Accession Number:
ADA191751
Title:
A Propeller Skew Optimization Method
Descriptive Note:
Professional paper
Corporate Author:
NAVAL OCEAN SYSTEMS CENTER SAN DIEGO CA
Personal Author(s):
Report Date:
1987-11-01
Pagination or Media Count:
13.0
Abstract:
A propeller operating in the turbulent wake of an axisymmetric body with appendages encounters wake non-uniformities which result in spatial and temporal fluctuations of blade angle-of-attack. These angle-of-attack fluctuations result in unsteady blade loadings and the generation of propeller noise, and the noise sources are characterized by three types of unsteady force mechanisms a turbulence injestion b vortex shedding and c blade-rate. The first two mechanisms typically generate continuous spectrum broadband radiated noise levels while blade-rate forces generate discrete frequency noise levels at various blade-passage frequencies and harmonics. This paper will address the reduction of blade-rate noise. The hull boundary layer behind an appendage is characterized by a complex velocity field typically having velocity excesses at inner radii and velocity defects at the outer radii. This type of velocity field has a complex harmonic content distribution and its effect on blade-rate noise cannot be predicted without detailed examination of the wake and the radial distribution of propeller blade forces. The reduction of blade-rate noise and thus vehicle vibration provides the motivation for the application of skew in propeller design. Keywords Turbulence injestion, Vortex shedding, Blade passage frequencies and harmonics, Blade rate.
Descriptors:
- *MARINE PROPELLERS
- *PROPELLER BLADES
- VELOCITY
- FREQUENCY
- SOURCES
- SPATIAL DISTRIBUTION
- VIBRATION
- OPTIMIZATION
- HARMONICS
- RATES
- TURBULENCE
- ANGLE OF ATTACK
- VORTEX SHEDDING
- BLADES
- REDUCTION
- VARIATIONS
- DEFECTS(MATERIALS)
- INTERNAL
- WAKE
- AXISYMMETRIC
- LEVEL(QUANTITY)
- EXTERNAL
- VEHICLES
- NOISE
- SKEWNESS
- RADIUS(MEASURE)
- FORCE(MECHANICS)
- RADIATED NOISE
- CONTINUOUS SPECTRA
- PROPELLERS
- PROPELLER NOISE
Subject Categories:
- Marine Engineering