Surveys of the Flow Fields at the Propeller Planes of Six 40 deg Sweptbsck Wing-Fuselage-Nacelle Combinations

摘要

The flow fields at the propeller planes of six 40 deg sweptback semi- span wing-fuselage-nacelle combinations were surveyed to provide data to enable the study of the characteristics of the flow fields and their effect on propeller-oscillating aerodynamic loads. The results of the surveys are presented in the form of angles that define the direction of the local velocity relative to the survey disk and as the ratios of the local velocities to free- stream velocity. These parameters are shown as functions of the angular position around the survey disk for given radial positions. Typical propeller-oscillating air loads, computed by the method of NACA TN 2192 using measured flow-field data, are presented to demonstrate the significance of the flow parameters. Also shown are comparisons of measured and predicted upflow angles for all models at a specific angle of attack. The results of the surveys show that variations of the flow parameters with angular position are predominantly first-order sinusoidal for the six models tested and, thus, are similar to results for an unswept-wing airplane reported in NACA TN 2192. The rotational flow angle is the major contributor to the oscillating aerodynamic loads and has its maximum and minimum values at the horizontal center line of the propeller disk, where its value is determined by the upflow angle. The upflow angles predicted by the methods of NACA TN's 2795 and 2894 were found to be in good agreement with measured angles.