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Applied Mathematics SeminarDate/Time/Room: Friday (02/28/2003) at 2:00pm in 304 Pickard Hall
Speaker:
Chaoqun Liu,
Department of Mathematics, University of Texas at Arlington "Coupled Cell Systems
Abstract:
This work consists of two parts. The first part is direct numerical
simulation (DNS) for flow separation and transition around a NACA 0012
airfoil with an attack angle of 40 and Reynolds number of 100,000. The
details of the flow separation, formation of the detached shear layer,
Kelvin- Helmoholtz instability (inviscid shear layer instability) and
vortex shedding, interaction of non-linear waves, breakdown, and
re-attachment are obtained and analyzed. Though no external disturbances
are introduced in the baseline case study, the self-excited mechanism is
observed, which may reveal the origin of the disturbance for airfoil with
attack angle. The power spectral density of pressure shows the low
frequency of vortex shedding caused by the Kelvin-Helmoholt instability
still dominates from the leading edge to trailing edge. The simulation
shows that the nonlinear wave interaction and breakdown is driven by the
generation and growth of the stream-wise vortex which leads to the
deformation, stretching, and eventually breakdown of the shedding prime
vortex. The second part is DNS for flow separation control by blowing jets
(steady, pulsed, and pitched and screwed jets). The effects of unsteady
blowing on the surface at the location just before the separation points
on the transition and separation are also studied. The separation zone is
significantly reduced (almost removed) after unsteady blowing technology
is applied. In this work, DNSUTA, a code with high-order accuracy and
high-resolution developed by the CFD group at University of Texas at
Arlington CFD is applied.
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