Publication Date:
2014-12-02
Description:
In this study the influence of cell tilting on flow dynamics and heat transport is explored experimentally within a rectangular cell (aspect ratios ${itGamma}_{x}=1$ and itGamma}_{y}=0.25$). The measurements are carried out over a wide range of tilt angles ($0leqslant {it eta}leqslant {mpi}/2 ext{rad}$) at a constant Prandtl number ($mathit{Pr}simeq 6.3$) and Rayleigh number ($mathit{Ra}simeq 4.42 imes 10^{9}$). The velocity measurements reveal that the large-scale circulation (LSC) is sensitive to the symmetry of the system. In the level case, the high-velocity band of the LSC concentrates at about a quarter of the cell width from the boundary. As the cell is slightly tilted (${it eta}simeq 0.04 ext{rad}$), the position of the high-velocity band quickly moves towards the boundary. With increasing ${it eta}$, the LSC changes gradually from oblique ellipse-like to square-like, and other more complicated patterns. Oscillations have been found in the temperature and velocity fields for almost all ${it eta}$, and are strongest at around ${it eta}simeq 0.48 ext{rad}$. As ${it eta}$ increases, the Reynolds number ($mathit{Re}$) initially also increases, until it reaches its maximum at the transition angle ${it eta}=0.15 ext{rad}$, after which it gradually decreases. The cell tilting causes a pronounced reduction of the Nusselt number ($mathit{Nu}$). As ${it eta}$ increases from 0 to 0.15, 1.05 and ${mpi}/2 ext{rad}$, the reduction of $mathit{Nu}$ is approximately 1.4 %, 5 % and 18 %, respectively. Over the ranges of $0leqslant {it eta}leqslant 0.15 ext{rad}$, $0.15leqslant {it eta}leqslant 1.05 ext{rad}$ and $1.05leqslant {it eta}leqslant {mpi}/2 ext{rad}$, the decay slopes are $8.57 imes 10^{-2}$, $3.27 imes 10^{-2}$ and $0.24 ext{rad}^{-1}$, respectively.
Print ISSN:
0022-1120
Electronic ISSN:
1469-7645
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
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