Accession Number:

ADA230219

Title:

Numerical Simulation of Nonlinear Receptivity in Boundary Layer Transition

Descriptive Note:

Annual rept. 1 Oct 1989-30 Sep 1990

Corporate Author:

ARIZONA UNIV TUCSON DEPT OF AEROSPACE AND MECHANICAL ENGINEERING

Personal Author(s):

Report Date:

1990-09-30

Pagination or Media Count:

12.0

Abstract:

The control of the transition from laminar to turbulent flow is of primary interest in many engineering applications. Delay or acceleration of transition to turbulent flow may enhance or restrain the fluid mixing, heat transfer or reduce the friction drag on aerodynamic bodies. This research considered basically two different approaches to influence the transition process. The first approach is based on the idea of changing the stability characteristics of the base flow. This approach we categorize as passive control. Examples of passive control include constant suction or blowing of fluid at the wall, favorable pressure gradient along the streamwise flow direction, or constant heating of the wall surface. The second approach to influence the transition process is termed active control. There the disturbance waves which are amplified because of the instability of the base flow are directly manipulated. The feasibility of this second approach and its potentially considerable advantages were demonstrated. In experiments where amplitude and phase controlled disturbances were produced by thin metal strips or actuators that were flush mounted on the surface of a flat plate. With proper phases and amplitudes, both naturally occurring and controlled forced Tollmien-Schlichting waves could be attenuated and thus the transition process delayed.

Subject Categories:

  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE