Experimental investigation of the effect of yaw angle on the inflow of a two-bladed propeller

Abstract

An experimental investigation has been performed to measure the inflow of a two-bladed propeller. This is conducted over a range of advance ratios (J=0.36 to 1.54) and yaw angles (γ=0 to 20∘) at a Reynolds number of Re≈111000, based on the chord length and advancing blade resultant velocity at the 70% spanwise position. Drawing on experimental results, three major qualitative trends are observed, that characterise the axial induced inflow of inclined propellers: the formation of an approximately sinusoidal inflow trend around the azimuth featuring broad regions of increased and reduced inflow, an azimuthal phase shift of the trend from the advancing and retreating blade positions, and the dependencies of the inflow maxima, minima and phase shift on advance ratio, yaw angle and radial position. These are subsequently compared against two widely used assumptions for calculating the aerodynamic environment of inclined propellers; firstly, that inflow at each radial and azimuthal element is calculated using an axial approximation of the whole propeller disc operating within the same condition as that element, and secondly, uniform induced inflow across the entire propeller plane. The comparison demonstrates the limitations of said assumptions by highlighting their inability to account for components of the trailed and shed vortical systems of the propeller wake.