Experimental investigations of non-rotating and rotating two-dimensional turbulence

Wells, Jennifer (2005) Experimental investigations of non-rotating and rotating two-dimensional turbulence. Masters thesis, Memorial University of Newfoundland.

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Abstract

This thesis explores the behavior of decaying quasi-two-dimensional turbulent flows in non-rotating and rotating reference frames. In the non-rotating case, results from a new series of experiments on quasi-two-dimensional turbulence decaying in a rectangular container are presented. The flows are generated electromagnetically in a density stratified fluid using a regular array of permanent magnets. Particle Imaging Velocimetry is then used to determine the velocity and vorticity fields. These fields are further used to determine the global characteristics of the flow such as the energy and enstrophy. The energy spectra of the flow is found to demonstrate an upscale energy transfer and a corresponding growth of the energy-weighted mean scale. Power law exponents are obtained for both the low and high wavenumber regions of the spectra. Growth of the Reynolds number of the flow was observed during the intermediate phase of the flow evolution. In the rotating case, results from a new series of experiments on turbulent flows decaying in a thin layer of water with a free surface in a rotating circular container are presented. The flow is again generated electromagnetically and analyzed using Particle Imaging Velocimetry to obtain the velocity and vorticity fields. The experimental results demonstrate the formation of a polar vortex and jets that are perturbed by stationary Rossby waves in experiments with higher values of the beta parameter. Blocking events similar to those occurring in the Earth's atmosphere were observed in the laboratory flows. The two-dimensional energy spectra of the flow demonstrate anisotropy in the space of the azimuthal and total wavenumbers. The one-dimensional energy spectra are characterized by a peak at the Rhines wavenumber.

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