Unsteady pressure measurements on a MAV wing for the design of a turbulence mitigation system

Abstract

Experiments at low Reynolds numbers were performed on a pressure tapped NACA2313 wing in a 3 × 2 × 9 meter wind tunnel under nominally smooth (Ti = 1.2%) and turbulent (Ti = 7.2%) flows at a mean flow velocity of 8ms -1 (Re ≈ 120,000). Unsteady surface pressures were measured to understand if this information could be used to resolve for turbulence-induced perturbations and furthermore utilize this information in a turbulence mitigation system. Although pressure tapping the majority of the chord is inevitability impractical for MAV application, it was discovered that a point local Coefficient of Pressure (Cp) held high correlation to the chord-wise Cp integration and allowed for a linear relationship to be formed between the two variables. The defined relationship provided a 95% confidence for angles of attack below stall and can be used to estimate the integrated cord-wise pressure coefficient at a particular span wise location. The relationship between a single pressure tap and the integrated Cp of that chord-wise section was valid for each two different span-wise locations with similar defining equations. As one pressure tap can be used to adequately estimate the integrated Cp on a chord-wise wing section, a limited amount of pressure taps across the wings span can approximate the pressure distribution across the span and approximate flight perturbations. This paper focusses on the implementation of unsteady pressure measurement and autopilot control logics for turbulence detection and mitigation.