Aerodynamic Study of a NACA 64418 Rectangular Wing under Forced Pitching Motions

Abstract

The aerodynamic behavior of a pitching NACA 64418 rectangular wing was experimentally studied in a subsonic wind tunnel. The wing had a chord c = 0.5 m, a span which covered the distance between the two parallel tunnel walls and an axis of rotation 0.35 c far from the leading edge. Based on pressure distribution and flow visualization, intermittent flow separation (double stall) was revealed near the leading edge suction side when the wing was stationary, at angles higher than 17° and Re = 0.5 × 106. Under pitching oscillations, aerodynamic loads were calculated by integrating the output data of fast responding surface pressure transducers for various mean angles of attack (αm (max) = 15°), reduced frequencies (kmax = 0.2) and angle amplitudes Δα in the interval [2°, 8°]. The impact of the above parameters up to Re = 0.75 × 106 on the cycle-averaged lift and pitching moment loops is discussed and the cycle aerodynamic damping coefficient is calculated. Moreover, the boundaries of the above parameters are defined for the case that energy is transferred from the flow to the wing (negative aerodynamic damping coefficient), indicating the conditions under which aeroelastic instabilities are probable to occur.

Deep learning based instance segmentation of particle streaks and tufts

“…Visually inspecting images of tufted models is still a common way to deduce the flow behavior in the different regions of the examined model, e.g. by identifying reversed or blurry tufts [29][30][31][32]. In [33], a quantitative analysis of tufts' behavior was performed, where statistics about each tuft's orientation were used to derive information about the local flow state.…”