Scaling and Configuration Effects on Helicopter Rotor Hub Interactional Aerodynamics

Abstract

A 1:17 scale model of a notional rotor hub of a large helicopter was tested in the Pennsylvania State University Applied Research Laboratory 12 in. test-section water tunnel. Objectives of the experiment were to quantify the effects of Reynolds number, advance ratio, and hub geometry configuration on the drag and shed wake of the rotor hub. A range of flow conditions was tested, with hub-diameter-based Reynolds numbers ranging from to and advance ratios ranging from 0.2 to 0.6, as well as nonrotating cases. Five hub geometry configurations were tested with various combinations of components including blade stubs, spiders, scissors, the swashplate, pitch links, and beanie fairing. Measurements included the steady and unsteady hub drag and particle image velocimetry at two downstream locations. Results include time-averaged and phase-averaged analyses of the unsteady drag and wake velocity. A strong dependence of the steady and unsteady hub drag and wake on the advance ratio, Reynolds number, and configuration was observed, demonstrating the importance of adequate Reynolds number scaling for model helicopter rotor hub tests.