted bluff body with cuboid shape is investigated. Therefore, the velocity field including the distribution of the turbulent kinetic energy is computed and compared with experimental Laser Doppler Anemometry data. Several different turbulence models, namely the standard k-ε model, the Wolfshtein two-layer k-ε model and a Large-Eddy approach are validated. Since the Large-Eddy model remains the only model representing the flow accurate, it is chosen for further investigations. The pressure distribution on the body and on the carrying surface around the body is analysed. The lift coefficients are computed for Reynolds numbers, ranging from 1.1 × 104 up to 4.4 × 104. The lengths of the separation zone above and the recirculation zone downstream the body are evaluated.

CFD Study of the Pressure Distribution on the Back of a 3-D Bluff Body (CUBE) of Air Flow in Different Reynolds Numbers

2009 ◽  
Author(s):  
Mohammad Javad Izadi ◽  
Pegah Asghari ◽  
Malihe Kamkar Delakeh
Keyword(s):  
Reynolds Number ◽  
Bluff Body ◽  
Free Stream ◽  
Fluid Flows ◽  
Reynolds Numbers ◽  
The Body ◽  
Stream Velocity ◽  
Bluff Bodies ◽  
Unsteady Forces ◽  
Flow Round

The study of flow around bluff bodies is important, and has many applications in industry. Up to now, a few numerical studies have been done in this field. In this research a turbulent unsteady flow round a cube is simulated numerically. The LES method is used to simulate the turbulent flow around the cube since this method is more accurate to model time-depended flows than other numerical methods. When the air as an ideal fluid flows over the cube, flow separate from the back of the body and unsteady vortices appears, causing a large wake behind the cube. The Near-Wake (wake close to the body) plays an important role in determining the steady and unsteady forces on the body. In this study, to see the effect of the free stream velocity on the surface pressure behind the body, the Reynolds number is varied from one to four million and the pressure on the back of the cube is calculated numerically. From the results of this study, it can be seen that as the velocity or the Reynolds number increased, the pressure on the surface behind the cube decreased, but the rate of this decrease, increased as the free stream flow velocity increased. For high free stream velocities the base pressure did not change as much and therefore the base drag coefficient stayed constant (around 1.0).

Drag Reduction of Bluff Bodies by Surface Control Based on a Force Theory

2007 ◽  
Author(s):  
Shih-Hao Yang ◽  
Chien C. Chang ◽  
Chin-Chou Chu ◽  
Shi-Hua Liao ◽  
R. L. Chern
Keyword(s):  
Circular Cylinder ◽  
Drag Reduction ◽  
Bluff Body ◽  
The Body ◽  
Bluff Bodies ◽  
Rational Basis ◽  
Surface Control

In the present study, we show how drag reduction of a bluff body can be achieved on a rational basis of a force theory. The force theory indicates where is the best location to apply the surface control to minimize the drag on the body. In particular, the method of drag reduction is illustrated for flow around a circular cylinder. It is shown that drag reduction for the circular cylinder can be as efficient as 46.5%.

Numerical Effect of Airflow From a Lower Canopy (Bluff Body) Into an Upper Canopy in Steady and Turbulent Condition

2008 ◽  
Author(s):  
Mohammad J. Izadi
Keyword(s):  
Drag Force ◽  
Bluff Body ◽  
Cross Sectional Area ◽  
The Body ◽  
Bluff Bodies ◽  
Variable Cross ◽  
Sectional Area ◽  
Cross Sectional ◽  
Varied Form ◽  
Two Bodies

In this paper, a 3-D flow field around two bluff bodies in an incompressible fluid is modeled [1]. Formations of these two bodies are top to top (One on the top of the other) with respect to the center of each other. The lower on has a constant cross sectional area with a vent of air at its apex and the upper one has a variable cross sectional area with no vent on it. The vertical distances between the bluff bodies, the cross sectional area, and also the vent ratio of bluff bodies are varied here. Vertical distances of these two bodies are varied form zero to half, equal, double and triple the radius of the body with a vent on it (lower body). Flow condition is considered 3D, steady, turbulent, and incompressible. The drag force on each body and also the pressure around the two bodies are calculated. From the numerical results, it can be seen that, the drag force is constant over the range of zero to twenty percent of the vent ratios and for higher vent ratios when the upper bluff body is smaller than the lower one the drag force decreased, and it increased when the upper bluff body is larger than the lower one.

Numerical Simulation of Vortex-Induced Vibrations on a Flexible Riser in Uniform Currents

2010 ◽  
Author(s):  
Changjiang He ◽  
Zhongdong Duan ◽  
Jinping Ou
Keyword(s):  
Damping Ratio ◽  
Three Dimensional ◽  
Cross Flow ◽  
The Body ◽  
Flexible Riser ◽  
Strongly Coupled ◽  
Vortex Induced Vibrations ◽  
Kinematic Equivalence ◽  
Uniform Currents ◽  
Phase Angles

A numerical model in a quasi-three-dimensional fashion is developed in this paper to simulate vortex-induced vibration of a flexible riser (the aspect ratio = 250, mass ratio, m* = 2.9, damping ratio, ζ = 0.01) in uniform current U∞ = [0.06, 0.80] m/s, (Reynolds number, Re = [0.01, 1.28]×104). Finite element method are and Finite volume method are applied in the structural and fluid domains respectively. Effects of fluid-structure interaction (FSI) are reckoned in by making use of kinematic equivalence of the relative flow between fluid and the body in inertial and non-inertial frames of reference. It is found transeverse motion and streamwise motion are strongly coupled, they have same changing trend at the same reduced velocity range, the upper branch appears in the range Vrn = U∞/fnD ≈ 5–7 for the generated nth mode, whilst the lock-in remains in the range Vrn ≈ 3–10, the phase angles decrease from about 90° in the initial branch to less than 45° in the lower branch. The RMS and envelop values of cross-flow displacements are 4∼6 times those of in-line, maximum amplitudes of about 1.2 diameters at cross-flow and 0.25 diameters at in-line have been observed. Standing wave response was observed as Vr1 = 6, the in-line response even contains the first and the second modes at the same time. The strouhal number, St is about 0.17 in the present cases.

Comparison of Calculated In-Line Vortex Induced Vibrations to Model Tests

2012 ◽  
Author(s):  
Elizabeth Passano ◽  
Carl M. Larsen ◽  
Halvor Lie
Keyword(s):  
Cross Flow ◽  
Added Mass ◽  
Model Tests ◽  
The Finite Element Method ◽  
Response Frequency ◽  
Flow Response ◽  
Vortex Induced Vibrations ◽  
Flow Directions ◽  
The Cross ◽  
Semi Empirical

The purpose of the present paper is to compare vortex-induced vibrations (VIV) in both in-line and cross-flow directions calculated by a semi-empirical computer program to experimental data. The experiments used are the Bearman and Chaplin experiments in which a model of a tensioned riser is partly exposed to current and partly in still water. The VIVANA program is a semi-empirical frequency domain program based on the finite element method. The program was developed by MARINTEK and the Norwegian University of Science and Technology (NTNU) to predict cross-flow response due to VIV. The fluid-structure interaction in VIVANA is described using added mass, excitation and damping coefficients. Later, curves for excitation, added mass and damping for pure in-line VIV response were added. These curves are valid for low current levels, before the onset of cross-flow VIV response. Recently, calculation of response from simultaneous cross-flow and in-line excitation has been included in VIVANA. The in-line response frequency is fixed at twice the cross-flow response frequency and the in-line added mass is adjusted so that this frequency becomes an eigenfrequency. A set of curves based on forces measured during combined cross-flow and inline motions are used. At present, the in-line excitation curves are not dependent on the cross-flow response amplitude. In the paper, in-line and cross-flow response predicted by VIVANA will be compared to the Bearman and Chaplin model tests. The choice of added mass and excitation coefficients will be discussed.

scholarly journals Bluff Bodies and Wake–Wall Interactions

2021 ◽  
Vol 53 (1) ◽  
pp. 347-376
Author(s):  
Mark C. Thompson ◽  
Thomas Leweke ◽  
Kerry Hourigan
Keyword(s):  
Bluff Body ◽  
Solid Wall ◽  
The Body ◽  
Body Motion ◽  
Flow Structures ◽  
Bluff Bodies ◽  
Solid Contact ◽  
Flow Transitions ◽  
Solid Walls ◽  
Wall Interactions

This review surveys the dramatic variations in wake structures and flow transitions, in addition to body forces, that appear as the motion of bluff bodies through a fluid occurs increasingly closer to a solid wall. In particular, we discuss the two cases of bluff bodies translating parallel to solid walls at varying heights and bluff bodies impacting on solid walls. In the former case, we highlight the changes to the wake structures as the flow varies from that of an isolated body to that of a body on or very close to the wall, including the effects when the body is rotating. For the latter case of an impacting body, we review the flow structures following impact and their transition to three-dimensionality. We discuss the issue of whether there is solid–solid contact between the bluff body and a wall and its importance to body motion.

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