Experimental study on dynamic stall of rigid and flexible hydrofoils in towing tank
Résumé
This paper presents extensive results from a new experimental setup that operates in the towing tank at Centrale Nantes. The original feature of the setup is its capability to simultaneously induce inflow and dynamical pitching motions to large scale innovative appendages, and measure strains and hydrodynamic performances. The dynamic stall regimes of two hydrofoils are studied by means of the influence of the Reynolds number and the reduced frequency. The first appendage is a rigid rudder-like hydrofoil. The second one is a flexible composite hydrofoil equipped with optical fibers with arrays of fiber bragg gratings to measure local strains. The rudder-like hydrofoil performances behave non-linearly, which is the consequence of boundary layer detachments due to the hydrofoil's thickness and the large angles of attack tested. A significant quasi-static hysteresis effect was also observed on the lift due to stall. The composite hydrofoil shows a more linear behavior, with an earlier and sharper stall effect. The data demonstrated setup capabilities to capture subtle flow phenomena. Finally, as the lift coefficient and the strains are assessed with independent measurement systems, their close proximity demonstrates the good accuracy of the experimental setup and the link between lift and structural bending deformation.
Origine | Publication financée par une institution |
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