Time-resolved stereo PIV measurements of an active Gurney flap system

Abstract

This paper presents the results of the Particle Image Velocimetry (PIV) measurements performed during the full-scale two-dimensional Active Gurney Flap (AGF) wind tunnel test campaign executed early 2014 as part of the Innovative Rotor Blades work package of the European Clean Sky – Green Rotorcraft initiative. The test article consisted of a main rotor blade section featuring a modified public domain airfoil fitted with a full-span AGF, driven by a flight representative actuator and mechanism. The objective of the test was to improve the understanding of the flow physics of a dynamically deploying upstream AGF, to provide a basis for the validation of numerical models and to serve as an integrated functionality test of the AGF actuator and mechanism. Besides forming a necessary stepping stone towards the rotor and flight test activities scheduled in the continuation of the project, the novelty of the test campaign lies in the time-resolved PIV measurements performed on an actively deploying upstream AGF. Two separate PIV camera arrangements were employed, one focusing on the direct vicinity of the AGF and one focusing on the shed wake behind the airfoil. Both sinusoidal and ramp-type deployments were considered at different deployment heights and frequencies. The first part of the paper presents the background and motivation of the test activities and describes the experimental test set-up. The second part of the paper presents the trailing-edge region velocity and vorticity fields acquired during a ramp-type deployment, including correlation with measured pressure profiles. Spectral analysis of the velocity fields captured at different AGF deployment heights reveals the AGF and trailing-edge vortex shedding frequencies, providing a useful basis for CFD validation.