A Table of Commonly Used Units in Fluid Mechanics

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A Table of Commonly Used Units in Fluid Mechanics

Commonly used units in CE319F (Elementary Fluid Mechanics) - ©S.A. Kinnas (to be continuously enhanced and improved!) Remember also multiples of units: h(ecto)=100; k(ilo)=10 3 ; M(ega)=10 6 ; G(iga)=10 9 ; T(era)=10 12 ; Peta=10 15 , and sub-multiples of units: c(enti)=10 -2 ; m(illi)=10 -3 ; m (micro)=10 -6 ; n(ano)=10 -9 ; pico=10 -12 Quantity SI units U.S. customary units Definitions/equations L (Length) m (=100 cm=1000 mm) ft (=12 inches=0.3048 m) M (Mass) kg slug [=32.2 lbm(pound mass)=14.59 kg] T (time) sec or s sec or s v (velocity) m/sec ft/sec Velocity=Distance/Time a (acceleration) m/sec2 ft/sec2 Acceleration=Velocity/Time w (angular velocity) rad(ians)/sec or sec-1 rad/sec or sec-1 v(elocity)=w*r(adius) f (frequency) cycles/sec = Hz (Hertz) = RPS (Revs Per Sec) [often RPM (Revs Per Min)] w=2 p f=2 p/T T (period) sec sec T=1/f F (Force) N(ewton)=1kg*1m/sec2 lbf (pound force)=1slug*1ft/sec2 Force=Mass*Acceleration W (Weight) 1kg (on earth) weighs: 1 slug (on earth) weighs: Weight=M*g(accel. of gravity) 1kg*9.81 m/sec2=9.81 N (=1 kp or kilopond) 1slug*32.2 ft/sec2=32.2 lbf g (accel. of gravity) g=9.81 m/sec2 g=32.2 ft/sec2 M(Moment) or Q(Torque) N.m lbf.ft Moment=Force*Arm(distance) W (Work) J(oule)=N.m lbf.ft Work=Force*Distance P (Power) W(att)=J/sec hp=550 lbf.ft/sec (1hp=0.746 kW) Power=Work/Time T (Temperature) oK(elvin)=273.15 + oC(elcius) oR(ankine)=459.67 + oF(ahrenheit) oF=9/5*oC+32 ; oC=(oF-32)*5/9 p (pressure) Pa(scal)=N/m2; 1bar=105 Pa; 1mbar=100Pa=1hPa; psi (lbf/in2) or psf (lbf/ft2) pressure=Normal Force/Area 1 atm = 101.3 kPa; 1 Torr=1 mmHg p (standard atm pressure) patm=101.3 kPa=1,013 mbar=760mmHg patm=14.696 psi =29.92 inHg t (shear stress) Pa(scal)=N/m2 psi (lbf/in2) or psf (lbf/ft2) shear stress=Shear Force/Area r (density) kg/m3 slugs/ft3 r=Mass/Volume g (specific weight) N/m3 lbf/ft3 g=Weight/Volume=r g S.G. (specific gravity) unitless! unitless! S.G.=g/gwater.=r/rwater m (dynamic viscosity) Pa.sec = N.sec/m2 (1 poise= 10-1 Pa.sec) lbf.sec/ft2 t=m dv/dy n (kinematic viscosity) m2/sec (1 stokes=10-4 m2/sec) ft2/sec n=m/r s (surface tension) N/m lbf/ft Force=s * Length Last updated: SAK 1/11/2013.

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