NUMBER The relationship between the TWO is given by the equation\(\FRAC{{{\delta }}}{\delta_t } = P_r^{ \frac{1}{3}}\)δ = the thickness of the hydrodynamic boundary layer; the region of flow where the velocity is less than 99% of the far-field velocity.δT = the thickness of the thermal boundary layer; the region of flow where the local temperature nearly reaches the value (99%) of the bulk flow temperatureIf Pr > 1 the MOMENTUM or hydrodynamic boundary layer will increase more compared to the thermal boundary layer. If Pr < 1 the thermal boundary layer will increase more compared to the momentum or hydrodynamic boundary layer.If Pr = 1 The the thermal boundary layer and momentum or hydrodynamic boundary layer will increase at the same rate.