The Effect of Structure-Borne Noise in Submarine Hull Plating on Boundary Layer Stability.
Abstract
This report deals with the potential boundary layer destabilizing action of machinery generated structure-borne noise in submarine hull plating. Boundary layer transition is assumed to be governed by the eigenvalues of the Orr-Sommerfeld equation and the structure-borne noise field is taken to be flexural in nature. The structure-borne noise field is decomposed into propagating wave fields and near-fields such as would surround foundation structures or other hull impedance discontinuities. It is found that for the frequency range generally associated with structure-borne noise, say 30 - 10 to the 4th power Hz, the propagating wave fields are not destabilizing in that they do not contain components which are coincident with the appropriate eigenvalues of the Orr-Sommerfeld equation. By contrast, the near-fields will contain components which are coincident with the potentially destabilizing, eigenvalues of the Orr-Sommerfeld equation. These near-fields are interpreted in terms of equivalent propagating fields to which they are found to be of (relatively) low level. Available experimental results are discussed in terms of the submarine environment and it is found that although transition may be affected by structure-borne noise levels less than, say, the expected free-stream turbulence levels, the measured noise levels required for destabiliziation are higher than one expects in submarine hull plating. Finally, a mechanical analogue to the Orr-Sommerfeld equation is presented in the form of a vibrating elastic plate resting on a locally reacting foundation of specific form. In the analogue Reynolds number becomes the cube of the slenderness ratio of the plate.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1977
- Accession Number
- ADA049311
Entities
People
- J. M. Garrelick
- M. C. Junger