VUFLUIDEXCH

User subroutine to define the mass flow rate/heat energy flow rate for fluid exchange.

User subroutine VUFLUIDEXCH:

can be used to define mass flow rate and/or heat energy flow rate for fluid exchange;
can be used when built-in fluid exchange property types cannot satisfactorily model the mass/heat energy flow;
can use and update solution-dependent state variables;
can use any field variables that are passed in; and
requires that the derivatives of mass/heat energy flow rates be defined with respect to pressure and temperature in the primary and secondary fluid cavities.

The following topics are discussed:

Conventions for defining mass flow/heat energy flow rate
User subroutine interface
Variables to be defined
Variables that can be updated
Variables passed in for information

Conventions for defining mass flow/heat energy flow rate

A positive mass/heat energy flow rate indicates flow from the primary fluid cavity to the secondary fluid cavity. A negative value for mass flow rate will be ignored if the fluid exchange is between a cavity and its environment.

User subroutine interface

      subroutine vufluidexch(
C Read only (unmodifiable)variables -
     1     nstatev, nfieldv, nprops, 
     2     stepTime, totalTime, dt,
     3     jCavType, fluExchName, effArea, amplitude,
     4     props, lExchEnv, pcavNew, pcavOld,
     5     ctempNew, ctempOld, cvol, cmass,                        
     6     rMix, CpMix, DCpDtemp,
     7     field, stateOld, 
C Write only (modifiable) variables 
     8     stateNew, rMassRate, rEneRate,
     9     DMassRateDPcav, DMassRateDTemp,
     *     DEneRateDPcav, DEneRateDTemp)
c
      include 'vaba_param.inc'
c
      dimension props(nprops),
     1     pcavNew(2), pcavOld(2),
     2     ctempNew(2), ctempOld(2), cvol(2), cmass(2),
     3     rMix(2), CpMix(2), dCpDtemp(2),
     4     field(nfieldv),
     5     stateOld(nstatev), stateNew(nstatev),
     6     DMassRateDPcav(2), DMassRateDTemp(2), 
     7     DEneRateDPcav(2), DEneRateDTemp(2)

c     Fluid cavity type
      parameter( iHydraulic     = 1,
     *           iAdiabaticGas  = 2,
     *           iIsothermalGas = 3)

      character*80 fluExchName

c	    User coding to calculate mass flow rate, 
c	    heat energy flow rate and its derivatives with respect
c	    to fluid cavity pressure and temperature.

      return
      end

Variables to be defined

rMassRate: Mass flow rate. The mass flow rate is negative if the flow is into the primary cavity.
DMassRateDPcav(2): Derivative of mass flow rate with respect to pressure in primary and secondary fluid cavities.
DMassRateDTemp(2): Derivative of mass flow rate with respect to temperature in primary and secondary fluid cavities.
rEneRate: Heat energy flow rate. The energy flow rate is negative if the flow is into the primary cavity.
DEneRateDPcav(2): Derivative of heat energy flow rate with respect to pressure in primary and secondary fluid cavities.
DEneRateDTemp(2): Derivative of heat energy flow rate with respect to temperature in primary and secondary fluid cavities.

Variables that can be updated

stateNew(nstatev): State variable for fluid exchange at the end of the increment. You define the size of this array by allocating space for it (see Allocating space for more information).

Variables passed in for information

nstatev: Number of user-defined state variables that are associated with this fluid exchange (you define this as described in Allocating space).
nfieldv: Number of user-defined external field variables.
nprops: User-specified number of user-defined fluid exchange properties required to define mass/heat energy flow rate.
stepTime: Value of time since the step began.
totalTime: Value of total time. The time at the beginning of the step is given by totalTime−stepTime.
dt: Time increment size.
jCavType: Indicator of fluid cavity type: 1 for fluid cavity with hydraulic fluids, 2 for fluid cavity with adiabatic gases, and 3 for fluid cavity with isothermal gases.
fluExchName: User-specified fluid exchange name.
effArea: Effective area for fluid exchange.
amplitude: Current value of the amplitude referenced for this fluid exchange. You must multiply the flow rates by the current amplitude value within the user subroutine if the amplitude is required.
props(nprop): User-defined fluid exchange properties.
lExchEnv: The fluid exchange is to the environment if lExchEnv=1 and to another fluid cavity if lExchEnv=0.
pcavNew(2): Pressure in primary and secondary fluid cavities at the end of the increment.
pcavOld(2): Pressure in primary and secondary fluid cavities at the beginning of the increment.
ctempNew(2): Temperature in primary and secondary fluid cavities at the end of the increment.
ctempOld(2): Temperature in primary and secondary fluid cavities at the beginning of the increment.
cvol(2): Volume of primary and secondary fluid cavities.
cmass(2): Mass of fluid in primary and secondary fluid cavities.
rMix(2): Gas constant of mixture in primary and secondary fluid cavities.
CpMix(2): Specific heat of mixture in primary and secondary fluid cavities.
DCpDtemp(2): Derivative of specific heat with respect to temperature for primary and secondary fluid cavities.
field(nfieldv): Field variables at orifice.
stateOld(nstatev): State variables for fluid exchange at the beginning of the increment.