A steady, laminar, and incompressible flow between a pair of infinite parallel plates is driven by a constant pressure gradient $(-d p / d x)$. The plates are separated by a distance $2 h$, as shown in the figure. The fully-developed velocity profile of the flow is
$$u(y)=-\frac{d p}{d x} \frac{h^{2}}{2 \mu}\left(1-\frac{y^{2}}{h^{2}}\right), $$
where $\mu$ is the dynamic viscosity.
The values of $y$, for which the local flow velocity is equal to the average flow velocity, are
- $\pm \dfrac{h}{2}$
- $\pm \dfrac{h}{\sqrt{2}}$
- $\pm \dfrac{h}{3}$
- $\pm \dfrac{h}{\sqrt{3}}$
