HART II: Experimental analysis and validation of ONERA methodology for the prediction of blade-vortex interaction

In 1994 and 2001, two experimental campaigns, called HART and HART II, were conducted in the DNW German-Dutch wind tunnel, in the framework of the US-German and US-French Memoranda of Understanding, in cooperation between NASA Langley, US Army Aeroflightdynamics Directorate (AFDD), DLR, DNW and ONERA. The experimental program was conducted with a BOlOS main rotor model. The objective of these campaigns was to study the effects of the Higher Harmonic pitch Control on the blade vortex interactions (responsible for BVI noise and high vibration levels). Different measurements were performed, such as blade pressure distributions, blade airloads, acoustic measurements, blade deformations, wake geometry, and velocity field. The HART II campaign extended the HART data with new measurements techniques, more especially the 3-components PIV technique for the wake measurements, performed jointly by the DNW and DLR teams. The first part of the paper concerns the postprocessing of PIV data performed at ONERA, which in first consists in analysing the flowfield and determining the locations of the vortex centres, and in a second step, in determining the vortex parameters. Then, in a second part, the validation of the different steps of the ONERA aero-acoustic computational chain is presented, showing satisfactory correlations with experiment.