machpi.f File Reference

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Functions/Subroutines
subroutine	machpi (MACH, PI, kappa, rgas)

Function/Subroutine Documentation

machpi()

subroutine machpi	(	real*8	MACH,
		real*8	PI,
		real*8	kappa,
		real*8	rgas
	)

!
!-----------------------------------------------------------------------
!                                                                      |
!     Dieses Unterprogramm berechnet die Mach-Zahl fuer das            |
!     eingegebene Druckverhaeltnis PI.                                 |
!                                                                      |
!     Eingabe-Groessen:                                                |
!       PI     = Druckverhaeltnis PS/PT                                |
!                                                                      |
!     Ausgabe-Groessen:                                                |
!       MACH   = Mach-Zahl                                             |
!                                                                      |
!-----------------------------------------------------------------------
!
      IMPLICIT CHARACTER*1 (a-z)
      real*8    pi, mach, ma2, kappa, rgas, kappam,kappax,pikrit
!
!-----------------------------------------------------------------------
!
      kappax = (kappa-1)/kappa
      kappam = 2. / (kappa - 1.)
      pikrit = (2./(kappa+1.)) ** (kappa/(kappa-1.))
!
      IF (pi.GE.1.) THEN
!       Druckverhaeltnis groesser gleich 1
        mach = 0.
      ELSEIF (pi.GT.pikrit) THEN
!       Druckverhaeltnis unterkritisch
        ma2  = kappam * (pi**(-kappax) - 1.)
        IF (ma2.GT.0) THEN
          mach = sqrt(ma2)
        ELSE
          mach = 0.
        ENDIF
      ELSEIF (pi.GT.0.) THEN
!       Druckverhaeltnis ueberkritisch
        mach = 1.
      ELSE
!       Druckverhaeltnis ungueltig
        mach = 1.e20
      ENDIF
!
      RETURN