source: palm/trunk/SOURCE/lpm_droplet_condensation.f90 @ 1182

 SUBROUTINE lpm_droplet_condensation

!--------------------------------------------------------------------------------!
! This file is part of PALM.
!
! PALM 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.
!
! PALM 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
! PALM. If not, see <http://www.gnu.org/licenses/>.
!
! Copyright 1997-2012  Leibniz University Hannover
!--------------------------------------------------------------------------------!
!
! Current revisions:
! ------------------
! 
!
! Former revisions:
! -----------------
! $Id: lpm_droplet_condensation.f90 1093 2013-02-02 12:58:49Z raasch $
!
! 1092 2013-02-02 11:24:22Z raasch
! unused variables removed
!
! 1071 2012-11-29 16:54:55Z franke
! Ventilation effect for evaporation of large droplets included
! Check for unreasonable results included in calculation of Rosenbrock method
! since physically unlikely results were observed and for the same
! reason the first internal time step in Rosenbrock method should be < 1.0E02 in
! case of evaporation
! Unnecessary calculation of ql_int removed
! Unnecessary calculations in Rosenbrock method (d2rdt2, drdt_m, dt_ros_last)
! removed
! Bugfix: factor in calculation of surface tension changed from 0.00155 to
! 0.000155
!
! 1036 2012-10-22 13:43:42Z raasch
! code put under GPL (PALM 3.9)
!
! 849 2012-03-15 10:35:09Z raasch
! initial revision (former part of advec_particles)
!
!
! Description:
! ------------
! Calculates change in droplet radius by condensation/evaporation, using
! either an analytic formula or by numerically integrating the radius growth
! equation including curvature and solution effects using Rosenbrocks method
! (see Numerical recipes in FORTRAN, 2nd edition, p. 731).
! The analytical formula and growth equation follow those given in
! Rogers and Yau (A short course in cloud physics, 3rd edition, p. 102/103).
!------------------------------------------------------------------------------!

    USE arrays_3d
    USE cloud_parameters
    USE constants
    USE control_parameters
    USE cpulog
    USE grid_variables
    USE interfaces
    USE lpm_collision_kernels_mod
    USE particle_attributes

    IMPLICIT NONE

    INTEGER ::  i, internal_timestep_count, j, jtry, k, n, ros_count

    INTEGER, PARAMETER ::  maxtry = 40

    LOGICAL ::  repeat

    REAL ::  aa, afactor, arg, bb, cc, dd, ddenom, delta_r, drdt, drdt_ini,    &
             dt_ros, dt_ros_next, dt_ros_sum, dt_ros_sum_ini, d2rdtdr, errmax, &
             err_ros, g1, g2, g3, g4, e_a, e_s, gg, new_r, p_int, pt_int,      &
             pt_int_l, pt_int_u, q_int, q_int_l, q_int_u, r_ros, r_ros_ini,    &
             sigma, t_int, x, y, re_p

!
!-- Parameters for Rosenbrock method
    REAL, PARAMETER ::  a21 = 2.0, a31 = 48.0/25.0, a32 = 6.0/25.0,        &
                        b1 = 19.0/9.0, b2 = 0.5, b3 = 25.0/108.0,          &
                        b4 = 125.0/108.0, c21 = -8.0, c31 = 372.0/25.0,    &
                        c32 = 12.0/5.0, c41 = -112.0/125.0,                &
                        c42 = -54.0/125.0, c43 = -2.0/5.0,                 &
                        errcon = 0.1296, e1 = 17.0/54.0, e2 = 7.0/36.0,    &
                        e3 = 0.0, e4 = 125.0/108.0, gam = 0.5, grow = 1.5, &
                        pgrow = -0.25, pshrnk = -1.0/3.0, shrnk = 0.5


    CALL cpu_log( log_point_s(42), 'lpm_droplet_condens', 'start' )

    DO  n = 1, number_of_particles
!
!--    Interpolate temperature and humidity.
!--    First determine left, south, and bottom index of the arrays.
       i = particles(n)%x * ddx
       j = particles(n)%y * ddy
       k = ( particles(n)%z + 0.5 * dz * atmos_ocean_sign ) / dz  &
           + offset_ocean_nzt                     ! only exact if equidistant

       x  = particles(n)%x - i * dx
       y  = particles(n)%y - j * dy
       aa = x**2          + y**2
       bb = ( dx - x )**2 + y**2
       cc = x**2          + ( dy - y )**2
       dd = ( dx - x )**2 + ( dy - y )**2
       gg = aa + bb + cc + dd

       pt_int_l = ( ( gg - aa ) * pt(k,j,i)   + ( gg - bb ) * pt(k,j,i+1)   &
                  + ( gg - cc ) * pt(k,j+1,i) + ( gg - dd ) * pt(k,j+1,i+1) &
                  ) / ( 3.0 * gg )

       pt_int_u = ( ( gg-aa ) * pt(k+1,j,i)   + ( gg-bb ) * pt(k+1,j,i+1)   &
                  + ( gg-cc ) * pt(k+1,j+1,i) + ( gg-dd ) * pt(k+1,j+1,i+1) &
                  ) / ( 3.0 * gg )

       pt_int = pt_int_l + ( particles(n)%z - zu(k) ) / dz * &
                           ( pt_int_u - pt_int_l )

       q_int_l = ( ( gg - aa ) * q(k,j,i)   + ( gg - bb ) * q(k,j,i+1)   &
                 + ( gg - cc ) * q(k,j+1,i) + ( gg - dd ) * q(k,j+1,i+1) &
                 ) / ( 3.0 * gg )

       q_int_u = ( ( gg-aa ) * q(k+1,j,i)   + ( gg-bb ) * q(k+1,j,i+1)   &
                 + ( gg-cc ) * q(k+1,j+1,i) + ( gg-dd ) * q(k+1,j+1,i+1) &
                 ) / ( 3.0 * gg )

       q_int = q_int_l + ( particles(n)%z - zu(k) ) / dz * &
                           ( q_int_u - q_int_l )

!
!--    Calculate real temperature and saturation vapor pressure
       p_int = hyp(k) + ( particles(n)%z - zu(k) ) / dz * ( hyp(k+1)-hyp(k) )
       t_int = pt_int * ( p_int / 100000.0 )**0.286

       e_s = 611.0 * EXP( l_d_rv * ( 3.6609E-3 - 1.0 / t_int ) )

!
!--    Current vapor pressure
       e_a = q_int * p_int / ( 0.378 * q_int + 0.622 )

!
!--    Thermal conductivity for water (from Rogers and Yau, Table 7.1),
!--    diffusivity for water vapor (after Hall und Pruppacher, 1976)
       thermal_conductivity_l = 7.94048E-05 * t_int + 0.00227011 
       diff_coeff_l           = 0.211E-4 * ( t_int / 273.15 )**1.94 * &
                                ( 101325.0 / p_int)
!
!--    Change in radius by condensation/evaporation
       IF ( particles(n)%radius >= 4.0E-5  .AND.  e_a/e_s < 1.0 )  THEN
!
!--       Approximation for large radii, where curvature and solution effects
!--       can be neglected but ventilation effect has to be included in case of
!--       evaporation.
!--       First calculate the droplet's Reynolds number
          re_p = 2.0 * particles(n)%radius * ABS( particles(n)%speed_z ) / &
                 molecular_viscosity
!
!--       Ventilation coefficient after Rogers and Yau, 1989
          IF ( re_p > 2.5 )  THEN
             afactor = 0.78 + 0.28 * SQRT( re_p )
          ELSE
             afactor = 1.0 + 0.09 * re_p
          ENDIF

          arg = particles(n)%radius**2 + 2.0 * dt_3d * afactor *              &
                           ( e_a / e_s - 1.0 ) /                              &
                           ( ( l_d_rv / t_int - 1.0 ) * l_v * rho_l / t_int / &
                             thermal_conductivity_l +                         &
                             rho_l * r_v * t_int / diff_coeff_l / e_s )

          new_r = SQRT( arg )

       ELSEIF ( particles(n)%radius >= 1.0E-6  .OR.  &
                .NOT. curvature_solution_effects )  THEN
!
!--       Approximation for larger radii in case that curvature and solution
!--       effects are neglected and ventilation effects does not play a role
          arg = particles(n)%radius**2 + 2.0 * dt_3d *                        &
                           ( e_a / e_s - 1.0 ) /                              &
                           ( ( l_d_rv / t_int - 1.0 ) * l_v * rho_l / t_int / &
                             thermal_conductivity_l +                         &
                             rho_l * r_v * t_int / diff_coeff_l / e_s )
          IF ( arg < 1.0E-16 )  THEN
             new_r = 1.0E-8
          ELSE
             new_r = SQRT( arg )
          ENDIF
       ENDIF

       IF ( curvature_solution_effects  .AND.                              &
            ( ( particles(n)%radius < 1.0E-6 ) .OR. ( new_r < 1.0E-6 ) ) ) &
       THEN
!
!--       Curvature and solutions effects are included in growth equation.
!--       Change in Radius is calculated with 4th-order Rosenbrock method
!--       for stiff o.d.e's with monitoring local truncation error to adjust
!--       stepsize (see Numerical recipes in FORTRAN, 2nd edition, p. 731).
!--       For larger radii the simple analytic method (see ELSE) gives
!--       almost the same results.

          ros_count = 0
          repeat = .TRUE.
!
!--       Carry out the Rosenbrock algorithm. In case of unreasonable results
!--       the switch "repeat" will be set true and the algorithm will be carried
!--       out again with the internal time step set to its initial (small) value.
!--       Unreasonable results may occur if the external conditions, especially the
!--       supersaturation, has significantly changed compared to the last PALM
!--       timestep.
          DO WHILE ( repeat )

             repeat = .FALSE.
!
!--          Surface tension after (Straka, 2009)
             sigma = 0.0761 - 0.000155 * ( t_int - 273.15 )

             r_ros = particles(n)%radius
             dt_ros_sum  = 0.0      ! internal integrated time (s)
             internal_timestep_count = 0

             ddenom  = 1.0 / ( rho_l * r_v * t_int / ( e_s * diff_coeff_l ) +  &
                               ( l_v / ( r_v * t_int ) - 1.0 ) *               &
                               rho_l * l_v / ( thermal_conductivity_l * t_int )&
                             )

             afactor = 2.0 * sigma / ( rho_l * r_v * t_int )

!
!--          Take internal time step values from the end of last PALM time step
             dt_ros_next = particles(n)%rvar1

!
!--          Internal time step should not be > 1.0E-2 in case of evaporation
!--          because larger values may lead to secondary solutions which are
!--          physically unlikely
             IF ( dt_ros_next > 1.0E-2  .AND.  e_a/e_s < 1.0 )  THEN
                dt_ros_next = 1.0E-3
             ENDIF
!
!--          If calculation of Rosenbrock method is repeated due to unreasonalble
!--          results during previous try the initial internal time step has to be
!--          reduced
             IF ( ros_count > 1 )  THEN
                dt_ros_next = dt_ros_next - ( 0.2 * dt_ros_next )
             ELSEIF ( ros_count > 5 )  THEN
!
!--             Prevent creation of infinite loop
                message_string = 'ros_count > 5 in Rosenbrock method'
                CALL message( 'lpm_droplet_condensation', 'PA0018', 2, 2, &
                               0, 6, 0 )
             ENDIF

!
!--          Internal time step must not be larger than PALM time step
             dt_ros = MIN( dt_ros_next, dt_3d )
!
!--          Integrate growth equation in time unless PALM time step is reached
             DO WHILE ( dt_ros_sum < dt_3d )

                internal_timestep_count = internal_timestep_count + 1

!
!--             Derivative at starting value
                drdt = ddenom / r_ros * ( e_a / e_s - 1.0 - afactor / r_ros + &
                                          bfactor / r_ros**3 )
                drdt_ini       = drdt
                dt_ros_sum_ini = dt_ros_sum
                r_ros_ini      = r_ros

!
!--             Calculate radial derivative of dr/dt
                d2rdtdr = ddenom * ( ( 1.0 - e_a/e_s ) / r_ros**2 + &
                                     2.0 * afactor / r_ros**3 -     &
                                     4.0 * bfactor / r_ros**5 )
!
!--             Adjust stepsize unless required accuracy is reached
                DO  jtry = 1, maxtry+1

                   IF ( jtry == maxtry+1 )  THEN
                      message_string = 'maxtry > 40 in Rosenbrock method'
                      CALL message( 'lpm_droplet_condensation', 'PA0347', 2, 2, &
                                    0, 6, 0 )
                   ENDIF

                   aa    = 1.0 / ( gam * dt_ros ) - d2rdtdr
                   g1    = drdt_ini / aa
                   r_ros = r_ros_ini + a21 * g1
                   drdt  = ddenom / r_ros * ( e_a / e_s - 1.0 - &
                                              afactor / r_ros + &
                                              bfactor / r_ros**3 )

                   g2    = ( drdt + c21 * g1 / dt_ros )&
                           / aa
                   r_ros = r_ros_ini + a31 * g1 + a32 * g2
                   drdt  = ddenom / r_ros * ( e_a / e_s - 1.0 - &
                                              afactor / r_ros + &
                                              bfactor / r_ros**3 )

                   g3    = ( drdt +  &
                             ( c31 * g1 + c32 * g2 ) / dt_ros ) / aa
                   g4    = ( drdt +  &
                             ( c41 * g1 + c42 * g2 + c43 * g3 ) / dt_ros ) / aa
                   r_ros = r_ros_ini + b1 * g1 + b2 * g2 + b3 * g3 + b4 * g4

                   dt_ros_sum = dt_ros_sum_ini + dt_ros

                   IF ( dt_ros_sum == dt_ros_sum_ini )  THEN
                      message_string = 'zero stepsize in Rosenbrock method'
                      CALL message( 'lpm_droplet_condensation', 'PA0348', 2, 2, &
                                    0, 6, 0 )
                   ENDIF
!
!--                Calculate error
                   err_ros = e1*g1 + e2*g2 + e3*g3 + e4*g4
                   errmax  = 0.0
                   errmax  = MAX( errmax, ABS( err_ros / r_ros_ini ) ) / eps_ros
!
!--                Leave loop if accuracy is sufficient, otherwise try again
!--                with a reduced stepsize
                   IF ( errmax <= 1.0 )  THEN
                      EXIT
                   ELSE
                      dt_ros = SIGN( MAX( ABS( 0.9 * dt_ros * errmax**pshrnk ), &
                                          shrnk * ABS( dt_ros ) ), dt_ros )
                   ENDIF

                ENDDO  ! loop for stepsize adjustment

!
!--             Calculate next internal time step
                IF ( errmax > errcon )  THEN
                   dt_ros_next = 0.9 * dt_ros * errmax**pgrow
                ELSE
                   dt_ros_next = grow * dt_ros
                ENDIF

!
!--             Estimated time step is reduced if the PALM time step is exceeded
                IF ( ( dt_ros_next + dt_ros_sum ) >= dt_3d )  THEN
                   dt_ros = dt_3d - dt_ros_sum
                ELSE
                   dt_ros = dt_ros_next
                ENDIF

             ENDDO
!
!--          Store internal time step value for next PALM step
             particles(n)%rvar1 = dt_ros_next

             new_r = r_ros
!
!--          Radius should not fall below 1E-8 because Rosenbrock method may
!--          lead to errors otherwise
             new_r = MAX( new_r, 1.0E-8 )
!
!--          Check if calculated droplet radius change is reasonable since in
!--          case of droplet evaporation the Rosenbrock method may lead to
!--          secondary solutions which are physically unlikely.
!--          Due to the solution effect the droplets may grow for relative
!--          humidities below 100%, but change of radius should not be too large.
!--          In case of unreasonable droplet growth the Rosenbrock method is
!--          recalculated using a smaller initial time step.
!--          Limiting values are tested for droplets down to 1.0E-7
             IF ( new_r - particles(n)%radius >= 3.0E-7  .AND.  &
                  e_a/e_s < 0.97 )  THEN
                ros_count = ros_count + 1
                repeat = .TRUE.
             ENDIF

          ENDDO    ! Rosenbrock method

       ENDIF

       delta_r = new_r - particles(n)%radius

!
!--    Sum up the change in volume of liquid water for the respective grid
!--    volume (this is needed later in lpm_calc_liquid_water_content for
!--    calculating the release of latent heat)
       i = ( particles(n)%x + 0.5 * dx ) * ddx
       j = ( particles(n)%y + 0.5 * dy ) * ddy
       k = particles(n)%z / dz + 1 + offset_ocean_nzt_m1
           ! only exact if equidistant

       ql_c(k,j,i) = ql_c(k,j,i) + particles(n)%weight_factor *            &
                                   rho_l * 1.33333333 * pi *               &
                                   ( new_r**3 - particles(n)%radius**3 ) / &
                                   ( rho_surface * dx * dy * dz )
       IF ( ql_c(k,j,i) > 100.0 )  THEN
          WRITE( message_string, * ) 'k=',k,' j=',j,' i=',i,      &
                       ' ql_c=',ql_c(k,j,i), ' &part(',n,')%wf=', &
                       particles(n)%weight_factor,' delta_r=',delta_r
          CALL message( 'lpm_droplet_condensation', 'PA0143', 2, 2, -1, 6, 1 )
       ENDIF

!
!--    Change the droplet radius
       IF ( ( new_r - particles(n)%radius ) < 0.0  .AND.  new_r < 0.0 ) &
       THEN
          WRITE( message_string, * ) '#1 k=',k,' j=',j,' i=',i,   &
                       ' e_s=',e_s, ' e_a=',e_a,' t_int=',t_int,  &
                       ' &delta_r=',delta_r,                      &
                       ' particle_radius=',particles(n)%radius
          CALL message( 'lpm_droplet_condensation', 'PA0144', 2, 2, -1, 6, 1 )
       ENDIF

!
!--    Sum up the total volume of liquid water (needed below for
!--    re-calculating the weighting factors)
       ql_v(k,j,i) = ql_v(k,j,i) + particles(n)%weight_factor * new_r**3

       particles(n)%radius = new_r

!
!--    Determine radius class of the particle needed for collision
       IF ( ( hall_kernel  .OR.  wang_kernel )  .AND.  use_kernel_tables ) &
       THEN
          particles(n)%class = ( LOG( new_r ) - rclass_lbound ) /  &
                               ( rclass_ubound - rclass_lbound ) * &
                               radius_classes
          particles(n)%class = MIN( particles(n)%class, radius_classes )
          particles(n)%class = MAX( particles(n)%class, 1 )
       ENDIF

    ENDDO

    CALL cpu_log( log_point_s(42), 'lpm_droplet_condens', 'stop' )


 END SUBROUTINE lpm_droplet_condensation