scholarly journals VIV Excitation Competition Between Bare and Buoyant Segments of Flexible Cylinders

2013 ◽  
Author(s):  
Zhibiao Rao ◽  
J. Kim Vandiver ◽  
Vikas Jhingran
Keyword(s):  
Model Test ◽  
Practical Problem ◽  
Excitation Frequency ◽  
Ocean Basin ◽  
Recent Model ◽  
Total Amplitude ◽  
Vortex Induced Vibration ◽  
Pipe Model ◽  
Exploration And Production ◽  
Different Diameters

This paper addresses a practical problem: “Under which coverage of buoyancy modules, would the Vortex Induced Vibration (VIV) excitation on buoyant segments dominate the response?” This paper explores the excitation competition between bare and buoyant segments of a 38 meter long model riser. The source of data is a recent model test, conducted by SHELL Exploration and Production at the MARINTEK Ocean Basin in Trondheim Norway. A pipe model with five buoyancy configurations was tested. The results of these tests show that (1) the excitation on the bare and buoyant regions could be identified by frequency, because the bare and buoyant regions are associated with two different frequencies due to the different diameters; (2) a new phenomenon was observed; A third frequency in the spectrum is found not to be a multiple of the frequency associated with either bare or buoyancy regions, but the sum of the frequency associated with bare region and twice of the frequency associated with buoyancy region; (3) the contribution of the response at this third frequency to the total amplitude is small; (4) the power dissipated by damping at each excitation frequency is the metric used to determine the winner of excitation competition. For most buoyancy configurations, the excitation on buoyancy regions dominates the VIV response; (5) a formula is proposed to predict the winner of the excitation competition between bare and buoyant segments for a given buoyancy coverage.

scholarly journals The Effect of Exposure Length on Vortex Induced Vibration of Flexible Cylinders

2012 ◽  
Author(s):  
Zhibiao Rao ◽  
J. Kim Vandiver ◽  
Vikas Jhingran ◽  
Octavio Sequeiros
Keyword(s):  
Strouhal Number ◽  
Model Test ◽  
Traveling Wave ◽  
Practical Problem ◽  
Recent Model ◽  
Response Frequency ◽  
Vortex Induced Vibration ◽  
Pipe Model ◽  
Exploration And Production ◽  
Exposure Length

This paper addresses a practical problem: “What portion of fairing or strake coverage may be lost or damaged, before the operator must take corrective measures?” This paper explores the effect of lost fairings (the exposure length) on Vortex-Induced Vibration (VIV) of flexible cylinders. The source of data is a recent model test, conducted by SHELL Exploration and Production. A 38m long pipe model with varying amounts of fairings was tested. Response as a function of percent exposure length is reported. Unexpected results are also reported: (i) the flexible ribbon fairings used in the experiment did not suppress VIV at speeds above 1 m/s; (ii) Above 1 m/s, a competition was observed between VIV excited in the faired and bare regions of the cylinder, (iii) Unusual traveling wave behavior was documented—waves generated in the bare region periodically changed direction, and exhibited variation in VIV response frequency. The results of these tests showed that (1) the excitation on the bare and faired regions could be identified by frequency, because the faired region exhibited a much lower Strouhal number; (2) as expected, the response to VIV on the bare region increased with exposure length; (3) the response to VIV on the faired region decreased with exposure length.

Analysis of Piezoelectric Power Harvesting with Composite Energy Converter in Thermal Environments

2010 ◽  
Vol 139-141 ◽  
pp. 2340-2345
Author(s):  
Sheng Wen ◽  
Tie Min Zhang ◽  
Xiu Li Yang
Keyword(s):  
Excitation Frequency ◽  
Electrical Energy ◽  
Induced Voltage ◽  
Energy Converter ◽  
Power Harvesting ◽  
Thermal Environments ◽  
Piezoelectric Energy ◽  
Different Diameters ◽  
Composite Energy ◽  
Good Agreement

A composite piezoelectric energy converter intended for Micro-electromechanical Systems (MEMS) from background vibrations is presented. The converter is composed of a piezoelectric circular plate bonded to a brass substrate with different diameters. The vibration of the structure is analyzed based on the thermal-piezoelectric-elastic theory and Kirchhoff’s assumption. The vibration solutions and the relation between the vibration and output charge are obtained. The effects of geometric characteristics and environment temperatures on the electrical energy generation are numerically discussed. The numerical results show that the vibration-induced voltage is proportional to the excitation frequency and the thickness of the device, but is inversely proportional to the temperature of the environment. The experimental data show good agreement with the energy conversion analytical model.

Vortex-Induced Vibration of Steel Catenary Riser Under Vessel Motion

2014 ◽  
Author(s):  
Jungao Wang ◽  
Shixiao Fu ◽  
Rolf Baarholm
Keyword(s):  
Wave Speed ◽  
Ocean Basin ◽  
Mean Square ◽  
Wall Effects ◽  
Vortex Induced Vibration ◽  
Steel Catenary Riser ◽  
Out Of Plane ◽  
Push Down ◽  
Vessel Motion ◽  
Scr Model

A truncated steel catenary riser (SCR) model was experimentally tested in the ocean basin by oscillating the top end of the model to simulate the heave and surge vessel motion in order to investigate the vortex-induced vibration (VIV) features. Out-of-plane VIV responses were generally analyzed revealing that although the root mean square (RMS) strain distributed rather broadband, the displacement was quite consistent within a narrowband from 0.2D to 0.3D, and the touch-down point (TDP) area was found not to be the place suffering the maximum out-of-plane VIV response due to near wall effects. What’s more, strong wave propagations were firstly reported and summarized as a distinguished feature for VIV of a SCR under vessel motions, and further results reveal that wave propagation during the ‘lift up’ phase was quite different from that during ‘push down’ in terms of both wave speed and ‘power-in’ region location which is assumed to be caused by the tension variation along the model.

Experimental Investigation of the Effects of the In-Line Top-Motion on the Vortex-Induced Vibration Response of a Flexible Riser

2020 ◽  
Author(s):  
Wei Yang ◽  
Chuanzhen Ma ◽  
Zhuang Kang ◽  
Cheng Zhang ◽  
Shaojie Li
Keyword(s):  
Experimental Investigation ◽  
Vibration Frequency ◽  
Flow Direction ◽  
Excitation Frequency ◽  
Cross Flow ◽  
Excitation Amplitude ◽  
Flexible Cylinder ◽  
Amplitude Analysis ◽  
Vortex Induced Vibration ◽  
Flexible Risers

Abstract In order to understand the relation between top-motion and VIV of flexible risers, this paper presents an experimental investigation on concomitant vortex-induced vibration and top-motion excitation with flexible risers. The riser can was mounted vertically, with the diameter of 2 cm and the length of 5 m. The responses of amplitude, frequency and other parameters were analyzed in detail under conditions of different excitation amplitude and frequency in uniform flow. It was found that the concomitant VIV and top-motion excitation significantly affects the flexible cylinder response when compared to the pure VIV tests. The amplitude analysis results show that when the reduced velocity is small (less than about 15), the top-motion excitation has an important influence on amplitude of in-line directions. However, the excitation amplitude and frequency of in-line direction have a little influence on amplitude of cross flow direction. The frequency analysis results show that when the reduced velocity is small (less than about 5), the riser motion amplitude is small and irregular in different excitation and when the reduced velocity is large (5 < Ur < 55), the in-line vibration frequency is two times the cross-flow vibration frequency. A strong connection between the top-motion excitation frequency and the vibration frequency was also found. Overall, some phenomena and characteristics observed in the VIV considering top-motion excitation are different from those in classic VIV, which may provide basic reference for the VIV investigation involving the effect of floating bodies.

scholarly journals Reynolds Number Effects on the Vortex-Induced Vibration of Flexible Marine Risers

2012 ◽  
Author(s):  
Themistocles L. Resvanis ◽  
Vikas Jhingran ◽  
J. Kim Vandiver ◽  
Stergios Liapis
Keyword(s):  
Reynolds Number ◽  
Field Experiments ◽  
Number Range ◽  
Vortex Induced Vibration ◽  
Marine Risers ◽  
Dimensionless Amplitude ◽  
Diameter Pipe ◽  
Reynolds Number Effects ◽  
Different Diameters ◽  
Reynolds Number Dependence

This paper explores the Reynolds number dependence of the Vortex-Induced Vibration (VIV) of flexible marine risers. Emphasis is placed on revealing the trends that exist between the Strouhal number and the Reynolds number and between the dimensionless amplitude (A/D) and Reynolds number. Data is drawn from recent towing tank experiments which used flexible cylinders of three different diameters. The 38m long pipes were exposed to uniform and sheared currents. The Reynolds number range extended from approximately 5,000 to 220,000 — well into the critical regime — with the larger diameter pipes responding in up to the 13th mode and the smaller diameter pipe responding well above the 20th mode. The results and trends from this set of experiments are compared to previous results from laboratory and field experiments.

scholarly journals The Identification of Power-In Region in Vortex-Induced Vibration of Flexible Cylinders

2014 ◽  
Author(s):  
Zhibiao Rao ◽  
Themistocles L. Resvanis ◽  
J. Kim Vandiver
Keyword(s):  
Fiber Optic ◽  
Lessons Learned ◽  
Recent Model ◽  
Strain Gauges ◽  
Flexible Cylinder ◽  
Vortex Induced Vibration ◽  
Sheared Flow ◽  
Primary Power ◽  
Novel Method ◽  
Secondary Power

This paper proposes a novel method to identify the power-in regions of long flexible cylinders subjected to vortex-induced vibration (VIV). It also attempts to address a practical problem: “Will a secondary power-in region appear after the primary power-in region is covered with suppression devices?” The source of data is a recent model test on a 38 meter long flexible cylinder, densely instrumented with fiber optic strain gauges and accelerometers. For pipes with partial coverage of suppression devices in uniform flow, the bare region would be expected to be a power-in region and the section with suppression devices is expected to be a power-out region. Experimental data from these types of tests are used to benchmark the proposed power-in zone identification method. The method is then used to identify the power-in zones on a bare cylinder in a sheared flow. This paper also explores the occurrence of secondary power-in regions that may exist, when suppression devices are placed in the primary power-in zone. Secondary power-in regions were observed. Lessons learned from the power-in region identification in sheared flows will be a useful tool for designer/engineers choosing where to place suppression devices.

VIV Response of a Subsea Jumper in Uniform Current

2013 ◽  
Author(s):  
Howard Wang ◽  
Jerry Huang ◽  
Sungho Lee ◽  
Paulo Gioielli ◽  
Wan Kan ◽  
...  
Keyword(s):  
Model Test ◽  
Cross Flow ◽  
Small Scale ◽  
Bottom Currents ◽  
Pipe Model ◽  
Sea Bottom ◽  
Standard Design ◽  
Level Model ◽  
Flow Vortex ◽  
High Level

Subsea jumpers are susceptible to in-line and/or cross-flow vortex induced vibration (VIV) fatigue damage due to sea bottom currents. However, there is no proven industry standard design analysis methodology currently available specifically for assessing subsea jumper VIV response. In 2012, ExxonMobil conducted a jumper VIV model test to assess the validity of potential jumper VIV prediction approaches. A towing test rig was used to expose a small scale jumper model to flow conditions simulating uniform bottom currents. The jumper model was instrumented to acquire acceleration, bending strain and end connection load data. Several accelerometers and strain gauges were installed to enable reconstruction of static and dynamic deformations and bending deflections along the jumper model. Towing tests at different orientations and tow speeds were performed on both a bare pipe model and a straked pipe model. The data were analyzed to examine the frequencies and amplitudes of the jumper vibration. The data from these experiments provide a benchmark for validating jumper VIV prediction approaches. In this paper, the model test program is presented including model testing philosophy, jumper design and fabrication, and high level model test results.

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