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.

A RANS Based Method for the Estimation of Ship Roll Damping With Forward Speed

2004 ◽  
Author(s):  
Kumar B. Salui ◽  
Vladimir Shigunov ◽  
Dracos Vassalos
Keyword(s):  
High Speed ◽  
Turbulence Modeling ◽  
Finite Difference Methods ◽  
Computer Hardware ◽  
Navier Stokes ◽  
Roll Motion ◽  
Ship Motions ◽  
Viscous Effects ◽  
Flow Models ◽  
Ship Roll

For the prediction of ship roll motion, viscous effects must be taken into account. Several methods, experimental and theoretical, have previously been used to calculate hydrodynamic forces in roll motion. Theoretical methods applied so far to this problem have been based mainly on potential flow models, which cannot account for viscous effects adequately or need pre-defined flow separation like vortex methods. Recent development of computer hardware enables application of methods based on flow field discretisation such as finite-difference methods to solution of problems of practical ship design such as ship motions and control. In the present study, a Reynolds-Averaged Navier-Stokes solver is used to calculate hydrodynamic loads during forced roll motion at different Froude numbers. The solution method adopted is based on unstructured finite-volume discretisation with collocated arrangement of flow variables. A pressure-correction algorithm (SIMPLE) is used for the pressure-velocity coupling. A standard k–ε model is used for the turbulence modeling. An advanced differencing scheme called high-resolution interface capturing (HRIC) is used for accurate resolution of the free surface in the scope of a multiphase-type description. A high-speed hard chine vessel with and without skeg is studied. Close agreement is found between the present calculations and experimental results.

Roll Damping Simulations of an Offshore Heavy Lift DP3 Installation Vessel Using the CFD Toolbox OpenFOAM

2020 ◽  
Author(s):  
Brecht Devolder ◽  
Florian Stempinski ◽  
Arjan Mol ◽  
Pieter Rauwoens
Keyword(s):  
Boundary Element ◽  
Damping Coefficient ◽  
Navier Stokes ◽  
Roll Motion ◽  
Viscous Effects ◽  
Roll Damping ◽  
Two Phase ◽  
Damping Behavior ◽  
External Moment ◽  
Heavy Lift

Abstract In this work, the roll damping behavior of the offshore heavy lift DP3 installation vessel Orion from the DEME group is studied. Boundary element codes using potential flow theory require a roll damping coefficient to account for viscous effects. In this work, the roll damping coefficient is calculated using the Computational Fluid Dynamics (CFD) toolbox OpenFOAM. The two-phase Navier-Stokes fluid solver is coupled with a motion solver using a partitioned fluid-structure interaction algorithm. The roll damping is assessed by the Harmonic Excited Roll Motion (HERM) technique. An oscillating external moment is applied on the hull and the roll motion is tracked. Various amplitudes and frequencies of the external moment and different forward speeds, are numerically simulated. These high-fidelity full-scale simulations result in better estimations of roll damping coefficients for various conditions in order to enhance the accuracy of efficient boundary element codes for wave-current-structure interactions simulations.

Shape Effects on Viscous Damping and Motion of Heaving Cylinders1

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Ronald W. Yeung ◽  
Yichen Jiang
Keyword(s):  
Fluid Motion ◽  
Vortex Method ◽  
The Body ◽  
Floating Body ◽  
Navier Stokes ◽  
Inviscid Fluid ◽  
Fluid Viscosity ◽  
Viscous Damping ◽  
Viscous Effects ◽  
Shape Effects

Fluid viscosity is known to influence hydrodynamic forces on a floating body in motion, particularly when the motion amplitude is large and the body is of bluff shape. While traditionally these hydrodynamic force or force coefficients have been predicted by inviscid-fluid theory, much recent advances had taken place in the inclusion of viscous effects. Sophisticated Reynolds-Averaged Navier–Stokes (RANS) software are increasingly popular. However, they are often too elaborate for a systematic study of various parameters, geometry or frequency, where many runs with extensive data grid generation are needed. The Free-Surface Random-Vortex Method (FSRVM) developed at UC Berkeley in the early 2000 offers a middle-ground alternative, by which the viscous-fluid motion can be modeled by allowing vorticity generation be either turned on or turned off. The heavily validated FSRVM methodology is applied in this paper to examine how the draft-to-beam ratio and the shaping details of two-dimensional cylinders can alter the added inertia and viscous damping properties. A collection of four shapes is studied, varying from rectangles with sharp bilge corners to a reversed-curvature wedge shape. For these shapes, basic hydrodynamic properties are examined, with the effects of viscosity considered. With the use of these hydrodynamic coefficients, the motion response of the cylinders in waves is also investigated. The sources of viscous damping are clarified.

CFD Simulation of Roll Damping Characteristics of a Ship Mid-Section With Bilge Keel

2016 ◽  
Author(s):  
Mohsin A. R. Irkal ◽  
S. Nallayarasu ◽  
S. K. Bhattacharyya
Keyword(s):  
Fluid Dynamics ◽  
Cfd Simulation ◽  
Experimental Studies ◽  
Ship Hull ◽  
Estimation Methods ◽  
Accurate Estimation ◽  
Roll Motion ◽  
Roll Damping ◽  
Damping Characteristics ◽  
Bilge Keel

The prediction of nonlinear roll motion of ships depends highly on the accurate estimation of roll damping. The nonlinear nature of roll damping arises from the viscous flow and the associated phenomenon of flow separation around the ship hull. Roll damping changes noticeably with a slight change in the ship hull geometry and appendages. The estimation methods employed in industry are highly empirical in nature. These empirical methods were derived from combinations of model tests conducted in wave flumes and basins, and some selected formulae used in fluid dynamics. These methods have limitations and the roll damping prediction show large variation with change in the ship parameters. The advances made in Computational Fluid Dynamics (CFD) in recent times, and validation of the CFD results using experimental studies, can help in predicting roll motion and damping more accurately. The present work uses CFD as a tool to estimate roll damping of a ship mid-section with bilge keel with validation using published experimental results.

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

2013 ◽  
Author(s):  
Gustavo O. Guarniz Avalos ◽  
Juan B. V. Wanderley ◽  
Antonio C. Fernandes
Keyword(s):  
Vortex Shedding ◽  
Numerical Scheme ◽  
Strong Influence ◽  
Stokes Equations ◽  
The Body ◽  
Navier Stokes ◽  
Roll Damping ◽  
Navier Stokes Equations ◽  
Decay Test ◽  
Bilge Keel

The roll damping decay is investigated for a Floating Production Storage and Offloanding (FPSO). For this purpose, a roll decay test of FPSO is simulated by means of the numerical solution of the incompressible two-dimensional Navier-Stokes equations. The numerical results are compared with experimental data for validating the numerical scheme implemented. The simulations indicated the strong influence of the bilge radius in the damping coefficient of the FPSO section. Interesting results were obtained regarding the time series of the displacement of the body and vortex shedding around the bilge keel.

A Two-Dimensional Numerical Simulation of Roll Damping Decay of a FPSO Using the Upwind TVD Scheme of Roe-Sweby

2012 ◽  
Author(s):  
Gustavo O. Guarniz Avalos ◽  
Juan B. V. Wanderley
Keyword(s):  
Stokes Equations ◽  
Navier Stokes ◽  
Tvd Scheme ◽  
Viscous Effects ◽  
Roll Damping ◽  
Navier Stokes Equations ◽  
Decay Test ◽  
Spurious Oscillations ◽  
Volume Method ◽  
Bilge Keel

The study of roll damping is investigated for a Floating Production Storage and Offloanding (FPSO). For this purpose, a roll decay test of FPSO is simulated by means of the numerical solution of the slightly compressible Navier-Stokes equations in 2D. The governing equations are solved using the finite volume method and the upwind TVD scheme of Roe-Sweby. The roll damping for rectangular hulls is dominated by viscous effects. Strong vortices are formed around the bilge keel. Hence, in this zone, there is a discontinuity of pressure that the TVD scheme will resolve and capture the physics of the phenomenon without spurious oscillations. The numerical results are compared with experimental data for validating the numerical scheme implemented.

Effects of Shaping on Viscous Damping and Motion of Heaving Cylinders

2011 ◽  
Author(s):  
Ronald W. Yeung ◽  
Yichen Jiang
Keyword(s):  
Dynamic Properties ◽  
Fluid Motion ◽  
Vortex Method ◽  
The Body ◽  
Floating Body ◽  
Navier Stokes ◽  
Inviscid Fluid ◽  
Fluid Viscosity ◽  
Viscous Damping ◽  
Viscous Effects

Fluid viscosity is known to influence hydrodynamic forces on a floating body in motion, particularly when the motion amplitude is large and the body is of a bluff shape. While these hydrodynamic force or force coefficients have been predicted traditionally by inviscid-fluid theory, much recent advances had taken place in the inclusion of viscous effects. Sophisticated RANS (Reynolds-Averaged Navier Stokes) software are increasingly popular. However, they are often too elaborate for a systematic study of various parameters, geometry or frequency, where many runs with extensive data grid generation are needed. The Free-Surface Random-Vortex Method (FSRVM), developed at UC Berkeley in the early 2000, offers a middle-ground alternative, by which the viscous-fluid motion can be modeled and yet allowing vorticity generation be either turned on or turned off. The heavily validated FSRVM methodology is applied in this paper to examine how the draft-to-beam ratio and the shaping details of two-dimensional cylinders can alter the added inertia and viscous damping properties. A collection of four shapes is studied, varying from rectangles with sharp bilge corners to a reversed-curvature wedge shape. For these shapes, basic hydro-dynamic properties are examined, with the effects of viscosity considered. With the use of these hydrodynamic coefficients, the motion response of the cylinders in waves are also investigated. The origin of viscous damping is clarified. It is a pleasure and honor for the authors to contribute to the Jo Pinkster Symposium, held in his honor in OMAE-2011.

Flexible flapping systems: computational investigations into fluid-structure interactions

2011 ◽  
Vol 115 (1172) ◽  
pp. 593-604 ◽  
Author(s):  
T. Fitzgerald ◽  
M. Valdez ◽  
M. Vanella ◽  
E. Balaras ◽  
B. Balachandran
Keyword(s):  
Stokes Equations ◽  
Fluid Model ◽  
Navier Stokes ◽  
Aerodynamic Load ◽  
Viscous Effects ◽  
Lattice Method ◽  
Predictive Tool ◽  
Computational Approaches ◽  
Vortex Interactions ◽  
Spatio Temporal

AbstractIn the present work, the authors examine two computational approaches that can be used to study flexible flapping systems. For illustration, a fully coupled interaction of a fluid system with a flapping profile performing harmonic flapping kinematics is studied. In one approach, the fluid model is based on the Navier-Stokes equations for viscous incompressible flow, where all spatio-temporal scales are directly resolved by means of Direct Numerical Simulations (DNS). In the other approach, the fluid model is an inviscid, potential flow model, based on the unsteady vortex lattice method (UVLM). In the UVLM model, the focus is on vortex structures and the fluid dynamics is treated as a vortex kinematics problem, whereas with the DNS model, one is able to form a more detailed picture of the flapping physics. The UVLM based approach, although coarse from a modeling standpoint, is computationally inexpensive compared to the DNS based approach. This comparative study is motivated by the hypothesis that flapping related phenomena are primarily determined by vortex interactions and viscous effects play a secondary role, which could mean that a UVLM based approach could be suitable for design purposes and/or used as a predictive tool. In most of the cases studied, the UVLM based approach produces a good approximation. Apart from aerodynamic load comparisons, features of the system dynamics generated by using the two computational approaches are also compared. The authors also discuss limitations of both approaches.

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