Practical Design Considerations for Managing Marine Growth on VIV Suppression Devices

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.

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

Volume 2: CFD and VIV ◽

10.1115/omae2015-41238 ◽

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.

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Active closed-loop vortex-induced vibration control of an elastically mounted circular cylinder at low Reynolds number using feedback rotary oscillations

Acta Mechanica ◽

10.1007/s00707-017-1960-y ◽

2017 ◽

Vol 229 (1) ◽

pp. 231-250 ◽

Cited By ~ 6

Author(s):

Seyyed M. Hasheminejad ◽

Amir H. Rabiee ◽

H. R. T. Bahrami

Keyword(s):

Reynolds Number ◽

Circular Cylinder ◽

Vibration Control ◽

Closed Loop ◽

Low Reynolds Number ◽

Vortex Induced Vibration ◽

Low Reynolds

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Simulations on Hydrodynamic Coefficients of Stationary Cactus-Shaped Cylinders at a Low Reynolds Number

Volume 2: CFD and FSI ◽

10.1115/omae2018-78472 ◽

2018 ◽

Author(s):

J. Wang ◽

C. Shi ◽

Y. Liu ◽

X. Bao

Keyword(s):

Reynolds Number ◽

Low Reynolds Number ◽

Bending Moment ◽

Hydrodynamic Coefficients ◽

Rotational Angle ◽

Desert Region ◽

Helical Strakes ◽

Wind Velocities ◽

Low Reynolds ◽

Very High

Flexible cylinders, such as marine risers, often experience sustained vortex-induced vibration (VIV). Both helical strakes and fairings are demonstrated to be effective in suppressing VIV, while, helical strakes result in large drag, which increases the rotational angle and bending moment at the riser hang-off location and, fairings are cumbersome in term of storage, installation and maintenance. This study was inspired by the giant Saguaro Cacti which grow in desert region. Saguaro Cacti have shallow root system, but can grow up to fifty feet in height and can withstand very high wind velocities. In this study, numerical simulations of flow past a stationary cactus-shaped cylinder are performed in two-dimensional field at a low Reynolds number of 200. The hydrodynamic coefficients and the vortex-shedding patterns of a cactus-shaped cylinder are compared with those of a circular cylinder. In addition, a set of two cactus-shaped cylinders of tandem arrangement are also studied to investigate the effects of wake. Results showed that a cactus-shaped cylinder can reduce the drag, lift, and Strouhal number, which suggests its potential as an alternative technology to suppress VIV of a riser.

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