# Formula: Poiseuille's Equation Volumetric Flow Rate    Length    Viscosity    Radius    Pressure

## Volumetric Flow Rate

Unit
Volumetric Flow Rate (Volume velocity) is the volume of a fluid (e.g. water) that passes through a cross-sectional area of a pipe per second. The volume flow is due to a pressure difference $$\Delta \mathit{\Pi} = \mathit{\Pi}_1 - \mathit{\Pi}_2$$ between the ends of the pipe.

## Length

Unit
Length of a pipe through which a fluid moves.

## Dynamic viscosity

Unit
Viscosity $$\eta$$ (pronounced: Eta) is a property of a fluid (liquid or gas) and describes how difficult it is to move a body through this fluid.

Liquid Viscosity $$\eta$$
Olive oil$$108 \cdot 10^{-3} \, \frac{\mathrm{kg}}{ \mathrm{m}\cdot \mathrm{s} }$$
Honey$$10\,000 \cdot 10^{-3} \, \frac{\mathrm{kg}}{ \mathrm{m}\cdot \mathrm{s} }$$
Glycerin$$1500 \cdot 10^{-3} \, \frac{\mathrm{kg}}{ \mathrm{m}\cdot \mathrm{s} }$$
Water$$1.008 \cdot 10^{-3} \, \frac{\mathrm{kg}}{ \mathrm{m}\cdot \mathrm{s} }$$
Tar$$100\,000 \cdot 10^{-3} \, \frac{\mathrm{kg}}{ \mathrm{m}\cdot \mathrm{s} }$$
Viscosity of some liquids.

Unit
Radius of the pipe through which a fluid moves. If you double the radius, then the flow rate becomes 16 times larger!

## Pressure at one end

Unit
Pressure at one end of the pipe. $$\Pi$$ is pronounced as "Pi".

## Pressure at the other end

Unit
Pressure at the other end of the pipe.

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