Pressure Drop due to Friction

Laminar Flow

Hagen-Poiseuille Equation—for laminar flow. \[\Delta P = \frac{32Lv\mu}{D^2}\] The above equation can be obtained from Eqn.(1) by substituting for \(f=16/\text{Re}\).

One of the use of Hagen-Poiseuille equation is in the experimental measurement of viscosity; by measuring the pressure drop and volumetric flow rate through a capillary tube of known length and diameter.