Accession Number:

ADA046057

Title:

The Influence of Sound upon Laminar Boundary Layer Instability

Descriptive Note:

Rept. for Oct 1975-Sep 1977

Corporate Author:

MASSACHUSETTS INST OF TECH CAMBRIDGE ACOUSTICS AND VIBRATION LAB

Personal Author(s):

Report Date:

1977-09-01

Pagination or Media Count:

89.0

Abstract:

This paper presents the results of an experimental investigation into the effects of pure-tone acoustic excitation on Tollmien-Schlichting waves in a subsonic Blasius boundary layer. Longitudinal growth rates were measured for naturally-existing waves in a low-noise, low-turbulence wind tunnel, and for waves excited by an externally imposed sound field. The results were compared to numerical results from the standard Orr-Sommerfeld equation. The excited Tollmien-Schlichting waves matched the theory well in most respects, and it was concluded that the acoustic excitation merely generated a larger initial wave amplitude, ahead of Branch I of the neutral stability curve. For excitation levels larger than the residual tunnel disturbances, this initial amplitude was constant and equal to the disturbance velocity of the sound wave. The naturally-existing waves showed growth rates smaller than theory predicted. This leads to the conclusion that natural waves are not initially two-dimensional.

Subject Categories:

  • Acoustics
  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE