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Fluids

Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

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Page 2: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

• Flow• Take shape of container• Liquids or gases• Exert pressure • Pressure = force / area

Fluids

http://i.ehow.com/images/GlobalPhoto/Articles/5122397/246186-main_Full.jpg

Page 3: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

Fluids• Move from high

pressure low pressure• If no pressure difference,

no motion (equilibrium)

http://images.google.com/imgres?imgurl=http://hyperphysics.phy-astr.gsu.edu/Hbase/fluids/flupic/bernlev.jpg&imgrefurl=http://hyperphysics.phy-astr.gsu.edu/Hbase/pman.html&usg=__zR0eA8X2YfzjNx1oK3YEqTgA9fg=&h=411&w=359&sz=33&hl=en&start=65&um=1&itbs=1&tbnid=ZKd7dOr6DEn4YM:&tbnh=125&tbnw=109&prev=/images%3Fq%3Dfluid%2Bpressure%2Bdifference%26ndsp%3D21%26hl%3Den%26safe%3Dactive%26rlz%3D1T4GGIH_enUS266US269%26sa%3DN%26start%3D63%26um%3D1

http://i.telegraph.co.uk/telegraph/multimedia/archive/01485/eyedrops_1485563c.jpg

http://rt492.org/dl/img/jetcar.gif

Page 4: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

Calculating fluid pressure• Pressure = force / area• Force measured in lbs or N• Area measured in cm2 or

inch2.• Area = Pr2 or length *

width• Radius = 1/2 diameter

http://www.sweethaven02.com/Aviation/AvEngines01/fig0101.gif

Page 5: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

Liquids

• Not compressible; pressure difference supplied by pump

• Basis for hydraulic systems (usually water or oil)

• More dense than gases; molecules close together

http://www.chemprofessor.com/liquids_files/image005.jpg

Page 6: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

Gases• Compressible; pressure

difference supplied by compressor

• Basis for pneumatic systems (usually utilize compressed air)

• Less dense and therefore more buoyant

http://www.grc.nasa.gov/WWW/K-12/airplane/Images/state.gif

Page 7: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

Basic components of fluid system• Tank, reservoir or accumulator – holds fluid• Pump (liquid) or compressor (gas) – creates

pressure difference• Valve or regulator – control flow• Actuator – device that changes fluid pressure

to linear or rotational mechanical movement. Often an arm, piston, etc.

• Conductor – pipe, tubing, hose

Page 8: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

Pascal’s Principle• Pressure exerted on confined fluid is transmitted equally

to all parts of the fluid within the closed container• P = F1 / A1 = F2 / A2

• Results:– Pressurized gas, when released, allows for propulsion

(rockets, balloons)– Pressure in hydraulic systems allows movement of very heavy

loads (hydraulic lift)

Page 9: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

Boyle’s Law• Volume increases when

pressure decreases (temp stays constant) P1V1 = P2V2

• When P goes up, V goes down (inverse relationship)

• Applies to astronauts walking in space, and to scuba divers

Page 10: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

Charles’ and Gay-Lussac’s Law

• Volume increases when temp increases (pressure stays constant). V1 / T1 = V2 / T2

• Hot air balloons use this concept

http://www.google.com/search?hl=en&safe=active&rlz=1T4GGIH_enUS266US269&q=Charles%27++law&start=10&sa=N

Page 11: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

Bernoulli’s Principle• Pressure of a moving fluid decreases as

velocity increases• Basis for airplane wing

design

http://www.sweethaven02.com/Aviation/AvEngines01/fig0101.gif

Page 12: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

Fluid Power PhysicsWork

Force multiplied by distanceMeasured in foot-poundsor Newton-meters

Example:How much work is completed by moving a 1000 lb force 2 ft?2000 foot-pounds of work

Page 13: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

Fluid Power PhysicsPowerThe rate of doing workWork over time in seconds

Example:How many units of power are needed to lift a 1000 pound force 2 feet in 2 seconds?

1000 units of power (1000lb x 2ft) / 2 s

Page 14: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

Fluid Power Principles -- UnitsWatt – measure of power in SI system

Pressure x volume flow rateHorsepower –measure of power in English

systemHydraulic horsepower is expressed as:

flow( gpm) pressure( psi)Horsepower=

1714( constant)

Page 15: Fluids. Flow Take shape of container Liquids or gases Exert pressure Pressure = force / area Fluids

Fluid Power PrinciplesCalculate the horsepower needed in the system below to lift a 10,000 lb force in 2 s.