Superstructures and heat transport in large-scale convection systems in large-scale convection systems

by Hiufai Yik
Doctoral thesis
Date of Examination:2024-02-16
Date of issue:2025-02-17
Advisor:Dr. Weiss Stephan
Referee:Dr. Weiss Stephan
Referee:Prof. Dr. Andreas Tilgner
Persistent Address: http://dx.doi.org/10.53846/goediss-11106

 

 

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Abstract

English

This thesis conducts a comprehensive investigation of Rayleigh-Bénard convection experimental and numerically in a rectangular cell, characterized by an aspect ratio of 5, exploring a wide range of Rayleigh numbers ($\Ra$) up to $10^{13}$ and Prandtl numbers ($\Pr$) from 0.79 to 0.92. The study delves into the spatial scaling of convection, particularly within the plume emitting and ejecting regions, at these high $\Ra$ values. Contrary to 2D predictions, our findings indicate no crossover in heat flux scaling between these regions. Notably, the Large Scale Circulation (LSC) in a 3D context exhibits multiple stable states within the same system. We also found LSC grow with $\Ra$, a significant deviation from 2D models. Additionally, the study reveals hysteresis behavior in the roll structures in extended geometry at both low and high $\Ra$. These findings contribute to a deeper understanding of turbulent convection, challenging existing theories and highlighting the complexity of high $\Ra$ fluid dynamics.
Keywords: Heat Transfer; Convection; Turbulence; Pattern Formation
 
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