Measurements of three-dimensional turbulent flow behind a propeller in a shear flow

This paper presents detailed measurements close behind a 0.49 m (1.615 ft), three-bladed propeller tested in the Virginia Polytechnic Institute and State University 2x2 m (6x6 ft) wind tunnel. Tests were run with a uniform approach flow as a baseline, and then the main test series was run with a variable mesh wire grid upstream to produce an approach flow with an essentially linear velocity gradient. The results are compared to elucidate the effects of the nonuniform approach flow. Several types of measurements are reported. First are gross quantities such as overall thrust and torque. The second type of measurements are mean (in the turbulence sense) quantities obtained with a five-port yawhead tube. All three components of the mean velocity and static pressure were obtained. The third type of measurements were made with an x-wire anemometer and an rms meter. These measurements yield all components of the turbulence intensities and stresses at a point averaged over many passes of the propeller blades. The last type of measurements were performed with the x-wire and a microcomputer. The computer is triggered to record many (approximately 160) traces from individual bladepassing events. These measurements are then processed to yield profiles of the mean velocities and turbulence intensities and stresses behind an individual blade.