@phdthesis{MalteseMelettideOliveira2021, author = {Maltese Meletti de Oliveira, Gabriel}, title = {High-performance computing and laboratory experiments on strato-rotational instabilities}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-54408}, school = {BTU Cottbus - Senftenberg}, year = {2021}, abstract = {Stratified vortices can be found from small to large scales in geophysical and astrophysical flows. On the one hand, tornadoes and hurricanes can lead to devastation and even a large number of casualties. On the other hand, vortices can distribute heat and momentum in the atmosphere which is important for a habitable environment on Earth. In the astrophysical context, accretion disks (from which solar systems are formed) can be seen as stratified vortices. In such systems, understanding the mechanisms that can result in an outward transport of angular momentum is a central problem. For a planet or star to be formed in a disk, angular momentum has to be carried away from its center to allow matter aggregation by gravity; otherwise, its rotation speed would be far too large, avoiding this matter aggregation (and the consequent star formation) to happen. In such gas systems, turbulence is the most likely mechanism to achieve such a large angular momentum transport. However, it was shown that the flow profile of accretion disks is stable with respect to purely shear instabilities, and the question arises about how the turbulence can be generated. Among other candidates, the strato-rotational instability (SRI) has attracted attention in recent years. The SRI is a purely hydrodynamic instability that can be modeled by a classical Taylor-Couette (TC) system with stable density stratification due to axial salinity or temperature gradients. In this thesis, a combined experimental and high-performance computing study of new specific behaviors of the strato-Rotational Instability (SRI) is performed. The density stratification causes a change in the marginal instability transition when compared to classical non-stratified TC systems, making the flow unstable in regions where - without stratification - it would be stable. This characteristic makes the SRI a relevant phenomenon in planetary and astrophysical applications, particularly in accretion disk theory. Despite many advances in the understanding of strato-rotational flows, the confrontation of experimental data with non-linear numerical simulations remains relevant, since it involves linear aspects and non-linear interactions of SRI modes which still need to be better understood. These comparisons also reveal new non-linear phenomena and patterns not yet observed in the SRI, that can contribute to our understanding of geophysical flows.}, subject = {Rotating flow; Stratified flow; Pattern formation; Particle image velocimetry; High performance computing; Rotierende Str{\"o}mungen; Geschichtete Str{\"o}mungen; Musterbildung; Particle image velocimetry; Direkte numerische Simulation; Rotationsstr{\"o}mung; Turbulente Str{\"o}mung; Schichtenstr{\"o}mung; Direkte numerische Simulation; Particle-Image-Velocimetry; Musterbildung}, language = {en} }