relaxation_profile.f90

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!! Time-stamp: <2016-11-23 11:33:01 pbrowne>
!!!
!!!    Subroutine to compute the relaxation strength
!!!    Copyright (C) 2016 Philip A. Browne
!!!
!!!    This program is free software: you can redistribute it and/or modify
!!!    it under the terms of the GNU General Public License as published by
!!!    the Free Software Foundation, either version 3 of the License, or
!!!    (at your option) any later version.
!!!
!!!    This program is distributed in the hope that it will be useful,
!!!    but WITHOUT ANY WARRANTY; without even the implied warranty of
!!!    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
!!!    GNU General Public License for more details.
!!!
!!!    You should have received a copy of the GNU General Public License
!!!    along with this program.  If not, see <http://www.gnu.org/licenses/>.
!!!
!!!    Email: p.browne @ reading.ac.uk
!!!    Mail:  School of Mathematical and Physical Sciences,
!!!           University of Reading,
!!!       Reading, UK
!!!       RG6 6BB
!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
subroutine relaxation_profile(tau,p,zero)
  use output_empire, only : emp_e
  use pf_control
  implicit none
  integer, parameter :: rk = kind(1.0d0)
  real(kind=rk), intent(in) :: tau
  real(kind=rk), intent(out) :: p
  logical, intent(out) :: zero

  select case (pf%relaxation_type)
  case ('zero_linear')
     if ( tau < pf%relaxation_freetime ) then
        p = 0.0d0
        zero = .true.
     else
        p = pf%nudgefac*(tau-pf%relaxation_freetime)/(1.0d0-pf&
             &%relaxation_freetime)
        zero = .false.
     end if
  case ('power_law')
     if ( tau < pf%relaxation_freetime ) then
        p = 0.0d0
        zero = .true.
     else
        p = pf%nudgefac * ((tau-pf%relaxation_freetime)/(1.0d0-pf&
             &%relaxation_freetime))**pf%power_law_p
     end if
  case ('exponential')
     if ( tau < pf%relaxation_freetime ) then
        p = 0.0d0
        zero = .true.
     else
        p = pf%nudgefac*(exp( (tau-pf%relaxation_freetime)/(1.0d0-pf&
             &%relaxation_freetime) ) - 1 )/exp(1.0d0)
        zero = .false.
     end if
  case ('constant')
     if ( tau < pf%relaxation_freetime ) then
        p = 0.0d0
        zero = .true.
     else
        p = pf%nudgefac
        zero = .false.
     end if
  case ('user')
     call user_relaxation_profile(tau,p,zero)
  case default
     write(emp_e,*) 'Wrong relaxation profile'
  end select
end subroutine relaxation_profile