Propeller Singing.
Abstract
A mathematical model is presented for the study of the propeller singing phenomenon as a self-excited oscillation. The singing system is regarded as made up of the blade element as a mechanical vibration system and the Karman vortex shedding mechanism as self-excited system, exhibiting strong nonlinearity and a tendency to be synchronized with periodic stimulation from outside under appropriate conditions satisfying stability criteria and 'positive work' requirements. The vortex shedding mechanism has been studied in the case of a circular cylinder rigidly held at right angles to the flow or made to oscillate transversely in a direction perpendicular to the stream. Stability criteria and positive work requirements have established a boundary between singing and silent stages. Wherever experimental results are available they seem to confirm theoretical results. The propeller singing phenomenon being two-dimensional depends strongly on the local flow condition and the geometry near the trailing edge. When the trailing edge is considered to be cylindrical, use can be made of the developed theory for the shed vorticity behind a cylinder. Expressions are developed for the propeller-generated noise when one or more propeller sections are at the synchronization stage. The sound levels calculated by these formulas are in good agreement with available experimental results. Apparently the 3-dimensional flow field associated with an operating propeller is dominated at the singing stage by the 2-dimensional vortex patterns. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1969
- Accession Number
- AD0865382
Entities
People
- Stavros Tsakonas
- Winnifred R. Jacobs
Organizations
- Stevens Institute of Technology