Experimental Investigation on Vortex-Induced Vibration of Risers With Staggered Buoyancy

2011 ◽  
Author(s):  
Lin Li ◽  
Shixiao Fu ◽  
Jianmin Yang ◽  
Tie Ren ◽  
Xuefeng Wang
Keyword(s):  
Experimental Investigation ◽  
Aspect Ratio ◽  
Fiber Bragg Grating ◽  
Cross Flow ◽  
Pitch Height ◽  
Towing Tank ◽  
Paper Model ◽  
Helical Strakes ◽  
Flexible Risers ◽  
Fbg Sensors

In this paper, model tests of a riser with an aspect ratio of 263 were performed in a towing tank by towing the model with constant speeds. The riser was tested with various configurations of buoyancy, including 0% coverage, 25% coverage, 50% coverage and 100% coverage of the buoyancy modules. Furthermore, for the 25% and 50% coverage conditions, the portion without buoyancy modules of the model was covered with helical strakes of 17.5D/0.25D (pitch/height). In the experiments, the strain information in cross-flow (CF) direction was measured using Fiber Bragg Grating (FBG) sensors. The VIV characters of flexible risers with different buoyancy configurations were studied and compared with each other in detail.

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.

Experimental Investigation on the Vortex-Induced Vibration of the Cylinders with Helical Strakes

2011 ◽  
Vol 117-119 ◽  
pp. 747-750
Author(s):  
Yang Zhou ◽  
Wei Ping Huang
Keyword(s):  
Experimental Investigation ◽  
Optimal Design ◽  
Cross Flow ◽  
Comprehensive Analysis ◽  
Design Parameters ◽  
Vortex Induced Vibration ◽  
Flow Response ◽  
Helical Strakes ◽  
Uniform Current ◽  
Made In

The tests on the vortex-induced vibration (VIV) of the cylinders with different helical strakes were carried out in a uniform current. Both in-line and cross-flow responses were measured and a comprehensive analysis was made in order to understand the phenomenon of VIV mitigation by helical strake and find optimal design parameters, which are more effective for VIV mitigation, of helical strakes. The results show that the cross flow response of the cylinders with helical strakes could be reduced significantly and its in-line response may be enhanced severely. Therefore, much attention should be paid to the design of helical strake.

scholarly journals An Experimental Evaluation of Vortex-Induced Vibration of a Riser Bundle With Gaps

2009 ◽  
Author(s):  
J. Kim Vandiver ◽  
Yongming Cheng ◽  
Vivek Jaiswal ◽  
Aditi Sheshadri ◽  
Alan Yu
Keyword(s):  
Free Vibration ◽  
Model Test ◽  
Flow Direction ◽  
Angle Of Attack ◽  
Cross Flow ◽  
Test Results ◽  
Vortex Induced Vibration ◽  
Towing Tank ◽  
Helical Strakes ◽  
Rigid Model

VIV model test results are presented for a bundle of three parallel pipes all lying in the same plane, similar to a riser with large kill and choke lines. The rigid model was attached to a spring-mounted frame in the MIT towing tank. The horizontal model was towed in the tank and allowed to respond in free vibration to vortex-induced vibration in the cross-flow direction. The angle of attack of the model was varied from 0 to 90 degrees. The model was tested with and without helical strakes. Without strakes the model exhibited significant vibration at 0 and 90 degrees angle of attack. Strakes suppressed VIV at all angles of attack.

Experimental investigation on tilt stabilizing effect of external toroidal field in low aspect ratio tokamak

1997 ◽  
Vol 4 (2) ◽  
pp. 315-322 ◽  
Author(s):  
A. Morita ◽  
Y. Ono ◽  
M. Katsurai ◽  
M. Yamada ◽  
S. Yoshikawa
Keyword(s):  
Experimental Investigation ◽  
Aspect Ratio ◽  
Toroidal Field ◽  
Low Aspect Ratio ◽  
Stabilizing Effect

A Multiple Fiber Grating Sensor System Using Code Division Multiple Access

2013 ◽  
Vol 765-767 ◽  
pp. 2444-2447 ◽  
Author(s):  
Wei Li ◽  
Yong Jia Zhang ◽  
Hong Qiao Wen
Keyword(s):  
Optical Fiber ◽  
Fiber Bragg Grating ◽  
Code Division Multiple Access ◽  
Multiple Access ◽  
Simulation Experiment ◽  
Fiber Grating ◽  
Sensing System ◽  
Fiber Grating Sensor ◽  
Fbg Sensors ◽  
Code Division Multiple

In order to increase the multiplying density of Fiber Bragg Grating (FBG) sensors, a novel FBG Sensing System based on CDMA technology has been developed. Simulation experiment indicates the CDMA technology combine with optical fiber grating sensing system together successfully. Furthermore, the system can distinguishes the FBG and enhance the FBG network band utilization.

An Experimental Investigation of the Dynamics of a Loosely Supported Tube Array

2017 ◽  
Author(s):  
Amro Elhelaly ◽  
Marwan Hassan ◽  
Atef Mohany ◽  
Soha Moussa
Keyword(s):  
Experimental Investigation ◽  
Impact Force ◽  
Cross Flow ◽  
Open Loop ◽  
Diameter Ratio ◽  
Force Level ◽  
Steam Generators ◽  
Flow Induced Vibration ◽  
System Integrity ◽  
Tube Bundles

The integrity of tube bundles is very important especially when dealing with high-risk applications such as nuclear steam generators. A major issue to system integrity is the flow-induced vibration (FIV). FIV is manifested through several mechanisms including the most severe mechanism; fluidelastic instability (FEI). Tube vibration can be constrained by using tube supports. However, clearances between the tube and their support are required to allow for thermal expansion and for other manufacturing considerations. The clearance between tubes may allow frequent impact and friction between tube and support. This in turn may cause fatigue and wear at support and potential for catastrophic tube failure. This study aims to investigate the dynamics of loosely supported tube array subjected to cross-flow. The work is performed experimentally in an open-loop wind tunnel to address this issue. A loosely-supported single flexible tube in both triangle and square arrays subjected to cross-flow with a pitch-to-diameter ratio of 1.5 and 1.733, respectively were considered. The effect of the flow approach angle, as well as the support clearance on the tube response, are investigated. In addition, the parameters that affect tube wear such as impact force level are presented.

Numerical Investigation of Local Cooling Enhancement Using Pin-Finned Channel With Incremental Impingement

2017 ◽  
Author(s):  
Susheel Singh ◽  
Sumanta Acharya ◽  
Forrest Ames
Keyword(s):  
Aspect Ratio ◽  
Mass Flow ◽  
Cross Flow ◽  
Surface Cooling ◽  
Local Cooling ◽  
Stagnation Region ◽  
Flow Rates ◽  
Pin Fins ◽  
Mass Flow Rates ◽  
The Impact

Flow and heat transfer in a low aspect ratio pin-finned channel, representative of an internally cooled turbine airfoil, is investigated using Large Eddy Simulations (LES). To achieve greater control of surface cooling distribution, a novel approach has been recently proposed in which coolant is injected incrementally through a series of holes located immediately behind a specially designed cutout region downstream of the pin-fins. Sheltering the coolant injection behind the pin-fins avoids the impact of the cross-flow buildup that deflects the impingement jet and isolates the surface from cooling. The longitudinal and transverse spacing of the pin-fins, arranged in a staggered fashion, is X/D = 1.046 and S/D = 1.625, respectively. The aspect ratio (H/D) of pin-fin channel is 0.5. Due to the presence of the sequential jets in the configuration, the local cooling rates can be controlled by controlling the jet-hole diameter which impacts the jet mass flow rate. Hence, four different hole diameters, denoted as Large (L), Medium (M) , Small (S), Petite (P) are tested for impingement holes, and their effects are studied. Several patterns of the hole-size distributions are studied. It is shown that the peak Nusselt number in the stagnation region below the jet correlates directly with the jet-velocity, while downstream the Nusselt numbers correlate with the total mass flow rates or the average channel velocity. The local cooling parameter defined as (Nu/Nu0)(1-ε) correlates with the jet/channel mass flow rates.

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