Influence of bilge-keel configuration on ship roll damping and roll response in waves

2020 ◽  
Vol 216 ◽  
pp. 107539
Author(s):  
Yichen Jiang ◽  
Yunfeng Ding ◽  
Yuan Sun ◽  
Yanlin Shao ◽  
Lei Sun
Keyword(s):  
Roll Damping ◽  
Ship Roll ◽  
Bilge Keel

A Piecewise Model for Prediction of Large Amplitude Total Ship Roll Damping

2011 ◽  
Author(s):  
Christopher C. Bassler ◽  
Arthur M. Reed ◽  
Alan J. Brown
Keyword(s):  
Large Amplitude ◽  
Roll Motion ◽  
Practical Implementation ◽  
Roll Damping ◽  
Damping Characteristics ◽  
Ship Roll ◽  
Piecewise Model ◽  
Physical Changes ◽  
Physical Phenomena ◽  
Bilge Keel

A piecewise model is presented to model total ship roll damping, with considerations for large amplitude roll motion effects, such as bilge keel interaction with the free-surface. The model is based on the consideration of distinct ship-specific physical phenomena, such as bilge keel emergence. Abrupt physical changes occur with these events, resulting in significant changes in the damping characteristics of the system. Without these considerations, roll motion may be under-predicted. Some additional considerations needed for the practical implementation of the proposed piecewise model are also discussed.

Roll damping decay of a FPSO with bilge keel

2014 ◽  
Vol 87 ◽  
pp. 111-120 ◽  
Author(s):  
Gustavo O.G. Avalos ◽  
Juan B.V. Wanderley ◽  
Antonio C. Fernandes ◽  
Allan C. Oliveira
Keyword(s):  
Roll Damping ◽  
Bilge Keel

Effect of Bilge Radius and Bilge Keel Height on Roll Damping Performance of Floating Structures

2021 ◽  
Author(s):  
Chang Seop Kwon ◽  
Joo-Sung Kim ◽  
Hyun Joe Kim
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Kinetic Energy ◽  
Floating Body ◽  
Rectangular Section ◽  
Roll Damping ◽  
Floating Structures ◽  
Free Decay ◽  
Computational Fluid Dynamics Cfd ◽  
Bilge Keel

Abstract A round bilge with a bilge keel structure is a key element which can alleviate roll motions of ships and floating structures by transferring the roll momentum of a floating body into the kinetic energy of water. This study presents a practical guide to properly designing a bilge radius and bilge keel height of a barge-shaped and tanker-shaped FPSOs. A parametric study to figure out the effect of bilge radius and bilge keel height on the roll damping performance is conducted through a series of numerical roll free decay simulations based on Computational Fluid Dynamics (CFD). The bilge radius is normalized by the half breadth of ship, and the bilge keel height is normalized by the maximum bilge keel height which is limited by the molded lines of a side shell and bottom shell. In addition, it is investigated to identify how the roll damping performance of a rectangular section differs from the result of a typical round bilge section with maximum available bilge keel height.

scholarly journals Bilge Keel Induced Roll Damping of an FPSO With Sponsons

2016 ◽  
Author(s):  
Babak Ommani ◽  
Nuno Fonseca ◽  
Trygve Kristiansen ◽  
Christopher Hutchison ◽  
Hanne Bakksjø
Keyword(s):  
Free Surface ◽  
Two Dimensions ◽  
The Body ◽  
Proximity Effects ◽  
Roll Damping ◽  
Damping Coefficients ◽  
Free Decay ◽  
Strip Theory ◽  
Decay Tests ◽  
Bilge Keel

The bilge keel induced roll damping of an FPSO with sponsons is investigated numerically and experimentally. The influence of the bilge keel size, on the roll damping is studied. Free decay tests of a three-dimensional ship model, for three different bilge keel sizes are used to determine roll damping coefficients. The dependency of the quadratic roll damping coefficient to the bilge keel height and the vertical location of the rotation center is studied using CFD. A Navier-Stokes solver based on the Finite Volume Method is adopted for solving the laminar flow of incompressible water around a section of the FPSO undergoing forced roll oscillations in two-dimensions. The free-surface condition is linearized by neglecting the nonlinear free-surface terms and the influence of viscous stresses in the free surface zone, while the body-boundary condition is exact. An averaged center of rotation is estimated by comparing the results of the numerical calculations and the free decay tests. The obtained two-dimensional damping coefficients are extrapolated to 3D by use of strip theory argumentations and compared with the experimental results. It is shown that this simplified approach can be used for evaluating the bilge keel induced roll damping with efficiency, considering unconventional ship shapes and free-surface proximity effects.

Ship Roll Motion Damping Using Bilge Keels – A Detailed CFD Investigation

2015 ◽  
Author(s):  
Joshua Counsil ◽  
Kevin McTaggart ◽  
Dominic Groulx ◽  
Kiari Boulama
Keyword(s):  
Experimental Studies ◽  
The Body ◽  
Navier Stokes ◽  
Roll Motion ◽  
Empirical Methods ◽  
Viscous Effects ◽  
Vortex Interactions ◽  
Ship Roll ◽  
Semi Empirical ◽  
Bilge Keel

A study has been undertaken to test the value of unsteady Reynolds-averaged Navier-Stokes (URANS) and traditional semi-empirical methods in the face of complex ship roll phenomena, and provide insight into the selection of bilge keel span for varying roll amplitudes. The computational fluid dynamics (CFD) code STAR-CCM+ is employed and two-dimensional submerged bodies undergoing forced roll motion are analyzed. The spatial resolution and timestepping scheme are validated by comparison with published numerical and experimental studies. The model is then applied to a fully-submerged circular cylinder with bilge keels of varying span and undergoing roll motion at varying angular amplitudes. Extracted hydrodynamic coefficients indicate that in general, increasing displacement amplitude and bilge keel span yields increased added mass and increased damping. The relationship is complex and highly dependent upon vortex interactions with each other and the body. The semi-empirical methods used for comparison yield good predictions for simple vortex interactions but fail where viscous effects are strong. Hence, URANS methods are shown to be necessary for friction-dominated flows while semi-empirical methods remain useful for initial design considerations.

scholarly journals Bilge-Keel Influence on Free Decay of Roll Motion of a Realistic Hull1

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Yichen Jiang ◽  
Ronald W. Yeung
Keyword(s):  
Free Surface ◽  
Fluid Motion ◽  
Three Dimensional ◽  
Vortex Method ◽  
Roll Motion ◽  
Two Dimensional ◽  
Desktop Computer ◽  
Roll Damping ◽  
Discrete Vortex ◽  
Bilge Keel

The prediction of roll motion of a ship with bilge keels is particularly difficult because of the nonlinear characteristics of the viscous roll damping. Flow separation and vortex shedding caused by bilge keels significantly affect the roll damping and hence the magnitude of the roll response. To predict the ship motion, the Slender-Ship Free-Surface Random-Vortex Method (SSFSRVM) was employed. It is a fast discrete-vortex free-surface viscous-flow solver developed to run on a standard desktop computer. It features a quasi-three-dimensional formulation that allows the decomposition of the three-dimensional ship-hull problem into a series of two-dimensional computational planes, in which the two-dimensional free-surface Navier–Stokes solver Free-Surface Random-Vortex Method (FSRVM) can be applied. In this paper, the effectiveness of SSFSRVM modeling is examined by comparing the time histories of free roll-decay motion resulting from simulations and from experimental measurements. Furthermore, the detailed two-dimensional vorticity distribution near a bilge keel obtained from the numerical model will also be compared with the existing experimental Digital Particle Image Velocimetry (DPIV) images. Next, we will report, based on the time-domain simulation of the coupled hull and fluid motion, how the roll-decay coefficients and the flow field are altered by the span of the bilge keels. Plots of vorticity contour and vorticity isosurface along the three-dimensional hull will be presented to reveal the motion of fluid particles and vortex filaments near the keels.

Some Topics for Estimation of Bilge Keel Component of Roll Damping

2019 ◽  
pp. 131-150
Author(s):  
Toru Katayama ◽  
Yuuki Yoshioka ◽  
Takahiro Kakinoki ◽  
Shugo Miyamoto ◽  
Yoshiho Ikeda
Keyword(s):  
Roll Damping ◽  
Bilge Keel

The Influence of Vortex Formation on the Damping of FPSOs With Large Width Bilge Keels

2012 ◽  
Author(s):  
Allan C. de Oliveira ◽  
Antonio Carlos Fernandes ◽  
Hélio Bailly Guimarães
Keyword(s):  
Pressure Distribution ◽  
Vortex Shedding ◽  
Vortex Formation ◽  
Roll Damping ◽  
Flat Bottom ◽  
Long Time ◽  
Large Width ◽  
Decay Tests ◽  
Visualization Techniques ◽  
Bilge Keel

The roll damping of a FPSO assessment is a different subject than the ship case. The fact that the FPSO is not moving changes the flow hydrodynamics in such a way that the well established understanding is no longer applied. This is so at least for certain particularities such as flat bottom, no lift effect due to zero velocity, and so on. Recent researches have proven the strong effect of the vortex shedding on the roll damping of a FPSO mainly when large width bilge keel are present. Although these effects are known by a long time for ships, the increase of the vortex magnitude due the large width bilge keels on a FPSO has let to uncertainties about the behavior of the structures and the situation is challenging. It has been understood that the vortex can modify deeply the pressure distribution along the FPSO hull in such way that the final roll dissipation is higher. Surprisingly, under certain conditions the memory effects are small. The use of visualization techniques allied to the analysis of several decay tests for the same hull can help the understanding of several aspects such as the uncertainty in the measurements and the vortex behavior.

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