Wakes of Idealized Propeller Shafts with Sleeves

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Authors
  1. Hally, D.
Corporate Authors
Defence R&D Canada - Atlantic, Dartmouth NS (CAN)
Abstract
The rotation of a bare propeller shaft on a twin screw ship can have a significant effect on the flow into the propeller plane, with consequent effects on the propeller efficiency and cavitation characteristics. TRANSOM, the DRDC Atlantic flow solver, was used to determine whether covering the shaft with a nonrotating sleeve along part of its length would improve the propeller inflow. Two sets of calculationswere performed. In the first a semi-infinite cylindrical shaft protruded from a flat plate. The shaft was covered along part of its length by a zero thickness stationary sleeve. To gain an understanding of the effects of the diameter of the sleeve relative to the shaft, a second set of calculations was performed in which the diameter of the sleeve was larger than that of the shaft. To avoid complications in gridding this configuration, the flat plate was removed; the shaft was infinite in both directions with a change in radius and a change fromnon-rotating to rotating in the middle. These calculations suggest that a sleeve will reduce the wake fraction in the propeller disk by delaying the formation of a vortex that entrains velocity deficit from the hull boundary layer. The sleeve also keeps the entrained velocity deficit closer to the shaft where it is less likely to induce cavitation. As the mismatch in radii of the sleeve and shaft increases, the entrained velocity deficit increases, so thinner sleeves should be preferred.
Keywords
Wakes;Propellers;Cavitation;Computational Fluid Dynamics;Boundary layers;TRANSOM;Spalart-Allmaras turbulence model
Report Number
DRDC-ATLANTIC-SL-2005-134 — Scientific Literature
Date of publication
31 Aug 2005
Number of Pages
8
DSTKIM No
CA026548
CANDIS No
524436
Format(s):
Electronic Document(PDF)

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