Propeller-Hub Interference Effects Using an Approximate Lifting Surface Theory.
Abstract
In order to provide for a more exact model of a marine propeller with a hub and yet avoid the complex computations necessary in an exact theory, an approximate lifting-surface theory was developed. The approximation fundamental to this development is that of Weissinger's, where an airfoil is replaced with a single bound vortex and its associated trailing vortex system at the 1/4 chord point, while the boundary conditions are satisfied only at the 3/4 chord point. The life coefficient obtained in this manner will approximate the results of thin airfoil and be exactly the same for the cases of circular arc and flat plate airfoils. This theory was subsequently used to find the induced normal velocity on the surface of a propeller's hub. The hub was broken up into a series of frustrums and the average induced velocity was found on an arc of the frustrum between two successive blades. This velocity was assumed constant over the entire frustrum. The induced normal velocity at each section of the hub was then incorporated into the A. M. O. Smith, and J. Pierce solution of the potential flow around an arbitrary body. Once this source distribution was found for uniform onset flow around the body and hub, the distribution was used along with the approximate lifting-surface theory to find the ideal lift coefficient, ideal angle of attack, and the maximum camber of the propeller section. Three computer programs were written to apply this theory to an actual propeller and HUB.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 15, 1977
- Accession Number
- ADA047565
Entities
People
- Karl Ludolph
Organizations
- Pennsylvania State University