Large-scale Flow In Inclined Thermal Convection

We report measurements of the properties of turbulent thermal convection of water over the Rayleigh-number range 1.52×10⁸?Ra?7.58×10⁸in a inclined cylindrical cell with an aspect ratio?=1.The measurements are carried out over a wide range of tilt angles?0^????75^??at a constant bulk temperature?T₀=40^?C?with Prandtl number Pr?4.3.Measurments of the heat transport?as expressed by the Nusselt number Nu?,as well as properties of the large scale circulation?LSC?obtained from temperature measurements along the sidewall,are presented.When there is no tilt,the Nu number can be described by a power-law dependence on?with an exponent close to 0.3 which is consistent with the GL model.However,when the tilt angles increases,the system heat transport weakens and then enhances to the local maximum value when the tilt angle is 60^?.When the tilt angle is larger than 60^?,the system turns to a laminr flow and the Nu starts to drop again.The motion of the large scale circulation can decompose into two different modes:the rotating mode and the translational or sloshing mode that is perpendicular to the vertical circulation plane of the LSC.To investigate the behaviour of the LSC in the presence of a tilt,we measured the average amplitude of the large scale circulation and found an increase with increasing tilt.In addition,the dynamics of the rotating angle?_mwas influenced by the tilt.The rotating angle was concentrated in one direction and random diffusion over all angles was suppressed.This could be seen in the probability density functions of?_m which became narrower.Over the investigated range of tilt angles,the standard deviation?_?of?_mwas inversely proportional to the tilt angle.