A 3D flow separation model for open propellers with blunt trailing edge

摘要

The panel method is widely used in the design and analysis of marine propellers. However, this method cannot handle propellers with a blunt trailing edge due to a lack of proper models for the flow separation downstream. In this study, a numerical scheme, i.e., the three-dimensional flow separation model, is proposed to enable the panel method to be applied to propellers with a blunt trailing edge. In this model, the flow separation zone is represented as an extension of the trailing edge. The criteria of zero local lifts and zero local moments over the extension of all blade sections are used to establish the equations that determine the shape of the flow separation zone. Those equations are solved either by the Newton-Raphson method or as an optimization problem. A low-order panel method coupled with a boundary layer solver (the viscous/inviscid interaction method) is used to predict the pressure distributions and forces for the extended geometry. To validate this model, the pressure distributions of the propeller blade are compared with those from solving the Reynolds-Averaged Navier-Stokes equations. The predicted open water characteristics of a controllable pitch propeller are compared with the experimental measurements at a wide range of advance ratios with different pitches. This model requires much less computational effort while preserving high accuracy, and thus can be used reliably in designing and analyzing propellers with a blunt trailing edge.