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source: palm/trunk/SOURCE/timestep.f90 @ 1053

Last change on this file since 1053 was 1053, checked in by hoffmann, 12 years ago
two-moment cloud physics implemented
Property svn:keywords set to `Id`
File size: 14.6 KB

Rev	Line
[1]	1	SUBROUTINE timestep
	2
[1036]	3	!--------------------------------------------------------------------------------!
	4	! This file is part of PALM.
	5	!
	6	! PALM is free software: you can redistribute it and/or modify it under the terms
	7	! of the GNU General Public License as published by the Free Software Foundation,
	8	! either version 3 of the License, or (at your option) any later 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 1997-2012 Leibniz University Hannover
	18	!--------------------------------------------------------------------------------!
	19	!
[258]	20	! Current revisions:
[866]	21	! ------------------
[1053]	22	! timestep is reduced in two-moment cloud scheme according to the maximum
	23	! terminal velocity of rain drops
[316]	24	!
[1]	25	! Former revisions:
	26	! -----------------
[3]	27	! $Id: timestep.f90 1053 2012-11-13 17:11:03Z hoffmann $
[110]	28	!
[1037]	29	! 1036 2012-10-22 13:43:42Z raasch
	30	! code put under GPL (PALM 3.9)
	31	!
[1002]	32	! 1001 2012-09-13 14:08:46Z raasch
	33	! all actions concerning leapfrog scheme removed
	34	!
[979]	35	! 978 2012-08-09 08:28:32Z fricke
	36	! restriction of the outflow damping layer in the diffusion criterion removed
	37	!
[867]	38	! 866 2012-03-28 06:44:41Z raasch
	39	! bugfix for timestep calculation in case of Galilei transformation,
	40	! special treatment in case of mirror velocity boundary condition removed
	41	!
[708]	42	! 707 2011-03-29 11:39:40Z raasch
	43	! bc_lr/ns replaced by bc_lr/ns_cyc
	44	!
[668]	45	! 667 2010-12-23 12:06:00Z suehring/gryschka
	46	! Exchange of terminate_coupled between ocean and atmosphere via PE0
	47	! Minimum grid spacing dxyz2_min(k) is now calculated using dzw instead of dzu
	48	!
[623]	49	! 622 2010-12-10 08:08:13Z raasch
	50	! optional barriers included in order to speed up collective operations
	51	!
[392]	52	! 343 2009-06-24 12:59:09Z maronga
	53	! Additional timestep criterion in case of simulations with plant canopy
	54	! Output of messages replaced by message handling routine.
	55	!
[226]	56	! 222 2009-01-12 16:04:16Z letzel
	57	! Implementation of a MPI-1 Coupling: replaced myid with target_id
	58	! Bugfix for nonparallel execution
	59	!
[110]	60	! 108 2007-08-24 15:10:38Z letzel
	61	! modifications to terminate coupled runs
	62	!
[3]	63	! RCS Log replace by Id keyword, revision history cleaned up
	64	!
[1]	65	! Revision 1.21 2006/02/23 12:59:44 raasch
	66	! nt_anz renamed current_timestep_number
	67	!
	68	! Revision 1.1 1997/08/11 06:26:19 raasch
	69	! Initial revision
	70	!
	71	!
	72	! Description:
	73	! ------------
	74	! Compute the time step under consideration of the FCL and diffusion criterion.
	75	!------------------------------------------------------------------------------!
	76
	77	USE arrays_3d
[1053]	78	USE cloud_parameters
[1]	79	USE control_parameters
	80	USE cpulog
	81	USE grid_variables
	82	USE indices
	83	USE interfaces
	84	USE pegrid
	85	USE statistics
	86
	87	IMPLICIT NONE
	88
[866]	89	INTEGER :: i, j, k, u_max_cfl_ijk(3), v_max_cfl_ijk(3)
[1]	90
[318]	91	REAL :: div, dt_diff, dt_diff_l, dt_plant_canopy, &
	92	dt_plant_canopy_l, &
	93	dt_plant_canopy_u, dt_plant_canopy_v, dt_plant_canopy_w, &
[1001]	94	dt_u, dt_v, dt_w, lad_max, &
[866]	95	u_gtrans_l, u_max_cfl, vabs_max, value, v_gtrans_l, v_max_cfl
[1]	96
	97	REAL, DIMENSION(2) :: uv_gtrans, uv_gtrans_l
	98	REAL, DIMENSION(nzb+1:nzt) :: dxyz2_min
	99
[667]	100
	101
[1]	102	CALL cpu_log( log_point(12), 'calculate_timestep', 'start' )
	103
	104	!
	105	!-- In case of Galilei-transform not using the geostrophic wind as translation
	106	!-- velocity, compute the volume-averaged horizontal velocity components, which
	107	!-- will then be subtracted from the horizontal wind for the time step and
	108	!-- horizontal advection routines.
	109	IF ( galilei_transformation .AND. .NOT. use_ug_for_galilei_tr ) THEN
	110	IF ( flow_statistics_called ) THEN
	111	!
	112	!-- Horizontal averages already existent, just need to average them
	113	!-- vertically.
	114	u_gtrans = 0.0
	115	v_gtrans = 0.0
	116	DO k = nzb+1, nzt
	117	u_gtrans = u_gtrans + hom(k,1,1,0)
	118	v_gtrans = v_gtrans + hom(k,1,2,0)
	119	ENDDO
	120	u_gtrans = u_gtrans / REAL( nzt - nzb )
	121	v_gtrans = v_gtrans / REAL( nzt - nzb )
	122	ELSE
	123	!
	124	!-- Averaging over the entire model domain.
	125	uv_gtrans_l = 0.0
	126	DO i = nxl, nxr
	127	DO j = nys, nyn
	128	DO k = nzb+1, nzt
	129	uv_gtrans_l(1) = uv_gtrans_l(1) + u(k,j,i)
	130	uv_gtrans_l(2) = uv_gtrans_l(2) + v(k,j,i)
	131	ENDDO
	132	ENDDO
	133	ENDDO
	134	uv_gtrans_l = uv_gtrans_l / REAL( (nxr-nxl+1)(nyn-nys+1)(nzt-nzb) )
	135	#if defined( __parallel )
[622]	136	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
[1]	137	CALL MPI_ALLREDUCE( uv_gtrans_l, uv_gtrans, 2, MPI_REAL, MPI_SUM, &
	138	comm2d, ierr )
	139	u_gtrans = uv_gtrans(1) / REAL( numprocs )
	140	v_gtrans = uv_gtrans(2) / REAL( numprocs )
	141	#else
	142	u_gtrans = uv_gtrans_l(1)
	143	v_gtrans = uv_gtrans_l(2)
	144	#endif
	145	ENDIF
	146	ENDIF
	147
[866]	148	!
	149	!-- Determine the maxima of the velocity components.
	150	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, u, 'abs', 0.0, &
	151	u_max, u_max_ijk )
	152	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, v, 'abs', 0.0, &
	153	v_max, v_max_ijk )
	154	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, w, 'abs', 0.0, &
	155	w_max, w_max_ijk )
	156
	157	!
	158	!-- In case of Galilei transformation, the horizontal velocity maxima have
	159	!-- to be calculated from the transformed horizontal velocities
	160	IF ( galilei_transformation ) THEN
	161	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, u, 'absoff', &
	162	u_gtrans, u_max_cfl, u_max_cfl_ijk )
	163	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, v, 'absoff', &
	164	v_gtrans, v_max_cfl, v_max_cfl_ijk )
	165	ELSE
	166	u_max_cfl = u_max
	167	v_max_cfl = v_max
	168	u_max_cfl_ijk = u_max_ijk
	169	v_max_cfl_ijk = v_max_ijk
	170	ENDIF
	171
	172
[1]	173	IF ( .NOT. dt_fixed ) THEN
	174	!
	175	!-- Variable time step:
	176	!
	177	!-- For each component, compute the maximum time step according to the
[866]	178	!-- CFL-criterion.
	179	dt_u = dx / ( ABS( u_max_cfl ) + 1.0E-10 )
	180	dt_v = dy / ( ABS( v_max_cfl ) + 1.0E-10 )
[1]	181	dt_w = dzu(MAX( 1, w_max_ijk(1) )) / ( ABS( w_max ) + 1.0E-10 )
	182
	183	!
	184	!-- Compute time step according to the diffusion criterion.
	185	!-- First calculate minimum grid spacing which only depends on index k
	186	!-- Note: also at k=nzb+1 a full grid length is being assumed, although
	187	!-- in the Prandtl-layer friction term only dz/2 is used.
	188	!-- Experience from the old model seems to justify this.
	189	dt_diff_l = 999999.0
	190
	191	DO k = nzb+1, nzt
[667]	192	dxyz2_min(k) = MIN( dx2, dy2, dzw(k)dzw(k) ) 0.125
[1]	193	ENDDO
	194
	195	!$OMP PARALLEL private(i,j,k,value) reduction(MIN: dt_diff_l)
	196	!$OMP DO
	197	DO i = nxl, nxr
	198	DO j = nys, nyn
	199	DO k = nzb+1, nzt
	200	value = dxyz2_min(k) / ( MAX( kh(k,j,i), km(k,j,i) ) + 1E-20 )
	201
	202	dt_diff_l = MIN( value, dt_diff_l )
	203	ENDDO
	204	ENDDO
	205	ENDDO
	206	!$OMP END PARALLEL
	207	#if defined( __parallel )
[622]	208	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
[1]	209	CALL MPI_ALLREDUCE( dt_diff_l, dt_diff, 1, MPI_REAL, MPI_MIN, comm2d, &
	210	ierr )
	211	#else
	212	dt_diff = dt_diff_l
	213	#endif
	214
	215	!
[316]	216	!-- Additional timestep criterion with plant canopies:
	217	!-- it is not allowed to extract more than the available momentum
	218	IF ( plant_canopy ) THEN
[318]	219
	220	dt_plant_canopy_l = 0.0
	221	DO i = nxl, nxr
	222	DO j = nys, nyn
	223	DO k = nzb+1, nzt
	224	dt_plant_canopy_u = cdc(k,j,i) * lad_u(k,j,i) * &
	225	SQRT( u(k,j,i)**2 + &
	226	( ( v(k,j,i-1) + &
	227	v(k,j,i) + &
	228	v(k,j+1,i) + &
	229	v(k,j+1,i-1) ) &
	230	/ 4.0 )**2 + &
	231	( ( w(k-1,j,i-1) + &
	232	w(k-1,j,i) + &
	233	w(k,j,i-1) + &
	234	w(k,j,i) ) &
	235	/ 4.0 )**2 )
	236	IF ( dt_plant_canopy_u > dt_plant_canopy_l ) THEN
	237	dt_plant_canopy_l = dt_plant_canopy_u
	238	ENDIF
	239	dt_plant_canopy_v = cdc(k,j,i) * lad_v(k,j,i) * &
	240	SQRT( ( ( u(k,j-1,i) + &
	241	u(k,j-1,i+1) + &
	242	u(k,j,i) + &
	243	u(k,j,i+1) ) &
	244	/ 4.0 )**2 + &
	245	v(k,j,i)**2 + &
	246	( ( w(k-1,j-1,i) + &
	247	w(k-1,j,i) + &
	248	w(k,j-1,i) + &
	249	w(k,j,i) ) &
	250	/ 4.0 )**2 )
	251	IF ( dt_plant_canopy_v > dt_plant_canopy_l ) THEN
	252	dt_plant_canopy_l = dt_plant_canopy_v
	253	ENDIF
	254	dt_plant_canopy_w = cdc(k,j,i) * lad_w(k,j,i) * &
	255	SQRT( ( ( u(k,j,i) + &
	256	u(k,j,i+1) + &
	257	u(k+1,j,i) + &
	258	u(k+1,j,i+1) ) &
	259	/ 4.0 )**2 + &
	260	( ( v(k,j,i) + &
	261	v(k,j+1,i) + &
	262	v(k+1,j,i) + &
	263	v(k+1,j+1,i) ) &
	264	/ 4.0 )**2 + &
	265	w(k,j,i)**2 )
	266	IF ( dt_plant_canopy_w > dt_plant_canopy_l ) THEN
	267	dt_plant_canopy_l = dt_plant_canopy_w
	268	ENDIF
	269	ENDDO
	270	ENDDO
	271	ENDDO
	272
	273	IF ( dt_plant_canopy_l > 0.0 ) THEN
[320]	274	!
	275	!-- Invert dt_plant_canopy_l and apply a security timestep factor 0.1
[318]	276	dt_plant_canopy_l = 0.1 / dt_plant_canopy_l
[320]	277	ELSE
	278	!
	279	!-- In case of inhomogeneous plant canopy, some processors may have no
	280	!-- canopy at all. Then use dt_max as dummy instead.
	281	dt_plant_canopy_l = dt_max
[318]	282	ENDIF
[320]	283
[316]	284	!
[318]	285	!-- Determine the global minumum
	286	#if defined( __parallel )
[622]	287	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
[866]	288	CALL MPI_ALLREDUCE( dt_plant_canopy_l, dt_plant_canopy, 1, MPI_REAL, &
[318]	289	MPI_MIN, comm2d, ierr )
	290	#else
	291	dt_plant_canopy = dt_plant_canopy_l
	292	#endif
[316]	293
	294	ELSE
	295	!
	296	!-- Use dt_diff as dummy value to avoid extra IF branches further below
	297	dt_plant_canopy = dt_diff
	298
	299	ENDIF
	300
	301	!
	302	!-- The time step is the minimum of the 3-4 components and the diffusion time
[1001]	303	!-- step minus a reduction (cfl_factor) to be on the safe side.
[1]	304	!-- The time step must not exceed the maximum allowed value.
[1053]	305	dt_3d = cfl_factor * MIN( dt_diff, dt_plant_canopy, dt_u, dt_v, dt_w, &
	306	dt_precipitation )
[1]	307	dt_3d = MIN( dt_3d, dt_max )
	308
	309	!
	310	!-- Remember the restricting time step criterion for later output.
[316]	311	IF ( MIN( dt_u, dt_v, dt_w ) < MIN( dt_diff, dt_plant_canopy ) ) THEN
[1]	312	timestep_reason = 'A'
[316]	313	ELSEIF ( dt_plant_canopy < dt_diff ) THEN
	314	timestep_reason = 'C'
[1]	315	ELSE
	316	timestep_reason = 'D'
	317	ENDIF
	318
	319	!
	320	!-- Set flag if the time step becomes too small.
	321	IF ( dt_3d < ( 0.00001 * dt_max ) ) THEN
	322	stop_dt = .TRUE.
[108]	323
[320]	324	WRITE( message_string, * ) 'Time step has reached minimum limit.', &
	325	'&dt = ', dt_3d, ' s Simulation is terminated.', &
	326	'&old_dt = ', old_dt, ' s', &
	327	'&dt_u = ', dt_u, ' s', &
	328	'&dt_v = ', dt_v, ' s', &
	329	'&dt_w = ', dt_w, ' s', &
	330	'&dt_diff = ', dt_diff, ' s', &
	331	'&dt_plant_canopy = ', dt_plant_canopy, ' s', &
[866]	332	'&u_max_cfl = ', u_max_cfl, ' m/s k=', u_max_cfl_ijk(1), &
[320]	333	' j=', u_max_ijk(2), ' i=', u_max_ijk(3), &
[866]	334	'&v_max_cfl = ', v_max_cfl, ' m/s k=', v_max_cfl_ijk(1), &
[320]	335	' j=', v_max_ijk(2), ' i=', v_max_ijk(3), &
[866]	336	'&w_max = ', w_max, ' m/s k=', w_max_ijk(1), &
[320]	337	' j=', w_max_ijk(2), ' i=', w_max_ijk(3)
[258]	338	CALL message( 'timestep', 'PA0312', 0, 1, 0, 6, 0 )
[108]	339	!
	340	!-- In case of coupled runs inform the remote model of the termination
	341	!-- and its reason, provided the remote model has not already been
	342	!-- informed of another termination reason (terminate_coupled > 0) before.
[222]	343	#if defined( __parallel )
[108]	344	IF ( coupling_mode /= 'uncoupled' .AND. terminate_coupled == 0 ) THEN
	345	terminate_coupled = 2
[667]	346	IF ( myid == 0 ) THEN
	347	CALL MPI_SENDRECV( &
	348	terminate_coupled, 1, MPI_INTEGER, target_id, 0, &
	349	terminate_coupled_remote, 1, MPI_INTEGER, target_id, 0, &
	350	comm_inter, status, ierr )
	351	ENDIF
	352	CALL MPI_BCAST( terminate_coupled_remote, 1, MPI_INTEGER, 0, comm2d, ierr)
[108]	353	ENDIF
[222]	354	#endif
[1]	355	ENDIF
	356
	357	!
[1001]	358	!-- Ensure a smooth value (two significant digits) of the timestep.
	359	div = 1000.0
	360	DO WHILE ( dt_3d < div )
	361	div = div / 10.0
	362	ENDDO
	363	dt_3d = NINT( dt_3d * 100.0 / div ) * div / 100.0
[1]	364
	365	!
[1001]	366	!-- Adjust the time step
	367	old_dt = dt_3d
[1]	368
[1001]	369	ENDIF
[1]	370
	371	CALL cpu_log( log_point(12), 'calculate_timestep', 'stop' )
	372
	373	END SUBROUTINE timestep

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