Detailed Turbulent Flowfield Measurements Immediately Behind a Propeller

An experimental investigation of the flow in the immediate vicinity of a free-running propeller was conducted in the VPI 2 m x 2m (6ftx6ft) wind tunnel. The performance of a three-bladed model propeller was measured for three-pitch/ diameter ratios. The P/D=1.572 model was selected for a detailed flow field study. The mean flow and all turbulence quantities were measured for three different axial stations behind the rotor .025,.23, and .50 diameters. The rest was done at a free stream velocity corresponding to a Reynolds number based on the propeller diameter of 2.58 x10^5. The results obtained showed that it is important to be as close as possible to the rotor place in order to get representative values for the flow parameters right at the disk plane. The blade tip effects were clear, and they manifest themselves in the form of higher peaks in turbulence intensity and shear stress profile. Measurements also indicated that the radial turbulence intensity represents the highest value, and the radial-peripheral correlation is the highest among the three velocity fluctuation correlation functions. The performance of the propeller model test was analyzed with a computerized theory, and the predictions were compared with experimental results. A satisfactory agreement was found as far as global values are concerned; the however less satisfactory agreement was obtained for detailed flow parameters.