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AIAA JOURNAL Vol. 40, No. 2, February 2002

Vol. 40, No. 2, February 2002
Unsteady Flow Evolution in Porous Chamber with Surface
Mass Injection, Part 2: Acoustic Excitation
Sourabh Apte¤
and Vigor Yang
Pennsylvania State University, University Park, Pennsylvania 16802
Our earlier work on injection-driven ows in a porous chamber is extended to explore the effect of forced
periodic excitations on the unsteady ow eld. Time-resolved simulations are performed to investigate the effects
of traveling acoustic waves on large-scale turbulent structures for various amplitudes and frequencies of imposed
excitations. The resultant oscillatory ow eld is decomposed into mean, periodic (or organized), and turbulent
(or random) motions using a time-frequency localization technique. Emphasis is placed on the interactions among
the three components of the ow eld. The primary mechanism for the transfer of energy from the mean to the
turbulent motionis provided by the nonlinear correlations among thevelocity uctuations,as observed instationary
turbulent ows. The unsteady, deterministic component gives rise to an additional mechanism for energy exchange
between the organized and turbulent motions and, consequently, produces increased turbulence levels at certain
acoustic frequencies. The periodic excitations lead to earlier laminar-to-turbulence transition than that observed
in stationary ows. The turbulence-enhanced momentum transport, on the other hand, leads to increased eddy
viscosity and tends to dissipate the vortical wave originating from the injection surface. The coupling between the
turbulent and acoustic motions results in signi cant changes in the unsteady ow evolution in a porous chamber.


Source: Apte, Sourabh V. - School of Mechanical, Industrial, and Manufacturing Engineering, Oregon State University
Yang, Vigor - School of Aerospace Engineering, Georgia Institute of Technology


Collections: Engineering