Dynamic Behaviour of a Flexible Yacht Sail Plan

• Dynamic fluid structure interaction of a sail plan is modeled in harmonic pitching • Aerodynamic forces oscillations show hysteresis phenomena • Neglecting the structural deformation underestimates the forces oscillations • Both aerodynamic and structure inertia affect loads in the rig.A numerical investigation of the dynamic Fluid Structure Interaction (FSI) of a yacht sail plan submitted to harmonic pitching is presented to address both issues of aerodynamic unsteadiness and structural deformation. The FSI model | Vortex Lattice Method uid model and Finite Element structure model | has been validated with full-scale measurements. It is shown that the dynamic behaviour of a sail plan subject to yacht motion clearly deviates from the quasi-steady theory. The aerodynamic forces presented as a function of the instantaneous apparent wind angle show hysteresis loops, suggesting that some energy is exchanged by the system. The area included in the hysteresis loop increases with the motion reduced frequency and amplitude. Comparison of rigid versus soft structures shows that FSI increases the energy exchanged by the system and that the oscillations of aerodynamic forces are underestimated when the structure deformation is not considered. Dynamic loads in the fore and aft rigging wires are dominated by structural and inertial effects. This FSI model and the obtained results may be useful firstly for yacht design, and also in the field of auxiliary wind assisted ship propulsion, or to investigate other marine soft structures.This work was supported by the French Naval Academy

A coupled electromagnetic / hydrodynamic model for the design of an integrated rim - driven naval propulsion system

This paper presents an analytical multi-physic modeling tool for the design optimization of a new kind of naval propulsion system. This innovative technology consists in an electrical permanent magnet motor that is integrated into a duct and surrounds a propeller. Compared with more conventional systems such as pods, the electrical machine and the propeller have the same diameter. Thus, their geometries, in addition to speed and torque, are closely related and a multidisciplinary design approach is relevant. Two disciplines are considered in this analytical model: electromagnetism and hydrodynamics. An example of systematic design for a typical application (a rim-driven thruster for a patrol boat) is then presented for a set of different design objectives (efficiency, mass, etc). The effects of each model are commente

Larviculture and Nutrition of Three of Florida’s High Value Food and Stock Enhancement Finfish, Common Snook (Centropomus undecimalis), Florida Pompano (Trachinotus carolinus) and Red Drum (Sciaenops ocellatus)

The main objective of this thesis was to gain new insights in three of Florida’s high value food and stock enhancement finfish nutrition (Common snook, Florida pompano and red drum) to improve larviculture protocols. The main bottleneck in snook production is the extremely low larval survival rate, which hinders subsequent research. This work first focused on the source of the larvae by looking at potential nutritional deficiencies in captive broodstock. The lipid composition of wild and captive common snook broodstock were compared to identify disparities and gain the information necessary for the formulation of a suitable diet for captive stocks. Results showed that captive snook lipid content was significantly higher than that of wild fish. However, cholesterol and arachidonic acid (ARA) levels were significantly lower compared to wild broodstock, with potential impact on steroid and prostaglandin production, reproductive behavior and gametogenesis. Eggs from captive broodstock incorporated high docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) levels and low ARA levels. Consequently, ARA/EPA ratio in captive eggs was more than half of that in wild eggs (2.3 ± 0.6 and 0.9 ± 0.1 respectively), with a probable perturbation in eicosanoid production and adverse effects on embryo and larval development. The large differences observed between wild and captive broodstock most likely contributed to the reproductive dysfunctions observed in captive snook broodstock (e.g. incomplete oocyte maturation, low milt production and poor egg quality). In addition, the presence of hydrocarbons was detected in the liver of most of the wild snook sampled. This requires further investigation to identify the source of the contamination, monitor a potential impact on reproductive performances and protect the species habitat. Another major bottleneck in marine fish rearing occurs during the transition from endogenous feeding to exogenous feeding, with mass mortality events linked to inadequate first feeding diets. To gain insight on the early fatty acid requirements and mobilization of pompano and snook larvae, the pattern of conservation and loss of fatty acids from the yolk sac during the endogenous feeding period and subsequent starvation was studied. In both species, fatty acids were utilized as an energy source after hatching. Mono-unsaturated fatty acids were catabolized, while saturated and poly-unsaturated fatty acids were conserved. High levels of arachidonic acid (ARA) in pompano and snook eggs (respectively 2.44 ± 0.1 and 5.43 ± 0.3 % of total fatty acids), as well as selective retention in the unfed larvae, suggested a high dietary requirement for this fatty acid during the early stages of larval development. The effect of an ARA supplementation was therefore investigated in snook larvae at the rotifer feeding stage. Larvae receiving the supplementation did incorporate higher levels of ARA, and DHA/EPA and ARA/EPA ratios were successfully modified to match those observed in wild eggs. No significant improvements in growth or survival were observed, however the success in fatty acid profile modification suggest a possible impact of the supplementation on a longer period of time and a possible effect on stress resistance. Probiotics have been shown to enhance larval performances of several species and this strategy was therefore investigated to evaluate a potential impact on Florida pompano, red drum and common snook larvae. The effect of a commercial mix of Bacillus sp. was studied on larval survival, growth and digestive enzyme activities. Larvae were fed either live feed enriched with Algamac 3050 (Control), Algamac 3050 and probiotics (PB), or the previous diet combined with a daily addition of probiotics to the tank water (PB+). Microbiological analyses were performed at the end of the pompano trial. Numbers of presumptive Vibrio sp. were low and not statistically different between treatments, therefore no additional microbiological analyses were performed on the system. At the end of the pompano and snook trial, standard lengths of larvae from the PB and PB+ treatments were significantly greater than for the control larvae. For both pompano and snook, trypsin specific activity was higher in PB and PB+ larvae compared to the control larvae. Similarly, alkaline phosphatase activity was higher for the pompano larvae fed the PB and PB+ treatments and for the snook larvae fed the PB+ treatment compared to the control larvae. No enhancement of growth or digestive enzymes activities was observed in red drum larvae. Yet, no negative effects were noticed and a longer trial period and the study of additional parameters could reveal different effects. In all three species, survival was not affected by the supplementation; however, stress exposure should be further investigated as the supplementation may strengthen the larvae, especially pompano and snook larvae where the Bacillus sp. supplementation appears to promote growth through an early maturation of the digestive system. Another key challenge in marine fish larval rearing resides in weaning the larvae onto dry micro-diets. This step is commonly concurrent with larvae metamorphosis into juveniles, with extensive morphological and physiological changes that are likely to influence nutritional requirements. In the present project, three microdiets were tested on weaning of Florida pompano larvae: Otohime, Gemma and a reference diet LR803. The experimental system was stocked with 11-day-old larvae, which were co-fed micro-diets and live food from 11 dph to 17 dph then micro-diets only until 28 dph. Survival from 11 dph to 28 dph was similar for all treatments, with an average of 33 %. At the end of the trial, the Gemma larvae were significantly longer and heavier than larvae fed the other diets. Fatty acid composition of the diets and larvae varied significantly between treatments. The Gemma larvae incorporated the lowest amount of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and arachidonic acid (ARA). However, they presented the highest DHA/EPA and ARA/EPA ratios, supporting the concept that the proportions of polyunsaturated fatty acids are of greater importance than their absolute amount. Results from the enzyme analysis showed that fishmeal is a suitable main source of protein for Florida pompano larvae and demonstrated the full functionality of the pancreas at 16 days post hatch. These results provide the basis of a suitable weaning diet for pompano larvae and indicate the possibility of a weaning time prior to 16 days post hatch, which is of high interest in commercial production. Overall, this research provides new data on common snook, pompano and red drum nutritional requirements with results that can be directly applied to help overcome major bottlenecks in the hatchery phase and improve rearing protocols

Experimental validation of unsteady models for wind / sails / rigging fluid structure interaction

International audienceThe aim of this paper is to present the work of experimental validation elements of the aero elastic and unsteady model ARAVANTI. Numerical and Experimental results comparison is made on the rigging and sails of a J80 sail boat. Yacht modelling demands to consider unsteady phenomena resulting from the sea state, variations of wind speed and direction, yacht motion or trimming by the crew. A dedicated instrumentation is developed to measure the loads in shrouds and tension points of the sail, the apparent wind, the yacht motion, the sails flying shape and the navigation data. A special effort is made on sensors calibration, physical measurement comprehension and data synchronisation. Comparison with numerical results shows that the loads and flying shapes are well predicted by the model

ePortfolios: Mediating the minefield of inherent risks and tensions

The ePortfolio Project at the Queensland University of Technology (QUT) exemplifies an innovative and flexible harnessing of current portfolio thinking and design that has achieved substantial buy-in across the institution with over 23000 active portfolios. Robust infrastructure support, curriculum integration and training have facilitated widespread take-up, while QUT’s early adoption of ePortfolio technology has enabled the concomitant development of a strong policy and systems approach to deal explicitly with legal and design responsibilities. In the light of that experience, this paper will highlight the risks and tensions inherent in ePortfolio policy, design and implementation. In many ways, both the strengths and weaknesses of ePortfolios lie in their ability to be accessed by a wider, less secure audience – either internally (e.g. other students and staff) or externally (e.g. potential employees and referees). How do we balance the obvious requirement to safeguard students from the potential for institutionally-facilitated cyber-harm and privacy breaches, with this generation’s instinctive personal and professional desires for reflections, private details, information and intellectual property to be available freely and with minimal restriction? How can we promote collaboration and freeform expression in the blog and wiki world but also manage the institutional risk that unauthorised use of student information and work so palpably carries with it? For ePortfolios to flourish and to develop and for students to remain engaged in current reflective processes, holistic guidelines and sensible boundaries are required to help safeguard personal details and journaling without overly restricting students’ emotional, collaborative and creative engagement with the ePortfolio experience. This paper will discuss such issues and suggest possible ways forward

Experimental validation of unsteady models for wind / sails / rigging fluid structure interaction

The aim of this paper is to present the work of experimental validation elements of the aero elastic and unsteady model ARAVANTI. Numerical and Experimental results comparison is made on the rigging and sails of a J80 sail boat. Yacht modelling demands to consider unsteady phenomena resulting from the sea state, variations of wind speed and direction, yacht motion or trimming by the crew. A dedicated instrumentation is developed to measure the loads in shrouds and tension points of the sail, the apparent wind, the yacht motion, the sails flying shape and the navigation data. A special effort is made on sensors calibration, physical measurement comprehension and data synchronisation. Comparison with numerical results shows that the loads and flying shapes are well predicted by the model

A Simulation Model for the Evaluation of the Electrical Power Potential Harnessed by a Marine Current Turbine in the Raz de Sein

This work is supported by Brest Métropole Océane (BMO) and the European Social Fund (ESF). It is done within the framework of the Marine Renewable Energy Commission of the Brittany Maritime Cluster (Pôle Mer Bretagne).International audienceThis paper deals with the development of a Matlab-Simulink model of a marine current turbine system through the modeling of the resource and the rotor. The purposes of the simulation model are two: performances and dynamic loads evaluation in different operating conditions and control system development for turbine operation based on pitch and speed control. In this case, it is necessary to find a compromise between the simulation model accuracy and the control loop computational speed. The Blade Element Momentum (BEM) approach is then used for the turbine modeling. As the developed simulation model is intended to be used as a sizing and site evaluation tool for current turbine installations, it has been applied to evaluate the extractable power from the Raz de Sein (Brittany, France). Indeed, tidal current data from the Raz de Sein are used to run the simulation model over various flow regimes and yield the power capture with time

URANSE simulation of an active variable-pitch cross-flow Darrieus tidal turbine: Sinusoidal pitch function investigation

This article describes a 2D CFD simulation implementation of a crossflow tidal turbine, the blades of which have their pitch modified during revolution. Unsteady flow around the turbine is computed with an URANSE method, using the solver ANSYS-CFX. Spatial and temporal discretizations have been studied. The pitch motion of the blades is obtained through mesh deformation, and the main rotation is implemented through sliding boundaries, with general grid interface model. The turbulence model used is kx SST. Langtry Menter transition model was tried but showed high discrepancies with experimental results. Five experimental cases were used to assess the accuracy of the simulation. It provided accurate computed forces for a wide range of tip speed ratios, and proved to be suitable for exploratory simulations. Harmonic pitch control was thus implemented for a tip speed ratio of 5, close to an operational value for a crossflow turbine. First, second and third harmonics pitch function were tested. It was shown that an improvement of more than 50% could be achieved with the second harmonics, with a large reduction in thrust. The flow inside the turbine and close to the blade was examined so that the case of performance improvement due to pitch control could be clearly understood. It was observed that turbine efficiency improvement requires a very slight recirculation and an angle of attack decrease on the upstream part of the turbine, and an angle of attack increase on the downstream part. The flow deceleration through the turbine was found to be a primary factor in pitch function as well. Moreover the hydrodynamic torque and thus the energy required to control the pitch were found to be insignificant

Fluid Structure Interaction of Yacht Sails in the Unsteady Regime

The dynamic Fluid Structure Interaction (FSI) of yacht sails submitted to a harmonic pitching motion is numerically investigated to address both issues of aerodynamic unsteadiness and structural deformation. The model consists in an implicit dynamic coupling algorithm between a Vortex Lattice Method model for the aerodynamics and a Finite Element Method model for the structure dynamics. It is shown that the dynamic behaviour of a sail plan subject to yacht motion clearly deviates from the quasi-steady theory. The aerodynamic forces oscillate with phase shifts with respect to the motion. This results in hysteresis phenomena, which show aerodynamic equivalent damping and stiffening effects of the unsteady behaviour. The area of the hysteresis loop corresponds to the amount of energy exchanged by the system and increases with the motion reduced frequency and amplitude. In the case of a rigid structure, the aerodynamic forces oscillations and the exchanged energy are lower than for a flexible structure

Comparative study of lipids and fatty acids in the liver, muscle, and eggs of wild and captive common snook broodstock

In this study, the lipid composition of wild and captive common snook broodstock were investigated to identify potential nutritional deficiencies and formulate suitable diets for captive stocks. Results showed captive snook incorporated significantly more lipid than their wild counterparts. However, cholesterol and arachidonic acid (ARA) levels were significantly lower compared to wild fish, which may impact steroid and prostaglandin production, reproductive behavior and gametogenesis. In eggs obtained from captive broodstock, high docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) levels, associated with low ARA contents were found. As a result, ARA/EPA ratio in captive eggs was less than half of that in wild eggs with the potential for negative consequences on embryo and larval development. In conclusion, large differences were noticed between wild and captive broodstock that may contribute to the reproductive dysfunctions observed in captive snook broodstock (e.g. incomplete oocyte maturation, low milt production and highly variable egg and larval quality). The wild snook survey also identified the presence of hydrocarbons in the liver, which should be further studied to identify a potential impact on the reproductive performances of a vulnerable population like common snook