Viscosity

What is Viscosity?

A measure of a fluid's internal resistance to flow, relating the shear stress within it to the rate at which it's being sheared. Curiously, it works in opposite directions with temperature — liquids thin out as they warm, while gases thicken slightly, because their viscosity comes from different molecular mechanisms.

The five clues

Engineerdle #46 described Viscosity with five clues, revealed one at a time from hardest to most direct. Each clue points at a different property of the concept.

1. 01A fluid's internal resistance to being deformed or sheared.
2. 02Honey has plenty of it; water has comparatively little.
3. 03It generally drops as a liquid warms up, and rises as a gas warms up.
4. 04It's the μ that shows up throughout the Navier-Stokes equations.
5. 05A measure of a fluid's resistance to flow, relating shear stress to shear rate.

More Fluid Mechanics concepts

• Venturi EffectPuzzle #50
• Reynolds NumberPuzzle #41
• Newtonian FluidPuzzle #36
• Non-Newtonian FluidPuzzle #31
• Pascal's LawPuzzle #13
• Archimedes' PrinciplePuzzle #8