Ben-Gurion University of the NegevAstrophysics and Cosmology GroupAstrophysics, Relativity, Cosmology, and Space Physics |
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Speaker: Nimrod Cohen (BGU) January 23 Investigation of stably temperature stratified turbulent flow in a lid driven cavity
The
goal of this thesis is to conduct a comprehensive experimental and
numerical investigation of hydrodynamics in sheared temperature
stratified turbulence. We examine fundamental aspects of shear
generated turbulence that are common to laboratory and atmospheric
temperature stratified flows, and compare such findings with the
numerical simulations. The obtained result my be useful in atmospheric
applications and contribute to better understanding of the fundamental
mechanisms driving atmospheric stably stratified boundary layers and
the turbulent transport of aerosols, that hopefully may lead to
improved prediction of nocturnal temperatures, contaminant
concentrations and feedback of the nocturnal boundary layer in regional
models.
We investigated experimentally and numerically stably temperature stratified turbulent flow in a three-dimensional rectangular lid-driven cavity at different magnitudes of the imposed temperature gradient, Richardson number varied in the range 0 < Ri < 0.294. We employed the state-of-the-art non-intrusive laser diagnostic techniques for probing turbulent flows. Particular emphasis was given to spatially resolved measurements of velocity and temperature fields. The flow fields in the experiments was measured using Particle Image Velocimetry (PIV) technique with LaVision Flow Master III system, and temperature fields was measured using a specially designed temperature probe equipped with twelve sensitive thermocouples. We preformed numerical simulation using ANSYS 13.0 software package to assess the performance of two popular k-epsilon and k-omega two-equation turbulence models and of a laminar flow model. The obtained experimental results were compared with the results of numerical simulations. It is found that k-omega two-equation turbulence model yields the results which agree with the experimental results for large scale features of the flow although numerical simulations fail to reproduce some important features in the flow. The discrepancy between temperature distribution and heat fluxes obtained in numerical simulation, and experiments is quite large. When Ri<<1, the buoyancy effect is outweighed by forced convection, and the flow characteristics are similar to those of a conventional lid driven cavity with a non-stratified fluid. Prominent stable stratification driven features are discernible when Ri ~ 0.3. |
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Last updated
by Uri Keshet, November
2011 |