An Investigation into the Self-righting of a Modern Racing Yacht in Waves

2001 ◽  
Vol 45 (03) ◽  
pp. 241-247
Author(s):  
Martin Renilson ◽  
Andrew Tuite
Keyword(s):  
The Self ◽  
Irregular Waves ◽  
Scale Model ◽  
Radius Of Gyration ◽  
Breaking Wave ◽  
Towing Tank ◽  
Dynamic Factors ◽  
Sailing Yacht ◽  
The Given

Ocean sailing yachts can, and do, capsize from time to time, and so the safety of those who sail on them is linked directly to their ability to self-right once capsized. Current regulations used for racing yachts are based on statical concepts, which have been shown to be inappropriate (Renilson et al 2000). In order to gain an understanding of the dynamic factors involved, experiments were conducted on a 1/12.5 scale model of an ocean sailing yacht in waves in the towing tank at the Australian Maritime College. Two different experimental procedures were developed: Testing in a single breaking wave, and testing in steep irregular waves. Four variations of the limit of positive stability were tested, together with one condition which had a different roll radius of gyration, without water on board the model. In addition, two variations of the limit of positive stability were tested to represent the condition with 4000 kg of water on board. From the tests it was possible to conclude that, for the given yacht, if the limit of positive stability is decreased from 119 deg to 104.7 deg the yacht is much less likely to self-right under the action of waves, with or without 4000 kg of water on board.

scholarly journals NON-BREAKING AND BREAKING WAVE LOADS ON A COOLING WATER OUTFALL

1978 ◽  
Vol 1 (16) ◽  
pp. 148
Author(s):  
G.R. Mogridge ◽  
W.W. Jamieson
Keyword(s):  
Water Level ◽  
Cooling Water ◽  
High Water ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Scale Model ◽  
Breaking Wave ◽  
Wave Loads ◽  
Eastern Canada ◽  
Spilling Breakers

Cooling water from a power generating station in Eastern Canada is pumped to an outfall and distributed into the ocean through discharge ports in the sidewalls of a diffuser cap. The cap is essentially a shell-type structure consisting of a submerged circular cylinder 26.5 ft in diameter and 14 ft high. It is located in 25 ft of water at low water level and 54 ft at high water level. Horizontal forces, vertical forces and overturning moments exerted by waves on a 1:36 scale model of the diffuser cap were measured with and without cooling water discharging from the outfall. Tests were run with regular and irregular waves producing both non-breaking and breaking wave loads on the diffuser cap. The overturning moments measured on the diffuser cap were up to 150 percent greater than those on a solid submerged cylinder sealed to the seabed. Unlike sealed cylinders, all of the wave loads measured on the relatively open structure reached maximum values at approximately the same time. The largest wave loads were measured on the diffuser structure when it was subjected to spilling breakers at low water level. For a given wave height, the spilling breakers caused wave loads up to 100 percent greater than those due to non-breaking waves.

Using the Rating Scale Model to Examine the Psychometric Properties of the Self-Efficacy Scale for Driver Competence

2011 ◽  
Vol 27 (3) ◽  
pp. 164-170 ◽  
Author(s):  
Anna Sundström
Keyword(s):  
Psychometric Properties ◽  
Self Efficacy ◽  
Rating Scale ◽  
Measurement Precision ◽  
The Self ◽  
Test Theory ◽  
Self Report ◽  
Scale Model ◽  
Validity And Reliability ◽  
Two Samples

This study evaluated the psychometric properties of a self-report scale for assessing perceived driver competence, labeled the Self-Efficacy Scale for Driver Competence (SSDC), using item response theory analyses. Two samples of Swedish driving-license examinees (n = 795; n = 714) completed two versions of the SSDC that were parallel in content. Prior work, using classical test theory analyses, has provided support for the validity and reliability of scores from the SSDC. This study investigated the measurement precision, item hierarchy, and differential functioning for males and females of the items in the SSDC as well as how the rating scale functions. The results confirmed the previous findings; that the SSDC demonstrates sound psychometric properties. In addition, the findings showed that measurement precision could be increased by adding items that tap higher self-efficacy levels. Moreover, the rating scale can be improved by reducing the number of categories or by providing each category with a label.

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.

The Compounding and Application Mechanism of Polycarboxylate-Based Superplasticizers in the Self-Compacting Concrete

2011 ◽  
Vol 250-253 ◽  
pp. 711-717 ◽  
Author(s):  
Miao Miao Gui ◽  
Yun Hui Fang ◽  
Zi Dong Lan ◽  
Fei Yu Yu ◽  
Tian Xing Lin ◽  
...  
Keyword(s):  
Steric Hindrance ◽  
Graft Copolymerization ◽  
Raw Materials ◽  
The Self ◽  
Main Mechanism ◽  
Self Compacting Concrete ◽  
The Given ◽  
Copolymerization Reaction

Polycarboxylate-based superplasticizers are synthesized by radical graft copolymerization reaction, and the products are divided into ester series (PC-1) and ether series (PC-2) on the basis of different big monomers. This article studies on influence of the different composition and dosages of the synthetic superplasticizers in the self-compacting concrete (SCC). The results show that the requirements of SCC workability can be achieved through simple adjustment kinds and dosages of the synthetic superplasticizers under the given mix proportions and the raw materials. And the main mechanism of the polycarboxylate-based superplasticizers is steric hindrance effect.

scholarly journals Full-scale self-propulsion simulation with a discretized propeller

2021 ◽  
Vol 4 (398) ◽  
pp. 15-23
Author(s):  
Zhang Qingshan ◽  
◽  
Chen Weimin ◽  
Du Yunlong ◽  
Dong Guoxiang ◽  
...  
Keyword(s):  
Boundary Layer Thickness ◽  
Polynomial Interpolation ◽  
Flow Characteristics ◽  
Uncertainty Assessment ◽  
Full Scale ◽  
The Self ◽  
High Fidelity ◽  
Cfd Simulations ◽  
Towing Tank ◽  
Grid Application

A comparison between towing tank testing and full-scale CFD simulations is presented at three different target speeds. For the current self-propulsion simulation, the self-propulsion point was obtained using polynomial interpolation. The studies of boundary layer thickness, a basic grid uncertainty assessment and verification were performed to give some confidence of grid application to current self-propulsion simulation. All simulations are performed using a commercial CFD software STAR-CCM+. It is concluded that with high-fidelity numerical methods, it’s possible to treat hull roughness and directly calculate full-scale flow characteristics, including the effects of the free surface, none-linearity, turbulence and the interaction between propeller, hull and the flow field.

Ocean Power Generator Using Flexible Piezoelectric Device

2013 ◽  
Author(s):  
Hidemi Mutsuda ◽  
Ryuta Watanabe ◽  
Shota Azuma ◽  
Yoshikazu Tanaka ◽  
Yasuaki Doi
Keyword(s):  
Electric Power ◽  
Wave Breaking ◽  
Strain Energy ◽  
Electrical Energy ◽  
Electric Polarization ◽  
Scale Model ◽  
Breaking Wave ◽  
Ocean Energy ◽  
Power Generator ◽  
Piezoelectric Device

We have developed a way of harvesting electrical energy from ocean power, e.g. tide, current wave, breaking wave and vortex, using a Flexible PiezoElectric Device (FPED) consisting of polyvinyledene fluoride (PVDF) and elastic material such as rubber, silicon and resin. The proposed FPED has a multi-layered structure with a distance δ between FPEDs located away from centerline of the FPED. When the FPED can be easily deformed by ocean power, the PVDF laminated in the FPED can be expanded and compressed and then the internal strain energy can be stored in the FPED. The electric power is generated when the electric polarization occurs in the PVDF. In this study, we have proposed an ocean power generator of EFHAS (Elastic Floating unit with HAnging Structures) consisting of floating unit and hanging unit using the FPEDs to obtain electric power from ocean energy. We investigated a structure of the EFHAS and also examined characteristics of motion and electric performance of the EFHAS (1/50–1/75 scale model. We made clear that the EFHAS could be useful as ocean power generator.

Experimental Assessment of the Performance of CECO Wave Energy Converter in Irregular Waves

2018 ◽  
Author(s):  
Claudio A. Rodríguez ◽  
F. Taveira-Pinto ◽  
P. Rosa-Santos
Keyword(s):  
Wave Energy ◽  
Transfer Functions ◽  
Nonlinear Effects ◽  
Model Tests ◽  
Experimental Results ◽  
Irregular Waves ◽  
Scale Model ◽  
Experimental Assessment ◽  
Simplified Approach ◽  
Wave Basin

A new concept of wave energy device (CECO) has been proposed and developed at the Hydraulics, Water Resources and Environment Division of the Faculty of Engineering of the University of Porto (FEUP). In a first stage, the proof of concept was performed through physical model tests at the wave basin (Rosa-Santos et al., 2015). These experimental results demonstrated the feasibility of the concept to harness wave energy and provided a preliminary assessment of its performance. Later, an extensive experimental campaign was conducted with an enhanced 1:20 scale model of CECO under regular and irregular long and short-crested waves (Marinheiro et al., 2015). An electric PTO system with adjustable damping levels was also installed on CECO as a mechanism of quantification of the WEC power. The results of regular waves tests have been used to validate a numerical model to gain insight into different potential configurations of CECO and its performance (López et al., 2017a,b). This paper presents the results and analyses of the model tests in irregular waves. A simplified approach based on spectral analyses of the WEC motions is presented as a means of experimental assessment of the damping level of the PTO mechanism and its effect on the WEC power absorption. Transfer functions are also computed to identify nonlinear effects associated to higher waves and to characterize the range of periods where wave absorption is maximized. Furthermore, based on the comparison of the present experimental results with those corresponding to a linear numerical potential model, some discussions are addressed regarding viscous and other nonlinear effects on CECO performance.

SLAM CHARACTERISTICS OF A HIGH-SPEED WAVE PIERCING CATAMARAN IN IRREGULAR WAVES

2021 ◽  
Vol 156 (A1) ◽  
Author(s):  
B J French ◽  
G A Thomas ◽  
M R Davis
Keyword(s):  
Vertical Velocity ◽  
Significant Wave Height ◽  
High Speed ◽  
Irregular Waves ◽  
Two Dimensional ◽  
Towing Tank ◽  
Filling Height ◽  
Load Distributions ◽  
Poor Indicator ◽  
Wave Elevations

Slam characteristics of a 112m INCAT wave piercing catamaran in a range of realistic irregular sea conditions are presented in this paper. Towing tank testing of a 2.5 m hydroelastic segmented catamaran model was used to gather a database of slam events in irregular seas. The model was instrumented to measure motions, centrebow surface pressures and forces, encountered wave elevations and wave elevations within the bow area tunnel arches. From these measurements characteristics of the vessel slamming behaviour are examined: in particular relative vertical velocity, centrebow immersion, archway wave elevations and slam load distributions. A total of 2,098 slam events were identified over 22 different conditions, each containing about 80 to 100 slam events. The data, although inherently scattered, shows that encounter wave frequency and significant wave height are important parameters with regard to centrebow slamming. Relative vertical velocity was found to be a poor indicator of slam magnitude and slams were found to occur before the centrebow arch tunnel was completely filled, supporting the application of a two-dimensional filling height parameter as a slam indicator.

Spraying Experiments with a Model Stern Trawler

1998 ◽  
Vol 42 (04) ◽  
pp. 260-265 ◽  
Author(s):  
K. K. Chung ◽  
E. P. Lozowski ◽  
W. P. Zakrzewski ◽  
R. Gagnon ◽  
T. Thompson
Keyword(s):  
Statistical Analysis ◽  
Froude Number ◽  
Significant Wave Height ◽  
Flux Distribution ◽  
Full Scale ◽  
Scale Model ◽  
Spray Droplet ◽  
Towing Tank ◽  
Ship Speed ◽  
Longitudinal Distance

With a view to formulating vessel spraying and icing models, 22 spraying experiments were performed in the IMD/NRC towing tank using a 1:13 scale model of the stern trawler MT Zandberg. Neglecting the effect of wind drag on the spray droplet trajectories, an empirical spray flux equation for the scale Zandberg was derived, based on a statistical analysis of the spraying data. Using Froude number scaling, this model-scale equation was transformed into a full-scale spray flux equation. This spraying study shows that the total spray flux generated during ship/wave collisions depends on ship speed (Vs) and significant wave height (H1/3) according to V3⅓, H7⅓ while the spray flux distribution over the foredeck varies exponentially with longitudinal distance. Using this full-scale spray flux equation, a spray trajectory model, taking wind drag effects into account, was subsequently developed.

Dynamic Instability of a High-Speed Planing Boat Model

2000 ◽  
Vol 37 (03) ◽  
pp. 146-152
Author(s):  
Eric Thornhill ◽  
Brian Veitch ◽  
Neil Bose
Keyword(s):  
Dynamic Stability ◽  
High Speed ◽  
Research Council ◽  
Dynamic Instability ◽  
National Research Council ◽  
Scale Model ◽  
Clear Water ◽  
Towing Tank ◽  
Stability Limits ◽  
Resistance Tests

A series of bare-hull resistance and self-propulsion tests were carried out on a 1/8 scale model of a 11.8 m long, waterjet-propelled planing hull in the clear water towing tank at the National Research Council of Canada's Institute for Marine Dynamics. The bare-hull resistance tests, performed with the waterjet inlets closed, spanned a range of eight model velocities and nine ballast conditions consisting of three displacements each with three positions of the longitudinal center of gravity. The hull was then fitted with two model waterjet thrusters and tested over the same speeds and ballast conditions. Dynamic instability, or porpoising, was seen during certain high-speed tests. A discussion of this behavior and its relation to published dynamic stability limits is given.

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