M2EN

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 commented.

This 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.

This work presents a full scale experimental study on the aero-elastic wind/sails/rig interaction in real navigation conditions with the aim to give an experimental validation of unsteady fluid structure interaction (FSI) models applied to yacht sails. An inboard instrumentation system has been developed on a J80 yacht to simultaneously and dynamically measure the navigation parameters, yacht's motion, and sails flying shape and loads in the standing and running rigging. The first results recorded while sailing upwind in head waves are shown. Variations of the measured parameters are characterized and related to the yacht motion (trim mainly). Correlations between the different parameters are examined.

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 fluid model and Finite Element structure modelhave 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.

A numerical investigation of the dynamic fluid structure interaction (FSI) of a yacht sail plan submitted to harmonic pitching is presented to analyse the system's dynamic behaviour and the effects of motion simplifications and rigging adjustments on aerodynamic forces. 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. It is shown that the hysteresis phenomenon dissipates some energy and that the dissipated energy increases strongly with the pitching reduced frequency and amplitude. The effect of reducing the real pitching motion to a simpler surge motion is investigated. Results show significant discrepancies with underestimated aerodynamic forces and no more hysteresis when a surge motion is considered. However, the superposition assumption consisting in a decomposition of the surge into two translations normal and collinear to the apparent wind is verified. Then, simulations with different dock tunes and backstay loads highlight the importance of rig adjustments on the aerodynamic forces and the dynamic behaviour of a sail plan. The energy dissipated by the hysteresis is higher for looser shrouds and a tighter backstay. (P. Bot).

A numerical comparison between two FSI models, based on inviscid and viscous flow solvers, is presented in this paper. The differences between aerodynamic coefficients, sail flying shape and pressures computed by both FSI tools are investigated for medium wind conditions. These differences are evaluated for different values of the main sheet length. The study has shown very close results when the main sheet is not over trimmed for medium true wind speed, but discrepancies increase when flow separation becomes significant. Then, an optimisation procedure based on inviscid FSI is performed to optimise the main sheet and car trims, in order to maximise an objective function based on the driving and side forces, in a case of low true wind speed. Limitations of the inviscid flow hypothesis are highlighted and the difficulties to use inviscid FSI models in an optimisation procedure, for a case of low true wind speed, are shown. NOMENCLATURE Cx-Driving force coefficient Cy-Side force coeff...

This work presents a full-scale experimental study on a sailing yacht in downwind conditions with simultaneous timeresolved measurements of pressures, sail shape and loads. Those on-water experiments on a J/80 class yacht permit the dynamic behaviour of the fluid structure system made of a light cloth sail and highly curved flow to be investigated. Aerodynamic forces on the asymmetric spinnaker were determined from pressure distribution and shape measurements and also from strain gauges located on the corners of the sail. Both time-averaged and instantaneous data are analysed. The time-averaged pressures and forces were studied according to the apparent wind angle. The pressure distribution and thus the loads tend to decrease when the apparent wind angle is increased. The standard deviation of pressures was largest near the luff, decreasing downstream. Simultaneous time series recordings of the pressure distributions, flapping sail shapes, and forces in the sheets show a strong correlation. Flapping of spinnaker creates pressure peaks at the leading edge, increasing the aerodynamic forces dynamically by 50 to 70%. These results will also give reliable benchmark data to validate unsteady fluid structure interaction predictions from numerical simulations of downwind sails.

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. This is an author-deposited version published in: http://sam.ensam.eu Handle IDRésumé : Le travail présenté concerne le développement d'une méthodologie de conception de systèmes hydroliens innovants de type RIM-DRIVEN pour la récupération de l'énergie des courants de marée. L'originalité d'un système RIM-DRIVEN réside dans la structure même de l'hydrolienne, inspirée directement des nouveaux systèmes de propulsion navale, où le rotor et le stator sont placés en périphérie de l'hélice et protégés par une tuyère, l'entrefer étant immergé. Au sein d'une structure de type RIM-DRIVEN les phénomènes électromécaniques, thermiques et hydrodynamique sont intimement couplés. Du fait du très fort couplage des phénomènes physiques au sein du système, cette méthodologie associe au sein d'un même environnement d'optimisation des modèles électromagnétiques et thermiques spécifiques de la génératrice avec des modèles hydrodynamique des performances de l'hélice et de l'écoulement dans l'entrefer. L'approche proposée est illustrée par une étude de cas qui concerne une machine de 10m de diamètre destinée à être implantée dans le Raz de Sein. Les modèles ont été validés par des résultats issus d'une campagne expérimentale sur un démonstrateur dédié. Abstract :Tthis paper deals with the study of an unconventional design of marine tidal turbine where the electrical generator is located in the periphery of the blades and where the magnetic gap is underwater. This kind of solution called "RIM DRIVEN" structure allows increasing the compactness and the robustness of the system. Due to the strong interaction of the multi physical phenomena, an electromagnetic model and a thermal model of the PM generator are associated with a hydrodynamic model of the blades and of the water flow in the underwater air gap. These models are used in a global coupled design approach in order to optimize, under constraints, the global efficiency of the system. This approach is illustrated in a case study which deals with the design of a 10m diameter tidal turbine. Proposed coupled models are validated by comparison with experimental data from the tests of an academic low power demonstrator.

This 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.