Experimental investigation and CFD simulation of heave damping effects due to circular plates attached to spar hull
TL;DR: In this article, an investigation of the wave excitation and hydrodynamic reaction forces acting on floating structures with and without damping elements is presented taking spar platform as the candidate structure.
Abstract: Damping elements are used in ships and offshore structures as response reduction devices for maintaining the motion response within acceptable limits. The design of these elements relies on a combination of empirical approach and past experience. In this paper, an investigation of the wave excitation and hydrodynamic reaction forces acting on floating structures with and without damping elements is presented taking spar platform as the candidate structure. Understanding the flow pattern and vortex structure around these circular heave damping plates helps correlate the energy dissipation and damping. In the present study, measurement of hydrodynamic damping and inertia forces and response were carried out to establish the relationship between wave frequency and damping ratio. Flow pattern around the damping elements has been simulated using computational fluid dynamics (CFD) approach. Furthermore, flow visualisation and velocity measurement using particle image velocimetry (PIV) technique has been carried...
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TL;DR: In this paper, a model of a semi-submersible floating offshore wind turbine with a vertical flap at its edge is presented, and the influence of the flap on the hydrodynamic coefficients is investigated through a results comparison with the plain solid one.
78 citations
TL;DR: In this paper, the hydrodynamic coefficients of multiple heave plates are studied for offshore structures to reduce heave responses in oscillating flows, and the added mass and drag coefficients for a single and double heave plate with circular, octagonal and square cross-sections are proposed to cover a wide range of application.
35 citations
TL;DR: In this article, the effect of wave radiation due to heave, surge, and pitch by a box-type floating structure based on computational fluid dynamics simulations using OpenFOAM is analyzed.
17 citations
TL;DR: In this article, an alternate hull form of a shape similar to a buoy with deep draft has been proposed in order to reduce the heave motion in long-period swells or near resonant period.
Abstract: Spar platforms are used for drilling, production, storage and offloading of oil in deep water. Spar with its deep draft and large inertia experience low heave and pitch motions in operating conditions. However, the heave motions can be large when encountered by long-period swells or near resonant period. The heave motion of the Spar platforms can be reduced by decreasing the water plane area, increasing the draft, the added mass and/or damping. Various alternatives to reduce the heave motion in long-period swells have been in the fore front of research for the last two decades. An alternate hull form of a shape similar to a buoy with deep draft has been proposed in this study. The buoy form Spar is a cylindrical floating vessel with curved surface near the water plane. The present study focus on the efficiency of the buoy form Spar in reducing the heave motion and increasing the heave natural period. A classic Spar of 31 m diameter and deep draft buoy form Spars with 25 and 20 m diameter at the water plan...
13 citations
TL;DR: In this article, the authors investigated the effect of Mathieu instability on the hydrodynamic response of a Spar hull in a near-resonant region of loading, especially in harsh met-ocean conditions.
Abstract: The use of Spar hulls in floating solutions for offshore oil and gas application is well established. However, the studies on hydrodynamic responses in near-resonant region of loading, especially in harsh met-ocean conditions are limited. The phenomenon of Mathieu instability and reducing its effect on hydrodynamic response using heave damping plate configurations has been investigated using experimental studies and numerical simulation. This near-resonant-coupled response has been investigated in this study by tuning the pitch and heave natural frequency of the Spar such that the ratio becomes half. This may lead to increased response due to Mathieu instability and hence this study will provide insight into the response characteristics. The experimental investigations were conducted in a laboratory wave basin using a scale model (1:150) Spar hull with four different configurations of heave damping plate in regular waves. The hydrodynamic response of the proposed configurations was measured and simulated ...
12 citations
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TL;DR: In this paper, the concept of a fractional volume of fluid (VOF) has been used to approximate free boundaries in finite-difference numerical simulations, which is shown to be more flexible and efficient than other methods for treating complicated free boundary configurations.
11,567 citations
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25 Oct 1990
TL;DR: In this paper, linear-wave induced motions and loads on floating structures were modeled as Second-order nonlinear problems. But the authors did not consider the effects of the wind and current on the floating structures.
Abstract: 1. Introduction 2. Sea environment 3. Linear-wave induced motions and loads on floating structures 4. Numerical methods for linear-wave induced motions and loads 5. Second-order non-linear problems 6. Current and wind loads 7. Viscous wave loads and damping 8. Stationkeeping 9. Water impact and entry References Index.
1,976 citations
"Experimental investigation and CFD ..." refers background or methods in this paper
...The heave responses of the spar models obtained from the experiments are expressed as the response amplitude operators (RAOs) and compared with the RAO obtained by a simplified approach as reported in Kirti (2009) is shown in Figure 17....
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...It can be seen from Equation (3) that the heave excitation force reduces with an increase in the heave added mass. This effect was considered by Haslum (2000) as the heave cancellation effect....
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...constitute the dynamic zone which is updated at each time step according to the velocity input from the UDF. The dynamic meshing technique adds or removes the layers of cells adjacent to the moving boundary, based on the height of the cells adjacent to the moving surface. This motion of the moving wall generates waves in the NWT which should be similar to those generated in the glass flume. An absorber was defined on the other end for preventing reflection using the porous media method described by Zhan et al. (2010) which works on the basis of energy dissipation mechanism....
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TL;DR: In this article, the authors investigated the hydrodynamic characteristics (added mass and damping) of oscillatory solid or porous disks using model scale experiments using forced oscillation model tests using a planar motion mechanism.
114 citations
"Experimental investigation and CFD ..." refers background in this paper
...Tao and Daniel (2008) conducted model tests on the hydrodynamic behaviour of solid and porous circular plates....
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TL;DR: In this paper, a finite difference method is employed to solve the incompressible Navier-Stokes equations in the primitive-variables formulation, and test cases were used to guide selection of the size of flow domain, numerical parameters, and to verify that the resultant method was both convergent and accurate.
100 citations
TL;DR: In this article, three vortex shedding modes, independent vortex shedding, interactive vortex shedding and uni-directional vortex shedding for flow induced by oscillatory vertical cylinder with a disk attached at its keel were presented.
79 citations
"Experimental investigation and CFD ..." refers background in this paper
...Tao and Thiagarajan (2003) demonstrated that damping decreases as the thickness of a disk increases....
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