DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING; LAFAYETTE COLLEGE
Abbreviations and Symbols
CE 251, Spring 2004
= fluid shear stress (shear force over a shear area) [F/L2]
p = fluid pressure (compressive force over an area: pounds per square inch (psi), Pascal (Pa) = N/
m2) [F/L2]
u = internal energy per unit mass (J/kg) [FL/M]
W = work (Joules) [FL]
= density [M/L3] (
w = 1000 kg/m3 = 1 g/cm3 = 1.94 slugs/ft3)
g = acceleration of gravity = 9.81 m/s2 = 32.2 ft/s2
= specific weight [F/L3] =
g (
w = 9.8 kN/m3 = 62.4 lbs/ft3)
SG = specific gravity [] =
x/
w =
x/
w
= dynamic viscosity (also called absolute viscosity) [Ft/L2] (
w = 1 x 10-3 N-s/m2 =
2.1 x 10-5 lb-s/ft2 @ 20C or 70F)
= kinematic viscosity [L2/t] =
(
w = 1 x 10-6 m2/s = 1.1 x 10-5 ft2/s @ 20C or 70F)
Ev = bulk modulus of elasticity [F/L2] (Evw = 2,170,500 kN/m2 = 318,000 psi)
= surface tension [F/L] (
aw = 0.073 N/m = 0.005 lb/ft)
R = specific gas constant = R/mw (Rair = 287 J/kg˚K) [FL/MT = L2/t2T]
c = specific heat: heat required to raise the temp of a unit mass by one degree (J/kg˚K)
k = adiabatic constant = ratio of c at const pressure to c at constant volume (cp/cv) (kair = 1.4)
r = radial distance from a pipe centerline [L]
y = perpendicular distance from a flow boundary [L]
h = fluid “head” [L], a vertical depth of fluid; pressure is often converted to an equivalent height
of fluid using h = p/
z = vertical height above some datum [L]
hL = head loss due to friction and turbulence [L]
V = average velocity through a cross-section of flow [L/t]
A = area [L2]
Q = volumetric flow rate = VA [L3/t]
v = velocity at a specific point in the flow [L/t]
v* = “friction velocity", an important parameter in boundary layer flow (not a true velocity) [L/t]
Re = Reynolds number, a dimensionless force ratio important in pipe flow (inertial/viscous)
Fr = Froude number, another dimensionless force ratio important in gravity flow
(inertial/gravity)
Note: dimensions are in brackets, F = force, M = mass, L = length, t = time, T = temp
