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S9 Fenômenos Não-Lineares e Caóticos em Engenharia |
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Titulo:
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NUMERICAL INVESTIGATION OF NONLINEAR EVOLUTION OF THREE-DIMENSIONAL WAVETRAINS IN FLAT PLATE BOUNDARY LAYERS
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Resumo :
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RECENT EXPERIMENTAL STUDIES ON THE NONLINEAR EVOLUTION OF
THREE-DIMENSIONAL WAVETRAINS HAVE SHOWN THE DEVELOPMENT OF A MEAN FLOW
DISTORTION THAT DOES NOT DECAY DESPITE THE DECAY OF THE FUNDAMENTAL
DISTURBANCES AFTER THE SECOND BRANCH OF THE INSTABILITY LOOP.
THIS MEAN FLOW DISTORTION HAS A SPANWISE STRUCTURE CONSISTING OF
POSITIVE AND NEGATIVE REGIONS DISTRIBUTED LIKE LONGITUDINAL STREAKS,
WHICH BECOME MORE COMPLEX AS THE NONLINEARITY DEVELOPS. IN ORDER TO
GAIN A BETTER INSIGHT INTO THE FLOW PHYSICS OF THIS PROBLEM NUMERICAL
SIMULATIONS ARE ALSO BEING CARRIED OUT. THE NUMERICAL MODEL IS BASED ON
THE PARABOLIZED STABILITY EQUATIONS (PSE) AND TAKES INTO ACCOUNT
BOTH NONLINEAR AND NONPARALLEL EFFECTS. THE NUMERICAL COMPUTATIONS SHOW
THAT THE NONLINEAR EVOLUTION OF THREE-DIMENSIONAL TOLLMIEN-SCHLICHTING
WAVES RESULTS IN THE DEVELOPMENT OF A MEAN FLOW DISTORTION CONTAINING
LONGITUDINAL VORTICES THAT DECAY VERY SLOWLY AFTER THE DECAY OF THE
INITIAL DISTURBANCES. THE STRONGEST VORTICES HAVE A SPANWISE WAVENUMBER
TWO TIMES THE WAVENUMBER OF THE FUNDAMENTAL TOLLMIEN-SCHLICHTING WAVES.
THE RESULTING STRUCTURE RESEMBLES THE STRUCTURE OBSERVED EXPERIMENTALLY
AND THE SPLITTING OF LONGITUDINAL STREAKS OBSERVED AT LATTER STAGES IS
CAPTURED BY THE COMPUTATION. THE NUMERICAL RESULTS PROVIDE ADDITIONAL
DATA ON WHICH TO BUILD A THEORETICAL MODEL OF THE MECHANISMS INVOLVED.
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Autores :
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Medeiros, Marcello A. Faraco de
Mendonça, Marcio T.
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Trabalho Completo :
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