<unit>
A unit of measurement is a definite magnitude of a physical quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same physical quantity. Any other value of the physical quantity can be expressed as a simple multiple of the unit of measurement. For example, length is a physical quantity, and metre meter is a unit of length that represents a definite predetermined length.
The node <units> in the *.spd file can be used to change some defaults or to add specialized units, which in principle are not supported. The structure and contents of this subtree <units> requires to have the format as further detailed in this document. The following attributes are available:
n - name
pn - printed name (decorated and translated)
p - Priority of the unit, it is regarded as more important than others units. The possible values for 'p' are 1, 2 and 3, as follows,
1 - It gives maximum priority, and therefore a unit with p="1" is the default unit in the GUI.
2 - A unit with p="2" is always shown in the combobox of below to facilitate the selection of the most used units.
3 - It gives lowest priority, and therefore a unit with p="3" could only be chosen when clicking on 'More units...' option in the combobox of below, which enables the user to choose the unit from a table.
factor - The conversion factor used to multiply a quantity when converting from one system of units to another. It is the mathematical tool for converting between units of measurement [1 unit=factor*unit(SI)]. Example: 1mm=10e-3 m.
help - To make easier to the user to identify the unit.
Example of <units> field: Species concentration and reference variable are not supported and therefore, both magnitudes are defined in the *.spd file, as follows,
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<units>
<unit_magnitude n="Reference_variable_unit" pn="Reference variable unit" default="U" SI_base="U" active="1">
<unit n="U" pn="ReferenceUnit" p="2" factor="1.0"/>
<unit n="ppm" pn="parts-per-million" p="2" factor="1.0e-6" help="parts-per-million"/>
<unit n="ppb" pn="parts-per-billion" p="2" factor="1.0e-9" help="parts-per-billion"/>
<unit n="%" pn="per-one-hundred" p="2" factor="0.01" help="per-one-hundred"/>
<unit n="%0" pn="per-one-thousand" p="2" factor="0.001" help="per-one-thousand"/>
<unit n="Np" pn="Nepper" p="2" factor="1.0" help="Nepper"/>
</unit_magnitude>
<unit_magnitude n="Species_concentration" pn="Species concentration" default="C" SI_base="C" active="1">
<unit n="C" pn="ReferenceUnit" p="2" factor="1"/>
<unit n="ppm" pn="parts-per-million" p="2" factor="1.0e-6" help="parts-per-million"/>
<unit n="ppb" pn="parts-per-billion" p="2" factor="1.0e-9" help="parts-per-billion"/>
<unit n="%" pn="per-one-hundred" p="2" factor="0.01" help="per-one-hundred"/>
<unit n="%0" pn="per-one-thousand" p="2" factor="0.001" help="per-one-thousand"/>
<unit n="mol" pn="mole" p="2" factor="1.0"/>
</unit_magnitude>
</units> |
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="1 |
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| Code Block | ||
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<container n="units" pn="Units" icon="units-16" help="Units definition">
<value n="units_mesh" pn="Geometry units" unit_mesh_definition="1" icon="units-16"/>
<value n="units_system" pn="Unit system" units_system_definition="1" icon="units-16" state="hidden">
<dependencies node="//*[@unit_definition or @unit_mesh_definition='1']" att1="change_units_system" v1="{@v}"/>
</value>
<container n="basic_units" pn="General units" icon="units-16" state="normal">
<value n="units_length" pn="Length" unit_definition="L"/>
<value n="units_mass" pn="Mass" unit_definition="M"/>
<value n="units_force" pn="Force" unit_definition="F"/>
<value n="units_pressure" pn="Pressure" unit_definition="P"/>
<value n="units_temperature" pn="Temperature" unit_definition="Temp"/>
<value n="units_time" pn="Time" unit_definition="T"/>
</container>
</container> |
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Unit system
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n
...
Int. system (SI)
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SI
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Imperial system
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imperial
...
- units_system - There are two systems used to define units, the possible values are:
SI - International system
imperial - Imperial system
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Some functions are useful for writing data with units defined into the calculation file. For more information about this issue, see the section called Writing the input file for calculation.
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<value n="ini_temp" pn="Initial temperature" v="20.0" unit_magnitude="Temp" units="°C"/> |
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pn
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n
...
Unit by default
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Length
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L
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m
...
Mass
...
M
...
kg
...
Time
...
T
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s
...
Temperature
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Temp
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K
...
Frequency
...
Frequency
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Hz
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Force
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F
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N
...
Pressure
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P
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Pa
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Energy
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Energy
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J
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Power
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Power
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W
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Angle
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Angle
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rad
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Solid_angle
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Solid_angle
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sr
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Velocity
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Velocity
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m/s
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Acceleration
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Acceleration
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m/s^2
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Area
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Area
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m^2
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Volume
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Volume
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m^3
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Density
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Density
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kg/m^3
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Electric current
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Electric_current
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A
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Amount of substance
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Amount_of_substance
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mol
...
Luminous intensity
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Luminous_intensity
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cd
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Electric charge
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Electric_charge
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C
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Electric potential
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Electric_potential
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V
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Capacitance
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Capacitance
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F
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Electric resistance
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Electric_resistance
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?
...
Electric conductance
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Electric_conductance
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S
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Magnetic flux
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Magnetic_flux
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Wb
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Magnetic flux density
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Magnetic_flux_density
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T
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Inductance
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Inductance
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H
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Delta phi
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DeltaPhi
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Δφ
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Delta temperature
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DeltaTemp
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ΔK
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Luminous flux
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Luminous_flux
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lm
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Illuminance
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Illuminance
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lx
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KinematicViscosity
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KinematicViscosity
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m^2/s
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Viscosity
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Viscosity
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Pa*s
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Permeability
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Permeability
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m^2
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| Code Block | ||
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<units> <unit_magnitude n="F" pn="Force" default="N" SI_base="N" active="kN"> <unit n="kN" pn="kilonewton" p="1" units_system="SI"/> </unit_magnitude> <unit_magnitude n="P" pn="Pressure" default="Pa" SI_base="Pa" active="MPa"> <unit n="MPa" pn="megapascal" p="1" units_system="SI"/> </unit_magnitude> </units> |
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