Sailing Yacht Capsizing

1983 ◽  
Author(s):  
Karl Kirkman ◽  
Toby J. Nagle ◽  
Joseph O. Salsich
Keyword(s):  
Linear Regression ◽  
Model Tests ◽  
Significant Progress ◽  
Wave Impact ◽  
Single Wave ◽  
Sailing Yacht

A joint SNAME/USYRU Project for Safety From Capsizing has led to significant progress in an understanding of the causes and mechanism of the single wave impact capsize. The paper traces the background of the project, outlines the approach selected in pursuing answers to the concerns of the yachting community, presents related findings from other research and describes capsizing model tests and the linear regression of the Fastnet '79 data.

Sailing Yacht Capsizing

1981 ◽  
Author(s):  
Olin J. Stephens ◽  
Karl L. Kirkman ◽  
Robert S. Peterson
Keyword(s):  
Stability Analysis ◽  
Dynamic Mechanism ◽  
Focused Attention ◽  
Breaking Wave ◽  
Wave Impact ◽  
Single Wave ◽  
Loss Of Life ◽  
Classical Stability ◽  
Sailing Yacht

The 1979 Fastnet focused attention upon yacht capsizes and resulting damage and loss of life. A classical stability analysis does not clearly reveal some of the characteristics of the modern racing yacht which may exacerbate a capsizing tendency. A review of the mechanism of a single-wave-impact capsize reveals inadequacies in static methods of stability analysis and hints at a connection between recent design trends and an increased frequency of capsize. The paper traces recent design trends, relates these to capsizing by a description of the dynamic mechanism of breaking wave impact, and outlines the unusual oceanography of the 1979 Fastnet which led to a heightened incidence of capsize.

scholarly journals EXTREME WAVE PRESSURES AND LOADS ON A PILE-SUPPORTED WHARF DECK - INFLUENCES OF AIR GAP AND WAVE DIRECTION

2018 ◽  
pp. 5
Author(s):  
Andrew Cornett
Keyword(s):  
Offshore Structures ◽  
Model Tests ◽  
Scale Model ◽  
Extreme Waves ◽  
Wave Direction ◽  
Coastal Structures ◽  
Extreme Wave ◽  
Wave Impact ◽  
The Past ◽  
Water Depths

Many deck-on-pile structures are located in shallow water depths at elevations low enough to be inundated by large waves during intense storms or tsunami. Many researchers have studied wave-in-deck loads over the past decade using a variety of theoretical, experimental, and numerical methods. Wave-in-deck loads on various pile supported coastal structures such as jetties, piers, wharves and bridges have been studied by Tirindelli et al. (2003), Cuomo et al. (2007, 2009), Murali et al. (2009), and Meng et al. (2010). All these authors analyzed data from scale model tests to investigate the pressures and loads on beam and deck elements subject to wave impact under various conditions. Wavein- deck loads on fixed offshore structures have been studied by Murray et al. (1997), Finnigan et al. (1997), Bea et al. (1999, 2001), Baarholm et al. (2004, 2009), and Raaij et al. (2007). These authors have studied both simplified and realistic deck structures using a mixture of theoretical analysis and model tests. Other researchers, including Kendon et al. (2010), Schellin et al. (2009), Lande et al. (2011) and Wemmenhove et al. (2011) have demonstrated that various CFD methods can be used to simulate the interaction of extreme waves with both simple and more realistic deck structures, and predict wave-in-deck pressures and loads.

Wave Impact Loads on the Bottom of Flat Decks

2021 ◽  
Author(s):  
Daniel de Oliveira Costa ◽  
Julia Araújo Perim ◽  
Bruno Guedes Camargo ◽  
Joel Sena Sales Junior ◽  
Antonio Carlos Fernandes ◽  
...  
Keyword(s):  
Scale Effects ◽  
Offshore Structures ◽  
Model Tests ◽  
Analytical Models ◽  
Navier Stokes ◽  
Impact Loads ◽  
Wave Impact ◽  
Wave Channel ◽  
Waves And Currents ◽  
The Impact

Abstract Slamming events due to wave impact on the underside of decks might lead to severe and potentially harmful local and/or global loads in offshore structures. The strong nonlinearities during the impact require a robust method for accessing the loads and hinder the use of analytical models. The use of computation fluid dynamics (CFD) is an interesting alternative to estimate the impact loads, but validation through experimental data is still essential. The present work focuses on a flat-bottomed model fixed over the mean free surface level submitted to regular incoming waves. The proposal is to reproduce previous studies through CFD and model tests in a different reduced scale to provide extra validation and to identify possible non-potential scale effects such as air compressibility. Numerical simulations are performed in both experiments’ scales. The numerical analysis is performed with a marine dedicated flow solver, FINE™/Marine from NUMECA, which features an unsteady Reynolds-averaged Navier-Stokes (URANS) solver and a finite volume method to build spatial discretization. The multiphase flow is represented through the Volume of Fluid (VOF) method for incompressible and nonmiscible fluids. The new model tests were performed at the wave channel of the Laboratory of Waves and Currents (LOC/COPPE – UFRJ), at the Federal University of Rio de Janeiro.

Numerical Study of Phase Change Influence on Wave Impact Loads in LNG Tanks on Floating Structures

2018 ◽  
Author(s):  
Matthieu Ancellin ◽  
Laurent Brosset ◽  
Jean-Michel Ghidaglia
Keyword(s):  
Natural Gas ◽  
Phase Change ◽  
Numerical Study ◽  
Model Tests ◽  
Impact Loads ◽  
Wave Impact ◽  
Floating Structures ◽  
Physical Phenomena ◽  
The Impact ◽  
Phase Phase

Understanding the physics of sloshing wave impacts is necessary for the improvement of sloshing assessment methodology based on sloshing model tests, for LNG membrane tanks on floating structures. The phase change between natural gas and liquefied natural gas is one of the physical phenomena involved during a LNG wave impact but is not taken into account during sloshing model tests. In this paper, some recent numerical and analytical works on the influence of phase change are summarized and discussed. For the impact of an ideally shaped wave, phase change influences two different steps of the impact in different ways: during the gas escape phase, phase change leads to a higher impact velocity; for entrapped gas pockets, phase change causes a reduction of the pressure in the gas pocket. However, this influence is quantitatively small. The generalization to more realistic wave shapes (including e.g. liquid aeration) should be the focus of future works.

Resonant Vibrations of Riser Guide Tubes Due to Wave Impact

2004 ◽  
Author(s):  
Arne Nestega˚rd ◽  
Arve Johan Kalleklev ◽  
Kjell Hagatun ◽  
Yu Lin Wu ◽  
Sverre Haver ◽  
...  
Keyword(s):  
High Frequency ◽  
Rapid Change ◽  
Ocean Basin ◽  
Model Tests ◽  
Slender Body ◽  
Irregular Waves ◽  
Resonant Vibrations ◽  
Wave Impact ◽  
Numerical Predictions ◽  
Steep Waves

The Kristin platform is a catenary moored semi-submersible production vessel (SSPV) intended for production of gas at the Kristin field at Haltenbanken. Kristin has 24 riser guide tubes for tie in of flexible risers, umbilicals and electric cables to the riser balcony. The riser guide tubes (RGT) provide the necessary guiding, support and protection for risers and cables. The guide tubes run vertically from the deck and through the extended east pontoon. The guide tubes are welded to the pontoon and horizontally supported at the underside of the balcony deck. During model tests of the Kristin platform performed in the Ocean Basin laboratory at Marintek, high frequency in-line vibrations of the RGTs were observed during passage of steep waves. The resonance period for the individual RGTs is 0.3 sec. To mitigate the vibration problem, a vibration suppression arrangement of stiff rods was introduced between the guide tubes. Model tests were performed with respect to extreme- and fatigue loads in regular and irregular waves, with and without the suppression arrangement. The model included the floating framework representing the hull and the 24 RGTs with correct diameter and resonance period. The model was suspended in a horizontal mooring system, giving resonance periods in surge and sway close to the prototype platform. A load-response model for the interaction between large steep waves and vertical flexible cylinders has been developed. A slender body load model derived from Morison’s equation is shown to be able to excite the resonant vibrations. The dominant part of the loading comes from the rapid change of added mass momentum, giving rise to an additional slamming term in the load formulation. The structural response is calculated from a recognized non-linear slender body response program. Numerical simulations have been carried out and compared with model tests for both regular and irregular waves. The numerical predictions confirm the effect observed in the model tests; i.e. connecting the tubes generally leads to a reduction of the high frequency response amplitudes.

scholarly journals DETERMINATION OF THE WAVE ATTACK ANTICIPATED UPON A STRUCTURE FROM LABORATORY AND FIELD OBSERVATIONS

2011 ◽  
Vol 1 (7) ◽  
pp. 37
Author(s):  
W.A. Venis
Keyword(s):  
Comparative Study ◽  
Model Tests ◽  
Water Levels ◽  
Field Observations ◽  
Wave Impact ◽  
Spring System ◽  
Mass Spring ◽  
The Comparative Study ◽  
The Impact

Model tests have been carried out to obtain an insight into the magnitude of the wave-pressures in various situations. These tests showed, that sharp high pressure peaks occur in addition to the pressures caused by the reflecting of the waves, which pressures are quasi-static. As the structure can be compared with a multiple mass-spring system these pressure-peaks may cause the whole construction to vibrate. Wave-attack therefore can be expressed in terms of impact. Moreover, calculations revealed that the impact pressures were critical factors in determining the strength of the structure. So many model tests were carried out to determine the design and location of the sluices. These tests involved numerous water-levels discharges and waves. Regarding the pressure-peaks a comparative study was made in the model, which led to the structure being designed in such a way that the occurrence of critical impacts was reduced to an acceptable minimum. As it was impossible to avoid the occurrence of impact pressures entirely it remained necessary to determine a basic load for the structure that takes care of the impact pressures. As it has not yet appeared possible physically to determine a theoretical maximum for the impact pressures, it has to be borne in mind that there is a probability that each pressure measured will be exceeded. So this paper describes, how the cumulative frequency curve of the impacts for the case mentioned in 1.1 sub a, which served as a basis for determining the basic load was arrived at by a certain combination of laboratory and field observations. The data used for this purpose were a. Results of wave-impact measurements on a model of the sluices. This model, built in accordance with the results of the comparative study, was situated in the wind-flume of the "de Voorst" hydraulic laboratory. b. Wave height measurements in the Haringvliet during 1957 and 1958. c. Wind-speed measurements on board the lightship Qoeree, likewise during 1957 and 1958. d. Tidal registrations at Hellevoetsluis from 1920 to 1960. e. Wind-force data from the Hook of Holland, likewise from 1920 to 1960.

Transducer Qualification for Wave Impact Load Measurements Using Wedge Drop Tests

2015 ◽  
Author(s):  
Zhenjia (Jerry) Huang ◽  
Robert Oberlies ◽  
Don Spencer ◽  
Jang Kim
Keyword(s):  
Impact Load ◽  
Research Work ◽  
Offshore Structures ◽  
Model Tests ◽  
Impact Loads ◽  
Dynamic Impact ◽  
Wave Impact ◽  
Impact Forces ◽  
Industry Practice ◽  
Drop Tests

For the design of offshore structures in harsh wave environments, it is essential to accurately determine the wave impact loads on the structure. To date, robust numerical prediction methods / algorithms for determining wave impact forces on offshore structures do not exist. Model testing continues to be the industry practice for determining wave impact forces on offshore structures. Accurate measurements of wave impact loads in model tests have been challenging for several decades. Transducers require the ability to capture the short duration, dynamic nature and high magnitude of impact loads. In order to qualify transducers for these types of measurements, we need to develop a way to physically impose dynamic impact loads on the transducers and to establish benchmark values that can be used to check the effectiveness of their measurements. In this paper, we present our recent research work on transducer qualification for wave impact load measurements, including their development, numerical analysis and wedge drop model tests. Our findings show that wedge drop tests can be used to impose dynamic impact loads for transducer qualification, and that the Wagner solution and / or validated computational fluid dynamics (CFD) simulations that include the effects of viscosity, compressibility and hydroelasticity can provide the appropriate benchmarking values. Numerical simulation results, model test measurements and findings on transducer qualification are presented and discussed in the paper.

The Evolving Role of the Towing Tank

1979 ◽  
Author(s):  
Karl L. Kirkman
Keyword(s):  
Scale Effects ◽  
Research Work ◽  
Model Tests ◽  
Profound Change ◽  
Towing Tank ◽  
Design Cycle ◽  
Sailing Yacht ◽  
Changing Role ◽  
Economic Considerations

The towing tank has been used regularly to attempt to refine sailing yacht forms almost since its introduction as a Naval Architectural tool. Unfortunately, the yachtsman's affair with tank testing has run hot and cold based upon misunderstandings of the correct role of model testing and economic considerations. Recent research work has caused profound change in the method for using the tank for design assistance, but the tank retains a necessary and economically suitable place in the design cycle if properly used. The paper explains the changing role of the tank and appropriate means of using model tests in light of our contemporary understanding of scale effects.

Inverse Estimation of Local Slamming Loads on a Jacket Structure

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Ying Tu ◽  
Thorvald C. Grindstad ◽  
Michael Muskulus
Keyword(s):  
Linear Regression ◽  
Breaking Waves ◽  
Least Square ◽  
Accurate Estimation ◽  
Impulse Response Functions ◽  
Force Estimation ◽  
Wave Impact ◽  
Ordinary Least Square ◽  
Scale Experiment ◽  
Deconvolution Techniques

Slamming loads from plunging breaking waves feature a high impulsive force and a very short duration. It is difficult to measure these loads directly in experiments due to the dynamics of the structures. In this study, inverse approaches are investigated to estimate the local slamming loads on a jacket structure using hammer test and wave test data from a model scale experiment. First, a state-of-the-art approach is considered. It uses two deconvolution techniques to first determine the impulse response functions and then to reconstruct the wave impact forces. Second, an easier applicable approach is proposed. It uses linear regression with the ordinary least square technique for the force estimation. The results calculated with these two approaches are highly identical. The linear regression approach can be extended to account for the loads transferred among different locations. This leads to lower and theoretically more accurate estimation of the loads compared to the previous two approaches. For the investigated case, the total impulse due to the wave is 22% lower. The estimated forces by the extended approach have a resolution at the millisecond level, which provides detailed information on the shape of the forces. The approach is an important tool for statistical investigations into the local slamming forces, and further on for the development of a reliable engineering model of the forces.

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