The program accepts any consistent set of engineering units. Examples of consistent sets of units for basic parameters are shown in the tables below. The user should use great care when converting from one system of units to another. An excellent reference on the subject of units and conversion between the imperial and SI systems can be found in [JPT1977]. The program does not perform conversions.
One exception to the conversion rule above: for quantities representing angles, conversions are performed in FLAC3D.
Angles are always entered on the command line (and in the user interface) in degrees, though they may be stored and used in radians. The exception is FISH, which (like most programming languages) assumes all angle values are in radians.
Thermal Analysis
All thermal quantities must be given in a consistent system of units.
No conversions are performed by the program. The tables below present examples of consistent sets of units for thermal parameters.
Table 3: System of SI units for thermal problems
Property
Units
Length
m
m
m
cm
Density
kg/m3
103 kg/m3
106 kg/m3
106 g/cm3
Stress
Pa
kPa
MPa
bar
Temperature
K
K
K
K
Time
s
s
s
s
Specific Heat
J/(kg K)
10-3 J/(kg K)
10-6 J/(kg K)
10-6 cal/(g K)
Thermal Conductivity
(W/mK)
(W/mK)
(W/mK)
(cal/s)/cm2 K4
Convective Heat-Trans. Coefficient
(W/m2 K)
(W/m2 K)
(W/m2 K)
(cal/s)/(cm2 K)
Radiative Heat-Trans. Coefficient
(W/m2 K4)
(W/m2 K4)
(W/m2 K4)
(cal/s)/cm2 K4
Flux Strength
W/m2
W/m2
W/m2
(cal/s)/cm2
Source Strength
W/m3
W/m3
W/m3
(cal/s)/cm3
Decay Constant
s-1
s-1
s-1
s-1
Table 4: System of imperial units for thermal problems
Property
Units
Length
ft
in
Density
slugs/ft3
snails/in3
Stress
lbf
psi
Temperature
R
R
Time
hr
hr
Specific Heat
(32.17)-1 Btu/(lb R)
(32.17)-1 Btu/(lb R)
Thermal Conductivity
(Btu/hr)/(ft R)
(Btu/hr)/(in R)
Convective Heat-Trans. Coefficient
(Btu/hr)/(ft2 R)
(Btu/hr)/(in2 R)
Radiative Heat-Trans. Coefficient
(Btu/hr)/(ft2 R4)
(Btu/hr)/(in2 R4)
Flux Strength
(Btu/hr)/ft2
(Btu/hr)/in2
Source Strength
(Btu/hr)/ft3
(Btu/hr)/in3
Decay Constant
hr-1
hr-1
where:
1K
= 1.8 R;
1J
= 0.239 cal = 9.48 × 10-4 Btu;
1J/kg K
= 2.39 × 10-4 btu/lb R;
1W
= 1 J/s = 0.239 cal/s = 3.412 Btu/hr;
1W/m K
= 0.578 Btu/(ft/hr R); and
1W/m2 K
= 0.176 Btu/ft2 hr R.
Note that temperatures may be quoted in the more common units of °C (instead of K) or °F (instead of R),
where:
Temp(°C)
= [Temp(°F) - 32]×(5/9);
Temp(°F)
= [1.8 Temp(°C) + 32];
Temp(°C)
= Temp(K) - 273; and
Temp(°F)
= Temp(R) - 460.
Fluid Analysis
Any set of units can be used as long as they are consistent with the units used in the mechanical calculation.