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      New Theories on Boundary Layer Transition and Turbulence Formation

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      Modelling and Simulation in Engineering

      Hindawi Limited

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          Abstract

          This paper is a short review of our recent DNS work on physics of late boundary layer transition and turbulence. Based on our DNS observation, we propose a new theory on boundary layer transition, which has five steps, that is, receptivity, linear instability, large vortex structure formation, small length scale generation, loss of symmetry and randomization to turbulence. For turbulence generation and sustenance, the classical theory, described with Richardson's energy cascade and Kolmogorov length scale, is not observed by our DNS. We proposed a new theory on turbulence generation that all small length scales are generated by “shear layer instability” through multiple level ejections and sweeps and consequent multiple level positive and negative spikes, but not by “vortex breakdown.” We believe “shear layer instability” is the “mother of turbulence.” The energy transferring from large vortices to small vortices is carried out by multiple level sweeps, but does not follow Kolmogorov's theory that large vortices pass energy to small ones through vortex stretch and breakdown. The loss of symmetry starts from the second level ring cycle in the middle of the flow field and spreads to the bottom of the boundary layer and then the whole flow field.

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          Most cited references 23

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            A simple dynamical model of intermittent fully developed turbulence

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                Author and article information

                Journal
                Modelling and Simulation in Engineering
                Modelling and Simulation in Engineering
                Hindawi Limited
                1687-5591
                1687-5605
                2012
                2012
                : 2012
                :
                : 1-22
                10.1155/2012/619419
                © 2012

                http://creativecommons.org/licenses/by/3.0/

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