tt_calc.f File Reference

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Functions/Subroutines
subroutine	tt_calc (xflow, Tt, Pt, kappa, r, A, Ts, icase)

Function/Subroutine Documentation

tt_calc()

subroutine tt_calc	(	real*8	xflow,
		real*8	Tt,
		real*8	Pt,
		real*8	kappa,
		real*8	r,
		real*8	A,
		real*8	Ts,
		integer	icase
	)

!     
!     this subroutine solves the implicit equation
!     f=xflow*dsqrt(Tt)/(a*Pt)-C*(TtdT)**expon*(Ttdt-1)**0.5d0
!     in order to find Tt when Ts , xflow, pt and a are given
!
!     author: Yannick Muller
!     
      implicit none
!
      integer icase,i
!     
      real*8 xflow,tt,pt,ts,kappa,r,f,df,a,expon,tt_old,c,ttzts,
     &     deltatt,ttzts_crit,qred,h1,h2,h3
!     
      expon=-0.5d0*(kappa+1.d0)/(kappa-1.d0)
!     
      c=dsqrt(2.d0/r*kappa/(kappa-1.d0))
!     
!     f=xflow*dsqrt(Tt)/(A*Pt)-C*(Tt/Ts)**expon*(Tt/Ts-1)**0.5d0
!
!     df=-C*Ttdt**expon*(expon/Ts*(Tt/Ts-1)**0.5d0
!     &     -0.5d0*Tt/Ts/Ts*(Tt/Ts-1.d0)**(-0.5d0))
!     
      if(dabs(xflow).le.1e-9) then
         tt=ts
         return
      endif
!
!     initial guess
!
      qred=abs(xflow)*dsqrt(ts)/(a*pt)
      tt=ts*(1+(qred**2/c**2))
!     
!     adiabatic
!     
      if(icase.eq.0) then
!
         ttzts_crit=(kappa+1.d0)/2.d0
!         
!     isothermal
!
      else
!     
         ttzts_crit=(1d0+(kappa-1.d0)/(2.d0*kappa))
!
      endif
!
      if(tt/ts.gt.ttzts_crit) then
         tt=ts*(ttzts_crit+1.d0)/2.d0
      endif
!
      i=0
      tt_old=tt
!
      do 
         i=i+1
         ttzts=tt/ts
         h1=ttzts-1.d0
         h2=dsqrt(h1)
         h3=ttzts**expon
!     
         f=c*h2*h3
!     
         df=0.5*dabs(xflow)/(a*pt*dsqrt(tt))
     &        -c*h2*h3*(expon/tt+1.d0/(2.d0*h1*ts))
!
         qred=abs(xflow)*dsqrt(tt)/(a*pt)
!
         f=qred-f
         deltatt=-f/df
!     
         tt=tt+deltatt
!     
         if((((dabs(tt-tt_old)/tt_old).le.1.e-8))
     &        .or.((dabs(tt-tt_old)).le.1.e-10) 
     &        .or.((dabs(f).le.1e-5).and.(deltatt.lt.1e-3))) then
!     
            if(tt/ts.gt.ttzts_crit) then
               tt=ts*ttzts_crit
            endif
            exit
         else if((i.gt.40)) then
            tt=0.99*ts*ttzts_crit
            exit
         endif
         tt_old=tt
      enddo
!     
      return