The 3D Transition to Turbulence in Wake Flows by Means of Direct Numerical Simulation |
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Authors: | Marianna Braza |
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Institution: | (1) Institut de Mécanique des Fluides de Toulouse, Unité Mixte C.N.R.S.-I.N.P.T. 5502, Av. du Prof. Camille Soula, 31400 Toulouse, France |
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Abstract: | The three-dimensional transition to turbulence in flows around bodies of non-rectangular configuration has been analysed physically
by performing direct numerical simulation to solve the system of Navier-Stokes equations. The successive stages of 3D transition,
beyond the first bifurcation, have been detected first in the incompressible regime, for a circular cylinder configuration.
The generation of streamwise vorticity, organised according to spanwise periodic cells has been associated with the development
of large-scale coherent spanwise undulations of the originally rectilinear (nominally 2D) alternating vortex rows. The wavelengths
of these undulations have been determined as a function of Reynolds number. As this parameter increases, a further inherent
change of the flow transition is obtained and analysed, the natural vortex dislocations pattern. Beyond this change, the increase
of Reynolds number yields an abrupt shortening of the spanwise wavelength and the flow undergoes another transition step,
whose critical Reynolds number is evaluated by the present DNS approach in association with the Ginzburg-Landau model. Therefore,
the linear and non-linear parts of the flow transition have been quantified by means of the amplitude evolution versus time obtained by the present DNS, in conjunction with the mentioned global oscillator model.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | instability transition DNS bluff-bodies wings incompressible flow |
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