The derivation of this expression from the Darcy-Weisbach equation combines the formula for the energy head loss factor with the equation for the kinematic viscosity.  Wilberforce's variation is a modification of Hagenbach's 
The derivation of this expression from the Darcy-Weisbach equation combines the formula for the energy head loss factor with the equation for the kinematic viscosity.  Wilberforce's variation is a modification of Hagenbach's equation, which contained a coefficient of kinetic friction that allowed it to be extended to turbulent flow.  One of its uses is to calculation of the number of capillaries in the body.  Stated delta-P equals 8-Q-mu-L divided by pi-R to the fourth power, FTP, name this equation, analogous to Ohm's Law for hydraulics, which predicts laminar flow through a uniform pipe.
The derivation of this expression from the Darcy-Weisbach equation combines the formula for the energy head loss factor with the equation for the kinematic viscosity.  
Poiseuille's law or equation