Jean Léonard Marie Poiseuille

From 1815 to 1816 he studied at the École Polytechnique in Paris. He was trained in physics and mathematics. In 1828 he earned his D.Sc. degree with a dissertation entitled Recherches sur la force du coeur aortique. He was interested in the flow of human blood in narrow tubes.

In 1838 he experimentally derived, and in 1840 and 1846 formulated and published, Poiseuille's law (now commonly known as the Hagen–Poiseuille equation, crediting Gotthilf Hagen as well), which applies to laminar flow, that is, non-turbulent flow of liquids through pipes of uniform section, such as blood flow in capillaries and veins.

The equation in standard fluid dynamics notation is[3][4]

${\displaystyle \Delta P={\frac {8\mu LQ}{\pi r^{4}}},}$

or

${\displaystyle \Delta P={\frac {128\mu LQ}{\pi d^{4}}},}$

or

${\displaystyle \Delta P={\frac {32\mu Lv}{d^{2}}},}$

where:

${\displaystyle \Delta P}$ is the pressure loss,

${\displaystyle L}$ is the length of pipe,

${\displaystyle \mu }$ is the dynamic viscosity,

${\displaystyle Q}$ is the volumetric flow rate,

${\displaystyle r}$ is the radius,

${\displaystyle d}$ is the diameter,

${\displaystyle \pi }$ is the mathematical constant π,

${\displaystyle v}$ is the velocity.

The poise, the unit of viscosity in the CGS system, was named after him. Attempts to introduce "poiseuille" as the name of the SI unit Pa·s had little success.