CIVIL ENGINEERING FORMULAS

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TABLE 12.1 Symbols, Terminology, Dimensions, and Units Used in Water Engineering

Symbol Terminology Dimensions USCS units SI units

A Area L^2 ft^2 mm^2

C Chezy roughness coefficient L1/2/T ft^5 /s m0.5/s

C 1 Hazen–Williams roughness coefficient L0.37/T ft0.37/s m0.37/s

d Depth L ft m

dc Critical depth L ft m

D Diameter L ft m

E Modulus of elasticity F/L^2 lb/in^2 MPa

F Force F lb N

g Acceleration due to gravity L/T^2 ft/s^2 m/s^2

H Total head, head on weir L ft m

h Head or height L ft m

hf Head loss due to friction L ft m

L Length L ft m

M Mass FT^2 /L lbs^2 /ft Ns^2 /m

n Manning’s roughness coefficient T/L1/3 s/ft1/3 s/m1/3

P Perimeter, weir height L ft m

P Force due to pressure F lb N

p Pressure F/L^2 psf MPa

Q Flow rate L^3 /T ft^3 /s m^3 /s

q Unit flow rate L^3 /TL ft^3 /(sft) m^3 /sm

r Radius L ft m

R Hydraulic radius L ft m

T Time T ss

t Time, thickness T, L s, ft s, m

V Velocity L/T ft/s m/s

W Weight F lb kg