HOW TO calculate diameter of a pipe to flow 50,000 cubic meters per hours

Continuity rule
vA=Q

Q=volumetric flow (given as 5E4 m^3/hr
A= pipe cross sectional area (A=pi*r^2) in m^2
v= fluid velocity in m/hr

v*pi*r^2=Q

or r=sqrt[Q/(pi*v)] if in the units above r (pipe radius) is in meters)

pipe diameter is 2 times the radius.

Now the problem is to find v (fluid velocity). This is a function of pressure drop, pipe roughness and fluid viscosity, or measured.

Rap