For a laminar flow through a circular pipe, the wall shear stress across a section is a function of _______
1
the pressure gradient \(\rm \frac{dp}{dz}\) and the radial coordinate r
2
the pressure gradient \(\rm \frac{dp}{dz}\) and the radius r
3
the pressure gradient \(\rm \frac{dp}{dz}\) and the axial velocity Vz
4
only the pressure gradient \(\rm \frac{dp}{dz}\)