SUBROUTINE UFLUID(RHO,CP,CT,PNEWDT,ENER,PRESS,DPRESS,PRESSI,
     1 TEMP,DTEMP,TEMPI,TIME,DTIME,KSTEP,KINC,NONUM,FLNAME,LFLAG)
C     
C     THIS USER SUBROUTINE MODELS A FLUID AS AN IDEAL GAS:
C     VARIABLES:
C        PAMB = AMBIENT PRESSURE
C        TABS = ABSOLUTE ZERO TEMPERATURE
C        PREF = REFERENCE PRESSURE FOR DENSITY
C        TREF = REFERENCE TEMPERATURE FOR DENSITY
C        RHOR = REFERENCE DENSITY
C
      INCLUDE 'ABA_PARAM.INC'
C
      CHARACTER*80 FLNAME
      DIMENSION TIME(2)

      PAMB = 14.7
      TABS = -460.
      PREF = 0.
      TREF = 200.
      RHOR = 10.
C
C		COMPUTE FOR FLUID DENSITY
C
      RHO=RHOR*((TREF-TABS)*(PRESS+PAMB))/((TEMP-TABS)*(PREF+PAMB))
C
C		COMPUTE FOR FLUID PRESSURE COMPLIANCE
C
      CP=(-1.0/RHOR)*((TEMP-TABS)*(PREF+PAMB))/((TREF-TABS)*
     1       (PRESS+PAMB)**2)
C
C		COMPUTE FOR FLUID TEMPERATURE COMPLIANCE
C
      CT=(1.0/RHOR)*(PREF+PAMB)/((TREF-TABS)*(PRESS+PAMB))
C
C		COMPUTE FOR ENERGY PER UNIT MASS
C
      ENER=(1.0/RHOR)*((TEMP-TABS)/(TREF-TABS)*(PREF+PAMB)*
     1        (LOG((PRESS+PAMB)/PAMB) - PRESS/(PRESS+PAMB)))
C
      RETURN
      END