fluid mechanics ch-8 buoyancy pressure flow. fluids fluids flow and alter shape which states of...
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Fluid Mechanics
Ch-8
Buoyancy
Pressure
Flow
Fluids
• Fluids flow and alter shape
• Which states of matter are fluid?
• Liquid• Gas• Plasma
Gasses fill and conform to their container
• Chlorine gas Cl2
Plasma’s conform to magnetic fields
• At PPPL they are experimenting on the fusion of hydrogen plasma
Density
= m/V• “rho” = mass/volume
• Density of Steam = 0.598 kg/m3
• Density of Mercury = 13.6 x 103 kg/m3
Buoyancy
• FB = Fg (of displaced fluid)
• = mog
Archimedes Principle
• Fnet = mfg - mog
Ships are rated as displacing tons of seawater
Fluid Pressure
• P = F/A
• Force/unit area
• Pounds/in2 (Psi)• Or N/m2 (Pascals)
4000 N/m2
• 107 Pascal
Fluid Pressure
• P = F/A
• Force/unit area
• PSI (lbs/insquared)
Pressure increases as area applied decreases
• F1/A1 = F2/A2
Hydraulics at the Dentist
Syringe hydraulic lift
• I raise a 10 N rock with a hydraulic piston that is 13 mm in radius using water connected to a 1.5 mm radius syringe. How much force is necessary for this lift to raise the rock?
Pressure as a Function of Depth
• P = Po + gh
Submarine Ballast Tanks
• The density of the whole device is adjusted by releasing compressed air
WWIII Submarine section
Buoyant force results from differing pressure at depth
FB=A(Po+gh2)-A(Po+gh1)
FB=g(h2-h1)A
FB=gV
FB=mfg That’s Archimedes
Principle
The Coanda Effect
• Fluid adheres to surfaces
• Flowing fluids are directed by curved surfaces
Bernouli’s Principle on Air foils
• Air flowing across and air foil flows faster across the top
• Pressure is lower of the air flows faster
• Fnet is upward
Coanda Effect breaks down at high angles of attack
• The Coanda effect guides the air flow along the surface
• The air flow breaks free and turbulent flow results
• Stall occurs
Coanda Develops First Jet engine aircraft, 1910
It crashes, he loses funding
Lost technologyfor 30 years