Effect of Marine Growth on an Elastically Mounted Circular Cylinder

Skaugset, Kjetil; Baarholm, Rolf

doi:10.1115/omae2008-57586

Cited by 9 publications

(4 citation statements)

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“…Similar tests of elastic mounted rigid cylinder section have been reported before [4] [5]. In these "2D" tests the rigid cylinder with strakes represents a section of a long flexible riser.…”

Section: Xmentioning

confidence: 58%

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Comprehensive Riser VIV Model Tests in Uniform and Sheared Flow

Lie

Braaten

Jhingran

et al. 2012

Volume 5: Ocean Engineering; CFD and VIV

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Despite of considerable research activity during the last decades considerable uncertainties still remain in prediction of Vortex Induced Vibrations (VIV) of risers. Model tests of risers subjected to current have been shown to be a useful method for investigation of the VIV behavior of risers with and without suppression devices.In order to get further insight on VIV of risers, an extensive hydrodynamic test program of riser models subjected to vortexinduced vibrations was undertaken during the winter 2010 by Shell Oil Company.The VIV-model test campaign was performed in the MARINTEK Offshore Basin Laboratory. A new test rig was constructed and showed to give good test conditions. Three different 38m long riser models were towed horizontally at different speeds, simulating uniform and linearly varying sheared current. Measurements were made In-Line (IL) and Cross-Flow (CF) of micro bending strains and accelerations along the risers. The test program compromised about 400 tests, which give a rich test material for further studies.In the present paper the test set-up and program are presented and selected results are reported. INTRODUCTIONThe key objectives of the riser VIV model test campaign were:

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Section: Xmentioning

confidence: 58%

“…One of the main results from the elastic mounted rigid cylinder tests [4], [5] was that both hard and soft marine growth lead to severe increase in the response compared to a clean straked riser. The transition between low and high VIV response is about 60% and 35% of the strake fin height for hard and smooth marine growth, respectively.…”

Section: Xmentioning

confidence: 99%

Comprehensive Riser VIV Model Tests in Uniform and Sheared Flow

Lie

Braaten

Jhingran

et al. 2012

Volume 5: Ocean Engineering; CFD and VIV

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show abstract

“…4) Finally, perfect strakes are assumed there. In practice these may be affected by marine growth, damaged, or deformed [34][35][36]. It remains to incorporate the effect of this on the excitation and added mass functions, so that it is accounted for in the assessment.…”

Section: Closing Remarksmentioning

confidence: 99%

Simplified VIV Response of Partially Strake-Covered Pipe Spans

Peek¹,

Yin²,

Wu³

et al. 2021

Preprint

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A simplified method for the fatigue assessment for partially strake-covered pipeline spans is provided and calibrated so that for the bare pipe case it is consistent with the current DNVGL Recommended Practice (DNVGL-RP-F105). It is based on a Rayleigh-Ritz approximation using the first undamped mode shape. In that sense it is equivalent to a single-mode analysis using Shear7, except that it accounts for frequency-dependent added mass, and the formulation is presented in a compact and convenient non-dimensional form. The method presented may also be considered a simplification of that in Vivana in that it does not account for propagating wave effects, and is therefore named “Sivana”.Like any frequency-domain method Sivana is based on the assumption of harmonic response. This requires excitation and added mass functions that define a harmonic hydrodynamic force as a function of the harmonic motion. On the other hand, current practice by DNVGL-RP-F105 is based on a response function, which gives VIV amplitude as function of reduced velocity and the Scruton mass-damping parameter Ks. To bridge this gap, an inversion technique is developed whereby the excitation function for bare pipe is derived from the DNVGL-RP-F105 response function, such that for bare pipe the Sivana calculation will lead to the same response amplitudes as DNVGL-RP-F105. The Sivana method is illustrated by an example involving a single span with different degrees of strake coverage centered at midspan.Although the Sivana method might be considered a natural and straight-forward extension of current span assessment practice to include partial strake coverage, caution is in order for certain approximations in the DNVGL-RP-F105 response function may be less appropriate for the use in this paper, than for the use envisioned by the developers of the DNVGL guidance.

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“…The interested reader is referred to the experiments by Baarholm and Skaugset [3,4] which very carefully investigated the effects of marine growth on straked rigid cylinders and analyzed different methods for simulating the marine growth on strakes. Their work is one of the most systematic attempts to simulate the marine growth on strakes.…”

Section: Description Of Experimentsmentioning

confidence: 99%

Effects of Strake Coverage and Marine Growth on Flexible Cylinder Vortex-Induced Vibrations1

Resvanis

Rao

Vandiver

2016

Journal of Offshore Mechanics and Arctic Engineering

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This paper presents some results from the recent SHELL tests at the MARINTEK basin. The tests involved towing densely instrumented flexible cylinders at Reynolds numbers up to 220,000. The main objective is to present the experimental results describing the effectiveness of different amounts of strake coverage and to explore the influence of simulated marine growth. The data are presented in terms of cross-flow (CF) response amplitudes and rainflow-counted damage rates due to the combined CF and in-line (IL) bending stresses. All the results are compared with the bare cylinder cases which will be used as a reference to determine how effective the strakes are in suppressing vortex-induced vibrations (VIV) and how this effectiveness can be affected by marine growth. The results show that even small bare sections (missing strakes) can lead to significant VIV response. Finally, the tests revealed that even moderate amounts of marine growth can quickly negate any suppression coming from the strakes.

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Effect of Marine Growth on an Elastically Mounted Circular Cylinder

Cited by 9 publications

References 0 publications

Comprehensive Riser VIV Model Tests in Uniform and Sheared Flow

Comprehensive Riser VIV Model Tests in Uniform and Sheared Flow

Simplified VIV Response of Partially Strake-Covered Pipe Spans

Effects of Strake Coverage and Marine Growth on Flexible Cylinder Vortex-Induced Vibrations1

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