\(\eta=\left(a\backslash\upsilon_{f}\right)^{\frac{1}{2}}y\ ;\text{\ \ }\psi=\left(a\upsilon_{f}\right)^{\frac{1}{2}}\text{xf}\left(\eta\right);\ \ \text{\ θ}\left(\eta\right)=\frac{T-T_{\infty}}{T_{f}-T_{\infty}}\text{\ .}\) (7)