侧向局部加热对流的周期性

Periodicity of Convection Under Lateral Local Heating

通过流体力学方程组的数值模拟,研究了侧向局部加热条件下Prandtl数Pr=0.0272时流体对流的周期性.结果表明:随着Grashof数Gr的增加,对流按稳态对流、单局部周期对流、双局部周期对流、准周期对流的顺序发展.当Gr<3.6×103时,对流为稳态;在3.6×103<Gr<6.78×104的范围内,对流属于单局部周期;在6.78×104<Gr<3.5×106范围内,对流具有双局部周期;当Gr≥3.5×106时,对流进入准周期.在稳态对流区间,壁面的加热区对应的对流圈的位置随着时间变化;在单局部周期对流区间,壁面的上加热区对应的对流圈内的核心部位随着时间周期移动;在双局部周期对流区间,壁面两个加热区对应的对流圈内的核心部位都随着时间周期移动;在准周期区间,在下未加热区对应的对流圈的上下部各存在随着时间准周期变化的小对流圈.在上述的对流周期变化范围内,对于一定的Pr,对流周期随着Gr增大而减小.

The periodicity of convection under lateral local heating with Prandtl number Pr=0.0272 was studied through numerical simulation of hydrodynamic equations.The results show that,convection develops in the order of steady⁃state convection,single⁃local⁃period convec⁃tion,double⁃local⁃period convection and quasi⁃period convection with the increase of Grashof number Gr.Convection is steady for Gr<3.6×103.In the range of 3.6×103<Gr<6.78×104,convec⁃tion has a single local period;in the range of 6.78×104<Gr<3.5×106,convection has double lo⁃cal periods;for Gr>3.5×106,convection has a quasi period.In the steady convection case,the position of the convection roll corresponding to the heating zone on the wall does not change with time.In the single⁃local⁃period convection case,the core of the convection roll corre⁃sponding to the upper heating zone on the wall moves periodically with time.In the double⁃lo⁃cal⁃period convection case,the cores of the convection rolls corresponding to the 2 heating zones on the wall move periodically with time.In the quasi⁃period convection case,there are small convection rolls with quasi⁃period variations in the upper and lower parts of the convec⁃tion loop corresponding to the lower unheated zone on the wall.In the range of the convection periods mentioned above,the convection period decreases with the increase of Grashof number Gr for given Prandtl number Pr.