An Experimental Set Up for the Study of the Retreating Blade Dynamic Stall

In the aim of research about retreating blade dynamic stall control for helicopter performance improvement, a new experimental rig has been designed consisting in a blade section model supported by a motorized strut that can move it in pitch around its quarter chord. The design and performance of the experimental rig have been purposely conceived to reproduce the deep dynamic stall condition of a full-scale retreating rotor blade section at 75% radius at high forward flight speed, in order to test real control systems of the dynamic stall phenomenon on helicopter blade sections. Several measurement techniques as, for instance, fast unsteady pressure measurements, hot wire anemometer and Particle Image Velocimetry (PIV), can be employed to completely characterise the time dependent flowfield. The paper describes the first series of experiments carried out on a NACA 23012 blade section to validate the rig performance and the measurements set up. The analysis of the comprehensive data set enabled to complete the description of the dynamic stall phenomenon for the NACA 23012 airfoil and can be suitable to be taken as a reference to validate CFD tools. After the validation tests, the experimental rig will enable to test real control systems of the dynamic stall phenomenon on helicopter blade sections.