Fluids Flashcards
What are the properties of an Ideal Fluid?
- Incompressible
- Steady/laminar flow
- Irrotational
- Non-viscous
Incompressible
Volume cannot change
Steady/Laminar Flow
fluid volume at any point is constant
Irrotational
always face in same directions
non viscous
- not sticky/no resistance
Density
p=m/V
- kg/m^3
Pressure only depends on …
depth
Pressure units
Pascals
Pa=N/m^2
F/A
If you go lower in sea depth pressure … and volume ….
increases
this is because of the weight of the water column above increases
v decreases
Pressure variation with depth
= pgy+P0
If bubbles are travelling through a tube that gets narrower what happens to the bubble size?
they increase as P decreases allowing them to expand
Archimedes Principal
- a body immersed in a fluid is subjected to an upwards force equal to the weight of the displaced fluid
How does a vacuum work?
the pressure inside is lower than outside pressure so the outside high pressure forces objects into the vacuum
Does air travel from high to low or low to high pressure?
high to low
What direction is the buoyancy force?
- upwards
What is the buoyancy force?
weight of the fluid displaces by the object
Formula for Fb
p(of fluid) x V(displaced) x g
What is the V displaced if the object is a)totally submerged and b) partially submerged?
a) V obj
b) V below H20
Bulk modulus units
Pa
Manometer
measuring pressure relative to atm pressure
Barometer
measures pressure using height of fluid
Pascal’s Principle
is extrernal P applied to one part of the incompressible fluid all other parts P changes accordingly
Rules for a fluid element path streamlines:
cannot cross
frozen in time
distance between relates to v (wide=slow, narrow=fast)
Continuity Equation
A1v1=A2v2
Volume flow rate
R=Av
- m^3/s
Flow rate
p x V x A
Flow rate
p x V x A
Do major ocean currents or rivers have faster flow rates?
have greater A but no
Bernoulli’s Principle
increase in pressure, decrease in speed of the fluid
decrease in pressure, increase in speed of the fluid
Bernoulli’s EQ
P1 + 1/2pv(1)^2 + pgy(1) = P2 + 1/2pv(2)^2 + pgy(2)
Ideal fluids obey…
Bernoulli and continuity equation
How is a ball held in a funnel demo?
air flow increases in narrow pipe which then causes a decrease in P gripping the ball in place
