Fluid Properties

Key Concept: Fluids have several basic properties including density, specific weight,

viscosity, and specific gravity that you need to know. Tables are available with standard

values of these properties.

In a Nut Shell: The table below lists the most important properties. There are several

models of fluids involving viscosity. The Newtonian model, where shear stress is directly

proportional to shear strain, involves the property of dynamic viscosity.

Property Symbol Dimensions Units

density (mass/volume)	ρ	FT^2/L^4 , M/L^3	slugs/ft^3 or kg/m^3
specific weight (weight/volume)	γ	F/L3, M/L^2T^2	lb/ft^3 or N/m^3 for water γ = 62.4 lb/ft^3
Specific gravity	SG	1, 1 (dimensionless)	fluid density / density of water
dynamic viscosity	μ	FT/L^2, M/LT	lb sec / ft^2 N sec / m^2
kinematic viscosity	ν	L^2/T, L^2/T	ft^2/sec or m^2/sec note: ν = μ / ρ

Note: Fluids include liquids and gases. Liquids are nearly incompressible whereas gases are

quite compressible. The study of elementary fluid mechanics centers mostly on liquids.

Return to Notes on Fluid Mechanics

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