# 10. Viscosity of Liquids

version from 2016-01-20 13:51

## Basics

ViscosityInternal Friction
Sheer Stress (τ)The force between 2 layers of liquids
Newtonian FluidsFluids which obey Newtons Law of Viscosity
Viscous FlowA type of fluid movement in which all particles move parallel to the axis of a containing pipe with little to no mixing or turbidity

## Sheer Stress (τ) Equation

τSheer Stress
FForce acting between 2 adj. layers
SContact area of layers

## Newtons Law of Viscous Flow:

τSheer Stress
FForce acting between 2 adj. layers
SContact area of layers
ŋCoefficient of Viscosity (Dynamic Viscosity)
∆vVelocity of liquid layer 2 - Velocity of liquid layer 1
∆yDistance between layers (vertically)

1. Newtonian fluids obey newtons Laws of Viscosity. They have a constant value of viscosity.
2. Non-newtonian fluids do NOT obey Newtons Laws of Viscosity. They do NOT have a constant value of viscosity. (e.g. Blood)

## How to measure Viscosity

Glass Capillary Viscometers: Measuring time taken for outflow of a defined amount of liquid
Particle Viscometers
Rotation Viscometers
Ultrasonic Viscometers: Measure the oscillations of a metallic strip immersed in liquid