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The Grashof number (Gr) is a dimensionless number in fluid dynamics and heat transfer which approximates the ratio of the buoyancy to viscous force acting on a fluid. It frequently arises in the study of situations involving natural convection. It is named after the German engineer Franz Grashof. ==Applications== The Grashof number is: : for vertical flat plates : for pipes : for bluff bodies where: : ''g'' is acceleration due to Earth's gravity : ''β'' is the (of thermal expansion|thermal expansion ) (equal to approximately 1/''T'', for ideal gases) : ''T''''s'' is the surface temperature : ''T''''∞'' is the bulk temperature : ''L'' is the vertical length : ''D'' is the diameter : ''ν'' is the kinematic viscosity. The ''L'' and ''D'' subscripts indicate the length scale basis for the Grashof Number. The transition to turbulent flow occurs in the range ''108 < GrL < 109'' for natural convection from vertical flat plates. At higher Grashof numbers, the boundary layer is turbulent; at lower Grashof numbers, the boundary layer is laminar. The product of the Grashof number and the Prandtl number gives the Rayleigh number, a dimensionless number that characterizes convection problems in heat transfer. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Grashof number」の詳細全文を読む スポンサード リンク
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