For a two-dimensional flow ( w =0 ), the mean velocity components lie on the x-y plane. One can consider the following

(a)
(b)
(c)
(d)

The turbulent boundary layer equation together with the equation of continuity become

	(9.1)
	(9.2)

Comparison with laminar boundary layer will reveal that laminar viscous flow per unit volume is replaced by where

Figure 9.1