Transition Noise - The Role of Fluctuating Displacement Thickness.

Abstract

The role of the fluctuating wall shear stress on the noise generated by incompressible boundary-layer transition was recently analyzed. The solutions of that analysis suggest that the shear stress mechanism generates hydrodynamic sound weakly in comparison say to the sound generated by a fully developed turbulent boundary layer flow. Because boundary-layer transition is a very unstable and non-steady flow, it is expected that other acoustic mechanisms exist. This paper examines one other; namely, that of the fluctuating boundary layer displacement thickness which is expected to occur as turbulent bursts are created and convected over the surface. The analysis shows that a weak monopole sound source occurs, and at low subsonic flow velocities, this source generates significant acoustic energy. Comparisons of the theoretical predictions with available experimental data support this conclusion.

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Document Details

Document Type
Technical Report
Publication Date
Mar 27, 1980
Accession Number
ADA085103

Entities

People

  • G. C. Lauchle

Organizations

  • Pennsylvania State University

Tags

Communities of Interest

  • Energy and Power Technologies
  • Ground and Sea Platforms
  • Weapons Technologies

DTIC Thesaurus Topics

  • Boundary Layer
  • Boundary Layer Flow
  • Boundary Layer Transition
  • Engineering
  • Equations
  • Experimental Data
  • Fluid Dynamics
  • Frequency
  • Jet Propulsion
  • Mach Number
  • Measurement
  • Mechanical Engineering
  • Navy
  • Shear Stresses
  • Steady Flow
  • Turbulent Boundary Layer
  • Turbulent Flow

Fields of Study

  • Physics

Readers

  • Acoustical Oceanography.
  • Fluid Mechanics and Fluid Dynamics.