key term - Viscosity

Definition

Viscosity is a measure of a fluid's resistance to deformation or flow. It quantifies the internal friction within the fluid when it is in motion.

5 Must Know Facts For Your Next Test

1. Viscosity determines how easily a fluid flows; higher viscosity means thicker, slower-flowing fluids.
2. The SI unit of viscosity is Pascal-seconds ($\text{Pa} \cdot \text{s}$), but the more common unit used in practice is the centipoise (cP).
3. Poiseuille's Law relates viscosity to the volumetric flow rate through a pipe, showing that flow rate decreases as viscosity increases.
4. Temperature affects viscosity; typically, fluids become less viscous as temperature increases.
5. In biological systems, blood viscosity is critical for understanding circulation and can change due to various health conditions.

Review Questions

Related terms

Laminar Flow:

A type of fluid flow where layers do not mix and move parallel to each other with smooth trajectories.

Poiseuille’s Law: A law that describes the volumetric flow rate through a pipe given by $Q = \frac{\pi R^4 (P_1 - P_2)}{8 \eta L}$, where $R$ is the radius, $P$ are pressures, $\eta$ is the dynamic viscosity, and $L$ is the length.

Newtonian Fluid: A fluid whose viscosity remains constant regardless of the applied stress or shear rate.