1,721,025 research outputs found
Comparative optimisation of first principles design methods with classification society rules for boat hull structures
No full text
US Office of Naval Research, Solid Mechanics Program Review
No full textThe purpose of this extended abstract is to provide an overview of activities relating to performance assessments. The work described is wide ranging and not intended to provide a detailed account of any particular approach
Analysis and prediction of motions of high speed planing craft in waves
No full textA theoretical method has been developed to model a high speed planing craft in waves with particular emphasis on the non-linearities associated with high speed motion. These non-linearities include, amongst others, hydrodynamic impact loading, bottom emergence and forces due to large changes in wetted surface area and wetted length.The method consists of a 2D time simulation model based on a modified stop theory approach. The hydrodynamic coefficients are usually considered to be constant for most linear applications. For planing craft in waves, the draft and wetted lengths are very time dependent and so the equations of motion are solved in the time domain.The benefits of a two-dimensional method include the ability to provide accurate solutions without the need to solve the full 3D fluid problems. The method is flexible enough to include an added resistance solution and investigation into hydroolastic responses.In order to validate the theoretical model, a high speed planing craft of simple prismatic geometry has been tested and the dynamics analysed through the use of standard towing tank equipment. However, in order to measure such effects as change in wetted area and length and spray sheet generation, a different technique is required. A new technique in data acquisition is presented whereby the data is acquired using a computer vision system. Computer vision is a technique involving the manipulation of digital pictures and object properties within the image measured and defined. The use of computer vision to analyse video footage of the high speed test provides a non-contact form of measurement; allows the experiment to be carried out repeatedly with emphasis on specified parameters with simultaneous visual observation of particular phenomena allowing cross correlation of the identified feature
A visual experimental technique for planing craft performance
No full textThe understanding and quantification of hydrodynamic lift requires a full appreciation of the phenomena associated with high-speed planing. Repeatability of results is a major problem with planing craft experiments due to the complexity of fluid flows; wetted lengths, for example, are difficult to measure because of the obscurity created by spray-jets. This difficulty in measurement can produce subjective interpretation. Therefore, reducing hydrodynamic lift using uncertainly defined factors, such as wetted data, can be misleading. This paper outlines an experimental method, Computer Vision Data Acquisition (CVDA), that can remove questions of uncertainty regarding dynamic phenomena by remotely capturing large amounts of planing data for immediate and archival use. An example of the importance of this form of data capture and analysis is described by the ability to validate predictive formulae for planing performance in calm water, and to further advance these formulae for predictions outside their designed realms: in waves
Natural resourcefulness
No full textDemand for natural or bio-derived composites is growing in tandem with tighter environmental legislation. Dr James Blake and Adam Sobey update Ship & Boat International on the latest composite research at the University of Southampton, including a boatbuilding project
Hygrothermal ageing of plant oil based marine composites
No full textIn this paper, the effect of hygrothermal ageing on the flexural properties of glass/epoxy, glass/linseed oil and glass/castor oil composites is reported. Plant oil based resins offer renewable and potentially less toxic alternatives to conventional largely petroleum based marine composites. The long-term performance of these novel composites needs to be investigated and understood before using them in structural applications. In this research it was found that in the unaged condition, the flexural properties of glass/epoxy were significantly higher than both glass/castor oil and glass/linseed oil composites. After ageing in water at 40 °C for 46 weeks, the properties of glass/castor oil were comparable to glass/epoxy while the properties of glass/linseed oil were remarkably lower. The decrease in glass/linseed oil performance was explained in terms of the changes in the failure modes caused by moisture uptake
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