Modelling of Roll Damping Effects for a Fishing Vessel With Forward Speed

2015 ◽  
Author(s):  
K. G. Aarsæther ◽  
D. Kristiansen ◽  
B. Su ◽  
C. Lugni
Keyword(s):  
Large Amplitude ◽  
Well Being ◽  
Roll Motion ◽  
Ship Motions ◽  
Limiting Factor ◽  
Real Problem ◽  
Forward Speed ◽  
Roll Damping ◽  
Damping Effects ◽  
Wave Induced

Vessels in the ocean-going fishing fleet are in general operating in almost all weather conditions. This includes operation in high sea-states which may lead to large amplitude ship motions, depending on the seakeeping characteristics of the vessel. Wave-induced ship motions are important factors for the safety and well-being of fishermen at work. Generally, potential flow theory overpredicts wave-induced roll motion amplitudes for conventional ship hulls. This is due to the presence of viscous damping effects in reality. Large amplitude roll motion of ships can be a real problem if no anti-rolling devices (e.g. bilge keels, anti-rolling tanks or roll-damping fins) are installed, as the roll damping coefficient of a ship is the limiting factor for the resonant roll motion amplitudes. The different components of roll damping for a ship at forward speed were investigated by Ikeda et al. [1], [2] and [3] and updated guidelines for numerical estimation of roll damping have been presented by the International Towing Tank Conference [4], where a component discrete type method for estimation of the damping is suggested. The different roll-damping components of Ikeda et al. has been complemented by skeg damping for smooth hulls [5]. This paper presents comparison between model experiments and the numerical results obtained from the guidelines [4] where the effects of bilge-keels and skeg are isolated.

Three-Dimensional Effects for a Ship Experiencing Large Amplitude Roll Motion

2011 ◽  
Author(s):  
Christopher C. Bassler ◽  
Ronald W. Miller
Keyword(s):  
Large Amplitude ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Roll Motion ◽  
Ship Motions ◽  
Forward Speed ◽  
Strip Theory ◽  
Calm Water ◽  
Large Amplitude Motions ◽  
3D Effects

Recent advancements have been made to consider the effects of large amplitude motions for roll damping models used for numerical ship motion performance assessments. These advancements have been focused on the development and expansion of models for potential flow simulation tools with sectional formulations. However, additional 3D effects due to vortex shedding, flow convection downstream, waves, and bilge keel emergence and submergence during large roll motion may be important, but are typically neglected in the sectional formulations. A series of RANS computations were performed for both 2D and 3D conditions of large amplitude ship roll motion, with and without forward speed, and in calm water and in waves. Comparisons were made to available experimental data for the 2D calm water conditions at zero-speed. These results were then assessed with the 3D conditions to develop improved understanding of additional 3D effects, including forward speed and waves, which should be considered for future developments of strip-theory approaches for ship motions prediction.

Experimental Study on a Relation Between Nonlinear Hydrodynamic Forces and Wave-Induced Ship Motions

2019 ◽  
Author(s):  
Masakazu Taguchi ◽  
Masashi Kashiwagi
Keyword(s):  
Large Amplitude ◽  
Equations Of Motion ◽  
Linear Equations ◽  
Hydrodynamic Forces ◽  
Ship Motion ◽  
Ship Motions ◽  
Practical Calculation ◽  
Wave Loads ◽  
Nonlinear Ship Motion ◽  
Wave Induced

Abstract Nowadays, in maritime industries, container ships increase in size and they have large flares, which may induce nonlinear wave loads in large-amplitude waves. It is also well known that hydrodynamic forces acting on a ship and resulting ship motions show nonlinearities at some range of wave frequencies. Therefore, we should investigate not only correct estimation of wave loads and ship motions, but also nonlinear ship-motion characteristics in large-amplitude waves. However, it is not that clear which nonlinear hydrodynamic force terms are dominating for the nonlinearity in the ship motions. Although the linear equations of motion have been used, they should be modified to incorporate at least the most important nonlinear hydrodynamic forces and to establish a practical calculation method taking account of only the indispensable nonlinear terms. In this research, we did extensive experimental measurement of hydrodynamic forces and wave-induced ship motions, with which we aim to understand what are practically important nonlinear terms, and to derive practical nonlinear ship motion equations through numerical computation and comparison with experimental data.

A Roll Damping Analysis of a Standard US Naval Hull Form (DTMB 5415)

2021 ◽  
Vol 163 (A1) ◽  
pp. 79-86
Author(s):  
L F Hu ◽  
Q T Gong ◽  
Z M Yuan ◽  
X Y Wang ◽  
J X Duan
Keyword(s):  
Numerical Simulation ◽  
Vof Method ◽  
Navier Stokes ◽  
Roll Motion ◽  
Ship Motions ◽  
Stability Criteria ◽  
Fluid Interface ◽  
Roll Damping ◽  
Hull Form ◽  
Us Navy

Accurate prediction of roll damping is important in calculating the roll motion of a ship. This paper presents a roll decay analysis of an intact US Navy Destroyer hull form (DTMB 5415) using a Navier–Stokes (NS) solver with the volume of fluid (VOF) method. Dynamic overset mesh techniques were employed to handle mesh updating required to obtain transient ship motions. The VOF method was used to capture the fluid interface. The effect of turbulence was considered by means of a k-w and a k-e model. A sensitivity analysis was conducted, in terms of the grid, timesteps and degree of freedom. The roll decay results of the numerical simulation have been compared with those of prior physical model testing (Gokce and Kinaci, 2018), and the different roll decay responses used to predict the roll damping. It is intended that this research be a useful step towards establishing intact ship stability criteria, as part of current research.

Damping Coefficients for Extreme Rolling and Capsize: An Analytical Approach

2000 ◽  
Vol 44 (01) ◽  
pp. 1-13 ◽  
Author(s):  
K. J. Spyrou ◽  
J. M. T. Thompson
Keyword(s):  
Hamiltonian System ◽  
Closed Form ◽  
Large Amplitude ◽  
Analytical Approach ◽  
Roll Motion ◽  
Elliptic Type ◽  
Roll Damping ◽  
Damping Coefficients ◽  
Linear And Nonlinear ◽  
The Law

A method to identify the law of roll motion decay from extreme angles is presented based on perturbations of the elliptic-type solutions of the corresponding Hamiltonian system. Restoring polynomials up to the 7th order are considered. It is shown that the decay law can be expressed in closed form for up to quintic restoring. The method should be especially useful for deriving linear and nonlinear roll damping coefficients in the context of ship capsize investigations where the large amplitude behavior, near to the angle of vanishing stability, needs to be taken into account.

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.

scholarly journals Comparison of AQWA, GL Rankine, MOSES, OCTOPUS, PDStrip and WAMIT With Model Test Results for Cargo Ship Wave-Induced Motions in Shallow Water

2015 ◽  
Author(s):  
Tim Gourlay ◽  
Alexander von Graefe ◽  
Vladimir Shigunov ◽  
Evert Lataire
Keyword(s):  
Shallow Water ◽  
Offshore Wind ◽  
Ship Motions ◽  
Forward Speed ◽  
Test Results ◽  
Ship Hulls ◽  
Cargo Transport ◽  
Model Geometry ◽  
Wave Induced ◽  
Offshore Wind Parks

A benchmarking study is carried out concerning wave-induced ship motions in shallow water, predicted with commercially available codes AQWA, GL Rankine, MOSES, OCTOPUS, PDStrip and WAMIT. Comparison is made with experiments for three cargo ship models tested at Flanders Hydraulics Research. The same IGES models of the ship hulls were used in all codes to ensure consistent representation of the model geometry. The comparisons may be used to assess the suitability of each code for zero-speed applications such as berthed ship motions and under-keel clearance, as well as forward-speed applications such as under-keel clearance in navigation channels. Another, quickly developing, application area that requires analysis of seaway-induced ship motions in shallow water, is analysis of motions, accelerations and loads on cargo transport, installation and service vessels for offshore wind parks.

Improving the Panel-Free Method for the Prediction of Ship Motions and Wave Induced Loads

2017 ◽  
Author(s):  
Wei Qiu ◽  
Heather Peng ◽  
Junshi Wang ◽  
Shahriar Nizam
Keyword(s):  
Simple Algorithm ◽  
Design Stage ◽  
Ship Motions ◽  
Wave Loads ◽  
Forward Speed ◽  
Early Design Stage ◽  
B Splines ◽  
Frequency Domain Methods ◽  
Nurbs Surfaces ◽  
Wave Induced

Frequency-domain methods are proven efficient and reliable, especially for zero forward speed, in early design stage for the prediction of ship motions and wave-induced wave loads. There are still challenges for ships with forward-speed due to the inaccuracy in the computation of m-terms. In this paper, the panel-free method is further improved to predict motions and wave-induced loads on real ships with forward speeds. A simple algorithm has been developed to re-arrange the control points for Non-Uniform Rational B-Splines (NURBS) surfaces. This method led to reliable and accurate m-term computations and therefore improved ship motion and load predictions. Validation studies have been carried out for a hydroelastic model of a frigate. Computed motions and loads were compared with experimental data.

Experimental Investigation of Viscous Roll Damping on the DTMB Model 5617 Hull Form

2007 ◽  
Author(s):  
Paisan Atsavapranee ◽  
Jason B. Carneal ◽  
David Grant ◽  
A. Scott Percival
Keyword(s):  
Flow Field ◽  
Lateral Force ◽  
Added Mass ◽  
Viscous Drag ◽  
Experimental Investigations ◽  
Roll Motion ◽  
Forward Speed ◽  
Roll Damping ◽  
Hull Form ◽  
Bilge Keel

A systematic series of model tests have been performed at NSWCCD to explore the mechanisms of roll damping around a conventional combatant hull form (DTMB model #5617) and an advanced tumble-home hull form (DTMB model #5613-1). Both free roll decay and forced oscillation experiments were carried out in calm water and in waves, over a range of forward speeds. These experimental investigations were performed within the overall context of continuing efforts to advance the capability to assess seakeeping, maneuvering, and dynamic stability characteristics of a surface combatant. Data gathered in these experiments are currently being utilized to develop empirical and analytical roll damping models and to validate the accuracy of simulation programs in the calculation of various components of hydrodynamic forces. This paper will specifically discuss a single-degree-of-freedom free roll decay experiment, with measurements of the appendage lateral force and the associated flow field generated during ship roll motion on the DTMB #5617 model. Using particle-image velocimetry (PIV) measurements, two-dimensional unsteady flow patterns around the bilge keels were performed to study the mechanisms of viscous roll damping due to bilge keels. In addition, lateral forces and moments on the bilge keels, rudders, and propellers have been measured to provide a direct assessment of component roll damping. Analysis for appendage forces and correlation with the measured flow field yield several new important insights into the physical mechanisms of bilge keel roll damping. Flow field observation reveals complex phenomena of viscous flow separations and vortex formation around the bilge keel during different phases of the roll motion cycle. The lateral force on the bilge keels was modeled as the sum of an added mass component and a viscous drag component. The viscous drag coefficients are found to depend strongly on ship forward speed and roll amplitude, but the added mass coefficients are relatively constant for the range of forward speed and roll amplitude investigated.

scholarly journals Stochastic Inverse Identification of Nonlinear Roll Damping Moment of a Ship Moving at Nonzero-Forward Speeds

2012 ◽  
Vol 2012 ◽  
pp. 1-22 ◽  
Author(s):  
S. L. Han ◽  
Takeshi Kinoshita
Keyword(s):  
Nonlinear Damping ◽  
Rolling Motion ◽  
Forward Speed ◽  
Roll Damping ◽  
Nonparametric Approach ◽  
Nonlinear Responses ◽  
Different Types ◽  
Experimental Trials ◽  
And Control ◽  
Ship Rolling

The nonlinear responses of ship rolling motion characterized by a roll damping moment are of great interest to naval architects and ocean engineers. Modeling and identification of the nonlinear damping moment are essential to incorporate the inherent nonlinearity in design, analysis, and control of a ship. A stochastic nonparametric approach for identification of nonlinear damping in the general mechanical system has been presented in the literature (Han and Kinoshits 2012). The method has been also applied to identification of the nonlinear damping moment of a ship at zero-forward speed (Han and Kinoshits 2013). In the presence of forward speed, however, the characteristic of roll damping moment of a ship is significantly changed due to the lift effect. In this paper, the stochastic inverse method is applied to identification of the nonlinear damping moment of a ship moving at nonzero-forward speed. The workability and validity of the method are verified with laboratory tests under controlled conditions. In experimental trials, two different types of ship rolling motion are considered: time-dependent transient motion and frequency-dependent periodic motion. It is shown that this method enables the inherent nonlinearity in damping moment to be estimated, including its reliability analysis.

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