kerbou.f

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!                   ********************************
                    DOUBLE PRECISION FUNCTION kerbou
!                   ********************************
!
     &( xk1   , xk2   , freq1  , freq2  , depth , teta1 , teta2 )
!
!***********************************************************************
! TOMAWAC   V6P3                                   20/06/2011
!***********************************************************************
!
!brief    COMPUTES THE COUPLING COEFFICIENT.
!
!history  EDF/DER/LNH
!+        11/06/98
!+        V1P1
!+
!
!history  N.DURAND (HRW), S.E.BOURBAN (HRW)
!+        13/07/2010
!+        V6P0
!+   Translation of French comments within the FORTRAN sources into
!+   English comments
!
!history  N.DURAND (HRW), S.E.BOURBAN (HRW)
!+        21/08/2010
!+        V6P0
!+   Creation of DOXYGEN tags for automated documentation and
!+   cross-referencing of the FORTRAN sources
!
!history  G.MATTAROLO (EDF - LNHE)
!+        20/06/2011
!+        V6P1
!+   Translation of French names of the variables in argument
!
!~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
!| DEPTH          |-->| WATER DEPTH
!| FREQ1          |-->| FREQUENCY OF COMPONENT 1
!| FREQ2          |-->| FREQUENCE OF COMPONENT 2
!| TETA1          |-->| DIRECTION OF COMPONENT 1
!| TETA2          |-->| DIRECTION OF COMPONENT 2
!| XK1            |-->| WAVE NUMBER OF COMPONENT 1
!| XK2            |-->| WAVE NUMBER OF COMPONENT 2
!~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
!
      USE declarations_tomawac, ONLY : deupi,gravit
!
      USE interface_tomawac, ex_kerbou => kerbou
      IMPLICIT NONE
!
!+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
!
      DOUBLE PRECISION, INTENT(IN) :: XK1,XK2,FREQ1,FREQ2,TETA1,TETA2
      DOUBLE PRECISION, INTENT(IN) :: DEPTH
!
!+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
!
      DOUBLE PRECISION VAR1,VAR2,VAR3,VAR4,DANG
!
!-----------------------------------------------------------------------
!
      var1  = xk1**2
      var2  = xk2**2
      var3  = xk1*xk2
      var4  = deupi**2*freq1*freq2
      dang  = cos(teta1-teta2)
!
      kerbou = gravit*0.5d0*(var1+var2+2.d0*var3*dang) +
     &         (var4/var3)*((var1+var2)*dang+var3*(1.d0+dang**2))/depth
!
!-----------------------------------------------------------------------
!
      RETURN
      END