Measurement of Pressure Distribution on a Conventional and a Highly Skewed Propeller Model

Abstract

Recently many researchers have performed the pressure measurement on propeller models to obtain reliable data for validating propeller theories. This paper describes the new experimental techniques and the results of the measurement of pressure distribution on the blade of propeller models. In the present measurement, two kinds of propeller models were used ; a conventional propeller and a highly skewed propeller. In order to measure the pressure not only under the non-cavitating condition but also the cavitating condition accurately, “Helmholtz chamber-type waterproof pressure transducers with high sensitivity” were employed.In earlier measurements, the measured pressure in some locations on the blades were greatly affected by the tortional or bending deformation of propeller blades. To remove such a detrimental effect, a special care has been taken of the attachment of pressure transducers to the propeller blades. In this paper, the pressure measurement performed by the improved procedure are described on two large propeller models working not only in uniform flow but in non-uniform flow. The present technique has the major advantage of the ability to measure unsteady pressure with high accuracy and no disruption to the measuring surface. The disadvantage is that the pressure transducers are very costly and specially fine techniques to install each pressure gauge in a chamber are demanded.Finally this paper discusses the comparison of pressure distribution between the measured results and computational results given by the existing propeller lifting surface theory on two types of propellers, both in uniform flow and in non-uniform flow produced by the wire mesh screen, respectively. On the conventional propeller, good agreements between the computation and the measurement in the pressure distribution on the back side were observed, while the theory presented higher pressure values on the face side at any advance ratios in the present measurement. On the other hand, in the case of the highly skewed propeller, wavy profiles of the pressure distribution on the back side were obtained under the respective advance ratios probably due to viscous effects. The discrepancy between the theory and the measurements for the highly skewed propeller is the same as that for the conventsonal propeller, except near the tip region of propeller blades.These discrpancies between the ewperiment and the theory should be attributed to the incomplete ness of the ewisting propeller lifting surface theory, that is, the two dimensional treatmdnt for thickness effects, the deformation of propeller blades and the neglect of viscous flow separation around the propeller blades.