Now, let y⁺ be finite, say of order one, in the limit of . The equation (18.9) becomes

(18.10)

Assuming that the wall is smooth and no additional parameters appear in the BC, we expect the solution of (18.10) to be

	(18.11)

Here, f(y⁺ ) and g(y⁺ ) are the laws of the wall. We obtain two different situations

    (a) Assume to be negligible at . The equation (18.9) becomes

(18.12)

Integrating (18.12) between 0 and y + and applying no-slip boundary condition, we obtain

(18.13)

This law of the wall is valid for . Such a region is called the viscous sublayer.

   (b) Assuming at , there is a region where the viscous forces are negligible and fluctuations dominate then from         (18.9), we have (for ).

(18.14)