Viscosity

Definition

Viscosity is a measure of a fluid's resistance to deformation or flow. It quantifies the internal friction between fluid layers as they move relative to each other.

5 Must Know Facts For Your Next Test

1. Viscosity is often measured in units of Pascal-seconds (Pa·s) or poise (P).
2. Newtonian fluids have a constant viscosity regardless of the applied shear rate.
3. Non-Newtonian fluids exhibit a change in viscosity with varying shear rates.
4. The coefficient of viscosity can be determined using devices like viscometers and rheometers.
5. Temperature significantly affects viscosity; generally, liquids become less viscous as temperature increases.

Review Questions

• What are the units commonly used to measure viscosity?
• How does temperature affect the viscosity of a liquid?
• What is the difference between Newtonian and non-Newtonian fluids in terms of viscosity?

Related terms

Shear Rate: The rate at which adjacent layers of fluid move with respect to each other, typically expressed in reciprocal seconds ($s^{-1}$).

Laminar Flow:

A type of fluid flow where fluid moves smoothly in parallel layers, with minimal disruption between them.

Reynolds Number:

$$\text{A dimensionless number that helps predict flow patterns in different fluid flow situations. It is given by } Re = \frac{\rho v L}{\mu}$$ where $\rho$ is density, $v$ is velocity, $L$ is characteristic length, and $\mu$ is dynamic viscosity.