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An Experimental Investigation of Nonequilibrium Physics and Dynamical Systems in Turbulent Fluids.

Bandi, Mahesh M (2006) An Experimental Investigation of Nonequilibrium Physics and Dynamical Systems in Turbulent Fluids. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Experiment 1 studies finite system size effects on temporal energy flux fluctuations in three-dimensional (3D) incompressible turbulence. The measured instantaneous energy flux shows that the turbulent energy transfer proceeds towards small spatial scales on average but frequently reverses direction (backscatter) to travel towards larger scales. The frequency of backscatter events is studied experimentally and through simulations. In Experiment 2 the third-order Eulerian structure function is measured for compressible turbulence on a free surface for the first time, and is found to scale linearly in space and agrees well with Kolmogorov's theory of 1941 (K41). K41 predicts the second-order Lagrangian structure function should scale linearly in time. However the experimental measurements show it instead scales as a power-law with exponent 1/2. Experiment 3 concerns measurement of entropy production rate in steady-state compressible turbulence. The analysis relies on the recent theory of Falkovich and Fouxon. The entropy rate is expected to equal the time integral of the lagrangian velocity divergence correlation function with a negative prefactor. The experimental results are found to disagree with this prediction. In addition, if the system is highly chaotic (follows SRB statistics), the system's entropy rate equals the sum of its Lyapunov exponents. The measured entropy rate agrees well with the sum of Lyapunov exponents obtained from simulations by Boffetta et. al. under flow conditions similar to the experiment. Experiment 4 presents a test of the Steady-State Fluctuation Theorem of Gallavotti and Cohen for entropy rate statistics collected from the individual lagrangian trajectories of experiment 3. The entropy rate statistics show excellent agreement with the Fluctuation Theorem within a limited interval of the probability distributions and limited window of averaging times.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Bandi, Mahesh Mmab77@pitt.eduMAB77
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairGoldburg, W. I.goldburg@pitt.eduGOLDBURG
Committee MemberErmentrout, B.bard@pitt.eduBARD
Committee MemberBoyanovsky, D.boyan@pitt.eduBOYAN
Committee MemberWu, X. -L.xlwu@pitt.eduXLWU
Committee MemberGoldschmidt, Y. Y.yadin@pitt.eduYADIN
Date: 6 October 2006
Date Type: Completion
Defense Date: 14 July 2006
Approval Date: 6 October 2006
Submission Date: 10 August 2006
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Physics
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Dynamical Systems; Fluid Turbulence; Nonequilibrium Physics; Nonlinear Dynamics; Statistical Mechanics
Other ID:, etd-08102006-020453
Date Deposited: 10 Nov 2011 19:58
Last Modified: 15 Nov 2016 13:48


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