Numerische Untersuchung von Wärme- und Impulstransport in horizontaler Konvektion bei großen Rayleighzahlen
Zusammenfassung der Projektergebnisse
In this project horizontal convection was studied using direct numerical simulations. A scaling model for horizontal convection was tested by extensive numerical simulations. Evidence was found for multiple scaling regimes. It was shown that the inherent asymmetry of horizontal convection complicates the identification of scaling regimes and that a domain decomposition spatially separating the unstable stratified region brought a significant improvement to the interpretation of the data. A central result is that a theoretical analysis based on scaling arguments provides a qualitatively good description of the parameter dependence of the occurrence of plumes and oscillations. It turned out that plumes are dominating for large Pr number horizontal convection, while oscillations and early chaos are prevalent for small Pr. The transition between the two regimes occurs at Pr around unity. A theoretical analysis of both structures brings forth a simpler interpretation and a better intuitive insight into the dynamics of horizontal convection and the appearance of different timescales. In addition, it was shown that applying travelling thermal waves in thermal convection results in an increased heat and momentum transport and leads to the formation of mean zonal flows. An analytical model of the zonal flow strength as a function of the thermal wave propagation speed showed excellent agreement for small Ra in the linear regime. Discrepancies for larger Ra were explained by non-linear effects. The effect of the sidewall thermal boundary conditions on heat transport and flow structures was studied as well. It was shown that the breakdown of the large-scale circulation is caused by the enlargement of the corner rolls. Based on the vorticity fluxes, two different regimes of corner roll growth have been identified, which are diffusively and convectively dominant, respectively, leading to different corner roll growth rates. The sidewall boundary conditions have a profound impact on the global flow structures and on the heat transport for Ra up to ≈ 10^9 .
Projektbezogene Publikationen (Auswahl)
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Classical and symmetrical horizontal convection: detaching plumes and oscillations. Journal of Fluid Mechanics, 892.
Reiter, Philipp & Shishkina, Olga
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Crossover of the relative heat transport contributions of plume ejecting and impacting zones in turbulent Rayleigh-Bénard convection (a). Europhysics Letters, 134(3), 34002.
Reiter, Philipp; Shishkina, Olga; Lohse, Detlef & Krug, Dominik
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Generation of zonal flows in convective systems by travelling thermal waves. Journal of Fluid Mechanics, 913.
Reiter, Philipp; Zhang, Xuan; Stepanov, Rodion & Shishkina, Olga
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Heat transport in a cell heated at the bottom and the side (a). EPL (Europhysics Letters), 134(3), 34001.
Teimurazov, Andrei; Reiter, Philipp; Shishkina, Olga & Frick, Peter
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Thermal boundary-layer structure in laminar horizontal convection. Journal of Fluid Mechanics, 915.
Yan, Bo; Shishkina, Olga & He, Xiaozhou
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Universal properties of penetrative turbulent Rayleigh-Bénard convection. Physical Review Fluids, 6(6).
Wang, Qi; Reiter, Philipp; Lohse, Detlef & Shishkina, Olga
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Data‐driven identification of the spatiotemporal structure of turbulent flows by streaming dynamic mode decomposition. GAMM-Mitteilungen, 45(1).
Yang, Rui; Zhang, Xuan; Reiter, Philipp; Lohse, Detlef; Shishkina, Olga & Linkmann, Moritz
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Flow states and heat transport in Rayleigh–Bénard convection with different sidewall boundary conditions. Journal of Fluid Mechanics, 936.
Reiter, Philipp; Zhang, Xuan & Shishkina, Olga
