1. The problem statement, all variables and given/known data A water injection line is made from smooth capillary tubing with inside diameter D = 25.0 mm . If the length of the pipe is 0.75 m and assuming laminar flow is present up to Re = 2000, find (i) the maximum average velocity at which the flow is laminar (ii) the pressure drop required to deliver this maximum velocity. [Answer: (i) u = 8 m/s; (ii) ∆p = 3 072 MPa ] 2. Relevant equations Everything related to laminar flows in pipes used the hagen poiseuille equation and Darcy's equations. u=-1/4μ*(dP/dx)(R^2-r^2) 3. The attempt at a solution Just some random substitutions, like setting -(dP/dx)=Δp/L and then equating that to Darcy's 4f/d*ρU^2/2 But the issue is the viscosity. I can't get rid of it, and I can't find it. Though I can understand why it is not given, as it would make things way too easy. Anything about viscosity?