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The effect of cell tilting on turbulent thermal convection in a rectangular cell
Published online by Cambridge University Press: 02 December 2014
Abstract
In this study the influence of cell tilting on flow dynamics and heat transport is explored experimentally within a rectangular cell (aspect ratios ${\it\Gamma}_{x}=1$ and
${\it\Gamma}_{y}=0.25$). The measurements are carried out over a wide range of tilt angles (
$0\leqslant {\it\beta}\leqslant {\rm\pi}/2\ \text{rad}$) at a constant Prandtl number (
$\mathit{Pr}\simeq 6.3$) and Rayleigh number (
$\mathit{Ra}\simeq 4.42\times 10^{9}$). 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 (
${\it\beta}\simeq 0.04\ \text{rad}$), the position of the high-velocity band quickly moves towards the boundary. With increasing
${\it\beta}$, 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
${\it\beta}$, and are strongest at around
${\it\beta}\simeq 0.48\ \text{rad}$. As
${\it\beta}$ increases, the Reynolds number (
$\mathit{Re}$) initially also increases, until it reaches its maximum at the transition angle
${\it\beta}=0.15\ \text{rad}$, after which it gradually decreases. The cell tilting causes a pronounced reduction of the Nusselt number (
$\mathit{Nu}$). As
${\it\beta}$ increases from 0 to 0.15, 1.05 and
${\rm\pi}/2\ \text{rad}$, the reduction of
$\mathit{Nu}$ is approximately 1.4 %, 5 % and 18 %, respectively. Over the ranges of
$0\leqslant {\it\beta}\leqslant 0.15\ \text{rad}$,
$0.15\leqslant {\it\beta}\leqslant 1.05\ \text{rad}$ and
$1.05\leqslant {\it\beta}\leqslant {\rm\pi}/2\ \text{rad}$, the decay slopes are
$8.57\times 10^{-2}$,
$3.27\times 10^{-2}$ and
$0.24\ \text{rad}^{-1}$, respectively.
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- © 2014 Cambridge University Press
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