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| Ikhennicheu, Maria; Gaurier, Benoit; Druault, Philippe; Germain, Gregory. |
| The present study aims at investigating turbulence characteristics in high flow velocity areas like those suitable for marine energy application. The Reynolds number, based on the rugosity height and mean flow velocity, is rather high: . For that purpose, experiments are carried out in a flume tank with as high as achievable in Froude similitude (in the tank: and ). Obstacles are canonical wall-mounted elements chosen to be representative of averaged bathymetric variations: a cube and a cube followed by an inclined floor. First, the wake topology past a canonical wall-mounted cube is illustrated from PIV measurements. Results show a flow behaviour already observed in the literature but for different upstream conditions ( and turbulence intensity). Second,... |
| Tipo: Text |
Palavras-chave: Turbulence; Experimental trials; Wall-mounted obstacles; PIV; POD; Quadrant method. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00449/56050/57570.pdf |
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| Gaurier, Benoit; Druault, Ph.; Ikhennicheu, Maria; Germain, Gregory. |
| In the main tidal energy sites like Alderney Race, turbulence intensity is high and velocity fluctuations may have a significant impact on marine turbines. To understand such phenomena better, a three-bladed turbine model is positioned in the wake of a generic wall-mounted obstacle, representative of in situ bathymetric variation. From two-dimensional Particle Image Velocimetry planes, the time-averaged velocity in the wake of the obstacle is reconstructed in the three-dimensional space. The reconstruction method is based on Proper Orthogonal Decomposition and enables access to a representation of the mean flow field and the associated shear. Then, the effect of the velocity gradient is observed on the turbine blade root force, for four turbine locations... |
| Tipo: Text |
Palavras-chave: Tidal turbine; Blade force; Turbulent wake; Experimental trials; PIV; POD. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00643/75535/76540.pdf |
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| Ikhennicheu, Maria; Germain, Gregory; Druault, Philippe; Gaurier, Benoit. |
| In high flow velocity areas like those suitable for tidal applications, turbulence intensity is high and flow variations may have a major impact on tidal turbines behaviour. Large boils that can be observed at the sea surface are emitted from the sea floor and may interact with the tidal turbines. These boils have then to be characterized. The Reynolds number, based on the rugosity height and the mean flow velocity, is rather high in this context: Re ¼ 2:5 107. For that purpose, experiments are carried out in a flume tank with Re as high as achievable in Froude similitude (in the tank: Re ¼ 2:5 105 and Fr ¼ 0:23) in order to study coherent flow structures emitted behind seabed obstacles. The obstacle is here a canonical square wall-mounted cylinder chosen... |
| Tipo: Text |
Palavras-chave: Turbulence; Experimental trials; Wall-mounted cylinder; PIV; LDV; POD; Lamb-Oseen. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00494/60527/64189.pdf |
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| Deparday, Julien; Bot, Patrick; Hauville, Frédéric; Augier, Benoit; Rabaud, Marc; Motta, Dario; Le Pelley, David. |
| While sailing offwind, the trimmer typically adjusts the downwind sail “on the verge of luffing”, occasionally letting the luff of the sail flap. Due to the unsteadiness of the spinnaker itself, maintaining the luff on the verge of luffing requires continual adjustments. The propulsive force generated by the offwind sail depends on this trimming and is highly fluctuating. During a flapping sequence, the aerodynamic load can fluctuate by 50% of the average load. On a J/80 class yacht, we simultaneously measured time-resolved pressures on the spinnaker, aerodynamic loads, boat data and wind data. Significant spatio-temporal patterns were detected in the pressure distribution. In this paper we present averages and main fluctuations of pressure distributions... |
| Tipo: Text |
Palavras-chave: Full scale experiment; Instrumented boat; Spinnaker; Fluid structure interaction; POD; Unsteady. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00597/70918/69156.pdf |
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