The Effects of Mixing Helical Strakes and Fairings on Marine Tubulars and Arrays

2015 ◽  
Author(s):  
Don W. Allen ◽  
Li Lee ◽  
Dean Henning ◽  
Stergios Liapis
Keyword(s):  
Fatigue Life ◽  
Reynolds Numbers ◽  
Vortex Induced Vibration ◽  
High Reynolds Numbers ◽  
Device Type ◽  
Different Types ◽  
Helical Strakes ◽  
High Reynolds ◽  
Viv Suppression ◽  
Tubular Array

Most deepwater tubulars experiencing high currents frequently require vortex-induced vibration (VIV) suppression to maintain an acceptable fatigue life. Helical strakes and fairings are the most popular types of VIV suppression devices in use today. It is quite common to use only one type of device (helical strakes or fairings) on a single tubular and, in fact, to use a single device type on an entire tubular array. The use of both styles of suppression devices on a single tubular has grown in popularity, but mixing them within an array is a relatively new concept. It is sometimes desirable to use one suppression device on one tubular and another suppression device on an adjacent or tandem tubular. This paper utilizes results from two different types of VIV experiments. The first consists of a long tubular at high Reynolds numbers with VIV suppression on the outer end where current speeds are the highest. The use of only fairings, only strakes, or a mixture of the two devices is examined. The second VIV experiment examines the use of helical strakes on one tubular and fairings on a tandem tubular. Results are compared to experiments with either helical strakes on both tubulars or fairings on both tubulars. This paper is intended to provide some direction, and in many cases assurance, for mixing helical strakes and fairings on deepwater tubulars.

Practical Design Considerations for Managing Marine Growth on VIV Suppression Devices

2015 ◽  
Author(s):  
Don W. Allen ◽  
Li Lee ◽  
Dean Henning ◽  
Stergios Liapis
Keyword(s):  
Reynolds Number ◽  
Fatigue Life ◽  
Strong Influence ◽  
Low Reynolds Number ◽  
Vortex Induced Vibration ◽  
Design Considerations ◽  
Drag Forces ◽  
Practical Design ◽  
Helical Strakes ◽  
Viv Suppression

Most deepwater tubulars experiencing high currents frequently require vortex-induced vibration (VIV) suppression to maintain an acceptable fatigue life. Helical strakes and fairings are the most popular VIV suppression devices in use today. Marine growth can significantly affect the VIV of a bare riser, often within just a few weeks or months after riser installation. Marine growth can have a strong influence on the performance of helical strakes and fairings on deepwater tubulars. This influence affects both suppression effectiveness as well as the drag forces on the helical strakes and fairings. Unfortunately, many VIV analyses and suppression designs fail to account for the effects of marine growth at all, even on a bare riser. This paper utilizes results from both high and low Reynolds number VIV test programs to provide some design considerations for managing marine growth for VIV suppression devices.

VIV Suppression Device Development and the Perils of Reynolds Number

2017 ◽  
Author(s):  
Don W. Allen ◽  
Nicole Liu
Keyword(s):  
Reynolds Number ◽  
Small Diameter ◽  
Reynolds Numbers ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
Helical Strakes ◽  
Low Reynolds ◽  
Offshore Industry ◽  
High Reynolds ◽  
Viv Suppression

Most deepwater tubulars experiencing high currents frequently require vortex-induced vibration (VIV) suppression to maintain an acceptable fatigue life. While helical strakes and fairings are by far the most popular VIV suppression devices used in the offshore industry today, a myriad of small alternations to these basic devices can significantly impact the observed levels of suppression effectiveness. Additionally, numerous novel VIV reduction devices are continually being developed and some new devices are progressing towards the product readiness phase. It is quite common to first test suppression devices at low Reynolds numbers due to the availability of smaller scale facilities that are typically more budget-friendly than larger scale facilities. For larger scale testing, it is usually simpler and less expensive to evaluate prototype suppression devices on shorter pipe sections that are spring mounted rather than test on longer flexible pipes. This paper utilizes results from historical VIV experiments to evaluate the merits of various test setups and scales and to underscore the importance of Reynolds number. An assortment of testing scales are presented including: a) small diameter tests at low Reynolds numbers; b) moderate diameter tests that incorporate at least part of the critical Reynolds number range; c) short pipe tests conducted at prototype Reynolds numbers; and d) long pipe tests conducted at high Reynolds numbers but at less than full scale suppression geometry. The use of computational fluid dynamics (CFD) is also briefly discussed.

Vortex Induced Vibration Tests of Smooth and Rough Flexible Cylinders at High Reynolds Numbers

2005 ◽  
Author(s):  
Don W. Allen ◽  
Dean L. Henning ◽  
Li Lee
Keyword(s):  
Surface Roughness ◽  
High Speed ◽  
Single Mode ◽  
Reynolds Numbers ◽  
Circular Path ◽  
Exterior Surface ◽  
Vortex Induced Vibration ◽  
High Reynolds Numbers ◽  
Sheared Flows ◽  
High Reynolds

Vortex-induced vibration (VIV) tests have been performed on long, flexible pipes with various levels of roughness, in sheared flows in a circular towing tank at high Reynolds numbers. The test pipes, made of fiberglass composite, were mounted horizontally beneath a rotating arm that has a span of 129 ft, and a width of 25 ft. As the towing bridge rotates, it drives the cylinder in a circular path in still water. The sheared flows experienced by the cylinder excite its VIV motion. The Reynolds numbers for the tests reported herein ranged from 152,000 to 339,000 at the high-speed end of the pipe. Two surface roughness levels were tested: one comprised of the exterior surface of a filament wound fiberglass pipe; and one with carpet glued to the exterior of the pipe. The VIV responses of the test cylinders, represented by displacement time traces, spectrum, and motion trajectories, are presented in this paper. Effects of the surface roughness and Reynolds numbers on the VIV responses are discussed. The response behavior of the cylinders varied from single-mode dominance to multi-mode responses, in addition to certain traveling wave activities. These results should be of interest to researchers and engineers in the area of vortex-induced vibrations.

The Effect of Coverage Length and Density on the Performance of Helical Strakes

2014 ◽  
Author(s):  
Don W. Allen ◽  
Stergios Liapis
Keyword(s):  
Reynolds Numbers ◽  
Substantial Effect ◽  
Global Response ◽  
Cylinder Length ◽  
High Reynolds Numbers ◽  
Helical Strakes ◽  
High Reynolds ◽  
The Cost

When utilizing helical strakes, a critical decision is how much of the tubular to cover with helical strakes. While minimizing the cost of the helical strakes is one objective, often it is not possible to fully cover a tubular due to connectors, anodes, and other appurtenances. There are also important questions around ascertaining the performance of helical strakes when only a portion of the tubular is covered, for example when the top portion of a tubular is straked and the remainder is left bare. This paper combines results from two testing programs on long cylinders towed at high Reynolds numbers to assess the performance of helical strakes with differing conditions along the cylinder length. The results show that the coverage length, density, and location of the helical strakes have a substantial effect on both the local and global response of the tubular.

TRANSONIC CROSS FLOW (M∞ = 0.8) OVER A CIRCULAR CYLINDER AT HIGH REYNOLDS NUMBERS

2012 ◽  
Vol 43 (5) ◽  
pp. 589-613
Author(s):  
Vyacheslav Antonovich Bashkin ◽  
Ivan Vladimirovich Egorov ◽  
Ivan Valeryevich Ezhov ◽  
Sergey Vladimirovich Utyuzhnikov
Keyword(s):  
Circular Cylinder ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds

Oscillatory control of separation at high Reynolds numbers

AIAA Journal ◽  
1999 ◽  
Vol 37 ◽  
pp. 1062-1071 ◽  
Author(s):  
A. Seifert ◽  
L. G. Pack
Keyword(s):  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds

Turbulent vortex breakdown at high Reynolds numbers

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 825-834
Author(s):  
F. Novak ◽  
T. Sarpkaya
Keyword(s):  
Vortex Breakdown ◽  
Reynolds Numbers ◽  
Turbulent Vortex ◽  
High Reynolds Numbers ◽  
High Reynolds

Drag Measurements on Long Thin Cylinders at Small Angles and High Reynolds Numbers

2004 ◽  
Author(s):  
William L. Keith ◽  
Kimberly M. Cipolla ◽  
David R. Hart ◽  
Deborah A. Furey
Keyword(s):  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds

An Experimental and Numerical Study of Heat Transfer and Pressure Loss in a Rectangular Channel With V-Shaped Ribs

2006 ◽  
Author(s):  
Michael Maurer ◽  
Jens von Wolfersdorf ◽  
Michael Gritsch
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Transfer Enhancement ◽  
High Reynolds Numbers ◽  
High Reynolds

An experimental and numerical study was conducted to determine the thermal performance of V-shaped ribs in a rectangular channel with an aspect ratio of 2:1. Local heat transfer coefficients were measured using the steady state thermochromic liquid crystal technique. Periodic pressure losses were obtained with pressure taps along the smooth channel sidewall. Reynolds numbers from 95,000 to 500,000 were investigated with V-shaped ribs located on one side or on both sides of the test channel. The rib height-to-hydraulic diameter ratios (e/Dh) were 0.0625 and 0.02, and the rib pitch-to-height ratio (P/e) was 10. In addition, all test cases were investigated numerically. The commercial software FLUENT™ was used with a two-layer k-ε turbulence model. Numerically and experimentally obtained data were compared. It was determined that the heat transfer enhancement based on the heat transfer of a smooth wall levels off for Reynolds numbers over 200,000. The introduction of a second ribbed sidewall slightly increased the heat transfer enhancement whereas the pressure penalty was approximately doubled. Diminishing the rib height at high Reynolds numbers had the disadvantage of a slightly decreased heat transfer enhancement, but benefits in a significantly reduced pressure loss. At high Reynolds numbers small-scale ribs in a one-sided ribbed channel were shown to have the best thermal performance.

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