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 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.

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.

Numerical Methods for the Prediction of the Bilge Keel Effects on the Response of Ship-Shaped Hulls

2007 ◽  
Author(s):  
Spyros A. Kinnas ◽  
Yi-Hsiang Yu ◽  
Vimal Vinayan
Keyword(s):  
Numerical Scheme ◽  
Hydrodynamic Interaction ◽  
Roll Motion ◽  
Length Scale ◽  
Hull Form ◽  
Longitudinal Length ◽  
Forced Roll ◽  
Hull Forms ◽  
Volume Method ◽  
Bilge Keel

This paper addresses the hydrodynamic interaction and response of typical FPSO/FSO and LNG hull-forms with bilge keels. The hull-forms are assumed to be slender with the longitudinal length-scale exceeding the other two physical dimensions. This assumption allows the modeling of the flow around the hull-form in a 2-D strip-wise manner. A Finite Volume Method (FVM) based numerical model is developed to analyze the flow around the 2-D hull-sections, with and without bilge keels. The effect of the bilge keels in the damping of hull motions is presented with the application of the numerical scheme to a hull in forced roll motion, and its transient response in roll and heave decay.

Comparison of RANS Method and Discrete Vortex Method on Simulating the Roll Motion of a Ship With Bilge Keels

2018 ◽  
Author(s):  
Yichen Jiang ◽  
Xiaojie Zhao ◽  
Zhihua Zeng ◽  
Tiezhi Sun ◽  
Jiawen Li ◽  
...  
Keyword(s):  
Numerical Models ◽  
Vortex Method ◽  
Roll Motion ◽  
Fluid Viscosity ◽  
Roll Damping ◽  
Discrete Vortex ◽  
Discrete Vortex Method ◽  
Numerical Predictions ◽  
Bilge Keel ◽  
Rans Method

The prediction of roll motion of a ship section with bilge keels is particularly difficult because the flow separation and vortex shedding under the hull significantly affect the behavior of roll damping. To predict the roll damping and roll motion directly, the numerical models must simulate the fluid viscosity. Recently, Reynolds-averaged Navier–Stokes (RANS) method and Discrete Vortex Method (DVM) have been applied in this area and show promising results. In this paper, we will use both methods to simulate the free roll-decay motion of a ship section with bilge keels. The numerical predictions of the roll time histories will be compared with experimental measurements. Besides, the numerically-predicted vorticity distributions at different time instants near a bilge keel will be shown and compared. Moreover, the computation times for both numerical methods will also be reported. In this work, we will conduct the comparison for a number of cases that are with different bilge-keel heights and bilge-keel installation angles. Thus, the accuracies and the computational efficiencies will be evaluated comprehensively.

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.

Experimental Study on Hydrodynamic Performance of Mini-AUV in Non-Uniform Flow Field

2019 ◽  
Author(s):  
Jiayuan Zhuang ◽  
Jian Cao ◽  
Yumin Su ◽  
Lei Zhang ◽  
Xianzhao Yu
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Lateral Force ◽  
Uniform Flow ◽  
Hydrodynamic Performance ◽  
Experimental Investigations ◽  
Complex Flow ◽  
Three Dimensional Flow ◽  
Drift Angle ◽  
Current Profiler

Abstract Experimental investigations of hydrodynamic performance of mini-AUV in non-uniform flow field were conducted in the basin of Harbin Engineering University, the revolved body and flat body of mini-AUV model were tested respectively. The three dimensional flow fields were generated by local jet of the underwater pump, and circulated in the basin. The three dimensional velocity distributions at different positions were measured by a Doppler current profiler. The three component balance was used to measure the drag, lateral force and yawing moment acting on the mini-AUV models depending on drift angle in the flow field, and the influence of complex flow field to the hydrodynamic performance of mini-AUV indicated that drag was not sensitive to drift angle and yawing moment was increased obviously. The conducted experiments could supply reference to the maneuverability research of mini-AUV in real marine environments in the future.

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.

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.

Analysis of Roll Motion due to Asymmetric Bilge Keels

2012 ◽  
Author(s):  
Nathan Tom ◽  
Robert Seah ◽  
Dominique Roddier
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Domain Model ◽  
Roll Motion ◽  
Roll Damping ◽  
Vessel Motion ◽  
Bilge Keel ◽  
Unequal Length

Traditional frequency domain based vessel motion analyses operate under the assumption that the roll damping contribution from the port and starboard bilge keels are equivalent. In this work, we examine the roll motion of a vessel with bilge keels of unequal length using a novel methodology. Experiments conducted during the FPSO Roll JIP suggest that waves approaching from port versus starboard will induce different motion amplitudes due to the unequal bilge keel length. We examine the results from different approaches, comparing the computed response from a frequency domain analysis against those provided by a time domain model using Orcaflex with bilge keel represented by drag elements.

Numerical predictions of ship motions at high forward speed

1991 ◽  
Vol 334 (1634) ◽  
pp. 241-252 ◽  
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Steady Flow ◽  
Added Mass ◽  
Numerical Results ◽  
Experimental Results ◽  
Ship Motions ◽  
Forward Speed ◽  
Numerical Predictions

A theory for ship motions at high forward speed is presented. The theory includes interaction between the steady and unsteady flow field. Numerical results for the steady flow and added mass and damping are compared with experimental results.

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