Spanwise Differences in Static and Dynamic Stall on a Pitching Rotor Blade Tip Model

An experimental investigation of static and dynamic stall on a rotor blade tip model with an aspect ratio of 6.2 at a chord Reynolcls number of900 ,000 and a Mach numbcr of0.16 is presented. The spatiotemporal behavior of the flow separation was analyzed using unstcady surface pressurc measurements ancl high-speecl particle image velocimetry. The maximum effective angle of attack prior to stall is shiftecl to approximately two-thirds of the span outboard because of an increasing angle of attack of the model towarcl the tip. Different stages of flow separation for static angles of attack were identified, inclucling the occurrence of two stall cells. Du ring dynamic stall, the leacling edge vortcx formation starts near the spanwise position of thc static stall onset. The subsequent spanwise evolution of the vortex formation results in two vorticcs for deep stall conclitions, covering the samc spanwisc arcas as thc two static stall cclls.