7.28 In Chapter 6 we learned that the ve- Tocity profile for fully developed laminar flow through a cylindrical pipe is given by U = Wol1 (r/Rp)2]ez. As shown in Fig- ure P7.6, however, when the fluid first enters the pipe, the velocity profile is uniform. Use a mass balance to determine the relationship be- tween the initial uniform velocity, W1, and the maximum velocity along the centerline of the fully developed flow, Wo. " (r. 0,2) = W, 12 (r. 0. 2) = W[-] Entrance length Fully developed flow Figure P7.6