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| Registros recuperados: 39 | |
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| SILVA,PAULO A.S.F.; OLIVEIRA,TAYGOARA F. DE; BRASIL JUNIOR,ANTONIO C.P.; VAZ,JERSON R.P.. |
| ABSTRACT Over the years most studies on wake characteristics have been devoted to wind turbines, while few works are related to hydrokinetic turbines. Among studies applied to rivers, depth and width are important parameters for a suitable design. In this work, a numerical study of the wake in a horizontal-axis hydrokinetic turbine is performed, where the main objective is an investigation on the wake structure, which can be a constraining factor in rivers. The present paper uses the Reynolds Averaged Navier Stokes (RANS) flow simulation technique, in which the Shear-Stress Transport (SST) turbulent model is considered, in order to simulate a free hydrokinetic runner in a typical river flow. The NREL-PHASE VI wind turbine was used to validate the numerical... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Hydrokinetic turbines; Wake characteristics; CFD; Turbulence. |
| Ano: 2016 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652016000602441 |
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| Dennis,David J.C.. |
| The inherent difficulty of understanding turbulence has led to researchers attacking the topic in many different ways over the years of turbulence research. Some approaches have been more successful than others, but most only deal with part of the problem. One approach that has seen reasonable success (or at least popularity) is that of attempting to deconstruct the complex and disorganised turbulent flow field into to a set of motions that are in some way organised. These motions are generally called "coherent structures". There are several strands to this approach, from identifying the coherent structures within the flow, defining their characteristics, explaining how they are created, sustained and destroyed, to utilising their features to model the... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Turbulence; Wall bounded flows; Coherent structures; Particle image velocimetry. |
| Ano: 2015 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652015000201161 |
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| Redjah, I.; Olivier, Frederic; Tremblay, R.; Myrand, B.; Pernet, Fabrice; Neumeier, U.; Chevarie, L.. |
| Soft-shell clam, Mya arenaria, culture on the east coast of Canada is characterized by high loss following seeding. To evaluate the importance of passive transport due to currents, an experimental flume study was designed. The purpose was to measure the effects of hydrodynamic conditions, substrate, and clam size on dispersal in controlled laboratory condition and to interpret these results in relation to field measurements. Unidirectional currents with gradual increasing velocities (0 to 60 cm s(-1)) were applied to three substrates (muddy sand, medium sand, and coarse sand) in which clams from one of three size classes (10, 15, and 20 mm) had burrowed. We also examined the resulting effects of turbulent kinetic energy on the erosion of medium-grain sand... |
| Tipo: Text |
Palavras-chave: Clam transport; Substratum erosion; Unidirectional currents; Turbulence; ADV; Flume. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00014/12507/9368.pdf |
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| Ponte, Aurelien; Klein, Patrice; Capet, Xavier; Le Traon, Pierre-yves; Chapron, Bertrand; Lherminier, Pascale. |
| High-resolution numerical experiments of ocean mesoscale eddy turbulence show that the wind-driven mixed layer (ML) dynamics affects mesoscale motions in the surface layers at scales lower than O(60 km). At these scales, surface horizontal currents are still coherent to, but weaker than, those derived from sea surface height using geostrophy. Vertical motions, on the other hand, are stronger than those diagnosed using the adiabatic quasigeotrophic (QG) framework. An analytical model, based on a scaling analysis and on simple dynamical arguments, provides a physical understanding and leads to a parameterization of these features in terms of vertical mixing. These results are valid when the wind-driven velocity scale is much smaller than that associated with... |
| Tipo: Text |
Palavras-chave: Mesoscale processes; Ocean dynamics; Turbulence. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00170/28076/26291.pdf |
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| Schapira, Mathilde; Seuront, Laurent. |
| Despite ample evidence of micro- and small-scale (i.e., millimeter- to meter-scale) phytoplankton and zooplankton patchiness in the ocean, direct observations of nutrient distributions and the ecological importance of this phenomenon are still relatively scarce. In this context, we first describe a simple procedure to continuously sample nutrients in surface waters, and subsequently provide evidence of the existence of microscale distribution of ammonium in the ocean. We further show that ammonium is never homogeneously distributed, even under very high conditions of turbulence. Instead, turbulence intensity appears to control nutrient patchiness, with a more homogeneous or a more heterogeneous distribution observed under high and low turbulence... |
| Tipo: Text |
Palavras-chave: Nutrient patchiness; Turbulence; Phytoplankton; Surge uptake; Nutrient depletion; Turbulent history. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00643/75527/76435.pdf |
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| Randelhoff, Achim; Ozierm, Laurent; Massicotte, Philippe; Becu, Guislain; Gali, Marti; Lacour, Leo; Dumont, Dany; Vladoiu, Anda; Marec, Claudie; Bruyant, Flavienne; Houssais, Marie-noelle; Tremblay, Jean-eric; Deslongchamps, Gabriele; Babin, Marcel. |
| During summer, phytoplankton can bloom in the Arctic Ocean, both in open water and under ice, often strongly linked to the retreating ice edge. There, the surface ocean responds to steep lateral gradients in ice melt, mixing, and light input, shaping the Arctic ecosystem in unique ways not found in other regions of the world ocean. In 2016, we sampled a high-resolution grid of 135 hydrographic stations in Baffin Bay as part of the Green Edge project to study the ice-edge bloom, including turbulent vertical mixing, the under-ice light field, concentrations of inorganic nutrients, and phytoplankton biomass. We found pronounced differences between an Atlantic sector dominated by the warm West Greenland Current and an Arctic sector with surface waters... |
| Tipo: Text |
Palavras-chave: Arctic; Phytoplankton; Ice edge; Spring bloom; Light; Turbulence. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00504/61530/65391.pdf |
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| Grasso, Florent; Ruessink, B. G.. |
| Waves breaking in the shallow surf zone near the shoreline inject turbulence into the water column that may reach the bed to suspend sediment. Breaking-wave turbulence in the surf zone is, however, poorly understood, which is one of the reasons why many process-based coastal-evolution models predict coastal change during severe storms inadequately. Here, we use data collected in two natural surf zones to derive a new parameterization for the stability function C-mu that determines the magnitude of the eddy viscosity nu(t) in two-equation turbulent-viscosity models, nu(t) = C(mu)k(2)/epsilon, where k is turbulent kinetic energy and epsilon is the turbulence dissipation rate. In both data sets, the ratio of turbulence production to dissipation is small... |
| Tipo: Text |
Palavras-chave: Eddy viscosity; Field measurements; Parameterization; Production; Surf zone; Turbulence. |
| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00114/22512/20204.pdf |
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| Togneri, Michael; Pinon, Grégory; Carlier, Clement; Choma Bex, Camille; Masters, Ian. |
| Turbulence is a crucial flow phenomenon for tidal energy converters (TECs), as it influences both the peak loads they experience and their fatigue life. To best mitigate its effects we must understand both turbulence itself and how it induces loads on TECs. To that end, this paper presents the results of blade element momentum theory (BEMT) simulations of flume-scale TEC models subjected to synthetic turbulent flows. Synthetic turbulence methods produce three-dimensional flowfields from limited data, without solving the equations governing fluid motion. These flowfields are non-physical, but match key statistical properties of real turbulence and are much quicker and computationally cheaper to produce. This study employs two synthetic turbulence generation... |
| Tipo: Text |
Palavras-chave: BEMT; SEM; Sandia; Tidal turbines; Turbulence; Simulation. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00501/61248/64828.pdf |
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| Aghanim, N.; Akrami, Y.; Alves, Mir; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Ballardini, M.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Basak, S.; Benabed, K.; Bernard, J. -p.; Bersanelli, M.; Bielewicz, P.; Bock, J. J.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bracco, A.; Bucher, M.; Burigana, C.; Calabrese, E.; Cardoso, J. -f.; Carron, J.; Chary, R. -r.; Chiang, H. C.; Colombo, L. P. L.; Combet, C.; Crill, B. P.; Cuttaia, F.; De Bernardis, P.; De Zotti, G.; Delabrouille, J.; Delouis, Jean Marc; Di Valentino, E.; Dickinson, C.; Diego, J. M.; Dore, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Ensslin, T. A.; Eriksen, H. K.; Falgarone, E.; Fantaye, Y.; Fernandez-cobos, R.; Ferriere, K.; Finelli, F.; Forastieri, F.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frolov, A.; Galeotta, S.; Galli, S.; Ganga, K.; Genova-santos, R. T.; Gerbino, M.; Ghosh, T.; Gonzalez-nuevo, J.; Gorski, K. M.; Gratton, S.; Green, G.; Gruppuso, A.; Gudmundsson, J. E.; Guillet, V.; Handley, W.; Hansen, F. K.; Helou, G.; Herranz, D.; Hivon, E.; Huang, Z.; Jaffe, A. H.; Jones, W. C.; Keihanen, E.; Keskitalo, R.; Kiiveri, K.; Kim, J.; Krachmalnicoff, N.; Kunz, M.; Kurki-suonio, H.; Lagache, G.; Lamarre, J. -m.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Le Jeune, M.; Levrier, F.; Liguori, M.; Lilje, P. B.; Lindholm, V.; Lopez-caniego, M.; Lubin, Pm; Ma, Y. -z.; Macias-perez, J. F.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Marcos-caballero, A.; Maris, M.; Martin, Pg; Martinez-gonzalez, E.; Matarrese, S.; Mauri, N.; Mcewen, J. D.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Miville-deschenes, M. -a.; Molinari, D.; Moneti, A.; Montier, L.; Morgante, G.; Moss, A.; Natoli, P.; Pagano, L.; Paoletti, D.; Patanchon, G.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Polastri, L.; Polenta, G.; Puget, J. -l.; Rachen, J. P.; Reinecke, M.; Remazeilles, M.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rubino-martin, J. A.; Ruiz-granados, B.; Salvati, L.; Sandri, M.; Savelainen, M.; Scott, D.; Sirignano, C.; Sunyaev, R.; Suur-uski, A. -s.; Tauber, J. A.; Tavagnacco, D.; Tenti, M.; Toffolatti, L.; Tomasi, M.; Trombetti, T.; Valiviita, J.; Vansyngel, F.; Van Tent, B.; Vielva, P.; Villa, F.; Vittorio, N.; Wandelt, B. D.; Wehus, I. K.; Zacchei, A.; Zonca, A.. |
| Observations of the submillimetre emission from Galactic dust, in both total intensity I and polarization, have received tremendous interest thanks to the Planck full-sky maps. In this paper we make use of such full-sky maps of dust polarized emission produced from the third public release of Planck data. As the basis for expanding on astrophysical studies of the polarized thermal emission from Galactic dust, we present full-sky maps of the dust polarization fraction p, polarization angle psi, and dispersion function of polarization angles ?. The joint distribution (one-point statistics) of p and N-H confirms that the mean and maximum polarization fractions decrease with increasing N-H. The uncertainty on the maximum observed polarization fraction, (max) =... |
| Tipo: Text |
Palavras-chave: Polarization; Magnetic fields; Turbulence; Dust; Extinction; Local insterstellar matter; Submillimeter: ISM. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00654/76632/77786.pdf |
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| Mycek, Paul; Gaurier, Benoit; Germain, Gregory; Pinon, Gregory; Rivoalen, Elie. |
| The ambient turbulence intensity in the upstream flow plays a decisive role in the behaviour of horizontal axis marine current turbines. Experimental trials, run in the IFREMER flume tank in Boulogne-Sur-Mer (France) for two different turbulence intensity rates, namely 3% and 15%, are presented. They show, for the studied turbine configuration, that while the wake of the turbine is deeply influenced by the ambient turbulence conditions, its mean performances turn out to be slightly modified. The presented conclusions are crucial in the view of implanting second generation turbines arrays. In addition, complete and detailed data sets (wake profiles and performance graphs) are made available to the scientific community in order to encourage further... |
| Tipo: Text |
Palavras-chave: Marine current turbine; Performance; Wake; Turbulence; Experiment; Flume tank. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00175/28647/27171.pdf |
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| Saint-michel, Brice; Dubrulle, B.; Marie, Louis; Ravelet, F.; Daviaud, F.. |
| We present a detailed study of a global bifurcation occuring in a turbulent von Karman swirling flow. In this system, the statistically steady states progressively display hysteretic behaviour when the Reynolds number is increased above the transition to turbulence. We examine in detail this hysteresis using asymmetric forcing conditions-rotating the impellers at different speeds. For very high Reynolds numbers, we study the sensitivity of the hysteresis cycle-using complementary particle image velocimetry and global mechanical measurements-to the forcing nature, imposing either the torque or the speed of the impellers. New mean states, displaying multiple quasi-steady states and negative differential responses, are experimentally observed in torque... |
| Tipo: Text |
Palavras-chave: Turbulence; Instability; Negative response; Symmetry. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00204/31503/29904.pdf |
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| Ikhennicheu, Maria; Germain, Gregory; Druault, Philippe; Gaurier, Benoit. |
| In high flow velocity areas like those suitable for marine energy application, bathymetry variations create strong velocity fluctuations in the water column. It is therefore essential to characterize the turbulence evolution in the wake of seabed elements which may impact the loads on tidal turbines. For that purpose, experiments are carried out in a flume tank with Re as high as achievable in Froude similitude, with bathymetry variations experimentally represented with various wall-mounted square elements of height H: a cylinder or a cube as unitary obstacles and combinations of these elements followed by an inclined floor to resemble smooth bathymetry changes. The onset flow is a simple boundary layer profile with height 1.3 H and a low turbulence... |
| Tipo: Text |
Palavras-chave: Turbulence; Experimental trials; Wall-mounted obstacles; PIV; LDV; Marine energy. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00502/61356/64997.pdf |
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| Registros recuperados: 39 | |
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