Force measurements and cross-flow estimation on a flapping bird-like airfoil

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Introduction 9 Figure 6: [5] - Vehicle Mass vs. Reynolds Number. 0:2 6 k 6 0:4 (see sec. 1) in unsteady conditions: the separation of the laminar boundary layer, contrary to the classical aerodynamics, becomes the norm and both the such and dynamic stall mechanisms generate, at the same time, the lift and the propulsion. In [8] is shown how the reduced frequency (see sec. 1) is very important to deflne the wake formation: at k • 1:5 it is found the dynamic-stall process and its associated shedding corresponded to a typical blufi-body-type 2 , for k‚ 2, a single leading-edge and trailing-edge vortex pair was shed into the wake (see Fig. 7). Rival and Tropea, in their paper [8], analyzed the wake formation during a pure-plunging motion and during a pure-pitching motion at difierent reduced frequency. They had also analyzed the lift and the moment coe–cient comparing they with a no apping case: some lift and moment hysteresis phenomena appear. The wake description is veryhardtodo, TuncerandKaya[6]triedtodescribeitnumericallybyoptimizingthe apping motion for maximum trust and propulsive e–ciency (see Fig. 8). In this case the reduced frequency is higher then 1 but it is possible to see the few before described vortex structures. The topic treated in this work is a step of a bigger project 3 about pitching and plunging airfoils, exible and not. In the step before [9], what is more, the distribution 2 Von K arman theory with multiple alternating vortices shed from the leading and trailing edges. 3 The responsible for the project is Dipl.-Ing. S. Bansmer of the Institut f˜ ur Str˜ omungsmechanik der TU Braunschweig under the supervision of Prof.Dr.-Ing. R. Radespiel

Anteprima della Tesi di Andrea Liberatoscioli

Anteprima della tesi: Force measurements and cross-flow estimation on a flapping bird-like airfoil, Pagina 6

Laurea liv.II (specialistica)

Facoltà: Ingegneria

Autore: Andrea Liberatoscioli Contatta »

Composta da 68 pagine.

 

Questa tesi ha raggiunto 88 click dal 21/06/2011.

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