Published online by Cambridge University Press: 02 December 2014
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
 ${\it\Gamma}_{x}=1$  and   ${\it\Gamma}_{y}=0.25$ ). The measurements are carried out over a wide range of tilt angles (
 ${\it\Gamma}_{y}=0.25$ ). 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 (
 $0\leqslant {\it\beta}\leqslant {\rm\pi}/2\ \text{rad}$ ) at a constant Prandtl number (  $\mathit{Pr}\simeq 6.3$ ) and Rayleigh 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 (
 $\mathit{Ra}\simeq 4.42\times 10^{9}$ ). 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
 ${\it\beta}\simeq 0.04\ \text{rad}$ ), 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
 ${\it\beta}$ , 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
 ${\it\beta}$ , and are strongest at around   ${\it\beta}\simeq 0.48\ \text{rad}$ . As
 ${\it\beta}\simeq 0.48\ \text{rad}$ . As   ${\it\beta}$  increases, the Reynolds number (
 ${\it\beta}$  increases, the Reynolds number (  $\mathit{Re}$ ) initially also increases, until it reaches its maximum at the transition angle
 $\mathit{Re}$ ) 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 (
 ${\it\beta}=0.15\ \text{rad}$ , after which it gradually decreases. The cell tilting causes a pronounced reduction of the Nusselt number (  $\mathit{Nu}$ ). As
 $\mathit{Nu}$ ). As   ${\it\beta}$  increases from 0 to 0.15, 1.05 and
 ${\it\beta}$  increases from 0 to 0.15, 1.05 and   ${\rm\pi}/2\ \text{rad}$ , the reduction of
 ${\rm\pi}/2\ \text{rad}$ , the reduction of   $\mathit{Nu}$  is approximately 1.4 %, 5 % and 18 %, respectively. Over the ranges of
 $\mathit{Nu}$  is approximately 1.4 %, 5 % and 18 %, respectively. Over the ranges of   $0\leqslant {\it\beta}\leqslant 0.15\ \text{rad}$ ,
 $0\leqslant {\it\beta}\leqslant 0.15\ \text{rad}$ ,   $0.15\leqslant {\it\beta}\leqslant 1.05\ \text{rad}$  and
 $0.15\leqslant {\it\beta}\leqslant 1.05\ \text{rad}$  and   $1.05\leqslant {\it\beta}\leqslant {\rm\pi}/2\ \text{rad}$ , the decay slopes are
 $1.05\leqslant {\it\beta}\leqslant {\rm\pi}/2\ \text{rad}$ , the decay slopes are   $8.57\times 10^{-2}$ ,
 $8.57\times 10^{-2}$ ,   $3.27\times 10^{-2}$  and
 $3.27\times 10^{-2}$  and   $0.24\ \text{rad}^{-1}$ , respectively.
 $0.24\ \text{rad}^{-1}$ , respectively.
 ${\it\gamma}=0.5$
                     
                  
               . J. Fluid Mech. 
               715, 314–334.CrossRefGoogle Scholar
                        ${\it\gamma}=0.5$
                     
                  
               . J. Fluid Mech. 
               715, 314–334.CrossRefGoogle Scholar