PIV-Based Examination of Deep Stall on an Oscillating Airfoil

<p>A number of studies suggest that the deep stall flow fields produced by a pure-pitch and a pure-plunge oscillating airfoil are equivalent when effective angles of attack are matched. This assumption is examined using particle image velocimetry (PIV). Sinusoidal oscillations of a pure-plunge and pure-pitch airfoil with matched reduced frequency k = 3.93 and with kinematically equivalent amplitudes of effective angle of attack are comparatively examined using results of PIV in a free surface water tunnel at AFRL/RB Wright Patterson AFB. Experiments were conducted at Re = 10000 and Re = 40000 based on free stream velocity and airfoil chord in order to observe the legitimacy of assuming Reynolds number insensitivity on the respective flow fields. Comparisons are made to computational flow field results collected in a separate but coordinated CFD effort. Results for both the pure-plunge case and the pure-pitch case confirm the Reynolds number insensitivity for the high frequency motions researched here. The resulting flow fields for pure-plunge case and the pure-pitch case were vastly different. Experimental results for the pure-plunge case closely resembled those achieved by computation. However the pure-pitch case experimental and computation results were dissimilar even after considering possible wall effects of the water tunnel. The flow field disagreement between the two motions is not surprising considering trailing edge kinematic dissimilarities.</p><p>This work has been selected by scholars as being culturally important and is part of the knowledge base of civilization as we know it. This work was reproduced from the original artifact and remains as true to the original work as possible. Therefore you will see the original copyright references library stamps (as most of these works have been housed in our most important libraries around the world) and other notations in the work.</p><p>This work is in the public domain in the United States of America and possibly other nations. Within the United States you may freely copy and distribute this work as no entity (individual or corporate) has a copyright on the body of the work.</p><p>As a reproduction of a historical artifact this work may contain missing or blurred pages poor pictures errant marks etc. Scholars believe and we concur that this work is important enough to be preserved reproduced and made generally available to the public. We appreciate your support of the preservation process and thank you for being an important part of keeping this knowledge alive and relevant.</p><br>