scholarly journals Investigation of Parametric Resonance in Roll for Container Carrier Ships

2015 ◽  
Author(s):  
Isar Ghamari ◽  
Odd M. Faltinsen ◽  
Marilena Greco
Keyword(s):  
Parametric Resonance ◽  
Potential Flow ◽  
Present Method ◽  
Design Stage ◽  
Sea Waves ◽  
Parametric Roll ◽  
Fishing Vessels ◽  
Strip Theory ◽  
Parametric Roll Resonance ◽  
2D And 3D

Parametric roll resonance is of concern for container and fishing vessels, especially in head-sea waves. Here this phenomenon is investigated with a numerical method based on potential-flow theory with viscous corrections for the roll damping. The seakeeping problem is handled by considering a strip theory and assuming a 5-DOF system. Nonlinearities are accounted for in the Froude-Krylov and hydrostatic loads. The solver has been validated against experiments on a C11 class container carrier ship in terms of parametric resonance occurrence and features for different ship forward speeds and headings, wavelengths, wave amplitudes and wave headings. The overall agreement is good but there are some discrepancies. For instance, the simulations show capsizing in some cases while it does not happen in the experiments. The results from present method can be used to generate 2D and 3D polar diagrams identifying the zones with parametric roll occurrence, and are very handy for masters aboard ships. This type of information is valuable at design stage and can be used aboard vessels for a safer voyage.

Numerical Analysis of a Surface Ship in Waves

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Shawn Aram
Keyword(s):  
Stokes Equations ◽  
Body Motion ◽  
Irregular Waves ◽  
Design Stage ◽  
Fluid Viscosity ◽  
Sea Waves ◽  
Added Resistance ◽  
Physical Mechanisms ◽  
Strip Theory ◽  
Seakeeping Analysis

Abstract Ship's resistance and engine power to sustain ship's speed in seaways are augmented due to complex non-linear interactions between the ship and the ambient sea (waves). Ship designers, in early design stage, use an ad hoc "sea margin" to account for the effects of seaways in selecting propeller and engine. A numerical tool capable of accurately predicting added resistance and power of a ship cruising in waves would greatly help select its powering (margin) requirement and determine the optimal operating point that can maximize the energy efficiency. For seakeeping analysis, strip theory-based methods have long been used. More recently, nonlinear time-domain three-dimensional (3D) panel methods have started being used widely. A more physics-based avenue to seakeeping analysis is offered by coupled solutions of two-phase unsteady Reynolds-Averaged Navier-Stokes equations and six degrees-of-freedom rigid-body motion (RBM) equations. The URANS approach also avails itself of including the effects of propulsors, either explicitly or approximately. By accounting for all the nonlinear effects in hydrodynamic forces and moments and the resulting ship motions, and the effects of fluid viscosity and turbulence, the coupled URANS-RBM method is believed not only able to predict added resistance and speed loss more accurately, but also to provide valuable insights into the physical mechanisms underlying added resistance and power. The objectives of this study are: (1) to validate a coupled URANS-RBM solver developed for high-fidelity prediction of added resistance, speed loss and added power on ships cruising in regular head sea and irregular waves, and (2) to conduct a detailed analysis of the interactions among ship hull, propeller and waves for a 1/49 scaled model of the ONR Tumblehome (ONRT) (Model 5613) in order to shed light on the physical mechanisms leading to added resistance, speed loss and added power. Figure 1 depicts the ONRT self-propellers with two 4-bladed propellers in regular waves. The main flow features such as the free surface, the hub vortices and blade-tip vortices from the propeller, as well as vortices generated by the sonar dome, shafts, shaft brackets and bilge keels are captured.

A Non-Linear Numerical Method for the Simulation of Parametric Roll Resonance in Regular Waves

2008 ◽  
Author(s):  
T. M. Ahmed ◽  
E. J. Ballard ◽  
D. A. Hudson ◽  
P. Temarel
Keyword(s):  
Numerical Method ◽  
Potential Flow ◽  
Degrees Of Freedom ◽  
Linear Time ◽  
Three Dimensional ◽  
Regular Waves ◽  
Time Step ◽  
Parametric Roll ◽  
Non Linear ◽  
Parametric Roll Resonance

In this paper, a non-linear time-domain method is used for the prediction of parametric roll resonance in regular waves, assuming the ship to be a system with three degrees of freedom in heave, pitch and roll. Coupled heave and pitch motions are obtained using a three-dimensional frequency-domain potential flow method which also provides the requisite hydrodynamic data of the ship in roll i.e. the potential flow based added inertia and damping. Periodic changes in the underwater hull geometry due to heave, pitch and the wave profile are calculated as a function of the instantaneous breadth. This is carried out using a two-dimensional approach i.e. for sections along the ship and at each time step. This formulation leads to a mathematical model that represents the roll equation of motion with third order non-linearities in the parametric excitation terms. Non-linearities in the roll damping and restoring terms are also accounted for. This method has been applied to two different hull forms, a post-Panamax C11 class containership and a transom stern Trawler, both travelling in regular waves. Special attention is focused on the influence of different operational aspects on parametric roll. Obtained results demonstrate that this numerical method succeeds in producing results similar to those available in the literature, both numerical and experimental.

Parametric Resonance of a Fishing Vessel With and Without Anti-Roll Tank: An Experimental and Numerical Study

2017 ◽  
Author(s):  
Isar Ghamari ◽  
Odd M. Faltinsen ◽  
Marilena Greco ◽  
Claudio Lugni
Keyword(s):  
Parametric Resonance ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Internal Flow ◽  
Mooring Line ◽  
Sea Waves ◽  
Fishing Vessel ◽  
Nonlinear Method ◽  
Line System ◽  
Fishing Vessels

Parametric resonance (PR) in roll is of concern for fishing vessels, especially in head-sea waves. Here the effect of passive anti-roll free-surface tank is investigated experimentally and numerically on realistic fishing-vessel geometry at zero forward speed. On the numerical side, the onboard tank is simulated using an open source computational fluid dynamic (CFD) development platform, OpenFOAM (Open Field Operation and Manipulation). The internal flow solver is coupled with the seakeeping solver, which is based on the weakly nonlinear method proposed in [1]. Experimentally, two different relevant scenarios were examined: 1) a 2D rectangular tank with shallow-water filling depth was forced to oscillate in roll and the loads induced on the tank were measured; 2) a fishing vessel was tested in a towing tank, prescribing regular head-sea waves. The vessel was examined both without and with anti-roll tanks and a mooring-line system was designed so to control the horizontal motions with limited effect on the parametric occurrence. The experiments on the fishing vessel are considered to assess the seakeeping solver. Both model tests and numerical results confirmed the effectiveness of an on-board tank in avoiding PR. For the examined cases with tank, the parametric resonance did not occur without forcing an initial roll. Moreover, the initial roll amplitude and roll phase relative to the heave motion matter for triggering the instability.

Nonlinear Parametric Rolling in Regular Waves: An Approximate Analytical Solution for the Response Curve in the Region of First Parametric Resonance

2006 ◽  
Vol 50 (03) ◽  
pp. 239-249
Author(s):  
Gabriele Bulian
Keyword(s):  
Analytical Solution ◽  
Parametric Resonance ◽  
Response Curve ◽  
Approximate Analytical Solution ◽  
Design Stage ◽  
Parametric Roll ◽  
Analytical Methodology ◽  
Early Design Stage ◽  
Experimental Planning ◽  
Highly Nonlinear

An approximate analytical solution for the parametric roll response curve in the first parametric resonance zone is presented. Comparisons between analytical predictions and results obtained by means of numerical time domain simulations are performed in order to check the accuracy of the method. The use of a highly nonlinear 1.5-DOF model allows the disclosure of the presence of fold and pitchfork bifurcations. The method can be a simple and good aid both in the early design stage and for experimental planning. As an exercise showing the capabilities of the analytical methodology, the influence of damping parameters on the roll response is analyzed for a roll-on/roll-off (RO/RO) Pax.

scholarly journals Numerical Study of Parametric Roll on a Fishing Vessel

2013 ◽  
Author(s):  
Marilena Greco ◽  
Claudio Lugni
Keyword(s):  
Parametric Resonance ◽  
Numerical Study ◽  
Excitation Frequency ◽  
Forward Speed ◽  
Sea Waves ◽  
Fishing Vessel ◽  
Research Activity ◽  
Parametric Roll ◽  
Water On Deck ◽  
Incident Waves

Present research activity examines numerically the occurrence of parametric roll on a fishing vessel interacting with regular head-sea waves. The adopted solver is an efficient 3-D numerical Domain-Decomposition strategy for the seakeeping of a 6-dof vessel without and with small forward speed and possibly subjected to bottom-slamming and water-on-deck events. Here, the vessel has been assumed at rest and the excitation frequency is varied in the first parametric resonance zone and occurrence and features of the instability are examined in terms of nonlinearities of the incident waves and roll natural-to-incident wave frequency ratio. The analysis is performed both fully within the potential-flow theory and examining the effect on the parametric resonance of the viscous correction to the roll damping obtained from free-decay 3D model tests on the same ship. A system of four cables, horizontal in the mean configuration, will be used experimentally to limit the horizontal vessel motions. Here the numerical solver is used to analyze the influence of cable stiffness and of cable configuration on the vessel behavior and to help the design of the physical set up. The vessel has deep draft and high mean freeboard, these aspects work against the occurrence of bottom slamming and water-on-deck events. Without forward speed, no bottom slamming phenomena were observed while limited number of water-on-deck events with small amount of shipped liquid was recorded for the highest-frequency incident waves with largest steepnesses, among those causing parametric roll.

An Approximate Method for Intact Stability of Fishing Vessels

1999 ◽  
Vol 36 (03) ◽  
pp. 171-174
Author(s):  
Hüseyin Yilmaz ◽  
Abdi Kükner
Keyword(s):  
Design Stage ◽  
Design Parameters ◽  
Preliminary Design ◽  
Ship Stability ◽  
Fishing Vessels ◽  
Initial Stability ◽  
Intact Stability ◽  
Preliminary Design Stage ◽  
Reduce Risk ◽  
Vessel Stability

It is well known that stability is the most important safety requirement for ships. One should have some information on ship stability at the preliminary design stage in order to reduce risk. Initial stability of ships is an important criterion and can be closely evaluated in terms of form parameters and vertical center of gravity. In this study, using some sample ship data, approximate formulations are derived by means of regression analysis for the calculations expressed in terms of ship preliminary design parameters that can easily provide approximate GM calculations. Thus designers can be provided with ship stability at the preliminary design stage, and also a set of appropriate design parameters for improving vessel stability can easily be determined.

Roll Reduction by Rudder Control for Two Ships During Underway Replenishment

1991 ◽  
Vol 35 (02) ◽  
pp. 141-150
Author(s):  
Ming-Chung Fang
Keyword(s):  
Resonance Frequency ◽  
Present Method ◽  
A Priori ◽  
Theoretical Method ◽  
Rolling Motion ◽  
Strip Theory ◽  
Replenishment At Sea

A theoretical method for analyzing roll reduction by rudder control for ships during underway replenishment is developed. The basic idea is that, when the rudder is operating, yaw and roll moments will be generated that affect the rolling motion. This idea has been proven to be valid for a single ship running in waves and, therefore, is also applied in the present paper. Using the well-developed strip theory for two ships advancing in waves, a better set of gain coefficients for roll reduction by rudder control can be predicted a priori. From the present results, it is found that suitable rudder control indeed can reduce rolling motion especially at the resonance frequency. The results obtained by the present method can offer some valuable information for a roll-reducing autopilot. Rudder control therefore can be considered as another tool for reducing rolling motion while two ships are executing underway replenishment at sea.

Sensitivity Analysis in Parametric Rolling of a Modern Cruise Ship Using Numerical Simulations in 6-DOF

2020 ◽  
Author(s):  
Bülent Düz
Keyword(s):  
Sensitivity Analysis ◽  
Numerical Simulations ◽  
Time Domain ◽  
Nonlinear Phenomenon ◽  
Cruise Ship ◽  
Parametric Roll ◽  
Parametric Rolling ◽  
Maximum Angle ◽  
Strip Theory ◽  
The Time Domain

Abstract Parametric roll is a nonlinear phenomenon that can result in large roll angles coupled with significant pitch motions. These motions might induce large loads on the ship structure, and compromise the safety of the crew and the cargo. The severity of the motions might reach to such levels that capsizing might occur. In this study sensitivity analysis in parametric rolling of a modern cruise ship is investigated using numerical simulations. Several parameters were considered as sources of uncertainty such as the combined effect of GM and roll radius of gyration, roll damping, ship speed, and fin characteristics. In terms of fin characteristics, fin angle rate and maximum angle, fin area and aspect ratio, and fin gains were investigated. Additionally, the non-ergodicity of parametric roll was studied as well as the effect of simulation duration on the statistics of parametric roll. The simulations were carried out with a hybrid time-domain seakeeping and manoeuvring code. The time-domain code was used in combination with a strip-theory based frequency-domain program in order to calculate diffraction and radiation forces as well as added-mass. The time-domain code was able simulate the dynamic behavior of a steered ship in 6-DOF, where the motions can be large up to the moment of capsize.

scholarly journals Detection of Parametric Roll Resonance using Bayesian Discrete-Frequency Model Selection

2018 ◽  
Vol 51 (29) ◽  
pp. 444-449
Author(s):  
Justin M. Kennedy ◽  
Jason J. Ford ◽  
Tristan Perez ◽  
Francis Valentinis
Keyword(s):  
Model Selection ◽  
Parametric Roll ◽  
Frequency Model ◽  
Discrete Frequency ◽  
Parametric Roll Resonance
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