Experiment on basic performance of a simple waterwheel/windmill with a cross-stream axis

Abstract

We conduct subsonic wind-tunnel experiments, in order to investigate the basic aerodynamic characteristics of an autorotating finite flat plate in uniform mainstream, which has a potential for unconventional waterwheels and windmills with very simple structures in addition to unusual mixers/diffusers. The present study focuses on both the effects of an aspect ratio AR and a tip-speed ratio Ω* upon autorotation of the flat plate with a low thickness-to-depth ratio λ = 1.3×10−2 – 2.0×10−2. We carry out the measurements using a torquemeter together with the synchronised measurements of the plate’s attack angle α for the analyses with phase-averaging technique. As a result, the (time-mean) torque coefficient CTTM tends to decreases with increasing Ω*, and CTTM tends to become large with increasing AR. (Time-mean) power coefficient CPTM shows that the present phenomenon is suitable for low-speed waterwheels and windmills.