creep.F90

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!+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
!
!  Function :  c r e e p
!
!> @file
!!
!! Creep response function for ice.
!!
!! @section Copyright
!!
!! Copyright 2009-2016 Ralf Greve
!!
!! @section License
!!
!! This file is part of SICOPOLIS.
!!
!! SICOPOLIS 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.
!!
!! SICOPOLIS 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 SICOPOLIS.  If not, see <http://www.gnu.org/licenses/>.
!<
!+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

!-------------------------------------------------------------------------------
!> Creep response function for ice.
!<------------------------------------------------------------------------------
function creep(sigma_val)

use sico_types
use sico_variables
use sico_vars

implicit none

real(dp)             :: creep
real(dp), intent(in) :: sigma_val

#if (FLOW_LAW==4)
real(dp), parameter :: sm_coeff_1 = 8.5112e-15_dp, &   ! s^-1 Pa^-1
                       sm_coeff_2 = 8.1643e-25_dp, &   ! s^-1 Pa^-3
                       sm_coeff_3 = 9.2594e-12_dp      ! Pa^-2
#endif

#if (FIN_VISC==1)

#if (FLOW_LAW==1)

creep = sigma_val*sigma_val
!       Glen's flow law (n=3)

#elif (FLOW_LAW==2)

creep = sigma_val**0.8_dp * gr_size**(-1.4_dp)
!       Goldsby-Kohlstedt flow law (n=1.8, d=1.4)

#elif (FLOW_LAW==3)

creep = sigma_val*sigma_val*sigma_val
!       Durham's flow law (n=4)

#endif

#elif (FIN_VISC==2)

#if (FLOW_LAW==1)

creep = sigma_val*sigma_val + sigma_res*sigma_res
!       Glen's flow (n=3) with additional finite viscosity

#elif (FLOW_LAW==2)

creep = (sigma_val**0.8_dp + sigma_res**0.8_dp) * gr_size**(-1.4_dp)
!       Goldsby-Kohlstedt flow law (n=1.8, d=1.4)
!       with additional finite viscosity

#elif (FLOW_LAW==3)

creep = sigma_val*sigma_val*sigma_val + sigma_res*sigma_res*sigma_res
!       Durham's flow law (n=4) with additional finite viscosity

#endif

#endif

#if (FLOW_LAW==4)

creep = sm_coeff_1 &
        + sm_coeff_2 * (sigma_val*sigma_val) &
          * (1.0_dp + sm_coeff_3 * (sigma_val*sigma_val))
!       Smith-Morland (polynomial) flow law, normalised to a dimensionless
!       rate factor with A(-10C)=1.

#endif

end function creep
!