Flow instabilities in inclined differentially heated square cavities

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dc.contributor.advisor Norris, Stuart
dc.contributor.author Maryada, Krishna Reddy
dc.date.accessioned 2020-11-04T00:43:12Z
dc.date.available 2020-11-04T00:43:12Z
dc.date.issued 2020 en
dc.identifier.uri http://hdl.handle.net/2292/53437
dc.description Full Text is available to authenticated members of The University of Auckland only. en
dc.description.abstract The instabilities responsible for the bifurcation of the flow in inclined differentially heated square cavities are investigated using two-dimensional numerical simulations. The incli-nation angle of the enclosure is varied from θ = −20° to θ = 85° with θ = 0° being the upright differentially heated cavity and θ = 90° being the Rayleigh-Benard configuration. The bifurcation of the flow is investigated for 0.4 ≤ Pr ≤ 1.4 concentrating on Pr = 0.6 and 0.71. For the Prandtl numbers investigated, the inclination angle of the enclosure greatly influenced the stability of the flow, with different types of instability bifurcating the flow at different angles. At negative inclination angles, a shear-driven instability adjacent to the natural convection boundary layers bifurcated the flow and (1,1) internal wave attractors characterised the periodic flow. At small inclination angles (−3° ≤ θ ≤ 18°), a shear-driven instability in the detached flow structure is present in the route to chaos but is not always the primary instability. The limit cycle regime of the flow that bifurcated due to this shear-driven instability is marked by standing internal wave modes which directly influ-enced the stability of the flow. The configurations supporting the lower-order internal wave modes required a higher Rayleigh number for the bifurcation of the flow into a limit cycle governed by the shear-driven instability. The effect of the internal wave modes is observed in both the inclined and upright cases so long as a shear-driven instability occurred in the detached flow structure. A few configurations bifurcated due to a localised high-frequency boundary-layer instability, despite the presence of a detached flow structure and the dynam-ics are influenced by the stable stratification of the central region of the enclosure. In the absence of a detached flow structure (for angles 23° ≤ θ ≤ 58°), the flow bifurcated due to a travelling-wave instability, whose dynamics depended on the inclination angle of the en-closure. At tilt angles close to the Rayleigh-Benard configuration (65° ≤ θ ≤ 85°), corner eddies are present at the primary bifurcation point, and the perturbations are amplified the most in these regions. These perturbations are observed at the periphery of the large-scale circulation, and the well-defined boundary layers disappear with increasing tilt angle.
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof Masters Thesis - University of Auckland en
dc.relation.isreferencedby UoA en
dc.rights Restricted Item. Full Text is available to authenticated members of The University of Auckland only. en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.
dc.rights.uri https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm en
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/nz/
dc.title Flow instabilities in inclined differentially heated square cavities
dc.type Thesis en
thesis.degree.discipline Mechanical Engineering
thesis.degree.grantor The University of Auckland en
thesis.degree.level Masters en
dc.date.updated 2020-10-13T01:15:20Z
dc.rights.holder Copyright: the author en

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