CalcMaxCFL.F90

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!                                                         ! 
!    FILE: CalcMaxCFL.F90                                 !
!    CONTAINS: subroutine CalcMaxCFL                      !
!                                                         ! 
!    PURPOSE: Compute the maximum value of the local CFL  !
!     stability condition for the explicit terms          !
!                                                         !
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

      subroutine CalcMaxCFL(cflm)
      use param
      use local_arrays, only: vx,vy,vz
      use decomp_2d
      use mpih
      implicit none
      real,intent(out)    :: cflm
      integer :: j,k,jp,kp,i,ip
      real :: qcf
      
      cflm=0.00000001d0
!                                                                       
!$OMP  PARALLEL DO &
!$OMP   DEFAULT(none) &
!$OMP   SHARED(xstart,xend,nxm,vz,vy,vx) &
!$OMP   SHARED(dz,dy,udx3m) &
!$OMP   PRIVATE(i,j,k,ip,jp,kp,qcf) &
!$OMP   REDUCTION(max:cflm)
      do i=xstart(3),xend(3)
        ip=i+1
        do j=xstart(2),xend(2)
          jp=j+1
          do k=1,nxm
           kp=k+1
            qcf=( abs((vz(k,j,i)+vz(k,j,ip))*0.5d0*dz) &
                 +abs((vy(k,j,i)+vy(k,jp,i))*0.5d0*dy) &
                 +abs((vx(k,j,i)+vx(kp,j,i))*0.5d0*udx3m(k)))

            cflm = max(cflm,qcf)
      enddo
      enddo
      enddo
!$OMP END PARALLEL DO
            
      call MpiAllMaxRealScalar(cflm)

      return  
      end