Computational study of statistically one-dimensional propagation of turbulence.
Technische Universität, Darmstadt
[Ph.D. Thesis], (2012)
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|Item Type:||Ph.D. Thesis|
|Title:||Computational study of statistically one-dimensional propagation of turbulence|
Symmetry analysis of the evolution equation of the two-point correlation tensor Rij (xk, rl, t) in the case of planar generation of turbulence in an otherwise quiescent semi-infinite body of fluid has revealed some interesting solutions concerning the statistical properties of turbulence and how they develop with distance from the generation source. The first solution concerns the classical case of shear-free turbulent diffusion. Here, the turbulent kinetic energy is distributed according to a power law x−n where n is a constant larger than one, and x is the normal distance to the forcing plane. The integral length scales of turbulence increase linearly with x. A second case is considered when the symmetry of scaling of space is broken by introducing confinement to the flow. The turbulent kinetic energy decays with x as exp (−x) and the integral length scales remain constant along x. A third case treated is turbulent diffusion in a rotating frame, where symmetry of scaling of time is broken. Turbulent kinetic energy is distributed according to x−2 and there is an upper limit to turbulence propagation. The purpose of the present work is to investigate characteristics of this type of flow by means of large eddy simulation. Turbulent fields are generated in a box of isotropic turbulence using standard procedures. Planar samples of the generated fields are fed as a series of unsteady and nonuniform boundary conditions to the zero initial fields in an elongated turbulence box and turbulence propagation is monitored. The three cases are distinguished in simulations by imposing periodic and slip boundary conditions on lateral sides of the simulation box for the cases of free and confined turbulent diffusion respectively, and by solving LES equations in the rotating frame of reference for the third case. Specifically, the present work discusses identification criteria of turbulent front from filtered fields of LES turbulence. Furthermore, propagation of the front and associated profiles of turbulent kinetic energy and vorticity are discussed and compared to experimental and direct numerical simulation results. Complementing the main results, principles of symmetry analysis of two-point correlation equations and a description of the algorithm used for generation of the isotropic and rotating homogeneous turbulence fields are given. Finally, the performance of the presently popular Reynolds-averaged models in the three cases is evaluated.
|Place of Publication:||Darmstadt|
|Classification DDC:||600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften|
|Divisions:||16 Department of Mechanical Engineering
16 Department of Mechanical Engineering > Fluid Mechanics and Aerodynamics (SLA)
|Date Deposited:||09 Jul 2012 07:37|
|Last Modified:||07 Dec 2012 12:05|
|Referees:||Tropea, Prof. Dr.- Cameron and Oberlack, Prof. Dr.- Martin and Jakirlic, Apl. Prof. Suad|
|Refereed:||15 May 2012|