Rawat, Subhandu. Coherent dynamics of large scale turbulent motions. PhD, Institut National Polytechnique de Toulouse, 2014
|
(Document in English)
PDF - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader 2MB |
Official URL: http://ethesis.inp-toulouse.fr/archive/00003011/
Abstract
My thesis work focused on ‘dynamical systems’ understanding of the large-scale dynamics in fully developed turbulent shear flow. In plane Couette flow, large-eddy simulation (L.E.S) is used to model small scale motions and to only resolve large-scale motions in order to compute nonlinear traveling waves (NTW) and relative periodic orbits (RPO). Artificial over-damping has been used to quench an increasing range of small-scale motions and prove that the motions in large-scale are self-sustained. The lower-branch traveling wave solutions that lie on laminar-turbulent basin boundary are obtained for these over-damped simulation and further continued in parameter space to upper branch solutions. This approach would not have been possible if, as conjectured in some previous investigations, large-scale motions in wall bounded shear flows are forced by mechanism based on the existence of active structures at smaller scales. In Poseuille flow, relative periodic orbits with shift-reflection symmetry on the laminar-turbulent basin boundary are computed using DNS. We show that the found RPO are connected to the pair of traveling wave (TW) solution via global bifurcation (saddle-node-infinite period bifurcation). The lower branch of this TW solution evolve into a spanwise localized state when the spanwise domain is increased. The upper branch solution develops multiple streaks with spanwise spacing consistent with large-scale motions in turbulent regime.
Item Type: | PhD Thesis |
---|---|
Uncontrolled Keywords: | |
Institution: | Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE) |
Laboratory name: | |
Research Director: | Cossu, Carlo and Rincon, François |
Statistics: | download |
Deposited On: | 02 Mar 2015 22:58 |
Repository Staff Only: item control page