Prediction and Measurement of Unsteady Blade Surface Pressures on an Open Rotor

Abstract

In this paper we present experimental measurements from high frequency unsteady pressure transducers on the blade surfaces of a counter-rotating open rotor and results obtained with full-annulus URANS simulations. A quantitative metric is introduced which can be used to evaluate the quality of the transmission of the front rotor flow features through the interpolating interface between the rotors. Comparisons are made for the open rotor operating at two angles of attack: 0° and 12°. The former setting is a datum case for ‘uninstalled’ operation; the latter setting represents ‘installed’ operation at an extreme angle of attack (AoA). Operation at 12° AoA causes the front rotor wake to vary around the annulus, and leads to shaft-order side-bands for interaction tones. The computational predictions of the interaction tones and shaft-order side-bands are of the correct frequencies and order of magnitude for both the low and the high AoA cases. An analysis of the propagation of the front rotor wakes and tip vortices shows that the use of a sufficiently fine grid is essential in order to accurately predict the unsteady pressure on the rear rotor surface.