FLASH4.6.1 API

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TABLE OF CONTENTS


[Functions] source/PhysicalConstants/PhysicalConstants_get

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NAME

  PhysicalConstants_get

SYNOPSIS

  call PhysicalConstants_get(character(len=*)(IN) :: name,
            real(OUT) :: value,
            real(IN,OPTIONAL) :: unitLength,
            real(IN,OPTIONAL) :: unitTime,
            real(IN,OPTIONAL) :: unitMass,
            real(IN,OPTIONAL) :: unitTemp,
            real(IN,OPTIONAL) :: unitCharge,
            real(IN,OPTIONAL) :: unitSubstAmount)

DESCRIPTION

    Retrieve the value of a physical constant.  Returns in CGS or MKS units, 
      depending upon status of runtime parameter pc_unitsBase.
    If called with optional unit arguments, the basic constant is converted and 
      returned with the requested units.

    This interface can also be used to convert a know unit of length, mass, time,
    temperature, charge, or substance amount to either another known unit (when
    the corresponding optional unitFoo argument is present), or to the corresponding
    base unit in CGS or MKS (when unitFoo is not present). This will happen if name
    does not match the name of a know constant but does match the name if a known
    unit.

    If the constant name is not recognized, or some other error, 
      returns value of 0

ARGUMENTS

  name:     character(len=*,IN) Name of the physical constant sought, or of an input unit
                                to convert.
                                See the implementation in PhysicalConstants_init.F90 or
                                any typical flash.log file for a list of implemented
                                constant names and unit names.
  value:      real(OUT)         returned value of the physical constant in appropriate units
  unitLength: real(IN,OPTIONAL) value will be returned with this requested unit for length
  unitMass:   real(IN,OPTIONAL) value will be returned with this requested unit for mass
  unitTime:   real(IN,OPTIONAL) value will be returned with this requested unit for time
  unitTemp:   real(IN,OPTIONAL) value will be returned with this requested unit for temperature
  unitCharge: real(IN,OPTIONAL) value will be returned with this requested unit for charge
  unitSubstAmount: real(IN,OPTIONAL) value will be returned with this requested unit for
                                     substance amount

PARAMETERS

  pc_unitsBase   [default "CGS"] set the default system of units, either "CGS" or "MKS"
                 CGS:  centimeters, grams, seconds, charge=esu
                 MKS:  meters, kilometers, seconds, charge=Coloumb
                     both systems have temperature in Kelvin

EXAMPLE

    Example of usage:
    use PhysicalConstants_interface,ONLY:  PhysicalConstants_get
    ............
    real ::   newton
    ............
    call PhysicalConstants_get("newton",newton,unitMass="kg",unitLength="cm")

    ! Get conversion factor from atomic mass units to kg:
    call PhysicalConstants_get("amu", amu2kg, unitMass="kg")

    ! Get conversion factor from atomic mass units to the current base
    ! unit for mass, either g or kg depending on the default system of units
    ! in effect:
    call PhysicalConstants_get("amu", atomic_mass_unit)

NOTES

   Because PhysicalConstants_get has optional arguments in the interface,
   the interface file PhysicalConstants_interface must be used in the calling routine.
  
   The constant named "Newton" does not indicate the SI unit
   of force (which has dimensions LENGTH^1 * TIME^(-2) * MASS^1), but
   Newton's gravitational constant G.