OpenFOAM – Units

Written by

March 19, 2020


Source: CFD Direct

Dimensional units

In continuum mechanics, properties are represented in some chosen units, e.g. mass in kilograms (kg  \relax \special {t4ht=), volume in cubic metres (  3 m   \relax \special {t4ht=), pressure in Pascals (    −1 −2 kgm   s   \relax \special {t4ht=). Algebraic operations must be performed on these properties using consistent units of measurement; in particular, addition, subtraction and equality are only physically meaningful for properties of the same dimensional units. As a safeguard against implementing a meaningless operation, OpenFOAM attaches dimensions to field data and physical properties and performs dimension checking on any tensor operation.

The I/O format for a dimensionSet is 7 scalars delimited by square brackets, e.g.

    [0 2 -1 0 0 0 0]

No. Property SI unit USCS unit

1 Mass kilogram (kg) pound-mass (lbm)
2 Length metre (m) foot (ft)
3 Time
— — — — second (s) — — — —
4 Temperature Kelvin (K) degree Rankine (∘ \relax \special {t4ht=R)
5 Quantity kilogram-mole (kgmol) pound-mole (lbmol)
6 Current
— — — — ampere (A) — — — —
7 Luminous intensity
— — — — candela (cd) — — — —

In this tutorial, you will learn how to works the units in OpenFOAM.

Tutorial: Heat Exchanger using ANSYS Fluent.

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