Mathematical Methods of Physics.

To investigate the dynamic response of a floating moored oscillating water column device under realistic sea states, a focused wave technique was developed in this study to generate user-defined wave trains in a wave basin equipped with a piston-type wavemaker. The experimental setup allowed for simultaneous measurements of the designed focused wave trains, internal chamber wave elevations and air pressure, dynamic tendon response and the model's global motion responses. Based on the experimental results it was found that to accurately replicate the theoretical wave time series, a minimal focal reconstruction of 200 components was required which resulted in a focused wave regeneration accuracy greater than 93% with strong repeatability. The tested model showed typical motion responses to that of generalised tension leg platform systems with significant surge offsets along with stiff heave and pitch motions. Applying vertical tendons to the system allowed for the floating offshore device to be exposed to deeper waters, and hence the larger energy source associated with deep water ocean waves.

Hydrodynamic performance of a floating offshore OWC wave energy converter: An experimental study

Risk assessment of LNG and FLNG vessels during manoeuvring in open sea

Experimental investigation of wave-in-deck impact events on a TLP model

This article describes a series of model tests conducted to examine extreme wave events associated with tropical cyclonic conditions and their impacts on an offshore deck structure. Extreme waves of a representative cyclonic sea state were examined in a towing tank within long-crested irregular wave trains. Experimental results presented include global forces and localised slamming pressures acting on a rigidly mounted box-shaped deck, which represents a simplified topside structure of a tension leg platform. The effect of static set-down on the still-water air gap was investigated by applying an equivalent reduction for the deck clearance. It was found that a small reduction of 20 mm (2.5 m full scale) in the original deck clearance can lead to a doubling of the magnitude of the horizontal force and the vertical upward-directed force components, as well as significantly increased slamming pressures in many locations on the deck underside.

/pdf/measurements-of-global-and-local-effects-of-wave-impact-on-a-3eooxtg8bf.pdf

Measurements of global and local effects of wave impact on a fixed platform deck

The risk assessment of wave-in-deck loading on fixed platform decks requires accurate prediction of both global and local loading. In this paper, the vertical loading generated on the bottom plate of a rigidly mounted box-shaped structure due to unidirectional regular waves is computed by means of two approaches. The first is a component-based approach based on Kaplan's method and the second is a computational fluid dynamics (CFD) approach based on the volume of fluid (VOF) method implemented in the commercial CFD code FLUENT. Different parameters including wave steepness and air gap are tested. The obtained results are validated against tank experiments. The study revealed that when the wave-in-deck events are measured globally and locally the load magnitude, its duration as well as its distribution is better evaluated and the uncertainty involved with these impulsive loads can be reduced. It was found that in many cases Kaplan's method underestimates the magnitude of the force in the upward direction. CFD force predictions were found to be in better agreement with the measured forces. Copyright © 2014 by the International Society of Offshore and Polar Engineers (ISOPE).

Vertical Wave-in-Deck Loading and Pressure Distribution on Fixed Horizontal Decks of Offshore Platforms

This paper describes a series of model tests of a rigidly mounted tension leg platform (TLP) subjected to extreme wave events corresponding to long-crested irregular wave trains of a 10,000-year cyclonic sea state. The experimental setup was instrumented to simultaneously measure wave surface elevations in the vicinity of the model, global wave impact forces and local pressure distribution on the underside of the model's topside deck. Model accelerations were also monitored for each wave impact event so that the inertial force due to structural dynamic response could be identified. The deck–column intersection areas were found to experience large wave-in-deck slamming pressures, in particular around the aft columns. A reduction of the deck clearance was found to increase the magnitude of the global horizontal forces; however, the global vertical forces and local wave-in-deck slamming pressures did not follow this trend.

/pdf/experimental-investigation-of-extreme-wave-impacts-on-a-15oj8pgt2h.pdf

Experimental investigation of extreme wave impacts on a rigid TLP model in cyclonic conditions

The reduction in design air gap has been considered as a threat in the amplification of wave-in-deck loads on both fixed and floating offshore platforms. In this paper, the wave-in-deck forces on a fixed plate of a rigidly mounted box-shaped structure due to monochromatic regular waves are computed by means of a computational fluid dynamics (CFD) approach based on the volume of fluid (VOF) method implemented in the commercial CFD codes. Different parameters including wave steepness and air gap are tested. The obtained results are validated against tank experiments. The measured peaks of force components were analysed using one-way ANOVA (analysis of variance) in order to test the force variation over time. CFD force predictions were found to be in good agreement with the measured forces.

/pdf/prediction-of-wave-in-deck-loads-on-offshore-structures-5g30wpiayr.pdf

Prediction of wave-in-deck loads on offshore structures using CFD

This paper presents an experimental and numerical investigation into the magnitude and distribution of the hydrodynamic loads affecting a fixed multicolumn offshore platform (rigidly mounted tension leg platform) when subjected to extreme wave events All wave load components, including wave-in-deck slamming pressures, were predicted using a commercial computational fluid dynamics (CFD) code STAR-CCM+ and compared against experimental measurements Slamming pressures were calculated using both data obtained locally at discrete points and globally averaged over the whole exposed area of the deck In all simulated cases, the deck area exposed to a wave-slamming event was found to be in contact with a water–air mixture with a significant proportion of air phase It was concluded that the slamming pressure data for the exposed area provided better insights into the pressure changes due to air compressibility and its content

/pdf/the-impact-of-extreme-wave-events-on-a-fixed-multicolumn-2sgg8poqix.pdf

Yuriy Drobyshevski

Papers

Experimental investigation of wave-in-deck impact events on a TLP model

Vertical Wave-in-Deck Loading and Pressure Distribution on Fixed Horizontal Decks of Offshore Platforms

Experimental investigation of extreme wave impacts on a rigid TLP model in cyclonic conditions

Prediction of wave-in-deck loads on offshore structures using CFD

The Impact of Extreme Wave Events on a Fixed Multicolumn Offshore Platform