Question

when flow is fully-develped, the pressure gradient in the axial direction along the center of the pipe is

Answer 1

Answer:

Zero

Explanation:

For this, it is necessary to use the  the Hagen-Poiseuille equation, which is a law of physics that describes an incompressible fluid of low viscosity through a tube of constant circular cross-section.

By derivating the Pressure over x it becomes zero

$\frac{dP}{dx} = 0$