I've established a relationship between the upper horizontal boundary layer $U$ and pressure gradient $G$ where $\mu$ is dynamic viscosity and h is the height of the pipe the fluid is travelling through
$$U=\frac {Gh^2} {6\mu}$$
And I'm now asked to sketch the velocity profile... apparently its a parabola from $y=0$ to $y=h$ but h is a constant, so $U$ is a constant, so I don't understand why it varies depending on $y$
If anyone could clear up why the velocity profile for this is what it is, I'd be very grateful.
Thank in a advance