\[\text{Gr}=\frac{\text { Inertia force } \times \text { buoyancy foce }}{\text { viscous force }}\]
\[\text{Gr}=\frac{\left(\rho \text{V}^{2} \text{L}^{2}\right) \times \rho \text{g} \beta\left(\text{T}_{\text{w}}-\text{T}_{\text{w}}\right) \text{L}^{3}}{(\mu \text{VL})^{2}}\] \[\text{Gr}=\frac{\rho^{2} \text{g} \beta\left(\text{T}_{\text{w}}-\text{T}_{\infty}\right) \text{L}^{3}}{\mu^{2}}=\text{g} \beta \text{L}^{3}\left(\text{T}_{\text{w}}-\text{T}_{o}\right) / v^{2}\]