Fluid Mechanics Ch. 2-3

Intensive property

Specific, independent of mass, pressure, temp, density

Extensive property

Dependent on amount, weight, and volume

Density

Mass / Volume. Units = kg/m³

Specific Volume

Inverse of density. Volume/ Mass

Incompressible Fluid

one whose density remains constant under varying pressure, meaning it cannot be significantly compressed. Ex. Water and oil

Compressible fluid

a liquid whose volume decreases under pressure

Density of water

1000 kg/m³

Specific Weight

ρ * g

Specific Gravity

ρ_fluid / ρ_water. Unitless

Pressure

Force / Area. Scalar not a vector. Changes vertically but not horizontally

1 Pa = …

1 N/m²

Atmospheric pressure

pressure exerted on a fluid by the atmosphere/ environment. Use density of air

Gauge pressure

Read from gauge. P_absolute - P_atmosphere

Absolute Pressure

Summation of gauge pressure and atmospheric pressureVa

Vacuum Pressure

Negative pressure

Psia

Absolute pressure

Psig

Gage Pressure

Hydrostatic condition

Fluids at rest. No shear only pressure

N = …

Kg * m / s²

J = …

N * mK

kW = …

J / S

Pressure of gas in container

Can assume it’s “equivalent” throughout container because of its very low densityP

Pascal’s Law

Pressure applied to confined fluid increases the pressure throughout by same amount. P₁=P₂ and F₂/F₁ = A₂/F₂

Barometer

Measures atmospheric pressure

Atmospheric pressure changes with…

AltitudeMano

Manometer

Measure of pressure differential

Manometer Rules

(1) No pressure change moving horizontally (2) Increase of pressure moving down (3) Decrease of pressure moving up

Differential Manometer

Manometers not exposed to atmosphere

Pressure Transducer

Sensor that measures gage pressure