Viscosity & Flow Rate

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Arizahkyi

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Viscosity is a measure of a fluid's resistance to flow.
In other words it is a measure of how slowly a fluid moves. The more slowly a liquid moves, the more viscous it is.
In liquids and gasses, this ability allows them to flow (they are fluids).
Viscosity is generated from the fact that these particles move, rub against each other or bump into one another.
These interactions between particles creates friction. The friction is what slows down the particles. We call this "internal friction."
Factors Affecting Viscosity:
Molecular interactions
Temperature
Molecular size and shape
When particles flow in a fluid they rub against each other. The more the particles rub against each other the more friction they create, causing them to slow down. This will increase the viscosity.
The higher the internal friction, the higher the viscosity.
Cohesion
A measure of how strongly particles of a fluid attract each other.
Fluids with a slower flow rate, such as maple syrup, have particles with greater cohesion (the particles are very attracted to each other and stick together).
Surface Tension
The attraction of particles on a liquid’s surface is called surface tension.
Adhesion
The force of attraction between different particles of different substances.
As the temperature of a fluid increases its viscosity decreases.
Viscosity decreases with increased temperatures because heat provides energy to the molecules in a fluid, giving them the energy to move faster!
This reduces internal friction because the particles interact for a shorter amount of time.
Larger particle size causes viscosity to increase. This is because larger particles takes up more space meaning that they will bump into each other easier causing more internal friction.
“How To” Determine Flow Rate of Water – Hose:
Turn it on
Time how long it takes to fill a 2L bottle
Then divide your volume in mL (2L=2000mL) by the time it took (in seconds)
Flow Rate is measured in mL/s