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Fluctuations in turbulent flows

Gaurav Prabhudesai 1, 2
2 Physique Non-Linéaire
LPENS (UMR_8023) - Laboratoire de physique de l'ENS - ENS Paris
Abstract : In this thesis, we study the velocity and temperature fluctuations in a turbulent flow and their implications on the propagation of acoustic waves in turbulence. The first part is devoted to the study of the spontaneous generation of temperature fluctuations by a turbulent flow. We demonstrate that these temperature fluctuations originate from two types of intermittent structures, vorticity filaments and dissipative structures. In the second part, we study the spatio-temporal fluctuations of velocity, using the coherence function. We demonstrate that the coherence function results from the sweeping of the velocity fluctuations in the inertial range by the slower fluctuations of the integral scale. The sweeping effect is particularly interesting for the study of turbulent flows, because it does not come within the scope of Kolmogorov’s K41 theory. Finally, we study the propagation of acoustic waves through a turbulent flow and in particular phase and amplitude fluctuations. We show that phase fluctuations can be deduced from the coherence function of turbulent speed fluctuations. These fluctuations thus result from a sweeping effect of the acoustic wave by the turbulent flow. We also measure the variation in the speed of sound induced by a multiple scattering effect of the turbulent flow.
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Submitted on : Wednesday, April 7, 2021 - 5:20:09 PM
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  • HAL Id : tel-03192088, version 1

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Gaurav Prabhudesai. Fluctuations in turbulent flows. Physics [physics]. Université Paris sciences et lettres, 2021. English. ⟨NNT : 2021UPSLE001⟩. ⟨tel-03192088⟩

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