source: palm/trunk/SOURCE/lpm_droplet_collision.f90 @ 2375

Last change on this file since 2375 was 2375, checked in by schwenkel, 4 years ago

improved aerosol initialization for bulk microphysics

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1!> @file lpm_droplet_collision.f90
2!------------------------------------------------------------------------------!
3! This file is part of PALM.
4!
5! PALM is free software: you can redistribute it and/or modify it under the
6! terms of the GNU General Public License as published by the Free Software
7! Foundation, either version 3 of the License, or (at your option) any later
8! version.
9!
10! PALM is distributed in the hope that it will be useful, but WITHOUT ANY
11! WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
12! A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
13!
14! You should have received a copy of the GNU General Public License along with
15! PALM. If not, see <http://www.gnu.org/licenses/>.
16!
17! Copyright 1997-2017 Leibniz Universitaet Hannover
18!------------------------------------------------------------------------------!
19!
20! Current revisions:
21! ------------------
22!
23!
24! Former revisions:
25! -----------------
26! $Id: lpm_droplet_collision.f90 2375 2017-08-29 14:10:28Z schwenkel $
27! Changed ONLY-dependencies
28!
29! 2312 2017-07-14 20:26:51Z hoffmann
30! Consideration of aerosol mass during collision. Average impact algorithm has
31! been removed.
32!
33! 2274 2017-06-09 13:27:48Z Giersch
34! Changed error messages
35!
36! 2123 2017-01-18 12:34:59Z hoffmann
37!
38! 2122 2017-01-18 12:22:54Z hoffmann
39! Some reformatting of the code.
40!
41! 2000 2016-08-20 18:09:15Z knoop
42! Forced header and separation lines into 80 columns
43!
44! 1884 2016-04-21 11:11:40Z hoffmann
45! Conservation of mass should only be checked if collisions took place.
46!
47! 1860 2016-04-13 13:21:28Z hoffmann
48! Interpolation of dissipation rate adjusted to more reasonable values.
49!
50! 1822 2016-04-07 07:49:42Z hoffmann
51! Integration of a new collision algortithm based on Shima et al. (2009) and
52! Soelch and Kaercher (2010) called all_or_nothing. The previous implemented
53! collision algorithm is called average_impact. Moreover, both algorithms are
54! now positive definit due to their construction, i.e., no negative weighting
55! factors should occur.
56!
57! 1682 2015-10-07 23:56:08Z knoop
58! Code annotations made doxygen readable
59!
60! 1359 2014-04-11 17:15:14Z hoffmann
61! New particle structure integrated.
62! Kind definition added to all floating point numbers.
63!
64! 1322 2014-03-20 16:38:49Z raasch
65! REAL constants defined as wp_kind
66!
67! 1320 2014-03-20 08:40:49Z raasch
68! ONLY-attribute added to USE-statements,
69! kind-parameters added to all INTEGER and REAL declaration statements,
70! kinds are defined in new module kinds,
71! revision history before 2012 removed,
72! comment fields (!:) to be used for variable explanations added to
73! all variable declaration statements
74!
75! 1092 2013-02-02 11:24:22Z raasch
76! unused variables removed
77!
78! 1071 2012-11-29 16:54:55Z franke
79! Calculation of Hall and Wang kernel now uses collision-coalescence formulation
80! proposed by Wang instead of the continuous collection equation (for more
81! information about new method see PALM documentation)
82! Bugfix: message identifiers added
83!
84! 1036 2012-10-22 13:43:42Z raasch
85! code put under GPL (PALM 3.9)
86!
87! 849 2012-03-15 10:35:09Z raasch
88! initial revision (former part of advec_particles)
89!
90!
91! Description:
92! ------------
93!> Calculates change in droplet radius by collision. Droplet collision is
94!> calculated for each grid box seperately. Collision is parameterized by
95!> using collision kernels. Two different kernels are available:
96!> Hall kernel: Kernel from Hall (1980, J. Atmos. Sci., 2486-2507), which
97!>              considers collision due to pure gravitational effects.
98!> Wang kernel: Beside gravitational effects (treated with the Hall-kernel) also
99!>              the effects of turbulence on the collision are considered using
100!>              parameterizations of Ayala et al. (2008, New J. Phys., 10,
101!>              075015) and Wang and Grabowski (2009, Atmos. Sci. Lett., 10,
102!>              1-8). This kernel includes three possible effects of turbulence:
103!>              the modification of the relative velocity between the droplets,
104!>              the effect of preferential concentration, and the enhancement of
105!>              collision efficiencies.
106!------------------------------------------------------------------------------!
107 SUBROUTINE lpm_droplet_collision (i,j,k)
108
109    USE arrays_3d,                                                             &
110        ONLY:  diss, ql_v, ql_vp
111
112    USE cloud_parameters,                                                      &
113        ONLY:  rho_l, rho_s
114
115    USE constants,                                                             &
116        ONLY:  pi
117
118    USE control_parameters,                                                    &
119        ONLY:  dt_3d, message_string, dz
120
121    USE cpulog,                                                                &
122        ONLY:  cpu_log, log_point_s
123
124    USE grid_variables,                                                        &
125        ONLY:  dx, dy
126
127    USE kinds
128
129    USE lpm_collision_kernels_mod,                                             &
130        ONLY:  ckernel, recalculate_kernel
131
132    USE particle_attributes,                                                   &
133        ONLY:  curvature_solution_effects, dissipation_classes, hall_kernel,   &
134               iran_part, number_of_particles, particles, particle_type,       &
135               prt_count, use_kernel_tables, wang_kernel
136
137    USE random_function_mod,                                                   &
138        ONLY:  random_function
139
140    USE pegrid
141
142    IMPLICIT NONE
143
144    INTEGER(iwp) ::  eclass   !<
145    INTEGER(iwp) ::  i        !<
146    INTEGER(iwp) ::  j        !<
147    INTEGER(iwp) ::  k        !<
148    INTEGER(iwp) ::  n        !<
149    INTEGER(iwp) ::  m        !<
150    INTEGER(iwp) ::  rclass_l !<
151    INTEGER(iwp) ::  rclass_s !<
152
153    REAL(wp) ::  collection_probability  !< probability for collection
154    REAL(wp) ::  ddV                     !< inverse grid box volume
155    REAL(wp) ::  epsilon                 !< dissipation rate
156    REAL(wp) ::  factor_volume_to_mass   !< 4.0 / 3.0 * pi * rho_l
157    REAL(wp) ::  xm                      !< droplet mass of super-droplet m
158    REAL(wp) ::  xn                      !< droplet mass of super-droplet n
159    REAL(wp) ::  xsm                     !< aerosol mass of super-droplet m
160    REAL(wp) ::  xsn                     !< aerosol mass of super-droplet n
161
162    REAL(wp), DIMENSION(:), ALLOCATABLE ::  weight    !< weighting factor
163    REAL(wp), DIMENSION(:), ALLOCATABLE ::  mass      !< total mass of super droplet
164    REAL(wp), DIMENSION(:), ALLOCATABLE ::  aero_mass !< total aerosol mass of super droplet
165
166    CALL cpu_log( log_point_s(43), 'lpm_droplet_coll', 'start' )
167
168    number_of_particles   = prt_count(k,j,i)
169    factor_volume_to_mass = 4.0_wp / 3.0_wp * pi * rho_l
170    ddV                   = 1.0_wp / ( dx * dy * dz )
171!
172!-- Collision requires at least one super droplet inside the box
173    IF ( number_of_particles > 0 )  THEN
174
175       IF ( use_kernel_tables )  THEN
176!
177!--       Fast method with pre-calculated collection kernels for
178!--       discrete radius- and dissipation-classes.
179          IF ( wang_kernel )  THEN
180             eclass = INT( diss(k,j,i) * 1.0E4_wp / 600.0_wp * &
181                           dissipation_classes ) + 1
182             epsilon = diss(k,j,i)
183          ELSE
184             epsilon = 0.0_wp
185          ENDIF
186
187          IF ( hall_kernel  .OR.  epsilon * 1.0E4_wp < 0.001_wp )  THEN
188             eclass = 0   ! Hall kernel is used
189          ELSE
190             eclass = MIN( dissipation_classes, eclass )
191          ENDIF
192
193       ELSE
194!
195!--       Collection kernels are re-calculated for every new
196!--       grid box. First, allocate memory for kernel table.
197!--       Third dimension is 1, because table is re-calculated for
198!--       every new dissipation value.
199          ALLOCATE( ckernel(1:number_of_particles,1:number_of_particles,1:1) )
200!
201!--       Now calculate collection kernel for this box. Note that
202!--       the kernel is based on the previous time step
203          CALL recalculate_kernel( i, j, k )
204
205       ENDIF
206!
207!--    Temporary fields for total mass of super-droplet, aerosol mass, and
208!--    weighting factor are allocated.
209       ALLOCATE(mass(1:number_of_particles), weight(1:number_of_particles))
210       IF ( curvature_solution_effects )  ALLOCATE(aero_mass(1:number_of_particles))
211
212       mass(1:number_of_particles)   = particles(1:number_of_particles)%weight_factor * &
213                                       particles(1:number_of_particles)%radius**3     * &
214                                       factor_volume_to_mass
215
216       weight(1:number_of_particles) = particles(1:number_of_particles)%weight_factor
217
218       IF ( curvature_solution_effects )  THEN
219          aero_mass(1:number_of_particles) = particles(1:number_of_particles)%weight_factor * &
220                                             particles(1:number_of_particles)%aux1**3       * &
221                                             4.0 / 3.0 * pi * rho_s
222       ENDIF
223!
224!--    Calculate collision/coalescence
225       DO  n = 1, number_of_particles
226
227          DO  m = n, number_of_particles
228!
229!--          For collisions, the weighting factor of at least one super-droplet
230!--          needs to be larger or equal to one.
231             IF ( MIN( weight(n), weight(m) ) .LT. 1.0 )  CYCLE
232!
233!--          Get mass of individual droplets (aerosols)
234             xn = mass(n) / weight(n)
235             xm = mass(m) / weight(m)
236             IF ( curvature_solution_effects )  THEN
237                xsn = aero_mass(n) / weight(n)
238                xsm = aero_mass(m) / weight(m)
239             ENDIF
240!
241!--          Probability that the necessary collisions take place
242             IF ( use_kernel_tables )  THEN
243                rclass_l = particles(n)%class
244                rclass_s = particles(m)%class
245
246                collection_probability  = MAX( weight(n), weight(m) ) *     &
247                                          ckernel(rclass_l,rclass_s,eclass) * ddV * dt_3d
248             ELSE
249                collection_probability  = MAX( weight(n), weight(m) ) *     &
250                                          ckernel(n,m,1) * ddV * dt_3d
251             ENDIF
252!
253!--          Calculate the number of collections and consider multiple collections.
254!--          (Accordingly, p_crit will be 0.0, 1.0, 2.0, ...)
255             IF ( collection_probability - FLOOR(collection_probability)    &
256                  .GT. random_function( iran_part ) )  THEN
257                collection_probability = FLOOR(collection_probability) + 1.0_wp
258             ELSE
259                collection_probability = FLOOR(collection_probability)
260             ENDIF
261
262             IF ( collection_probability .GT. 0.0 )  THEN
263!
264!--             Super-droplet n collects droplets of super-droplet m
265                IF ( weight(n) .LT. weight(m) )  THEN
266
267                   mass(n)   = mass(n)   + weight(n) * xm * collection_probability
268                   weight(m) = weight(m) - weight(n)      * collection_probability
269                   mass(m)   = mass(m)   - weight(n) * xm * collection_probability
270                   IF ( curvature_solution_effects )  THEN
271                      aero_mass(n) = aero_mass(n) + weight(n) * xsm * collection_probability
272                      aero_mass(m) = aero_mass(m) - weight(n) * xsm * collection_probability
273                   ENDIF
274
275                ELSEIF ( weight(m) .LT. weight(n) )  THEN
276
277                   mass(m)   = mass(m)   + weight(m) * xn * collection_probability
278                   weight(n) = weight(n) - weight(m)      * collection_probability
279                   mass(n)   = mass(n)   - weight(m) * xn * collection_probability
280                   IF ( curvature_solution_effects )  THEN
281                      aero_mass(m) = aero_mass(m) + weight(m) * xsn * collection_probability
282                      aero_mass(n) = aero_mass(n) - weight(m) * xsn * collection_probability
283                   ENDIF
284
285                ELSE
286!
287!--                Collisions of particles of the same weighting factor.
288!--                Particle n collects 1/2 weight(n) droplets of particle m,
289!--                particle m collects 1/2 weight(m) droplets of particle n.
290!--                The total mass mass changes accordingly.
291!--                If n = m, the first half of the droplets coalesces with the
292!--                second half of the droplets; mass is unchanged because
293!--                xm = xn for n = m.
294!--
295!--                Note: For m = n this equation is an approximation only
296!--                valid for weight >> 1 (which is usually the case). The
297!--                approximation is weight(n)-1 = weight(n).
298                   mass(n)   = mass(n)   + 0.5_wp * weight(n) * ( xm - xn )
299                   mass(m)   = mass(m)   + 0.5_wp * weight(m) * ( xn - xm )
300                   IF ( curvature_solution_effects )  THEN
301                      aero_mass(n) = aero_mass(n) + 0.5_wp * weight(n) * ( xsm - xsn )
302                      aero_mass(m) = aero_mass(m) + 0.5_wp * weight(m) * ( xsn - xsm )
303                   ENDIF
304                   weight(n) = weight(n) - 0.5_wp * weight(m)
305                   weight(m) = weight(n)
306
307                ENDIF
308
309             ENDIF
310
311          ENDDO
312
313          ql_vp(k,j,i) = ql_vp(k,j,i) + mass(n) / factor_volume_to_mass
314
315       ENDDO
316
317       IF ( ANY(weight < 0.0_wp) )  THEN
318             WRITE( message_string, * ) 'negative weighting factor'
319             CALL message( 'lpm_droplet_collision', 'PA0028',      &
320                            2, 2, -1, 6, 1 )
321       ENDIF
322
323       particles(1:number_of_particles)%radius = ( mass(1:number_of_particles) /   &
324                                                   ( weight(1:number_of_particles) &
325                                                     * factor_volume_to_mass       &
326                                                   )                               &
327                                                 )**0.33333333333333_wp
328
329       IF ( curvature_solution_effects )  THEN
330          particles(1:number_of_particles)%aux1 = ( aero_mass(1:number_of_particles) / &
331                                                    ( weight(1:number_of_particles)    &
332                                                      * 4.0_wp / 3.0_wp * pi * rho_s   &
333                                                    )                                  &
334                                                  )**0.33333333333333_wp
335       ENDIF
336
337       particles(1:number_of_particles)%weight_factor = weight(1:number_of_particles)
338
339       DEALLOCATE( weight, mass )
340       IF ( curvature_solution_effects )  DEALLOCATE( aero_mass )
341       IF ( .NOT. use_kernel_tables )  DEALLOCATE( ckernel )
342
343!
344!--    Check if LWC is conserved during collision process
345       IF ( ql_v(k,j,i) /= 0.0_wp )  THEN
346          IF ( ql_vp(k,j,i) / ql_v(k,j,i) >= 1.0001_wp  .OR.                      &
347               ql_vp(k,j,i) / ql_v(k,j,i) <= 0.9999_wp )  THEN
348             WRITE( message_string, * ) ' LWC is not conserved during',           &
349                                        ' collision! ',                           &
350                                        ' LWC after condensation: ', ql_v(k,j,i), &
351                                        ' LWC after collision: ', ql_vp(k,j,i)
352             CALL message( 'lpm_droplet_collision', 'PA0040', 2, 2, -1, 6, 1 )
353          ENDIF
354       ENDIF
355
356    ENDIF
357
358    CALL cpu_log( log_point_s(43), 'lpm_droplet_coll', 'stop' )
359
360 END SUBROUTINE lpm_droplet_collision
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