1. Fluids

2. 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

3. 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%26sa fe%3Dactive%26rlz%3D1T4GGIH_enUS266US269%26sa%3DN%26start%3D63%26um%3D1 http://i.telegraph.co.uk/telegraph/multimedia/archive/01485/ey edrops_1485563c.jpg http://rt492.org/dl/img/jetcar.gif

4. Calculating fluid pressure Pressure = force / area Force measured in lbs or N Area measured in cm 2 or inch 2. Area = P r 2  or length * width Radius =  1/2 diameter http://www.sweethaven02.com/Aviation/AvEngines01/fig0101.gif

5. 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

6. 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

7. 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

8. Pascal’s Principle Pressure exerted on confined fluid is transmitted equally to all parts of the fluid within the closed container P = F 1 / A 1 = F 2 / A 2 Results: – Pressurized gas, when released, allows for propulsion (rockets, balloons) – Pressure in hydraulic systems allows movement of very heavy loads (hydraulic lift)

9. Boyle’s Law Volume increases when pressure decreases (temp stays constant) P 1 V 1 = P 2 V 2 When P goes up, V goes down (inverse relationship) Applies to astronauts walking in space, and to scuba divers

10. Charles’ and Gay- Lussac’s Law Volume increases when temp increases (pressure stays constant). V 1 / T 1 = V 2 / T 2 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

11. 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

12. Fluid Power Physics Work Force multiplied by distance Measured in foot-pounds or Newton-meters Example: How much work is completed by moving a 1000 lb force 2 ft? 2000 foot-pounds of work

13. Fluid Power Physics Power The rate of doing work Work 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

14. Fluid Power Principles -- Units Watt – measure of power in SI system Pressure x volume flow rate Horsepower –measure of power in English system Hydraulic horsepower is expressed as:

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