Instability and mixing in a turbulent stratified Taylor-Couette Flow
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In this thesis, we investigate mixing mechanisms in a stably stratified turbulent Taylor-Couette flow, which is the flow in the annular region of two co-axial cylinders, both capable of rotating at different speeds independently, in the presence of vertical stable stratification. Oglethorpe (2014) found that, for an initially linearly stratified Taylor-Couette (STC) flow with fixed outer cylinder, the flow spontaneously forms well-mixed layers of constant height separated by sharp density gradient interfaces. She also observed a quasi-periodic mixing phenomenon across the interfaces. Through laser induced fluorescence and particle images velocimetery, we discover the structure of this mixing instability. We find that the mixing occurs as a result of a flow phenomenon generated by two in-phase boundary trapped waves, with azimuthal wavenumber