1,721,028 research outputs found
Development of high performance composite bend-twist coupled blades for a horizontal axis tidal turbine
No full textDevelopment of a design methodology for a composite, bend-twist coupled, tidal turbine blade has been undertaken. Numerical modelling was used to predict the response of the main structural member for the adaptive blade. An experimental method for validation is described. The analysis indicates a non-linear blade twist response
The re-examination of IOR yacht performance - obtaining data for velocity prediction and sensitivity to data accuracy and quality
No full textThe International Offshore Rule (IOR) provided a handicap system for racing yachts in the 1970s, 80s and 90s. It was accepted worldwide and many of the famous yacht designers of today made their name in the high profile events that took place under this rule. There is a large body of commentary and opinion regarding yachts of this era, in which the rule allowed the designer to explore the design space in search of designs that rated lower than their size. Yachts, particularly in the early IOR era, were designed through experience, knowledge of the rule and inherent talent. Computing power was low and the subject of velocity prediction was in its infancy. This paper examines a method of undertaking a velocity prediction of yachts of this era using data provided by the designers, namely lines plans and rating certificates. A performance sensitivity analysis is conducted examining aspects such as measured versus sailing trim, lack of geometric data, influence of waves and sail configurations. The results show that subtle changes in input data, associated with the yacht, can be measured in terms of performance. This will allow for the future comparison of fleets of boats and provide some data to confirm or contradict the sailing community narrative regarding IOR yacht performance
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
An alternative design of steel-concrete-steel sandwich beam
No full textA steel-concrete-steel sandwich beam represents a special form of sandwich structure. Originated in civil/structural engineering applications, it is now being developed for shipbuilding/offshore applications. The research trend is to introduce either a new shear connector system or a lightweight concrete. This paper presents an alternative construction of steel-concrete-steel sandwich beam in which the new concept design of aligning the shear connector in the inclined direction is proposed. The novel bi-directional corrugated-strip-core system is presented. The possibility of implement this core system using available sandwich construction techniques is presented. The advantages of the novel bi-directional corrugated-strip-core steel-concrete-steel sandwich beam are preliminarily studied in both the unfilled and concrete-filled state. The analytical study based on the force-distortion relationship technique of the repetitive unit cell shows that the transverse shear stiffness of the unfilled sandwich beam depends on the inclined direction of the proposed core. The numerical study of the concrete-filled sandwich beam type also shows the possibility to increase the transverse shear strength
The development of a bio-inspired method to recover energy from unsteady flow
No full textIt has been long understood that swimming marine animals exhibit far superior speed, manoeuvrability and efficiency than any manmade object. Despite this, lessons learned from nature are very rarely applied to engineering applications. In particular; it is understood that fish have the ability to alter their mode of swimming to interact with naturally produced vortices as a method of conserving energy and in certain instances extract energy from a flow. This thesis looks at the development of a bio-inspired method of recovering energy from unsteady flow with the specific application of powering an Autonomous Underwater Vehicle (AUV). During the course of this investigation, the novel techniques used by fish when swimming to reduce their power consumption and in certain instances extract energy from an unsteady flow shall be discussed; with particular emphasis on the way fish utilize vortices, namely the Kármán gait. It shall be demonstrated that by modelling the body of a torpedo shaped AUV as a slender flexible cylinder with tapering end pieces, an analytical model to predict the dynamic stability for a slender flexible cylinder in a uniform axial flow shows a reasonable comparison to experimental observations assuming the ends are suitably slender. It shall be demonstrated that by placing a flexible cylinder in an unsteady flow a similar mechanism to that used by fish to extract energy from an unsteady flow can be exploited to get a slender flexible cylinder to move upstream with no power input, in effect giving the device a propulsive efficiency greater than 100%. A discussion on devices that could be used to capture energy with an estimate of the likely magnitude of power recovery shall be given
Dynamic analysis of composite marine structures using full-field measurement techniques
No full textComposite materials are increasingly used in structural applications within the marine industry. Due to the geometric complexity of marine structures, there is a practical requirement that they are assembled by joining smaller component pieces using either mechanical fasteners or adhesive bonding. in this paper Digital image Correlation (DiC) is used to provide full-field analysis of the complex strain fields generated within an adhesively bonded composite single lap joint. Tests are undertaken quasi-statically and at high rate, demonstrating a significant change in the assembly response between laboratory testing conditions and dynamic loading events typical of the marine environment. The work demonstrates the potential of applying full-field experimental technique to provide detailed analysis of complex structural problems, typical of large marine structures
Use of cryogenic buoyancy systems for controlled removal of heavy objects from the seabed
No full textThe concept design of a lightweight cryogenic marine heavy lift buoyancy system has been investigated. The approach makes use of a novel cryogenic system for provision of buoyancy within the ocean environment. The objective is to be able to lift or lower large displacement objects under full remote control. The nature of subsea lifting and lowering operations requires a high degree of precise control for operational safety, reasons and to preserve the structural integrity of the load. The lift operation occurs in two phases: Development of lift to overcome seabed suction, and then rapid reduction of buoyancy to maintain a controlled ascent. Descent involves controlled release of the buoyancy. The proposed buoyancy system consists of a buoyancy chamber and an integral cryogenic gas generation unit. The application of an on-board gas generation unit allows the removal of the engineering challenges associated with use of compressors and the concomitant complex manifold of connecting umbilical pipe work. It provides for a fully remote system completely eliminating all risk associated with extensive physical surface to subsea connection throughout the entire lift operation.
The opening stages of the project work include the development of a system that will operate efficiently and effectively to a depth of 350m. An initial general arrangement for the buoyancy system has been developed. A number of these systems involve considerable design and development, these include: structural design of the buoyancy chamber, mechanical systems to control and connection to the lift device, the cryogenic system itself and overall process control systems. As part of the design process for such an arrangement, numerical simulation of the complete system has been undertaken in order to develop mechanical, cryogenic and process control systems efficiently and effectively. This system simulation has been developed using Matlab Simulink. This paper considers the overall design concept and associated system development issues. These are illustrated through use of the time accurate simulation of alternative design configurations that confirm the viability of the concept. A main conclusion is that minimisation of the dry weight of the system is critical to cost-effective operation of the project
Stress analysis of finger joints in pultruded GRP material
No full textPre-formed composite components have the potential to provide an economical alternative to traditional construction techniques for the manufacture of ship structures. The marine industry at present employs the use of aluminium extrusions in the construction of decks and superstructures that could be replaced with pultruded glass reinforced plastic (GRP) profiles. The length of the pultruded section is limited and therefore, efficient and economic jointing techniques must be developed that can withstand the loads applied to ship structures. This paper evaluates finger joints in GRP components manufactured from material that models pultruded construction. Various joint geometries are examined, load displacement behaviour is established and Thermoelastic Stress Analysis (TSA) is used to provide the full field stress distribution over the joint. Calibration techniques are described for the TSA. The results of the TSA are compared with the load displacement behaviour. It is shown that by increasing fingertip angle there is a decrease in load carrying capacity, a decrease in shear stress and an increase in stress concentration factor at the finger joint tip. The results from the experimental work were used to validate a numerical model that provides data for initial joint optimisation
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