Rawhere_{x,c}=Gr_{x,c}Pr =g β(T_{s}-T_{∞})x^{3}ν α

Ra Rayleigh number Gr Grashof number Pr Prandtl number g gravity TThe Rayleigh number is named after Lord Rayleigh._{s}Temperature of surface T_{∞}Quiescent temperature ν kinematic viscosity α thermal diffusivity