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source: palm/trunk/SOURCE/timestep.f90 @ 3454

Last change on this file since 3454 was 3311, checked in by raasch, 6 years ago
Stokes drift is regarded in timestep calculation, check if ocean mode is used for invalid combinations
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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 3311 2018-10-05 12:34:56Z schwenkel $
27	! Stokes drift is regarded in timestep calculation
28	!
29	! 3274 2018-09-24 15:42:55Z knoop
30	! Modularization of all bulk cloud physics code components
31	!
32	! 3241 2018-09-12 15:02:00Z raasch
33	! unused variables removed
34	!
35	! 3120 2018-07-11 18:30:57Z gronemeier
36	! Put ABS( km ) in computation of time step according to the diffusion criterion
37	!
38	! 3084 2018-06-19 15:30:55Z gronemeier
39	! limit increase of dt_3d only in case of RANS mode
40	!
41	! 3083 2018-06-19 14:03:12Z gronemeier
42	! limit dt_3d to be at maximum 2*old_dt; define old_dt at beginning of routine
43	! Add km/kh_max
44	!
45	! 3049 2018-05-29 13:52:36Z Giersch
46	! Error messages revised
47	!
48	! 3045 2018-05-28 07:55:41Z Giersch
49	! Error message revised
50	!
51	! 2718 2018-01-02 08:49:38Z maronga
52	! Corrected "Former revisions" section
53	!
54	! 2696 2017-12-14 17:12:51Z kanani
55	! Change in file header (GPL part)
56	!
57	! 2365 2017-08-21 14:59:59Z kanani
58	! Vertical grid nesting: Sync fine and coarse grid timestep (SadiqHuq)
59	!
60	! 2258 2017-06-08 07:55:13Z suehring
61	! Bugfix, add pre-preprocessor directives to enable non-parrallel mode
62	!
63	! 2168 2017-03-06 13:08:38Z suehring
64	!
65	! 2130 2017-01-24 16:25:39Z raasch
66	! bugfix: in case of nested runs the stop condition in case of too small
67	! timesteps is communicated to all parent/child processes,
68	! some formatting done
69	!
70	! 2118 2017-01-17 16:38:49Z raasch
71	! OpenACC directives and related part of code removed
72	!
73	! 2000 2016-08-20 18:09:15Z knoop
74	! Forced header and separation lines into 80 columns
75	!
76	! 1849 2016-04-08 11:33:18Z hoffmann
77	! Adapted for modularization of microphysics
78	!
79	! 1682 2015-10-07 23:56:08Z knoop
80	! Code annotations made doxygen readable
81	!
82	! 1484 2014-10-21 10:53:05Z kanani
83	! Changes due to new module structure of the plant canopy model:
84	! calculations and parameters related to the plant canopy model removed
85	! (the limitation of the canopy drag, i.e. that the canopy drag itself should
86	! not change the sign of the velocity components, is now assured for in the
87	! calculation of the canopy tendency terms in subroutine plant_canopy_model)
88	!
89	! 1342 2014-03-26 17:04:47Z kanani
90	! REAL constants defined as wp-kind
91	!
92	! 1322 2014-03-20 16:38:49Z raasch
93	! REAL functions provided with KIND-attribute
94	!
95	! 1320 2014-03-20 08:40:49Z raasch
96	! ONLY-attribute added to USE-statements,
97	! kind-parameters added to all INTEGER and REAL declaration statements,
98	! kinds are defined in new module kinds,
99	! old module precision_kind is removed,
100	! revision history before 2012 removed,
101	! comment fields (!:) to be used for variable explanations added to
102	! all variable declaration statements
103	!
104	! 1257 2013-11-08 15:18:40Z raasch
105	! openacc porting
106	! bugfix for calculation of advective timestep in case of vertically stretched
107	! grids
108	!
109	! 1092 2013-02-02 11:24:22Z raasch
110	! unused variables removed
111	!
112	! 1053 2012-11-13 17:11:03Z hoffmann
113	! timestep is reduced in two-moment cloud scheme according to the maximum
114	! terminal velocity of rain drops
115	!
116	! 1036 2012-10-22 13:43:42Z raasch
117	! code put under GPL (PALM 3.9)
118	!
119	! 1001 2012-09-13 14:08:46Z raasch
120	! all actions concerning leapfrog scheme removed
121	!
122	! 978 2012-08-09 08:28:32Z fricke
123	! restriction of the outflow damping layer in the diffusion criterion removed
124	!
125	! 866 2012-03-28 06:44:41Z raasch
126	! bugfix for timestep calculation in case of Galilei transformation,
127	! special treatment in case of mirror velocity boundary condition removed
128	!
129	! Revision 1.1 1997/08/11 06:26:19 raasch
130	! Initial revision
131	!
132	!
133	! Description:
134	! ------------
135	!> Compute the time step under consideration of the FCL and diffusion criterion.
136	!------------------------------------------------------------------------------!
137	SUBROUTINE timestep
138
139
140	USE arrays_3d, &
141	ONLY: dzu, dzw, kh, km, u, u_stokes_zu, v, v_stokes_zu, w
142
143	USE control_parameters, &
144	ONLY: cfl_factor, coupling_mode, dt_3d, dt_fixed, dt_max, &
145	galilei_transformation, old_dt, message_string, rans_mode, &
146	stop_dt, terminate_coupled, terminate_coupled_remote, &
147	timestep_reason, u_gtrans, use_ug_for_galilei_tr, v_gtrans
148
149	USE cpulog, &
150	ONLY: cpu_log, log_point
151
152	USE grid_variables, &
153	ONLY: dx, dx2, dy, dy2
154
155	USE indices, &
156	ONLY: nxl, nxlg, nxr, nxrg, nyn, nyng, nys, nysg, nzb, nzt
157
158	USE interfaces
159
160	USE kinds
161
162	USE bulk_cloud_model_mod, &
163	ONLY: dt_precipitation
164
165	USE pegrid
166
167	USE pmc_interface, &
168	ONLY: nested_run
169
170	USE statistics, &
171	ONLY: flow_statistics_called, hom, u_max, u_max_ijk, v_max, v_max_ijk,&
172	w_max, w_max_ijk
173
174	USE vertical_nesting_mod, &
175	ONLY: vnested, vnest_timestep_sync
176
177	IMPLICIT NONE
178
179	INTEGER(iwp) :: i !<
180	INTEGER(iwp) :: j !<
181	INTEGER(iwp) :: k !<
182	INTEGER(iwp) :: km_max_ijk(3) = -1 !< index values (i,j,k) of location where km_max occurs
183	INTEGER(iwp) :: kh_max_ijk(3) = -1 !< index values (i,j,k) of location where kh_max occurs
184
185	LOGICAL :: stop_dt_local !< local switch for controlling the time stepping
186
187	REAL(wp) :: div !<
188	REAL(wp) :: dt_diff !<
189	REAL(wp) :: dt_diff_l !<
190	REAL(wp) :: dt_u !<
191	REAL(wp) :: dt_u_l !<
192	REAL(wp) :: dt_v !<
193	REAL(wp) :: dt_v_l !<
194	REAL(wp) :: dt_w !<
195	REAL(wp) :: dt_w_l !<
196	REAL(wp) :: km_max !< maximum of Km in entire domain
197	REAL(wp) :: kh_max !< maximum of Kh in entire domain
198	REAL(wp) :: u_gtrans_l !<
199	REAL(wp) :: v_gtrans_l !<
200
201	REAL(wp), DIMENSION(2) :: uv_gtrans !<
202	REAL(wp), DIMENSION(2) :: uv_gtrans_l !<
203	REAL(wp), DIMENSION(3) :: reduce !<
204	REAL(wp), DIMENSION(3) :: reduce_l !<
205	REAL(wp), DIMENSION(nzb+1:nzt) :: dxyz2_min !<
206
207
208	CALL cpu_log( log_point(12), 'calculate_timestep', 'start' )
209	!
210	!-- Save former time step as reference
211	old_dt = dt_3d
212
213	!
214	!-- In case of Galilei-transform not using the geostrophic wind as translation
215	!-- velocity, compute the volume-averaged horizontal velocity components, which
216	!-- will then be subtracted from the horizontal wind for the time step and
217	!-- horizontal advection routines.
218	IF ( galilei_transformation .AND. .NOT. use_ug_for_galilei_tr ) THEN
219	IF ( flow_statistics_called ) THEN
220	!
221	!-- Horizontal averages already existent, just need to average them
222	!-- vertically.
223	u_gtrans = 0.0_wp
224	v_gtrans = 0.0_wp
225	DO k = nzb+1, nzt
226	u_gtrans = u_gtrans + hom(k,1,1,0)
227	v_gtrans = v_gtrans + hom(k,1,2,0)
228	ENDDO
229	u_gtrans = u_gtrans / REAL( nzt - nzb, KIND=wp )
230	v_gtrans = v_gtrans / REAL( nzt - nzb, KIND=wp )
231	ELSE
232	!
233	!-- Averaging over the entire model domain.
234	u_gtrans_l = 0.0_wp
235	v_gtrans_l = 0.0_wp
236	DO i = nxl, nxr
237	DO j = nys, nyn
238	DO k = nzb+1, nzt
239	u_gtrans_l = u_gtrans_l + u(k,j,i)
240	v_gtrans_l = v_gtrans_l + v(k,j,i)
241	ENDDO
242	ENDDO
243	ENDDO
244	uv_gtrans_l(1) = u_gtrans_l / &
245	REAL( (nxr-nxl+1)(nyn-nys+1)(nzt-nzb), KIND=wp )
246	uv_gtrans_l(2) = v_gtrans_l / &
247	REAL( (nxr-nxl+1)(nyn-nys+1)(nzt-nzb), KIND=wp )
248	#if defined( __parallel )
249	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
250	CALL MPI_ALLREDUCE( uv_gtrans_l, uv_gtrans, 2, MPI_REAL, MPI_SUM, &
251	comm2d, ierr )
252	u_gtrans = uv_gtrans(1) / REAL( numprocs, KIND=wp )
253	v_gtrans = uv_gtrans(2) / REAL( numprocs, KIND=wp )
254	#else
255	u_gtrans = uv_gtrans_l(1)
256	v_gtrans = uv_gtrans_l(2)
257	#endif
258	ENDIF
259	ENDIF
260
261	!
262	!-- Determine the maxima of the velocity components, including their
263	!-- grid index positions.
264	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, u, 'abs', 0.0_wp, &
265	u_max, u_max_ijk )
266	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, v, 'abs', 0.0_wp, &
267	v_max, v_max_ijk )
268	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, w, 'abs', 0.0_wp, &
269	w_max, w_max_ijk )
270
271	IF ( .NOT. dt_fixed ) THEN
272	!
273	!-- Variable time step:
274	!-- Calculate the maximum time step according to the CFL-criterion,
275	!-- individually for each velocity component
276	dt_u_l = 999999.9_wp
277	dt_v_l = 999999.9_wp
278	dt_w_l = 999999.9_wp
279	DO i = nxl, nxr
280	DO j = nys, nyn
281	DO k = nzb+1, nzt
282	dt_u_l = MIN( dt_u_l, ( dx / &
283	( ABS( u(k,j,i) - u_gtrans + u_stokes_zu(k) ) &
284	+ 1.0E-10_wp ) ) )
285	dt_v_l = MIN( dt_v_l, ( dy / &
286	( ABS( v(k,j,i) - v_gtrans + v_stokes_zu(k) ) &
287	+ 1.0E-10_wp ) ) )
288	dt_w_l = MIN( dt_w_l, ( dzu(k) / &
289	( ABS( w(k,j,i) ) + 1.0E-10_wp ) ) )
290	ENDDO
291	ENDDO
292	ENDDO
293
294	#if defined( __parallel )
295	reduce_l(1) = dt_u_l
296	reduce_l(2) = dt_v_l
297	reduce_l(3) = dt_w_l
298	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
299	CALL MPI_ALLREDUCE( reduce_l, reduce, 3, MPI_REAL, MPI_MIN, comm2d, ierr )
300	dt_u = reduce(1)
301	dt_v = reduce(2)
302	dt_w = reduce(3)
303	#else
304	dt_u = dt_u_l
305	dt_v = dt_v_l
306	dt_w = dt_w_l
307	#endif
308
309	!
310	!-- Compute time step according to the diffusion criterion.
311	!-- First calculate minimum grid spacing which only depends on index k.
312	!-- When using the dynamic subgrid model, negative km are possible.
313	dt_diff_l = 999999.0_wp
314
315	DO k = nzb+1, nzt
316	dxyz2_min(k) = MIN( dx2, dy2, dzw(k)dzw(k) ) 0.125_wp
317	ENDDO
318
319	!$OMP PARALLEL private(i,j,k) reduction(MIN: dt_diff_l)
320	!$OMP DO
321	DO i = nxl, nxr
322	DO j = nys, nyn
323	DO k = nzb+1, nzt
324	dt_diff_l = MIN( dt_diff_l, dxyz2_min(k) / &
325	( MAX( kh(k,j,i), ABS( km(k,j,i) ) ) &
326	+ 1E-20_wp ) )
327	ENDDO
328	ENDDO
329	ENDDO
330	!$OMP END PARALLEL
331	#if defined( __parallel )
332	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
333	CALL MPI_ALLREDUCE( dt_diff_l, dt_diff, 1, MPI_REAL, MPI_MIN, comm2d, &
334	ierr )
335	#else
336	dt_diff = dt_diff_l
337	#endif
338
339	!
340	!-- The time step is the minimum of the 3-4 components and the diffusion time
341	!-- step minus a reduction (cfl_factor) to be on the safe side.
342	!-- The time step must not exceed the maximum allowed value.
343	dt_3d = cfl_factor * MIN( dt_diff, dt_u, dt_v, dt_w, dt_precipitation )
344	dt_3d = MIN( dt_3d, dt_max )
345	!
346	!-- In RANS mode, the time step must not increase by more than a factor of 2
347	IF ( rans_mode ) dt_3d = MIN( dt_3d, dt_max, 2.0_wp * old_dt )
348
349	!
350	!-- Remember the restricting time step criterion for later output.
351	IF ( MIN( dt_u, dt_v, dt_w ) < dt_diff ) THEN
352	timestep_reason = 'A'
353	ELSE
354	timestep_reason = 'D'
355	ENDIF
356
357	!
358	!-- Set flag if the time step becomes too small.
359	IF ( dt_3d < ( 0.00001_wp * dt_max ) ) THEN
360	stop_dt = .TRUE.
361
362	!
363	!-- Determine the maxima of the diffusion coefficients, including their
364	!-- grid index positions.
365	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, km, 'abs', &
366	0.0_wp, km_max, km_max_ijk )
367	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, kh, 'abs', &
368	0.0_wp, kh_max, kh_max_ijk )
369
370	WRITE( message_string, * ) 'Time step has reached minimum limit.', &
371	'&dt = ', dt_3d, ' s Simulation is terminated.', &
372	'&old_dt = ', old_dt, ' s', &
373	'&dt_u = ', dt_u, ' s', &
374	'&dt_v = ', dt_v, ' s', &
375	'&dt_w = ', dt_w, ' s', &
376	'&dt_diff = ', dt_diff, ' s', &
377	'&u_max = ', u_max, ' m/s k=', u_max_ijk(1), &
378	' j=', u_max_ijk(2), ' i=', u_max_ijk(3), &
379	'&v_max = ', v_max, ' m/s k=', v_max_ijk(1), &
380	' j=', v_max_ijk(2), ' i=', v_max_ijk(3), &
381	'&w_max = ', w_max, ' m/s k=', w_max_ijk(1), &
382	' j=', w_max_ijk(2), ' i=', w_max_ijk(3), &
383	'&km_max = ', km_max, ' m2/s2 k=', km_max_ijk(1), &
384	' j=', km_max_ijk(2), ' i=', km_max_ijk(3), &
385	'&kh_max = ', kh_max, ' m2/s2 k=', kh_max_ijk(1), &
386	' j=', kh_max_ijk(2), ' i=', kh_max_ijk(3)
387	CALL message( 'timestep', 'PA0312', 0, 1, 0, 6, 0 )
388	!
389	!-- In case of coupled runs inform the remote model of the termination
390	!-- and its reason, provided the remote model has not already been
391	!-- informed of another termination reason (terminate_coupled > 0) before.
392	#if defined( __parallel )
393	IF ( coupling_mode /= 'uncoupled' .AND. terminate_coupled == 0 ) THEN
394	terminate_coupled = 2
395	IF ( myid == 0 ) THEN
396	CALL MPI_SENDRECV( &
397	terminate_coupled, 1, MPI_INTEGER, target_id, 0, &
398	terminate_coupled_remote, 1, MPI_INTEGER, target_id, 0, &
399	comm_inter, status, ierr )
400	ENDIF
401	CALL MPI_BCAST( terminate_coupled_remote, 1, MPI_INTEGER, 0, &
402	comm2d, ierr)
403	ENDIF
404	#endif
405	ENDIF
406
407	!
408	!-- In case of nested runs all parent/child processes have to terminate if
409	!-- one process has set the stop flag, i.e. they need to set the stop flag
410	!-- too.
411	IF ( nested_run ) THEN
412	stop_dt_local = stop_dt
413	#if defined( __parallel )
414	CALL MPI_ALLREDUCE( stop_dt_local, stop_dt, 1, MPI_LOGICAL, MPI_LOR, &
415	MPI_COMM_WORLD, ierr )
416	#endif
417	ENDIF
418
419	!
420	!-- Ensure a smooth value (two significant digits) of the timestep.
421	div = 1000.0_wp
422	DO WHILE ( dt_3d < div )
423	div = div / 10.0_wp
424	ENDDO
425	dt_3d = NINT( dt_3d * 100.0_wp / div ) * div / 100.0_wp
426
427	ENDIF
428
429	!
430	!-- Vertical nesting: coarse and fine grid timestep has to be identical
431	IF ( vnested ) CALL vnest_timestep_sync
432
433	CALL cpu_log( log_point(12), 'calculate_timestep', 'stop' )
434
435	END SUBROUTINE timestep

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