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source: palm/trunk/SOURCE/timestep.f90 @ 3275

Last change on this file since 3275 was 3274, checked in by knoop, 6 years ago
Modularization of all bulk cloud physics code components
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1	!> @file timestep.f90
2	!------------------------------------------------------------------------------!
3	! This file is part of the PALM model system.
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 1997-2018 Leibniz Universitaet Hannover
18	!------------------------------------------------------------------------------!
19	!
20	! Current revisions:
21	! ------------------
22	!
23	!
24	! Former revisions:
25	! -----------------
26	! $Id: timestep.f90 3274 2018-09-24 15:42:55Z knoop $
27	! Modularization of all bulk cloud physics code components
28	!
29	! 3241 2018-09-12 15:02:00Z raasch
30	! unused variables removed
31	!
32	! 3120 2018-07-11 18:30:57Z gronemeier
33	! Put ABS( km ) in computation of time step according to the diffusion criterion
34	!
35	! 3084 2018-06-19 15:30:55Z gronemeier
36	! limit increase of dt_3d only in case of RANS mode
37	!
38	! 3083 2018-06-19 14:03:12Z gronemeier
39	! limit dt_3d to be at maximum 2*old_dt; define old_dt at beginning of routine
40	! Add km/kh_max
41	!
42	! 3049 2018-05-29 13:52:36Z Giersch
43	! Error messages revised
44	!
45	! 3045 2018-05-28 07:55:41Z Giersch
46	! Error message revised
47	!
48	! 2718 2018-01-02 08:49:38Z maronga
49	! Corrected "Former revisions" section
50	!
51	! 2696 2017-12-14 17:12:51Z kanani
52	! Change in file header (GPL part)
53	!
54	! 2365 2017-08-21 14:59:59Z kanani
55	! Vertical grid nesting: Sync fine and coarse grid timestep (SadiqHuq)
56	!
57	! 2258 2017-06-08 07:55:13Z suehring
58	! Bugfix, add pre-preprocessor directives to enable non-parrallel mode
59	!
60	! 2168 2017-03-06 13:08:38Z suehring
61	!
62	! 2130 2017-01-24 16:25:39Z raasch
63	! bugfix: in case of nested runs the stop condition in case of too small
64	! timesteps is communicated to all parent/child processes,
65	! some formatting done
66	!
67	! 2118 2017-01-17 16:38:49Z raasch
68	! OpenACC directives and related part of code removed
69	!
70	! 2000 2016-08-20 18:09:15Z knoop
71	! Forced header and separation lines into 80 columns
72	!
73	! 1849 2016-04-08 11:33:18Z hoffmann
74	! Adapted for modularization of microphysics
75	!
76	! 1682 2015-10-07 23:56:08Z knoop
77	! Code annotations made doxygen readable
78	!
79	! 1484 2014-10-21 10:53:05Z kanani
80	! Changes due to new module structure of the plant canopy model:
81	! calculations and parameters related to the plant canopy model removed
82	! (the limitation of the canopy drag, i.e. that the canopy drag itself should
83	! not change the sign of the velocity components, is now assured for in the
84	! calculation of the canopy tendency terms in subroutine plant_canopy_model)
85	!
86	! 1342 2014-03-26 17:04:47Z kanani
87	! REAL constants defined as wp-kind
88	!
89	! 1322 2014-03-20 16:38:49Z raasch
90	! REAL functions provided with KIND-attribute
91	!
92	! 1320 2014-03-20 08:40:49Z raasch
93	! ONLY-attribute added to USE-statements,
94	! kind-parameters added to all INTEGER and REAL declaration statements,
95	! kinds are defined in new module kinds,
96	! old module precision_kind is removed,
97	! revision history before 2012 removed,
98	! comment fields (!:) to be used for variable explanations added to
99	! all variable declaration statements
100	!
101	! 1257 2013-11-08 15:18:40Z raasch
102	! openacc porting
103	! bugfix for calculation of advective timestep in case of vertically stretched
104	! grids
105	!
106	! 1092 2013-02-02 11:24:22Z raasch
107	! unused variables removed
108	!
109	! 1053 2012-11-13 17:11:03Z hoffmann
110	! timestep is reduced in two-moment cloud scheme according to the maximum
111	! terminal velocity of rain drops
112	!
113	! 1036 2012-10-22 13:43:42Z raasch
114	! code put under GPL (PALM 3.9)
115	!
116	! 1001 2012-09-13 14:08:46Z raasch
117	! all actions concerning leapfrog scheme removed
118	!
119	! 978 2012-08-09 08:28:32Z fricke
120	! restriction of the outflow damping layer in the diffusion criterion removed
121	!
122	! 866 2012-03-28 06:44:41Z raasch
123	! bugfix for timestep calculation in case of Galilei transformation,
124	! special treatment in case of mirror velocity boundary condition removed
125	!
126	! Revision 1.1 1997/08/11 06:26:19 raasch
127	! Initial revision
128	!
129	!
130	! Description:
131	! ------------
132	!> Compute the time step under consideration of the FCL and diffusion criterion.
133	!------------------------------------------------------------------------------!
134	SUBROUTINE timestep
135
136
137	USE arrays_3d, &
138	ONLY: dzu, dzw, kh, km, u, v, w
139
140	USE control_parameters, &
141	ONLY: cfl_factor, coupling_mode, dt_3d, dt_fixed, dt_max, &
142	galilei_transformation, old_dt, message_string, rans_mode, &
143	stop_dt, terminate_coupled, terminate_coupled_remote, &
144	timestep_reason, u_gtrans, use_ug_for_galilei_tr, v_gtrans
145
146	USE cpulog, &
147	ONLY: cpu_log, log_point
148
149	USE grid_variables, &
150	ONLY: dx, dx2, dy, dy2
151
152	USE indices, &
153	ONLY: nxl, nxlg, nxr, nxrg, nyn, nyng, nys, nysg, nzb, nzt
154
155	USE interfaces
156
157	USE kinds
158
159	USE bulk_cloud_model_mod, &
160	ONLY: dt_precipitation
161
162	USE pegrid
163
164	USE pmc_interface, &
165	ONLY: nested_run
166
167	USE statistics, &
168	ONLY: flow_statistics_called, hom, u_max, u_max_ijk, v_max, v_max_ijk,&
169	w_max, w_max_ijk
170
171	USE vertical_nesting_mod, &
172	ONLY: vnested, vnest_timestep_sync
173
174	IMPLICIT NONE
175
176	INTEGER(iwp) :: i !<
177	INTEGER(iwp) :: j !<
178	INTEGER(iwp) :: k !<
179	INTEGER(iwp) :: km_max_ijk(3) = -1 !< index values (i,j,k) of location where km_max occurs
180	INTEGER(iwp) :: kh_max_ijk(3) = -1 !< index values (i,j,k) of location where kh_max occurs
181
182	LOGICAL :: stop_dt_local !< local switch for controlling the time stepping
183
184	REAL(wp) :: div !<
185	REAL(wp) :: dt_diff !<
186	REAL(wp) :: dt_diff_l !<
187	REAL(wp) :: dt_u !<
188	REAL(wp) :: dt_u_l !<
189	REAL(wp) :: dt_v !<
190	REAL(wp) :: dt_v_l !<
191	REAL(wp) :: dt_w !<
192	REAL(wp) :: dt_w_l !<
193	REAL(wp) :: km_max !< maximum of Km in entire domain
194	REAL(wp) :: kh_max !< maximum of Kh in entire domain
195	REAL(wp) :: u_gtrans_l !<
196	REAL(wp) :: v_gtrans_l !<
197
198	REAL(wp), DIMENSION(2) :: uv_gtrans !<
199	REAL(wp), DIMENSION(2) :: uv_gtrans_l !<
200	REAL(wp), DIMENSION(3) :: reduce !<
201	REAL(wp), DIMENSION(3) :: reduce_l !<
202	REAL(wp), DIMENSION(nzb+1:nzt) :: dxyz2_min !<
203
204
205	CALL cpu_log( log_point(12), 'calculate_timestep', 'start' )
206	!
207	!-- Save former time step as reference
208	old_dt = dt_3d
209
210	!
211	!-- In case of Galilei-transform not using the geostrophic wind as translation
212	!-- velocity, compute the volume-averaged horizontal velocity components, which
213	!-- will then be subtracted from the horizontal wind for the time step and
214	!-- horizontal advection routines.
215	IF ( galilei_transformation .AND. .NOT. use_ug_for_galilei_tr ) THEN
216	IF ( flow_statistics_called ) THEN
217	!
218	!-- Horizontal averages already existent, just need to average them
219	!-- vertically.
220	u_gtrans = 0.0_wp
221	v_gtrans = 0.0_wp
222	DO k = nzb+1, nzt
223	u_gtrans = u_gtrans + hom(k,1,1,0)
224	v_gtrans = v_gtrans + hom(k,1,2,0)
225	ENDDO
226	u_gtrans = u_gtrans / REAL( nzt - nzb, KIND=wp )
227	v_gtrans = v_gtrans / REAL( nzt - nzb, KIND=wp )
228	ELSE
229	!
230	!-- Averaging over the entire model domain.
231	u_gtrans_l = 0.0_wp
232	v_gtrans_l = 0.0_wp
233	DO i = nxl, nxr
234	DO j = nys, nyn
235	DO k = nzb+1, nzt
236	u_gtrans_l = u_gtrans_l + u(k,j,i)
237	v_gtrans_l = v_gtrans_l + v(k,j,i)
238	ENDDO
239	ENDDO
240	ENDDO
241	uv_gtrans_l(1) = u_gtrans_l / &
242	REAL( (nxr-nxl+1)(nyn-nys+1)(nzt-nzb), KIND=wp )
243	uv_gtrans_l(2) = v_gtrans_l / &
244	REAL( (nxr-nxl+1)(nyn-nys+1)(nzt-nzb), KIND=wp )
245	#if defined( __parallel )
246	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
247	CALL MPI_ALLREDUCE( uv_gtrans_l, uv_gtrans, 2, MPI_REAL, MPI_SUM, &
248	comm2d, ierr )
249	u_gtrans = uv_gtrans(1) / REAL( numprocs, KIND=wp )
250	v_gtrans = uv_gtrans(2) / REAL( numprocs, KIND=wp )
251	#else
252	u_gtrans = uv_gtrans_l(1)
253	v_gtrans = uv_gtrans_l(2)
254	#endif
255	ENDIF
256	ENDIF
257
258	!
259	!-- Determine the maxima of the velocity components, including their
260	!-- grid index positions.
261	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, u, 'abs', 0.0_wp, &
262	u_max, u_max_ijk )
263	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, v, 'abs', 0.0_wp, &
264	v_max, v_max_ijk )
265	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, w, 'abs', 0.0_wp, &
266	w_max, w_max_ijk )
267
268	IF ( .NOT. dt_fixed ) THEN
269	!
270	!-- Variable time step:
271	!-- Calculate the maximum time step according to the CFL-criterion,
272	!-- individually for each velocity component
273	dt_u_l = 999999.9_wp
274	dt_v_l = 999999.9_wp
275	dt_w_l = 999999.9_wp
276	DO i = nxl, nxr
277	DO j = nys, nyn
278	DO k = nzb+1, nzt
279	dt_u_l = MIN( dt_u_l, ( dx / &
280	( ABS( u(k,j,i) - u_gtrans ) + 1.0E-10_wp ) ) )
281	dt_v_l = MIN( dt_v_l, ( dy / &
282	( ABS( v(k,j,i) - v_gtrans ) + 1.0E-10_wp ) ) )
283	dt_w_l = MIN( dt_w_l, ( dzu(k) / &
284	( ABS( w(k,j,i) ) + 1.0E-10_wp ) ) )
285	ENDDO
286	ENDDO
287	ENDDO
288
289	#if defined( __parallel )
290	reduce_l(1) = dt_u_l
291	reduce_l(2) = dt_v_l
292	reduce_l(3) = dt_w_l
293	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
294	CALL MPI_ALLREDUCE( reduce_l, reduce, 3, MPI_REAL, MPI_MIN, comm2d, ierr )
295	dt_u = reduce(1)
296	dt_v = reduce(2)
297	dt_w = reduce(3)
298	#else
299	dt_u = dt_u_l
300	dt_v = dt_v_l
301	dt_w = dt_w_l
302	#endif
303
304	!
305	!-- Compute time step according to the diffusion criterion.
306	!-- First calculate minimum grid spacing which only depends on index k.
307	!-- When using the dynamic subgrid model, negative km are possible.
308	dt_diff_l = 999999.0_wp
309
310	DO k = nzb+1, nzt
311	dxyz2_min(k) = MIN( dx2, dy2, dzw(k)dzw(k) ) 0.125_wp
312	ENDDO
313
314	!$OMP PARALLEL private(i,j,k) reduction(MIN: dt_diff_l)
315	!$OMP DO
316	DO i = nxl, nxr
317	DO j = nys, nyn
318	DO k = nzb+1, nzt
319	dt_diff_l = MIN( dt_diff_l, dxyz2_min(k) / &
320	( MAX( kh(k,j,i), ABS( km(k,j,i) ) ) &
321	+ 1E-20_wp ) )
322	ENDDO
323	ENDDO
324	ENDDO
325	!$OMP END PARALLEL
326	#if defined( __parallel )
327	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
328	CALL MPI_ALLREDUCE( dt_diff_l, dt_diff, 1, MPI_REAL, MPI_MIN, comm2d, &
329	ierr )
330	#else
331	dt_diff = dt_diff_l
332	#endif
333
334	!
335	!-- The time step is the minimum of the 3-4 components and the diffusion time
336	!-- step minus a reduction (cfl_factor) to be on the safe side.
337	!-- The time step must not exceed the maximum allowed value.
338	dt_3d = cfl_factor * MIN( dt_diff, dt_u, dt_v, dt_w, dt_precipitation )
339	dt_3d = MIN( dt_3d, dt_max )
340	!
341	!-- In RANS mode, the time step must not increase by more than a factor of 2
342	IF ( rans_mode ) dt_3d = MIN( dt_3d, dt_max, 2.0_wp * old_dt )
343
344	!
345	!-- Remember the restricting time step criterion for later output.
346	IF ( MIN( dt_u, dt_v, dt_w ) < dt_diff ) THEN
347	timestep_reason = 'A'
348	ELSE
349	timestep_reason = 'D'
350	ENDIF
351
352	!
353	!-- Set flag if the time step becomes too small.
354	IF ( dt_3d < ( 0.00001_wp * dt_max ) ) THEN
355	stop_dt = .TRUE.
356
357	!
358	!-- Determine the maxima of the diffusion coefficients, including their
359	!-- grid index positions.
360	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, km, 'abs', &
361	0.0_wp, km_max, km_max_ijk )
362	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, kh, 'abs', &
363	0.0_wp, kh_max, kh_max_ijk )
364
365	WRITE( message_string, * ) 'Time step has reached minimum limit.', &
366	'&dt = ', dt_3d, ' s Simulation is terminated.', &
367	'&old_dt = ', old_dt, ' s', &
368	'&dt_u = ', dt_u, ' s', &
369	'&dt_v = ', dt_v, ' s', &
370	'&dt_w = ', dt_w, ' s', &
371	'&dt_diff = ', dt_diff, ' s', &
372	'&u_max = ', u_max, ' m/s k=', u_max_ijk(1), &
373	' j=', u_max_ijk(2), ' i=', u_max_ijk(3), &
374	'&v_max = ', v_max, ' m/s k=', v_max_ijk(1), &
375	' j=', v_max_ijk(2), ' i=', v_max_ijk(3), &
376	'&w_max = ', w_max, ' m/s k=', w_max_ijk(1), &
377	' j=', w_max_ijk(2), ' i=', w_max_ijk(3), &
378	'&km_max = ', km_max, ' m2/s2 k=', km_max_ijk(1), &
379	' j=', km_max_ijk(2), ' i=', km_max_ijk(3), &
380	'&kh_max = ', kh_max, ' m2/s2 k=', kh_max_ijk(1), &
381	' j=', kh_max_ijk(2), ' i=', kh_max_ijk(3)
382	CALL message( 'timestep', 'PA0312', 0, 1, 0, 6, 0 )
383	!
384	!-- In case of coupled runs inform the remote model of the termination
385	!-- and its reason, provided the remote model has not already been
386	!-- informed of another termination reason (terminate_coupled > 0) before.
387	#if defined( __parallel )
388	IF ( coupling_mode /= 'uncoupled' .AND. terminate_coupled == 0 ) THEN
389	terminate_coupled = 2
390	IF ( myid == 0 ) THEN
391	CALL MPI_SENDRECV( &
392	terminate_coupled, 1, MPI_INTEGER, target_id, 0, &
393	terminate_coupled_remote, 1, MPI_INTEGER, target_id, 0, &
394	comm_inter, status, ierr )
395	ENDIF
396	CALL MPI_BCAST( terminate_coupled_remote, 1, MPI_INTEGER, 0, &
397	comm2d, ierr)
398	ENDIF
399	#endif
400	ENDIF
401
402	!
403	!-- In case of nested runs all parent/child processes have to terminate if
404	!-- one process has set the stop flag, i.e. they need to set the stop flag
405	!-- too.
406	IF ( nested_run ) THEN
407	stop_dt_local = stop_dt
408	#if defined( __parallel )
409	CALL MPI_ALLREDUCE( stop_dt_local, stop_dt, 1, MPI_LOGICAL, MPI_LOR, &
410	MPI_COMM_WORLD, ierr )
411	#endif
412	ENDIF
413
414	!
415	!-- Ensure a smooth value (two significant digits) of the timestep.
416	div = 1000.0_wp
417	DO WHILE ( dt_3d < div )
418	div = div / 10.0_wp
419	ENDDO
420	dt_3d = NINT( dt_3d * 100.0_wp / div ) * div / 100.0_wp
421
422	ENDIF
423
424	!
425	!-- Vertical nesting: coarse and fine grid timestep has to be identical
426	IF ( vnested ) CALL vnest_timestep_sync
427
428	CALL cpu_log( log_point(12), 'calculate_timestep', 'stop' )
429
430	END SUBROUTINE timestep

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