Accession Number : ADA298179

Title :   Numerical Modeling of Propeller Tip Flows with Wake Sheet Roll-up in Three Dimensions.

Descriptive Note : Technical rept.,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF OCEAN ENGINEERING

Personal Author(s) : Pyo, Sangwoo

PDF Url : ADA298179

Report Date : JUL 1995

Pagination or Media Count : 157

Abstract : A boundary element method is applied to the prediction of the flow around propeller blades, with emphasis at the tip region. The presented work is divided into three major parts. In the first part, a new panel arrangement, namely the FLow Adapted Grid (FLAG), is proposed. This grid is normal to the blade leading edge outline and adjusted to the force free wake geometry at the trailing edge. The location of the tip vortex detachment point is determined by an iterative method. The effectiveness and robustness of the flow adapted grid are demonstrated through numerical validation tests and through comparisons with existing experiments. The flow adapted grid is found to improve: (a) the predicted velocity flow field and the pressure distribution at the tip, (b) the convergence of an iterative pressure Kutta condition, and (c) the overall numerical performance of the method and its consistency to lifting surface theory. The second part addresses an algorithm for predicting the three-dimensional vortex sheet roil-up. A higher order panel method, which combines a hyper- boloidal panel geometry with a biquadratic dipole distribution, is used in order to accurately model the highly rolled-up regions. For given radial circulation distributions, the predicted wake shapes are shown to be convergent and consistent to those predicted from other methods. In the final part of this thesis, the flow adapted grid and the three-dimensional wake sheet roll-up algorithm are combined in order to estimate the propeller loading/trailing wake interaction. Predicted forces, circulation distributions and tip vortex trajectories are shown to agree well to those measured in experiments.

Descriptors :   *WAKE, *FLOW, *MARINE PROPELLERS, *PROPELLER BLADES, MATHEMATICAL MODELS, ROLL, PANELS, GRIDS, NUMERICAL ANALYSIS, VORTICES, THREE DIMENSIONAL, SHEETS, LEADING EDGES, TRAILING EDGES, PROPELLERS.

Subject Categories : Marine Engineering

Distribution Statement : APPROVED FOR PUBLIC RELEASE