Comportement aérodynamique d'une éolienne offshore flottante soumise à un effet de houle

International audienceThe flowfield around the rotor blades of a wind turbine may be quite complex due to the occurrence of several aerodynamic phenomena. It is all the more true for floating offshore wind turbines (FOWT), for which the six rigid-body motions of the floating platform can induce blade/wake interactions. Therefore conventional numerical approaches for wind turbine applications, such as BEM, may be questionable for an accurate prediction of floating wind turbine aerodynamic loads. Consequently, the current paper investigates the aerodynamic behavior of a FOWT subjected to several prescribed motions, representative of a wave movement, based on CFD simulations. These results, obtained on the NREL 5-MW wind turbine, are compared to previous results found in the literature and analyzed to provide a better understanding of the involved aerodynamic phenomena

Progress Towards Fuselage Drag Reduction via Active Flow Control: A Combined CFD and Experimental Effort

A combined computational and experimental effort has been undertaken to study fuselage drag reduction on a generic, non-proprietary rotorcraft fuselage by the application of active ow control. Fuselage drag reduction is an area of research interest to both the United States and France and this area is being worked collaboratively as a task under the United States/France Memorandum of Agreement on Helicopter Aeromechanics. In the first half of this task, emphasis is placed on the US generic fuselage, the ROBIN-mod7, with the experimental work being conducted on the US side and complementary US and French CFD analysis of the baseline and controlled cases. Fuselage simulations were made using Reynolds-averaged Navier-Stokes ow solvers and with multiple turbulence models. Comparisons were made to experimental data for numerical simulations of the isolated fuselage and for the fuselage as installed in the tunnel, which includes modeling of the tunnel contraction, walls, and support fairing. The numerical simulations show that comparisons to the experimental data are in good agreement when the tunnel and model support are included. The isolated fuselage simulations compare well to each other, however, there is a positive shift in the centerline pressure when compared to the experiment. The computed flow separation locations on the rear ramp region had only slight differences with and without the tunnel walls and model support. For the simulations, the flow control slots were placed at several locations around the flow separation lines as a series of eight slots that formed a nearly continuous U-shape. Results from the numerical simulations resulted in an estimated 35% fuselage drag reduction from a steady blowing flow control configuration and a 26% drag reduction for unsteady zero-net-mass flow control configuration. Simulations with steady blowing show a delayed flow separation at the rear ramp of the fuselage that increases the surface pressure acting on the ramp, thus decreasing the overall fuselage pressure drag

Validation of Boundary-Layer-Transition Computations for a Rotor with Axial Inflow

Boundary-layer-transition computations are performed using the in-house finite-volume solvers elsA by ONERA and TAU by DLR. Reynolds-averaged Navier-Stokes simulations, using the Langtry-Menter model as well as semiempirical transition criteria, are presented using both solvers for a rotor in climb. The numerical results are compared to temperature-sensitive paint experiments conducted at DLR's rotor test facility. Concerning the Langtry-Menter computation, transition occurs with both solvers due to laminar separation close to the trailing edge, further downstream than seen in the experiment. Semi-empirical transition criteria predict transition within both codes due to laminar separation, which was not detected in the experiments. When only considering the AHD criterion, the transition locations within the numerical simulations and the experiment are in good agreement along the entire span in all three considered test cases. In addition, numerical results are presented for a test case with cyclic pitch. These unsteady boundary-layer transition computations are carried out using the semi-empirical transition criteria approach of DLR-TAU. In accordance with the static test cases, the results are promising, as long as the laminar-separation criterion is deactivated

Assessment of Boundary Layer Transition Prediction Methods for Rotating Blades

Boundary-layer-transition computations are performed using the in-house finite-volume solvers elsA by ONERA and TAU by DLR. Reynolds-averaged Navier-Stokes simulations, using the Langtry-Menter model as well as semiempirical transition criteria, are presented using both solvers for a rotor in climb. The numerical results are compared to temperature-sensitive paint experiments conducted at DLR's rotor test facility. Concerning the Langtry-Menter computation, transition occurs with both solvers due to laminar separation close to the trailing edge, further downstream than seen in the experiment. The transition locations using AHD semi-empirical transition criterion are in good agreement along the entire span in all three considered test cases. In addition, numerical results are presented for a test case with cyclic pitch. These unsteady boundary-layer transition computations are carried out using the semi-empirical transition criteria approach of DLR-TAU. In accordance with the static test cases, the results are promising, as long as the laminar-separation criterion is deactivated

Characterization of Simian Immunodeficiency Virus SIVSM/Human Immunodeficiency Virus Type 2 Vpx Function in Human Myeloid Cells▿

Human immunodeficiency virus type 2 (HIV-2)/simian immunodeficiency virus SIVSM Vpx is incorporated into virion particles and is thus present during the early steps of infection, when it has been reported to influence the nuclear import of viral DNA. We recently reported that Vpx promoted the accumulation of full-length viral DNA following the infection of human monocyte-derived dendritic cells (DCs). This positive effect was exerted following the infection of DCs with cognate viruses and with retroviruses as divergent as HIV-1, feline immunodeficiency virus, and even murine leukemia virus, leading us to suggest that Vpx counteracted an antiviral restriction present in DCs. Here, we show that Vpx is required, albeit to a different extent, for the infection of all myeloid but not of lymphoid cells, including monocytes, macrophages, and monocytoid THP-1 cells that had been induced to differentiate with phorbol esters. The intracellular localization of Vpx was highly heterogeneous and cell type dependent, since Vpx localized differently in HeLa cells and DCs. Despite these differences, no clear correlation between the functionality of Vpx and its intracellular localization could be drawn. As a first insight into its function, we determined that SIVSM/HIV-2 and SIVRCM Vpx proteins interact with the DCAF1 adaptor of the Cul4-based E3 ubiquitin ligase complex recently described to associate with HIV-1 Vpr and HIV-2 Vpx. However, the functionality of Vpx proteins in the infection of DCs did not strictly correlate with DCAF1 binding, and knockdown experiments failed to reveal a functional role for this association in differentiated THP-1 cells. Lastly, when transferred in the context of a replication-competent viral clone, Vpx was required for replication in DCs

Projet Action Scientifique 2015, Céramique du haut Moyen Âge en Île-de-France

Project Action Scientifique 2015, rapport Inra

Projet Action Scientifique 2016, Céramique du haut Moyen Âge en Île-de-France

Project Action Scientifique 2015, rapport Inra