Imperial and SI Fluid Mechanics Dimensions and Units

Imperial (USCS) and SI dimensions and units terminology

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The table below list the most common units used in the

  • Imperial or USCS - United States Customary Units
  • International System of Units - SI system
Terminology Dimensions Imperial Units
(USCS)		 SI-units
Acceleration due to gravity L/T2 ft/s2 m/s2
Area L2 ft2 m2
Chezy roughness coefficient L1/2/T ft1/2/s m1/2/s
Critical Depth L ft m
Density FT2/L4 lb s2/ft4 kg s2/m4
Depth L ft m
Depth in open channel L ft m
Diameter L ft m
Distance from solid boundary L ft m
Flow rate L3/T ft3/s m3/s
Force F lb N
Force due to pressure F lb N
Hazen Williams roughness coefficient L0.37/T ft0.37/s m0.37/s
Head loss due to friction L ft m
Head of height L ft m
Head of weir L ft m
Height above datum L ft m
Hydraulic radius L ft m
Kinematic viscosity L2/T ft2/s m2/s
Length L ft m
Manning's roughness coefficient T/L1/3 s/ft1/3 s/m1/3
Mass FT2/L lb s2/ft N s2/m
Modulus of elasticity F/L2 lb/in2 (psi) Pa
Perimeter, Weir Height L ft m
Pressure F/L2 lb/ft2 Pa
Radius L ft m
Shear stress F/L2 lb/ft2 Pa
Size of roughness L ft m
Specific weight F/L3 lb/ft3 kg/m3
Surface tension F/L lb/ft kg/m
Time T s s
Thickness L ft m
Time T s s
Total head L ft m
Unit flow rate L3/TL ft3/(s ft) m3/(s ft)
Velocity L/T ft/s m/s
Viscosity FT/L2 lb s/ft Pa s
Weight F lbf N
  • L - length
  • F - force
  • T - time

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Related Topics

  • Fluid Mechanics - The study of fluids - liquids and gases. Involves various properties of the fluid, such as velocity, pressure, density and temperature, as functions of space and time.

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