Accession Number:

ADA456687

Title:

Robust Controller for Turbulent and Convective Boundary Layers

Descriptive Note:

Final rept. 1 Apr 2003-31 Mar 2006

Corporate Author:

CALIFORNIA UNIV LOS ANGELES DEPT OF MECHANICAL AND AEROSPACE ENGINEERING

Personal Author(s):

Report Date:

2006-08-01

Pagination or Media Count:

69.0

Abstract:

Linear feedback controllers and estimators have been designed from the governing equations of a channel flow, linearized about the laminar mean flow, and a layer of heated fluid, linearized about the no-motion state. Spectral decomposition involving a two-dimensional Fourier expansion and a Chebyshev-Galerkin projection cast these linearized equations into state-space form that decoupled to independent Fourier wavenumber sub-systems. The control law are designed by applying Linear Quadratic Gaussian LQG synthesis to these sub-systems. The size of the controller is reduced by both limiting the number of sub-systems, on which LQG synthesis is applied, as well as applying system theoretic model reduction techniques to each sub-system. This methodology has produced highly effective controllers to suppress convection in a heated fluid layer, but has found only moderate success with the channel flow. While the Oberbeck-Boussinesq equations heated fluid layer provides a direct measure of Rayleigh-B enard convection, the Poiseuille flow equations do not. The feedback control laws for channel flow could only indirectly affect viscous drag. An open-loop optimization has been applied to the channel flow control problem in an effort to capture more of the nonlinear dynamics and, thereby, affect the viscous drag directly. During these experiments, it has been discovered that upstream traveling waves of blowing and suction not only reduces the skin-friction drag in a channel but also sustains it below laminar levels.

Subject Categories:

  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE