Accession Number:

AD0488867

Title:

FLOW NOISE TRANSMITTED THROUGH DOMES OR ACOUSTICALLY MODIFIED BY NON-RIGID BOUNDARIES

Descriptive Note:

Interim progress rept.

Corporate Author:

CONTROL DATA CORP MELVILLE NY TRG DIV

Personal Author(s):

• Chase, David M.

Report Date:

1966-01-01

Pagination or Media Count:

225.0

Abstract:

Flow-induced noise generated by pressure fluctuations in a turbulent boundary layer is studied here theoretically with regard to its acoustic transmission through a dome to a transducer element or array. Particular attention is given to a unilayer dome in the form of a finite slab, described as a fluid but serving as a prototype for a realizable solid slab. A similar dome with a thin outer cover having nonvanishing impedance is also considered. Likewise, attention is given to acoustic modification of the flow noise on a flush element due to mobility of the surrounding baffle. To demonstrate clearly what properties of the boundary layer pressure fluctuations are essential, high- and low-wavenumber ranges are distinguished in the wavenumber spectrum of pressure at given frequency, the former range corresponding to possible generation by a convected eddy field. By various approximations and simplification of boundary conditions, the contributions of these respective ranges to the frequency spectrum of average pressure on a dome-shielded element are related to their respective contributions in the reference case of an element flush-mounted in a rigid plate.

Descriptors:

• *FLUID FLOW
• *SONAR DOMES
• *SOUND TRANSMISSION
• ACOUSTIC DETECTORS
• APPROXIMATION(MATHEMATICS)
• EXCITATION
• FOCUSING
• INTEGRAL TRANSFORMS
• MEMBRANES
• METAL PLATES
• NOISE
• PERTURBATION THEORY
• PRESSURE
• RESONANCE
• RESPONSE
• SIGNAL TO NOISE RATIO
• TRANSDUCERS
• TURBULENT BOUNDARY LAYER
• WATER WAVES

Subject Categories:

• Acoustic Detection and Detectors
• Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE