Abstract
Direct numerical simulations are performed for the turbulent mixing layer and the turbulent plane wake. Coherent structures are qualitatively analyzed by means of graphic visualizations. In all cases, transition to turbulence is triggered by random noise superimposed onto a unidirectional basic flow. In the case of three-dimensional incompressible mixing layers, two regimes are found according to whether this noise is more two-dimensional or more three-dimensional. In the case of three-dimensional incompressible plane wakes, we first observe the formation of two staggered mixing-layers of opposite signs. Each of them features spanwise primary vortices connected together by streamwise secondary vortices. The interaction between the two layers then intensifies, until a Kármán street forms. At this moment, closed vortex loops bridging primary vortices of unlike signs are observed. Two-dimensional compressible mixing-layer simulations verify that compressibility effects inhibit the spreading of mixing layers. Eddy-shocklets are found when the convective Mach number reaches 0.8. A two-dimensional simulation of a spatially-growing plane wake is also presented.
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© 1991 Springer Science+Business Media Dordrecht
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Comte, P., Fouillet, Y., Gonze, MA., Lesieur, M., Metais, O., Normand, X. (1991). Generation of coherent structures in free shear layers. In: Metais, O., Lesieur, M. (eds) Turbulence and Coherent Structures. Fluid Mechanics and Its Applications, vol 2. Springer, Dordrecht. https://doi.org/10.1007/978-94-015-7904-9_4
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DOI: https://doi.org/10.1007/978-94-015-7904-9_4
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