Accession Number:

ADA139911

Title:

Flow Noise and Outer Decoupler Studies

Descriptive Note:

Technical rept.

Corporate Author:

ORI INC ROCKVILLE MD

Report Date:

1982-12-03

Pagination or Media Count:

91.0

Abstract:

This program has started on the development of a rudimentary description of the nature of the low-wavenumber noise production mechanisms and features. Certain responses and mechanisms must be considered and included in even a minimal model of the turbulent boundary layer TBL low-wavenumber pressure fluctuation production processes and the attendant stipulation of outer decoupler design guidelines. The observed features of the noise spectra must include 1 Cyclic, self-sustaining nonlinear interactions of packets of finite-amplitude Tollmien-Schlicting waves intrinsically subject to large phase modulations. 2 The continuous spectrum of modes of response of the TBL to Reynolds stress bursts. 3 Nonlinear interactions between the continuous spectrum modes. This report shows that the interacting fluctuations are of spacial scale 2 delta and lie at small angles theta or 10 deg to the wall. Therefore, it develops, from first principles, design criteria for outer decouplers that defeat the low wavenumber flow noise by 1 Responding to pressure fluctuations in a scale-selective fashion, transmitting with adequate fidelity the acoustic waves of interest but rejecting the fluctuation carrier components of scale 2 delta and 2 Rejecting the noise component that arrives at the decoupler at grazing incidence angles. The resultant design constraints are manifold but achievable.

Subject Categories:

  • Submarine Engineering
  • Acoustics
  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE