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source: palm/trunk/SOURCE/pres.f90 @ 2834

Last change on this file since 2834 was 2718, checked in by maronga, 7 years ago
deleting of deprecated files; headers updated where needed
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1	!> @file pres.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: pres.f90 2696 2017-12-14 17:12:51Z kanani $
27	! Corrected "Former revisions" section
28	!
29	! 2696 2017-12-14 17:12:51Z kanani
30	! Change in file header (GPL part)
31	! poismg_noopt modularized (MS)
32	!
33	! 2298 2017-06-29 09:28:18Z raasch
34	! comment changed + some formatting
35	!
36	! 2233 2017-05-30 18:08:54Z suehring
37	!
38	! 2232 2017-05-30 17:47:52Z suehring
39	! Adjustments to new topography and surface concept
40	!
41	! 2118 2017-01-17 16:38:49Z raasch
42	! OpenACC directives and related code removed
43	!
44	! 2073 2016-11-30 14:34:05Z raasch
45	! openmp bugfix for calculation of new divergence
46	!
47	! 2037 2016-10-26 11:15:40Z knoop
48	! Anelastic approximation implemented
49	!
50	! 2000 2016-08-20 18:09:15Z knoop
51	! Forced header and separation lines into 80 columns
52	!
53	! 1932 2016-06-10 12:09:21Z suehring
54	! Initial version of purely vertical nesting introduced.
55	!
56	! 1931 2016-06-10 12:06:59Z suehring
57	! Rename multigrid into multigrid_noopt and multigrid_fast into multigrid
58	!
59	! 1929 2016-06-09 16:25:25Z suehring
60	! Bugfix: weight_substep for initial call, replace by local variable
61	!
62	! 1918 2016-05-27 14:35:57Z raasch
63	! sum of divergence is also calculated when pres is called before the initial
64	! first time step,
65	! stearing is modified by using intermediate_timestep_count = 0 in order to
66	! determine if pres is called before the first initial timestep,
67	! bugfix: in case of Neumann conditions for pressure both at bottom and top,
68	! mean vertical velocity is also removed for the first time step
69	! bugfix for calculating divergences
70	!
71	! 1908 2016-05-25 17:22:32Z suehring
72	! New divergence for output into RUN_CONTROL file is calculated only at last
73	! Runge-Kutta step
74	!
75	! 1845 2016-04-08 08:29:13Z raasch
76	! nzb_2d replace by nzb_u\|v_inner
77	!
78	! 1799 2016-04-05 08:35:55Z gronemeier
79	! Bugfix: excluded third dimension from horizontal volume flow calculation
80	!
81	! 1762 2016-02-25 12:31:13Z hellstea
82	! Introduction of nested domain feature
83	!
84	! 1682 2015-10-07 23:56:08Z knoop
85	! Code annotations made doxygen readable
86	!
87	! 1575 2015-03-27 09:56:27Z raasch
88	! poismg_fast + respective module added, adjustments for psolver-queries
89	!
90	! 1342 2014-03-26 17:04:47Z kanani
91	! REAL constants defined as wp-kind
92	!
93	! 1320 2014-03-20 08:40:49Z raasch
94	! ONLY-attribute added to USE-statements,
95	! kind-parameters added to all INTEGER and REAL declaration statements,
96	! kinds are defined in new module kinds,
97	! old module precision_kind is removed,
98	! revision history before 2012 removed,
99	! comment fields (!:) to be used for variable explanations added to
100	! all variable declaration statements
101	!
102	! 1318 2014-03-17 13:35:16Z raasch
103	! module interfaces removed
104	!
105	! 1306 2014-03-13 14:30:59Z raasch
106	! second argument removed from routine poisfft
107	!
108	! 1257 2013-11-08 15:18:40Z raasch
109	! openacc loop and loop vector clauses removed, independent clauses added,
110	! end parallel replaced by end parallel loop
111	!
112	! 1221 2013-09-10 08:59:13Z raasch
113	! openACC porting of reduction operations, loops for calculating d are
114	! using the rflags_s_inner multiply flag instead of the nzb_s_inner loop index
115	!
116	! 1212 2013-08-15 08:46:27Z raasch
117	! call of poisfft_hybrid removed
118	!
119	! 1117 2013-03-27 11:15:36Z suehring
120	! Bugfix in OpenMP parallelization.
121	!
122	! 1113 2013-03-10 02:48:14Z raasch
123	! GPU-porting of several loops, some loops rearranged
124	!
125	! 1111 2013-03-08 23:54:10Z
126	! openACC statements added,
127	! ibc_p_b = 2 removed
128	!
129	! 1092 2013-02-02 11:24:22Z raasch
130	! unused variables removed
131	!
132	! 1036 2012-10-22 13:43:42Z raasch
133	! code put under GPL (PALM 3.9)
134	!
135	! 1003 2012-09-14 14:35:53Z raasch
136	! adjustment of array tend for cases with unequal subdomain sizes removed
137	!
138	! Revision 1.1 1997/07/24 11:24:44 raasch
139	! Initial revision
140	!
141	!
142	! Description:
143	! ------------
144	!> Compute the divergence of the provisional velocity field. Solve the Poisson
145	!> equation for the perturbation pressure. Compute the final velocities using
146	!> this perturbation pressure. Compute the remaining divergence.
147	!------------------------------------------------------------------------------!
148	SUBROUTINE pres
149
150
151	USE arrays_3d, &
152	ONLY: d, ddzu, ddzu_pres, ddzw, dzw, p, p_loc, rho_air, rho_air_zw, &
153	tend, u, v, w
154
155	USE control_parameters, &
156	ONLY: bc_lr_cyc, bc_ns_cyc, conserve_volume_flow, dt_3d, &
157	gathered_size, ibc_p_b, ibc_p_t, intermediate_timestep_count, &
158	intermediate_timestep_count_max, mg_switch_to_pe0_level, &
159	nest_domain, outflow_l, outflow_n, outflow_r, &
160	outflow_s, psolver, subdomain_size, topography, volume_flow, &
161	volume_flow_area, volume_flow_initial
162
163	USE cpulog, &
164	ONLY: cpu_log, log_point, log_point_s
165
166	USE grid_variables, &
167	ONLY: ddx, ddy
168
169	USE indices, &
170	ONLY: nbgp, ngp_2dh_outer, nx, nxl, nxlg, nxl_mg, nxr, nxrg, nxr_mg, &
171	ny, nys, nysg, nys_mg, nyn, nyng, nyn_mg, nzb, nzt, nzt_mg, &
172	wall_flags_0
173
174	USE kinds
175
176	USE pegrid
177
178	USE pmc_interface, &
179	ONLY: nesting_mode
180
181	USE poisfft_mod, &
182	ONLY: poisfft
183
184	USE poismg_mod
185
186	USE poismg_noopt_mod
187
188	USE statistics, &
189	ONLY: statistic_regions, sums_divnew_l, sums_divold_l, weight_pres, &
190	weight_substep
191
192	USE surface_mod, &
193	ONLY : bc_h
194
195	IMPLICIT NONE
196
197	INTEGER(iwp) :: i !<
198	INTEGER(iwp) :: j !<
199	INTEGER(iwp) :: k !<
200	INTEGER(iwp) :: m !<
201
202	REAL(wp) :: ddt_3d !<
203	REAL(wp) :: d_weight_pres !<
204	REAL(wp) :: localsum !<
205	REAL(wp) :: threadsum !<
206	REAL(wp) :: weight_pres_l !<
207	REAL(wp) :: weight_substep_l !<
208
209	REAL(wp), DIMENSION(1:3) :: volume_flow_l !<
210	REAL(wp), DIMENSION(1:3) :: volume_flow_offset !<
211	REAL(wp), DIMENSION(1:nzt) :: w_l !<
212	REAL(wp), DIMENSION(1:nzt) :: w_l_l !<
213
214	LOGICAL :: nest_domain_nvn !<
215
216
217	CALL cpu_log( log_point(8), 'pres', 'start' )
218
219
220	!
221	!-- Calculate quantities to be used locally
222	ddt_3d = 1.0_wp / dt_3d
223	IF ( intermediate_timestep_count == 0 ) THEN
224	!
225	!-- If pres is called before initial time step
226	weight_pres_l = 1.0_wp
227	d_weight_pres = 1.0_wp
228	weight_substep_l = 1.0_wp
229	ELSE
230	weight_pres_l = weight_pres(intermediate_timestep_count)
231	d_weight_pres = 1.0_wp / weight_pres(intermediate_timestep_count)
232	weight_substep_l = weight_substep(intermediate_timestep_count)
233	ENDIF
234
235	!
236	!-- Multigrid method expects array d to have one ghost layer.
237	!--
238	IF ( psolver(1:9) == 'multigrid' ) THEN
239
240	DEALLOCATE( d )
241	ALLOCATE( d(nzb:nzt+1,nys-1:nyn+1,nxl-1:nxr+1) )
242
243	!
244	!-- Since p is later used to hold the weighted average of the substeps, it
245	!-- cannot be used in the iterative solver. Therefore, its initial value is
246	!-- stored on p_loc, which is then iteratively advanced in every substep.
247	IF ( intermediate_timestep_count <= 1 ) THEN
248	DO i = nxl-1, nxr+1
249	DO j = nys-1, nyn+1
250	DO k = nzb, nzt+1
251	p_loc(k,j,i) = p(k,j,i)
252	ENDDO
253	ENDDO
254	ENDDO
255	ENDIF
256
257	ELSEIF ( psolver == 'sor' .AND. intermediate_timestep_count <= 1 ) THEN
258
259	!
260	!-- Since p is later used to hold the weighted average of the substeps, it
261	!-- cannot be used in the iterative solver. Therefore, its initial value is
262	!-- stored on p_loc, which is then iteratively advanced in every substep.
263	p_loc = p
264
265	ENDIF
266
267	!
268	!-- Conserve the volume flow at the outflow in case of non-cyclic lateral
269	!-- boundary conditions
270	!-- WARNING: so far, this conservation does not work at the left/south
271	!-- boundary if the topography at the inflow differs from that at the
272	!-- outflow! For this case, volume_flow_area needs adjustment!
273	!
274	!-- Left/right
275	IF ( conserve_volume_flow .AND. ( outflow_l .OR. outflow_r ) ) THEN
276
277	volume_flow(1) = 0.0_wp
278	volume_flow_l(1) = 0.0_wp
279
280	IF ( outflow_l ) THEN
281	i = 0
282	ELSEIF ( outflow_r ) THEN
283	i = nx+1
284	ENDIF
285
286	DO j = nys, nyn
287	!
288	!-- Sum up the volume flow through the south/north boundary
289	DO k = nzb+1, nzt
290	volume_flow_l(1) = volume_flow_l(1) + u(k,j,i) * dzw(k) &
291	* MERGE( 1.0_wp, 0.0_wp, &
292	BTEST( wall_flags_0(k,j,i), 1 ) &
293	)
294	ENDDO
295	ENDDO
296
297	#if defined( __parallel )
298	IF ( collective_wait ) CALL MPI_BARRIER( comm1dy, ierr )
299	CALL MPI_ALLREDUCE( volume_flow_l(1), volume_flow(1), 1, MPI_REAL, &
300	MPI_SUM, comm1dy, ierr )
301	#else
302	volume_flow = volume_flow_l
303	#endif
304	volume_flow_offset(1) = ( volume_flow_initial(1) - volume_flow(1) ) &
305	/ volume_flow_area(1)
306
307	DO j = nysg, nyng
308	DO k = nzb+1, nzt
309	u(k,j,i) = u(k,j,i) + volume_flow_offset(1) &
310	* MERGE( 1.0_wp, 0.0_wp, &
311	BTEST( wall_flags_0(k,j,i), 1 ) &
312	)
313	ENDDO
314	ENDDO
315
316	ENDIF
317
318	!
319	!-- South/north
320	IF ( conserve_volume_flow .AND. ( outflow_n .OR. outflow_s ) ) THEN
321
322	volume_flow(2) = 0.0_wp
323	volume_flow_l(2) = 0.0_wp
324
325	IF ( outflow_s ) THEN
326	j = 0
327	ELSEIF ( outflow_n ) THEN
328	j = ny+1
329	ENDIF
330
331	DO i = nxl, nxr
332	!
333	!-- Sum up the volume flow through the south/north boundary
334	DO k = nzb+1, nzt
335	volume_flow_l(2) = volume_flow_l(2) + v(k,j,i) * dzw(k) &
336	* MERGE( 1.0_wp, 0.0_wp, &
337	BTEST( wall_flags_0(k,j,i), 2 ) &
338	)
339	ENDDO
340	ENDDO
341
342	#if defined( __parallel )
343	IF ( collective_wait ) CALL MPI_BARRIER( comm1dx, ierr )
344	CALL MPI_ALLREDUCE( volume_flow_l(2), volume_flow(2), 1, MPI_REAL, &
345	MPI_SUM, comm1dx, ierr )
346	#else
347	volume_flow = volume_flow_l
348	#endif
349	volume_flow_offset(2) = ( volume_flow_initial(2) - volume_flow(2) ) &
350	/ volume_flow_area(2)
351
352	DO i = nxlg, nxrg
353	DO k = nzb+1, nzt
354	v(k,j,i) = v(k,j,i) + volume_flow_offset(2) &
355	* MERGE( 1.0_wp, 0.0_wp, &
356	BTEST( wall_flags_0(k,j,i), 2 ) &
357	)
358	ENDDO
359	ENDDO
360
361	ENDIF
362
363	!
364	!-- Remove mean vertical velocity in case that Neumann conditions are
365	!-- used both at bottom and top boundary, and if not a nested domain in a
366	!-- normal nesting run. In case of vertical nesting, this must be done.
367	!-- Therefore an auxiliary logical variable nest_domain_nvn is used here, and
368	!-- nvn stands for non-vertical nesting.
369	!-- This cannot be done before the first initial time step because ngp_2dh_outer
370	!-- is not yet known then.
371	nest_domain_nvn = nest_domain
372	IF ( nest_domain .AND. nesting_mode == 'vertical' ) THEN
373	nest_domain_nvn = .FALSE.
374	ENDIF
375
376	IF ( ibc_p_b == 1 .AND. ibc_p_t == 1 .AND. &
377	.NOT. nest_domain_nvn .AND. intermediate_timestep_count /= 0 ) &
378	THEN
379	w_l = 0.0_wp; w_l_l = 0.0_wp
380	DO i = nxl, nxr
381	DO j = nys, nyn
382	DO k = nzb+1, nzt
383	w_l_l(k) = w_l_l(k) + w(k,j,i) &
384	* MERGE( 1.0_wp, 0.0_wp, &
385	BTEST( wall_flags_0(k,j,i), 3 ) &
386	)
387	ENDDO
388	ENDDO
389	ENDDO
390	#if defined( __parallel )
391	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
392	CALL MPI_ALLREDUCE( w_l_l(1), w_l(1), nzt, MPI_REAL, MPI_SUM, &
393	comm2d, ierr )
394	#else
395	w_l = w_l_l
396	#endif
397	DO k = 1, nzt
398	w_l(k) = w_l(k) / ngp_2dh_outer(k,0)
399	ENDDO
400	DO i = nxlg, nxrg
401	DO j = nysg, nyng
402	DO k = nzb+1, nzt
403	w(k,j,i) = w(k,j,i) - w_l(k) &
404	* MERGE( 1.0_wp, 0.0_wp, &
405	BTEST( wall_flags_0(k,j,i), 3 ) &
406	)
407	ENDDO
408	ENDDO
409	ENDDO
410	ENDIF
411
412	!
413	!-- Compute the divergence of the provisional velocity field.
414	CALL cpu_log( log_point_s(1), 'divergence', 'start' )
415
416	IF ( psolver(1:9) == 'multigrid' ) THEN
417	!$OMP PARALLEL DO SCHEDULE( STATIC ) PRIVATE (i,j,k)
418	DO i = nxl-1, nxr+1
419	DO j = nys-1, nyn+1
420	DO k = nzb, nzt+1
421	d(k,j,i) = 0.0_wp
422	ENDDO
423	ENDDO
424	ENDDO
425	ELSE
426	!$OMP PARALLEL DO SCHEDULE( STATIC ) PRIVATE (i,j,k)
427	DO i = nxl, nxr
428	DO j = nys, nyn
429	DO k = nzb+1, nzt
430	d(k,j,i) = 0.0_wp
431	ENDDO
432	ENDDO
433	ENDDO
434	ENDIF
435
436	localsum = 0.0_wp
437	threadsum = 0.0_wp
438
439	#if defined( __ibm )
440	!$OMP PARALLEL PRIVATE (i,j,k) FIRSTPRIVATE(threadsum) REDUCTION(+:localsum)
441	!$OMP DO SCHEDULE( STATIC )
442	DO i = nxl, nxr
443	DO j = nys, nyn
444	DO k = nzb+1, nzt
445	d(k,j,i) = ( ( u(k,j,i+1) - u(k,j,i) ) * rho_air(k) * ddx + &
446	( v(k,j+1,i) - v(k,j,i) ) * rho_air(k) * ddy + &
447	( w(k,j,i) * rho_air_zw(k) - &
448	w(k-1,j,i) * rho_air_zw(k-1) ) * ddzw(k) &
449	) * ddt_3d * d_weight_pres &
450	* MERGE( 1.0_wp, 0.0_wp, &
451	BTEST( wall_flags_0(k,j,i), 0 ) &
452	)
453	ENDDO
454	!
455	!-- Compute possible PE-sum of divergences for flow_statistics
456	DO k = nzb+1, nzt
457	threadsum = threadsum + ABS( d(k,j,i) ) &
458	* MERGE( 1.0_wp, 0.0_wp, &
459	BTEST( wall_flags_0(k,j,i), 0 ) &
460	)
461	ENDDO
462
463	ENDDO
464	ENDDO
465
466	IF ( intermediate_timestep_count == intermediate_timestep_count_max .OR. &
467	intermediate_timestep_count == 0 ) THEN
468	localsum = localsum + threadsum * dt_3d * weight_pres_l
469	ENDIF
470	!$OMP END PARALLEL
471	#else
472
473	!$OMP PARALLEL PRIVATE (i,j,k)
474	!$OMP DO SCHEDULE( STATIC )
475	DO i = nxl, nxr
476	DO j = nys, nyn
477	DO k = 1, nzt
478	d(k,j,i) = ( ( u(k,j,i+1) - u(k,j,i) ) * rho_air(k) * ddx + &
479	( v(k,j+1,i) - v(k,j,i) ) * rho_air(k) * ddy + &
480	( w(k,j,i) * rho_air_zw(k) - &
481	w(k-1,j,i) * rho_air_zw(k-1) ) * ddzw(k) &
482	) * ddt_3d * d_weight_pres &
483	* MERGE( 1.0_wp, 0.0_wp, &
484	BTEST( wall_flags_0(k,j,i), 0 ) &
485	)
486	ENDDO
487	ENDDO
488	ENDDO
489	!$OMP END PARALLEL
490
491	!
492	!-- Compute possible PE-sum of divergences for flow_statistics. Carry out
493	!-- computation only at last Runge-Kutta substep.
494	IF ( intermediate_timestep_count == intermediate_timestep_count_max .OR. &
495	intermediate_timestep_count == 0 ) THEN
496	!$OMP PARALLEL PRIVATE (i,j,k) FIRSTPRIVATE(threadsum) REDUCTION(+:localsum)
497	!$OMP DO SCHEDULE( STATIC )
498	DO i = nxl, nxr
499	DO j = nys, nyn
500	DO k = nzb+1, nzt
501	threadsum = threadsum + ABS( d(k,j,i) )
502	ENDDO
503	ENDDO
504	ENDDO
505	localsum = localsum + threadsum * dt_3d * weight_pres_l
506	!$OMP END PARALLEL
507	ENDIF
508	#endif
509
510	!
511	!-- For completeness, set the divergence sum of all statistic regions to those
512	!-- of the total domain
513	IF ( intermediate_timestep_count == intermediate_timestep_count_max .OR. &
514	intermediate_timestep_count == 0 ) THEN
515	sums_divold_l(0:statistic_regions) = localsum
516	ENDIF
517
518	CALL cpu_log( log_point_s(1), 'divergence', 'stop' )
519
520	!
521	!-- Compute the pressure perturbation solving the Poisson equation
522	IF ( psolver == 'poisfft' ) THEN
523
524	!
525	!-- Solve Poisson equation via FFT and solution of tridiagonal matrices
526	CALL poisfft( d )
527
528	!
529	!-- Store computed perturbation pressure and set boundary condition in
530	!-- z-direction
531	!$OMP PARALLEL DO PRIVATE (i,j,k)
532	DO i = nxl, nxr
533	DO j = nys, nyn
534	DO k = nzb+1, nzt
535	tend(k,j,i) = d(k,j,i)
536	ENDDO
537	ENDDO
538	ENDDO
539
540	!
541	!-- Bottom boundary:
542	!-- This condition is only required for internal output. The pressure
543	!-- gradient (dp(nzb+1)-dp(nzb))/dz is not used anywhere else.
544	IF ( ibc_p_b == 1 ) THEN
545	!
546	!-- Neumann (dp/dz = 0). Using surfae data type, first for non-natural
547	!-- surfaces, then for natural and urban surfaces
548	!-- Upward facing
549	!$OMP PARALLEL DO PRIVATE( i, j, k )
550	DO m = 1, bc_h(0)%ns
551	i = bc_h(0)%i(m)
552	j = bc_h(0)%j(m)
553	k = bc_h(0)%k(m)
554	tend(k-1,j,i) = tend(k,j,i)
555	ENDDO
556	!
557	!-- Downward facing
558	!$OMP PARALLEL DO PRIVATE( i, j, k )
559	DO m = 1, bc_h(1)%ns
560	i = bc_h(1)%i(m)
561	j = bc_h(1)%j(m)
562	k = bc_h(1)%k(m)
563	tend(k+1,j,i) = tend(k,j,i)
564	ENDDO
565
566	ELSE
567	!
568	!-- Dirichlet. Using surface data type, first for non-natural
569	!-- surfaces, then for natural and urban surfaces
570	!-- Upward facing
571	!$OMP PARALLEL DO PRIVATE( i, j, k )
572	DO m = 1, bc_h(0)%ns
573	i = bc_h(0)%i(m)
574	j = bc_h(0)%j(m)
575	k = bc_h(0)%k(m)
576	tend(k-1,j,i) = 0.0_wp
577	ENDDO
578	!
579	!-- Downward facing
580	!$OMP PARALLEL DO PRIVATE( i, j, k )
581	DO m = 1, bc_h(1)%ns
582	i = bc_h(1)%i(m)
583	j = bc_h(1)%j(m)
584	k = bc_h(1)%k(m)
585	tend(k+1,j,i) = 0.0_wp
586	ENDDO
587
588	ENDIF
589
590	!
591	!-- Top boundary
592	IF ( ibc_p_t == 1 ) THEN
593	!
594	!-- Neumann
595	!$OMP PARALLEL DO PRIVATE (i,j,k)
596	DO i = nxlg, nxrg
597	DO j = nysg, nyng
598	tend(nzt+1,j,i) = tend(nzt,j,i)
599	ENDDO
600	ENDDO
601
602	ELSE
603	!
604	!-- Dirichlet
605	!$OMP PARALLEL DO PRIVATE (i,j,k)
606	DO i = nxlg, nxrg
607	DO j = nysg, nyng
608	tend(nzt+1,j,i) = 0.0_wp
609	ENDDO
610	ENDDO
611
612	ENDIF
613
614	!
615	!-- Exchange boundaries for p
616	CALL exchange_horiz( tend, nbgp )
617
618	ELSEIF ( psolver == 'sor' ) THEN
619
620	!
621	!-- Solve Poisson equation for perturbation pressure using SOR-Red/Black
622	!-- scheme
623	CALL sor( d, ddzu_pres, ddzw, p_loc )
624	tend = p_loc
625
626	ELSEIF ( psolver(1:9) == 'multigrid' ) THEN
627
628	!
629	!-- Solve Poisson equation for perturbation pressure using Multigrid scheme,
630	!-- array tend is used to store the residuals.
631
632	!-- If the number of grid points of the gathered grid, which is collected
633	!-- on PE0, is larger than the number of grid points of an PE, than array
634	!-- tend will be enlarged.
635	IF ( gathered_size > subdomain_size ) THEN
636	DEALLOCATE( tend )
637	ALLOCATE( tend(nzb:nzt_mg(mg_switch_to_pe0_level)+1,nys_mg( &
638	mg_switch_to_pe0_level)-1:nyn_mg(mg_switch_to_pe0_level)+1,&
639	nxl_mg(mg_switch_to_pe0_level)-1:nxr_mg( &
640	mg_switch_to_pe0_level)+1) )
641	ENDIF
642
643	IF ( psolver == 'multigrid' ) THEN
644	CALL poismg( tend )
645	ELSE
646	CALL poismg_noopt( tend )
647	ENDIF
648
649	IF ( gathered_size > subdomain_size ) THEN
650	DEALLOCATE( tend )
651	ALLOCATE( tend(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
652	ENDIF
653
654	!
655	!-- Restore perturbation pressure on tend because this array is used
656	!-- further below to correct the velocity fields
657	DO i = nxl-1, nxr+1
658	DO j = nys-1, nyn+1
659	DO k = nzb, nzt+1
660	tend(k,j,i) = p_loc(k,j,i)
661	ENDDO
662	ENDDO
663	ENDDO
664
665	ENDIF
666
667	!
668	!-- Store perturbation pressure on array p, used for pressure data output.
669	!-- Ghost layers are added in the output routines (except sor-method: see below)
670	IF ( intermediate_timestep_count <= 1 ) THEN
671	!$OMP PARALLEL PRIVATE (i,j,k)
672	!$OMP DO
673	DO i = nxl-1, nxr+1
674	DO j = nys-1, nyn+1
675	DO k = nzb, nzt+1
676	p(k,j,i) = tend(k,j,i) * &
677	weight_substep_l
678	ENDDO
679	ENDDO
680	ENDDO
681	!$OMP END PARALLEL
682
683	ELSEIF ( intermediate_timestep_count > 1 ) THEN
684	!$OMP PARALLEL PRIVATE (i,j,k)
685	!$OMP DO
686	DO i = nxl-1, nxr+1
687	DO j = nys-1, nyn+1
688	DO k = nzb, nzt+1
689	p(k,j,i) = p(k,j,i) + tend(k,j,i) * &
690	weight_substep_l
691	ENDDO
692	ENDDO
693	ENDDO
694	!$OMP END PARALLEL
695
696	ENDIF
697
698	!
699	!-- SOR-method needs ghost layers for the next timestep
700	IF ( psolver == 'sor' ) CALL exchange_horiz( p, nbgp )
701
702	!
703	!-- Correction of the provisional velocities with the current perturbation
704	!-- pressure just computed
705	IF ( conserve_volume_flow .AND. ( bc_lr_cyc .OR. bc_ns_cyc ) ) THEN
706	volume_flow_l(1) = 0.0_wp
707	volume_flow_l(2) = 0.0_wp
708	ENDIF
709
710	!$OMP PARALLEL PRIVATE (i,j,k)
711	!$OMP DO
712	DO i = nxl, nxr
713	DO j = nys, nyn
714
715	DO k = nzb+1, nzt
716	w(k,j,i) = w(k,j,i) - dt_3d * &
717	( tend(k+1,j,i) - tend(k,j,i) ) * ddzu(k+1) &
718	* weight_pres_l &
719	* MERGE( 1.0_wp, 0.0_wp, &
720	BTEST( wall_flags_0(k,j,i), 3 ) &
721	)
722	ENDDO
723
724	DO k = nzb+1, nzt
725	u(k,j,i) = u(k,j,i) - dt_3d * &
726	( tend(k,j,i) - tend(k,j,i-1) ) * ddx &
727	* weight_pres_l &
728	* MERGE( 1.0_wp, 0.0_wp, &
729	BTEST( wall_flags_0(k,j,i), 1 ) &
730	)
731	ENDDO
732
733	DO k = nzb+1, nzt
734	v(k,j,i) = v(k,j,i) - dt_3d * &
735	( tend(k,j,i) - tend(k,j-1,i) ) * ddy &
736	* weight_pres_l &
737	* MERGE( 1.0_wp, 0.0_wp, &
738	BTEST( wall_flags_0(k,j,i), 2 ) &
739	)
740	ENDDO
741
742	ENDDO
743	ENDDO
744	!$OMP END PARALLEL
745
746	!
747	!-- Sum up the volume flow through the right and north boundary
748	IF ( conserve_volume_flow .AND. bc_lr_cyc .AND. bc_ns_cyc .AND. &
749	nxr == nx ) THEN
750
751	!$OMP PARALLEL PRIVATE (j,k)
752	!$OMP DO
753	DO j = nys, nyn
754	!$OMP CRITICAL
755	DO k = nzb+1, nzt
756	volume_flow_l(1) = volume_flow_l(1) + u(k,j,nxr) * dzw(k) &
757	* MERGE( 1.0_wp, 0.0_wp, &
758	BTEST( wall_flags_0(k,j,nxr), 1 )&
759	)
760	ENDDO
761	!$OMP END CRITICAL
762	ENDDO
763	!$OMP END PARALLEL
764
765	ENDIF
766
767	IF ( conserve_volume_flow .AND. bc_ns_cyc .AND. bc_lr_cyc .AND. &
768	nyn == ny ) THEN
769
770	!$OMP PARALLEL PRIVATE (i,k)
771	!$OMP DO
772	DO i = nxl, nxr
773	!$OMP CRITICAL
774	DO k = nzb+1, nzt
775	volume_flow_l(2) = volume_flow_l(2) + v(k,nyn,i) * dzw(k) &
776	* MERGE( 1.0_wp, 0.0_wp, &
777	BTEST( wall_flags_0(k,nyn,i), 2 )&
778	)
779	ENDDO
780	!$OMP END CRITICAL
781	ENDDO
782	!$OMP END PARALLEL
783
784	ENDIF
785
786	!
787	!-- Conserve the volume flow
788	IF ( conserve_volume_flow .AND. ( bc_lr_cyc .AND. bc_ns_cyc ) ) THEN
789
790	#if defined( __parallel )
791	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
792	CALL MPI_ALLREDUCE( volume_flow_l(1), volume_flow(1), 2, MPI_REAL, &
793	MPI_SUM, comm2d, ierr )
794	#else
795	volume_flow = volume_flow_l
796	#endif
797
798	volume_flow_offset(1:2) = ( volume_flow_initial(1:2) - volume_flow(1:2) ) / &
799	volume_flow_area(1:2)
800
801	!$OMP PARALLEL PRIVATE (i,j,k)
802	!$OMP DO
803	DO i = nxl, nxr
804	DO j = nys, nyn
805	DO k = nzb+1, nzt
806	u(k,j,i) = u(k,j,i) + volume_flow_offset(1) &
807	* MERGE( 1.0_wp, 0.0_wp, &
808	BTEST( wall_flags_0(k,j,i), 1 ) &
809	)
810	ENDDO
811	DO k = nzb+1, nzt
812	v(k,j,i) = v(k,j,i) + volume_flow_offset(2) &
813	* MERGE( 1.0_wp, 0.0_wp, &
814	BTEST( wall_flags_0(k,j,i), 2 ) &
815	)
816	ENDDO
817	ENDDO
818	ENDDO
819
820	!$OMP END PARALLEL
821
822	ENDIF
823
824	!
825	!-- Exchange of boundaries for the velocities
826	CALL exchange_horiz( u, nbgp )
827	CALL exchange_horiz( v, nbgp )
828	CALL exchange_horiz( w, nbgp )
829
830	!
831	!-- Compute the divergence of the corrected velocity field,
832	!-- A possible PE-sum is computed in flow_statistics. Carry out computation
833	!-- only at last Runge-Kutta step.
834	IF ( intermediate_timestep_count == intermediate_timestep_count_max .OR. &
835	intermediate_timestep_count == 0 ) THEN
836	CALL cpu_log( log_point_s(1), 'divergence', 'start' )
837	sums_divnew_l = 0.0_wp
838
839	!
840	!-- d must be reset to zero because it can contain nonzero values below the
841	!-- topography
842	IF ( topography /= 'flat' ) d = 0.0_wp
843
844	localsum = 0.0_wp
845	threadsum = 0.0_wp
846
847	!$OMP PARALLEL PRIVATE (i,j,k) FIRSTPRIVATE(threadsum) REDUCTION(+:localsum)
848	#if defined( __ibm )
849	!$OMP DO SCHEDULE( STATIC )
850	DO i = nxl, nxr
851	DO j = nys, nyn
852	DO k = nzb+1, nzt
853	d(k,j,i) = ( ( u(k,j,i+1) - u(k,j,i) ) * rho_air(k) * ddx + &
854	( v(k,j+1,i) - v(k,j,i) ) * rho_air(k) * ddy + &
855	( w(k,j,i) * rho_air_zw(k) - &
856	w(k-1,j,i) * rho_air_zw(k-1) ) * ddzw(k) &
857	) * MERGE( 1.0_wp, 0.0_wp, &
858	BTEST( wall_flags_0(k,j,i), 0 ) &
859	)
860	ENDDO
861	DO k = nzb+1, nzt
862	threadsum = threadsum + ABS( d(k,j,i) )
863	ENDDO
864	ENDDO
865	ENDDO
866	#else
867	!$OMP DO SCHEDULE( STATIC )
868	DO i = nxl, nxr
869	DO j = nys, nyn
870	DO k = nzb+1, nzt
871	d(k,j,i) = ( ( u(k,j,i+1) - u(k,j,i) ) * rho_air(k) * ddx + &
872	( v(k,j+1,i) - v(k,j,i) ) * rho_air(k) * ddy + &
873	( w(k,j,i) * rho_air_zw(k) - &
874	w(k-1,j,i) * rho_air_zw(k-1) ) * ddzw(k) &
875	) * MERGE( 1.0_wp, 0.0_wp, &
876	BTEST( wall_flags_0(k,j,i), 0 ) &
877	)
878	ENDDO
879	ENDDO
880	ENDDO
881	!
882	!-- Compute possible PE-sum of divergences for flow_statistics
883	!$OMP DO SCHEDULE( STATIC )
884	DO i = nxl, nxr
885	DO j = nys, nyn
886	DO k = nzb+1, nzt
887	threadsum = threadsum + ABS( d(k,j,i) )
888	ENDDO
889	ENDDO
890	ENDDO
891	#endif
892
893	localsum = localsum + threadsum
894	!$OMP END PARALLEL
895
896	!
897	!-- For completeness, set the divergence sum of all statistic regions to those
898	!-- of the total domain
899	sums_divnew_l(0:statistic_regions) = localsum
900
901	CALL cpu_log( log_point_s(1), 'divergence', 'stop' )
902
903	ENDIF
904
905	CALL cpu_log( log_point(8), 'pres', 'stop' )
906
907
908	END SUBROUTINE pres

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