Abstract
Stereo PIV measurements has been performed behind the inclined plate, angle of attack 5 and 10 deg. Occurrence and dynamics of streamwise structures behind the plate trailing edge have been studied in details using POD method. The streamwise structures are represented by vortices and low- and highvelocity regions, probably streaks. The obtained results support the hypothesis of an airfoil-flow force interaction by Hoffman and Johnson [1,2].
Highlights
The motivation of the presented study is supporting new ideas about principle of flight by Hoffman and Johnson from KTH Stockholm, see [1,2]
The simple experiment is made with the simplest airfoil possible represented by a flat plate in uniform flow and moderate angle of attack
Flat plate inclined with angle of attack 5 and 10 degs has been placed in a uniform low turbulence stream
Summary
The motivation of the presented study is supporting new ideas about principle of flight by Hoffman and Johnson from KTH Stockholm, see [1,2]. The new hypothesis of physical mechanism of flight relies on existence of streamwise vortical structures on the suction side of the airfoil and within its wake. The vortices origin is supposed to be the instability of the boundary layer subjected to adverse pressure gradient on the airfoil suction side (i.e. upper) – see [3]. Some consequences of the hypothesis are shown in [4,5,6]. The experimental results are of a qualitative nature only, they reveals existence of streamwise vortices above the plate without any doubt. The stereo-PIV method has been used for evaluation all 3 velocity components in the measuring plane. The measuring plane has been located perpendicular to the main flow, 35 mm behind the plane trailing edge covering the span 60 mm in the flow-field middle position.
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