What are fluids?
Liquid or gases
What are the 2 types of fluid flow?
Laminar and turbulent
Describe laminar flow
- layers of liquid slide past eachother without disturbance
- layers are seperate + dont cross
- no friction bw layers
Describe turbulent flow
- liquid layers mix + cross over
- high friction
Why are things like car spoilers made more streamlined?
- to reduce friction
- less turbulent air at back of car + more laminar
- reduces drag
Describe the fluid flow in a pipe
- velocity of fluid is highest in middle of pipe
- flow rate in and out of pipe is constant
Define Bernoulli’s principle
If velocity increases, pressure decreases
(The sum of pressure energy + kinetic energy is constant at any point)
How does the shape of a wing cause planes to fly?
- wing is longer on top
- so air must travel further over top of wing
- air travels faster over top of wing
- so produces a lower pressure
- opp happens on bottom
- overall upward force on wing
Why must all the air travel over the top of a wing at the same time?
To keep mass flow rate constant
How does the shape of a spoiler help race cars stay on the ground?
- spoiler is longer on bottom of spoiler
- so air travels further over bottom of spoiler
- so air travels faster over bottom
- causing a lower pressure
- opp happens on top
- overall there is a downward force on spoiler
Define viscosity
Measure of a fluids resistance to movement
What are the 2 types of fluid?
Newtonian
Non - newtonian
Describe viscosity of a newtonian fluid
- viscosity is constant if temp stays the same
- effect of changing temp on viscosity is diff for liquids + gases
Why does the viscosity dec as temp inc for a newtonian LIQUID?
- liquid density inc
- particles have more energy at higher temps
- weakens forces bw them
- flow more easily + faster
- flow velocity inc
Why does the viscosity increase as temp increases for a newtonian GAS?
-increase in thermal energy inc number of collisions bw particles
- inc gases resistance to movement + cant move around as fast
Describe the viscosity of non - newtonian fluids
Viscosity can change when a shear force is applied
And when temp changes
What are 2 types of non - newtonian fluids?
Shear thinning
Shear thickening
Describe viscosity of shear thickening fluids e.g ooblek
- viscosity inc when shear force is applied
- particles resist movement
- becomes tougher
Describe viscosity of shear thinning fluids e.g paint
- viscosity dec when shear force is applied
- layers of particles slide over each more easily
