Flow Induced Motions on Multi Column Floaters

Waals, Olaf; Phadke, Amal C.; Bultema, Stephen

doi:10.1115/omae2007-29539

Cited by 32 publications

(20 citation statements)

References 27 publications

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“…This characteristic was observed in previous studies of multi-column floating platform hull without appurtenances [6], [7], [8], and also in spars with appurtenances [3], [9]. This characteristic was observed in previous studies of multi-column floating platform hull without appurtenances [6], [7], [8], and also in spars with appurtenances [3], [9].…”

Section: Resultssupporting

confidence: 78%

“…At lower mass ratios the added mass becomes relatively more important compared to the platform mass in affecting the motion of the platform and the flow pattern around the platform, and higher VIM amplitudes may occur for a wider range of reduced velocities [6]. While the mass ratios for semi-submersibles and spars are close to unity, the mass ratio for a TLP is much less than unity since the platform is not freely floating but supports the tension of the tendons.…”

Section: Model Test Set-upmentioning

confidence: 99%

“…Hence, a test set-up using low friction air bearings similar to that used in [6] is adopted. Hence, a test set-up using low friction air bearings similar to that used in [6] is adopted.…”

Section: Model Test Set-upmentioning

confidence: 99%

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The Effect of Appurtenances on the VIM Performance of a TLP for Southeast Asia

et al. 2014

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In Southeast Asia, the characteristic operating environment is strong and persistent currents with small to moderate waves, which encourages vortex induced motion (VIM) in floating platforms. Scaled model tests have always been used by the industry to check the performance of floating platforms including VIM. With improved hardware and software capacilities, numerical methods such as Computational Fluid Dynamics (CFD) analysis are now able to simulate floating platform motions in viscous fluid flow and thus have the potential to complement model tests in VIM studies. Hull appurtenances such as tendon porches, steel catenary riser (SCR) porches, caissons, pipes, chains, fairleads and anodes interact with the boundary layers and affect the points of flow separation along the hull columns which control the vortex shedding pattern of the hull. In this study, the effect of appurtenances on the VIM performance of a Tension Leg Platform (TLP) for Southeast Asian environment is investigated using a series of model tests and CFD analysis.The findings from this study may be used as a reference to properly account for the effect of VIM. The measured or calculated amplitudes of VIM may be used as input for additional load conditions to be considered in the design of the tendon mooring and riser systems of the TLP.Previous studies by others on the same subject were carried out for spars. Multi-column floating platforms do not have strakes on the columns unlike spars. Thus, significant difference in VIM behaviors between multi-column floating platforms and spars is expected. The wake is expected to remain turbulent in both full scale and model scale. For smooth cylinders, the separation point along the columns is scale dependent and this may affect the VIM responses. If the flow separates from a sharp appurtenance like a pipe, the VIM behaviors should be similar in full scale and in model scale. The results from CFD analysis generally agree with those from model test. The differences in the results from the two methods are discussed and areas for further investigation suggested.Significant VIM can adversely impact the platform mooring and riser systems in terms of both strength and fatigue life requirement and has to be properly accounted for in the platform design. Left unchecked, VIM can lead to loss of production due to unplanned repairs of the risers.

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Section: Resultssupporting

confidence: 78%

Section: Model Test Set-upmentioning

confidence: 99%

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The Effect of Appurtenances on the VIM Performance of a TLP for Southeast Asia

et al. 2014

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“…Additionally, a MARIN DDS design [14] was also simulated, aiming to further validate the present numerical model with previously published experiment data. The main characteristics of the MARIN model are shown in Table 4.…”

Section: Computational Overviewmentioning

confidence: 82%

“…Leverette [13]. Waals et al [14] studied the draft effects on VIM. When the draft changed from a typical conventional semi-submersible to a DDS, significant increases of VIM were observed.…”

mentioning

confidence: 99%

Experimental and numerical study on vortex-induced motions of a deep-draft semi-submersible

Liang

Tao

Xiao

et al. 2017

Applied Ocean Research

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An experimental study on vortex-induced motions (VIM) of a deep-draft semi-submersible (DDS) was carried out in a towing tank, with the aim to investigate the VIM effects on the overall hydrodynamics of the structure. In order to study the fluid physics associated with VIM of the DDS, a comprehensive numerical simulation was conducted to examine the characteristics of vortex shedding processes and their interactions due to multiple cylindrical columns. The experimental measurements were obtained for horizontal plane motions including transverse, in-line and yaw motions as well as drag and lift forces on the structure. Spectral analysis was further carried out based on the recorded force time history. These data were subsequently used to validate the numerical model. Detailed numerical results on the vortex flow characteristics revealed that during the “lock-in”, the vortex shedding processes of the upstream columns enhance the vortex shedding processes of the downstream columns leading to the rapid increase of the magnitude of VIM. In addition to the experimental measurements, for the two uniform flow incidences (0° and 45°) investigated, comprehensive numerical data of the parametric study on the VIM characteristics at a wide range of current strength will also serve as quality benchmarks for future study and provide guidance for practical design

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Hydrodynamic Scale Model Tests for Offshore Structures

Cozijn

Serraris

2017

Encyclopedia of Maritime and Offshore Engineering

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Hydrodynamic scalemodel tests are an indispensible part of the design of offshore structures, delivering information on platform motions and accelerations, mooring loads, impact pressures, relative wave heights, and other design aspects. The modelling capabilities of calculation tools have increased significantly in the past decades and their results are more and more reliable. However, in many cases, model tests do still have a fundamental role in the design and assessment of the platform or vessel, for example, to confirm calculation results for proven concepts or to investigate the behavior of new floater types. The main advantage of scale model tests is that all relevant physics are automatically included. This does not mean that the correct execution of model tests is an easy task. The models, instrumentation, environmental conditions, test procedures, and data analysis all require careful attention. The article aims at discussing these aspects and can thus be considered as an introduction for those new to hydrodynamic scale model testing.

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Flow Induced Motions on Multi Column Floaters

Cited by 32 publications

References 27 publications

The Effect of Appurtenances on the VIM Performance of a TLP for Southeast Asia

The Effect of Appurtenances on the VIM Performance of a TLP for Southeast Asia

Experimental and numerical study on vortex-induced motions of a deep-draft semi-submersible

Hydrodynamic Scale Model Tests for Offshore Structures

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