Search

A general mathematical formulation is given for the three dimensional boundary-layer flow on a rotating propeller blade. The basic equations are presented in a nonorthogonal coordinate system which rotates with the blade. Finite difference methods are used to develop a computer code for solving the laminar and turbulent boundary-layer equations. The Reynolds stress tensor is modeled by an algebraic eddy-viscosity formulation. In general, the equations are solved numerically using the standard Keller box method. However, regions of flow reversal across the boundary-layer are computed by the characteristics box method. A companion geometry computer code, developed to model propeller geometry characteristics, and an existing inviscid flow code for computing propeller blade pressures are combined with the boundary-layer computer code to form an efficient computation scheme. For a given potential-flow solution, a typical boundary-layer solution of 690 grid points requires 64 seconds CPU time on a CYBER 176 computer. Computed results are presented for several propeller blade geometries. The rotating segment solution compares well with analytical and experimental data. Predictions for a model propeller also compare favorably with experimental data and illustrate that two-dimensional theory may provide adequate predictions for applications where crossflow effects are not important. Geometry effects of warp and skew are shown to be small for the boundary-layer predictions on three model propellers., Presented at ONR Symposium (15th), Hamburg, Germany, 3-7 Sep 84.

A comprehensive set of experimental data for flow over the stern of a three-dimensional model having 2:1 elliptic transverse cross sections, suitable for analytical comparisons, is presented. Included in this set are surface pressure and shear stress distributions, static pressure and mean velocity profiles, and Reynolds stresses. The eddy viscosity and mixing length values obtained from the measured Reynolds stresses and mean velocity gradients are also presented. The measured and derived data are compared with the predictions of existing three-dimensional theoretical methods. These comparisons confirm the need for improved prediction techniques in the thick turbulent boundary-layer region of the stern. (Author)

Measurements of the boundary-layer characteristics and pressure distribution on three axisymmetric bodies with and without a propeller in operation are correlated with analytical techniques for computing (1) the interaction between the hull boundary layer flow and the potential flow and (2) the interaction between the operating propeller and the thick stern boundary layer. The agreement between the measured and computed shear stresses, pressure distributions, and velocity profiles was satisfactory except over the last 5 percent of body length on the two fullest afterbodies. An inviscid propeller-stern-boundary-layer interaaction model was developed and found to give accurate predictions of effective velocity profiles. The experimental results show that the potential-flow propeller-hull interaction methods give accurate predictions for thrust deduction and the propeller-induced pressure distribution. The present analytical techniques will be useful for predicting the full-scale effective velocity profile for propeller design when account is taken of the effects of Reynolds number, roughness, and propeller suction in modifying the nominal velocity profiles. (Author)

A comprehensive set of experimental pressure, velocity and turbulence data are presented for two simple three-dimensional models having 2:1 and 3:1 elliptical transverse cross sections. The Lighthill displacement body concept is used to predict the pressure distributions over the models. The predicted pressure distributions are in good agreement with the measured pressure distributions. Around the corner regions over the major axes of the models the three-dimensional boundary-layer equations do not predict well the measured mean velocity distributions. In these regions the boundary layers are much thicker than the cross section dimensions and differences in curvatures between the flow and body surface are very large. However, over large areas of relatively flat body surfaces, the computed and measured mean velocity distributions are in good agreement., This article is from the Proceedings of the Symposium on the Numerical and Physical Aspects of Aerodynamic Flows (2nd), 17-20 Jan 83, California State Univ. Long Beach, AD-A134 151.