A 1% Error in Diameter Is a 4% Error in Flow Rate — Half a Cell of Wall and Poiseuille's Constant
·8 min read
Pipe flow rate rides on the fourth power of the diameter. The same exponent explains a mesh with the wall half a cell off and Poiseuille's 1838 tubes.
How Far Must Water Flow Before It Becomes a Parabola — Entrance Length and Hagen–Poiseuille
·5 min read
In laminar pipe flow a flat inlet needs about 0.05 Re diameters to become a parabola, and 64/Re is not valid until that station.