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timestep.f90 @ 667

Last change on this file since 667 was 667, checked in by suehring, 14 years ago

summary:

Gryschka:

Coupling with different resolution and different numbers of PEs in ocean and atmosphere is available
Exchange of u and v from ocean surface to atmosphere surface
Mirror boundary condition for u and v at the bottom are replaced by dirichlet boundary conditions
Inflow turbulence is now defined by flucuations around spanwise mean
Bugfixes for cyclic_fill and constant_volume_flow

Suehring:

New advection added ( Wicker and Skamarock 5th order ), therefore:
- New module advec_ws.f90
- Modified exchange of ghost boundaries.
- Modified evaluation of turbulent fluxes
- New index bounds nxlg, nxrg, nysg, nyng

advec_ws.f90

Advection scheme for scalars and momentum using the flux formulation of
Wicker and Skamarock 5th order.
Additionally the module contains of a routine using for initialisation and
steering of the statical evaluation. The computation of turbulent fluxes takes
place inside the advection routines.
In case of vector architectures Dirichlet and Radiation boundary conditions are
outstanding and not available. Furthermore simulations within topography are
not possible so far. A further routine local_diss_ij is available and is used
if a control of dissipative fluxes is desired.

check_parameters.f90

Exchange of parameters between ocean and atmosphere via PE0
Check for illegal combination of ws-scheme and timestep scheme.
Check for topography and ws-scheme.
Check for not cyclic boundary conditions in combination with ws-scheme and
loop_optimization = 'vector'.
Check for call_psolver_at_all_substeps and ws-scheme for momentum_advec.

Different processor/grid topology in atmosphere and ocean is now allowed!
Bugfixes in checking for conserve_volume_flow_mode.

exchange_horiz.f90

Dynamic exchange of ghost points with nbgp_local to ensure that no useless
ghost points exchanged in case of multigrid. type_yz(0) and type_xz(0) used for
normal grid, the remaining types used for the several grid levels.
Exchange is done via MPI-Vectors with a dynamic value of ghost points which
depend on the advection scheme. Exchange of left and right PEs is 10% faster
with MPI-Vectors than without.

flow_statistics.f90

When advection is computed with ws-scheme, turbulent fluxes are already
computed in the respective advection routines and buffered in arrays
sums_xxxx_ws_l(). This is due to a consistent treatment of statistics
with the numerics and to avoid unphysical kinks near the surface. So some if-
requests has to be done to dicern between fluxes from ws-scheme other advection
schemes. Furthermore the computation of z_i is only done if the heat flux
exceeds a minimum value. This affects only simulations of a neutral boundary
layer and is due to reasons of computations in the advection scheme.

inflow_turbulence.f90

Using nbgp recycling planes for a better resolution of the turbulent flow near
the inflow.

init_grid.f90

Definition of new array bounds nxlg, nxrg, nysg, nyng on each PE.
Furthermore the allocation of arrays and steering of loops is done with these
parameters. Call of exchange_horiz are modified.
In case of dirichlet bounday condition at the bottom zu(0)=0.0
dzu_mg has to be set explicitly for a equally spaced grid near bottom.
ddzu_pres added to use a equally spaced grid near bottom.

init_pegrid.f90

Moved determination of target_id's from init_coupling
Determination of parameters needed for coupling (coupling_topology, ngp_a, ngp_o)
with different grid/processor-topology in ocean and atmosphere

Adaption of ngp_xy, ngp_y to a dynamic number of ghost points.
The maximum_grid_level changed from 1 to 0. 0 is the normal grid, 1 to
maximum_grid_level the grids for multigrid, in which 0 and 1 are normal grids.
This distinction is due to reasons of data exchange and performance for the
normal grid and grids in poismg.
The definition of MPI-Vectors adapted to a dynamic numer of ghost points.
New MPI-Vectors for data exchange between left and right boundaries added.
This is due to reasons of performance (10% faster).

ATTENTION: nnz_x undefined problem still has to be solved!!!!!!!!
TEST OUTPUT (TO BE REMOVED) logging mpi2 ierr values

parin.f90

Steering parameter dissipation_control added in inipar.

Makefile

Module advec_ws added.

Modules

Removed u_nzb_p1_for_vfc and v_nzb_p1_for_vfc

For coupling with different resolution in ocean and atmophere:
+nx_a, +nx_o, ny_a, +ny_o, ngp_a, ngp_o, +total_2d_o, +total_2d_a,
+coupling_topology

Buffer arrays for the left sided advective fluxes added in arrays_3d.
+flux_s_u, +flux_s_v, +flux_s_w, +diss_s_u, +diss_s_v, +diss_s_w,
+flux_s_pt, +diss_s_pt, +flux_s_e, +diss_s_e, +flux_s_q, +diss_s_q,
+flux_s_sa, +diss_s_sa
3d arrays for dissipation control added. (only necessary for vector arch.)
+var_x, +var_y, +var_z, +gamma_x, +gamma_y, +gamma_z
Default of momentum_advec and scalar_advec changed to 'ws-scheme' .
+exchange_mg added in control_parameters to steer the data exchange.
Parameters +nbgp, +nxlg, +nxrg, +nysg, +nyng added in indices.
flag array +boundary_flags added in indices to steer the degradation of order
of the advective fluxes when non-cyclic boundaries are used.
MPI-datatypes +type_y, +type_y_int and +type_yz for data_exchange added in
pegrid.
+sums_wsus_ws_l, +sums_wsvs_ws_l, +sums_us2_ws_l, +sums_vs2_ws_l,
+sums_ws2_ws_l, +sums_wspts_ws_l, +sums_wssas_ws_l, +sums_wsqs_ws_l
and +weight_substep added in statistics to steer the statistical evaluation
of turbulent fluxes in the advection routines.
LOGICALS +ws_scheme_sca and +ws_scheme_mom added to get a better performance
in prognostic_equations.
LOGICAL +dissipation_control control added to steer numerical dissipation
in ws-scheme.

Changed length of string run_description_header

pres.f90

New allocation of tend when ws-scheme and multigrid is used. This is due to
reasons of perforance of the data_exchange. The same is done with p after
poismg is called.
nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng when no
multigrid is used. Calls of exchange_horiz are modified.

bugfix: After pressure correction no volume flow correction in case of
non-cyclic boundary conditions
(has to be done only before pressure correction)

Call of SOR routine is referenced with ddzu_pres.

prognostic_equations.f90

Calls of the advection routines with WS5 added.
Calls of ws_statistics added to set the statistical arrays to zero after each
time step.

advec_particles.f90

Declaration of de_dx, de_dy, de_dz adapted to additional ghost points.
Furthermore the calls of exchange_horiz were modified.

asselin_filter.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng

average_3d_data.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng

boundary_conds.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng
Removed mirror boundary conditions for u and v at the bottom in case of
ibc_uv_b == 0. Instead, dirichelt boundary conditions (u=v=0) are set
in init_3d_model

calc_liquid_water_content.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng

calc_spectra.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng for
allocation of tend.

check_open.f90

Output of total array size was adapted to nbgp.

data_output_2d.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng in loops and
allocation of arrays local_2d and total_2d.
Calls of exchange_horiz are modified.

data_output_2d.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng in loops and
allocation of arrays. Calls of exchange_horiz are modified.
Skip-value skip_do_avs changed to a dynamic adaption of ghost points.

data_output_mask.f90

Calls of exchange_horiz are modified.

diffusion_e.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng

diffusion_s.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng

diffusion_u.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng

diffusion_v.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng

diffusion_w.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng

diffusivities.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng

diffusivities.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng.
Calls of exchange_horiz are modified.

exchange_horiz_2d.f90

Dynamic exchange of ghost points with nbgp, which depends on the advection
scheme. Exchange between left and right PEs is now done with MPI-vectors.

global_min_max.f90

Adapting of the index arrays, because MINLOC assumes lowerbound
at 1 and not at nbgp.

init_3d_model.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng in loops and
allocation of arrays. Calls of exchange_horiz are modified.
Call ws_init to initialize arrays needed for statistical evaluation and
optimization when ws-scheme is used.
Initial volume flow is now calculated by using the variable hom_sum.
Therefore the correction of initial volume flow for non-flat topography
removed (removed u_nzb_p1_for_vfc and v_nzb_p1_for_vfc)
Changed surface boundary conditions for u and v in case of ibc_uv_b == 0 from
mirror bc to dirichlet boundary conditions (u=v=0), so that k=nzb is
representative for the height z0

Bugfix: type conversion of '1' to 64bit for the MAX function (ngp_3d_inner)

init_coupling.f90

determination of target_id's moved to init_pegrid

init_pt_anomaly.f90

Call of exchange_horiz are modified.

init_rankine.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng.
Calls of exchange_horiz are modified.

init_slope.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng.

header.f90

Output of advection scheme.

poismg.f90

Calls of exchange_horiz are modified.

prandtl_fluxes.f90

Changed surface boundary conditions for u and v from mirror bc to dirichelt bc,
therefore u(uzb,:,:) and v(nzb,:,:) is now representative for the height z0
nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng

production_e.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng

read_3d_binary.f90

+/- 1 replaced with +/- nbgp when swapping and allocating variables.

sor.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng.
Call of exchange_horiz are modified.
bug removed in declaration of ddzw(), nz replaced by nzt+1

subsidence.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng.

sum_up_3d_data.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng.

surface_coupler.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng in
MPI_SEND() and MPI_RECV.
additional case for nonequivalent processor and grid topopolgy in ocean and
atmosphere added (coupling_topology = 1)

Added exchange of u and v from Ocean to Atmosphere

time_integration.f90

Calls of exchange_horiz are modified.
Adaption to slooping surface.

timestep.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng.

user_3d_data_averaging.f90, user_data_output_2d.f90, user_data_output_3d.f90,
user_actions.f90, user_init.f90, user_init_plant_canopy.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng.

user_read_restart_data.f90

Allocation with nbgp.

wall_fluxes.f90

nxl-1, nxr+1, nys-1, nyn+1 replaced by nxlg, nxrg, nysg, nyng.

write_compressed.f90

Array bounds and nx, ny adapted with nbgp.

sor.f90

bug removed in declaration of ddzw(), nz replaced by nzt+1

Property svn:keywords set to Id

File size: 15.8 KB

Line
1	SUBROUTINE timestep
2
3	!------------------------------------------------------------------------------!
4	! Current revisions:
5	! -----------------
6	!
7	!
8	! Exchange of terminate_coupled between ocean and atmosphere via PE0
9	!
10	! Minimum grid spacing dxyz2_min(k) is now calculated using dzw instead of dzu
11	!
12	!
13	! Former revisions:
14	! -----------------
15	! $Id: timestep.f90 667 2010-12-23 12:06:00Z suehring $
16	!
17	! 622 2010-12-10 08:08:13Z raasch
18	! optional barriers included in order to speed up collective operations
19	!
20	! 343 2009-06-24 12:59:09Z maronga
21	! Additional timestep criterion in case of simulations with plant canopy
22	! Output of messages replaced by message handling routine.
23	!
24	! 222 2009-01-12 16:04:16Z letzel
25	! Implementation of a MPI-1 Coupling: replaced myid with target_id
26	! Bugfix for nonparallel execution
27	!
28	! 108 2007-08-24 15:10:38Z letzel
29	! modifications to terminate coupled runs
30	!
31	! RCS Log replace by Id keyword, revision history cleaned up
32	!
33	! Revision 1.21 2006/02/23 12:59:44 raasch
34	! nt_anz renamed current_timestep_number
35	!
36	! Revision 1.1 1997/08/11 06:26:19 raasch
37	! Initial revision
38	!
39	!
40	! Description:
41	! ------------
42	! Compute the time step under consideration of the FCL and diffusion criterion.
43	!------------------------------------------------------------------------------!
44
45	USE arrays_3d
46	USE control_parameters
47	USE cpulog
48	USE grid_variables
49	USE indices
50	USE interfaces
51	USE pegrid
52	USE statistics
53
54	IMPLICIT NONE
55
56	INTEGER :: i, j, k
57
58	REAL :: div, dt_diff, dt_diff_l, dt_plant_canopy, &
59	dt_plant_canopy_l, &
60	dt_plant_canopy_u, dt_plant_canopy_v, dt_plant_canopy_w, &
61	dt_u, dt_v, dt_w, lad_max, percent_change, &
62	u_gtrans_l, vabs_max, value, v_gtrans_l
63
64	REAL, DIMENSION(2) :: uv_gtrans, uv_gtrans_l
65	REAL, DIMENSION(nzb+1:nzt) :: dxyz2_min
66
67
68
69	CALL cpu_log( log_point(12), 'calculate_timestep', 'start' )
70
71	!
72	!-- Determine the maxima of the velocity components.
73	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, u, 'abs', &
74	u_max, u_max_ijk )
75	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, v, 'abs', &
76	v_max, v_max_ijk )
77	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, w, 'abs', &
78	w_max, w_max_ijk )
79
80	!
81	!-- In case maxima of the horizontal velocity components have been found at the
82	!-- bottom boundary (k=nzb), the corresponding maximum at level k=1 is chosen
83	!-- if the Dirichlet-boundary condition ('mirror') has been set. This is
84	!-- necessary, because otherwise in case of Galilei-transform a far too large
85	!-- velocity (having the respective opposite sign) would be used for the time
86	!-- step determination (almost double the mean flow velocity).
87	IF ( ibc_uv_b == 0 ) THEN
88	IF ( u_max_ijk(1) == nzb ) THEN
89	u_max = -u_max
90	u_max_ijk(1) = nzb + 1
91	ENDIF
92	IF ( v_max_ijk(1) == nzb ) THEN
93	v_max = -v_max
94	v_max_ijk(1) = nzb + 1
95	ENDIF
96	ENDIF
97
98	!
99	!-- In case of Galilei-transform not using the geostrophic wind as translation
100	!-- velocity, compute the volume-averaged horizontal velocity components, which
101	!-- will then be subtracted from the horizontal wind for the time step and
102	!-- horizontal advection routines.
103	IF ( galilei_transformation .AND. .NOT. use_ug_for_galilei_tr ) THEN
104	IF ( flow_statistics_called ) THEN
105	!
106	!-- Horizontal averages already existent, just need to average them
107	!-- vertically.
108	u_gtrans = 0.0
109	v_gtrans = 0.0
110	DO k = nzb+1, nzt
111	u_gtrans = u_gtrans + hom(k,1,1,0)
112	v_gtrans = v_gtrans + hom(k,1,2,0)
113	ENDDO
114	u_gtrans = u_gtrans / REAL( nzt - nzb )
115	v_gtrans = v_gtrans / REAL( nzt - nzb )
116	ELSE
117	!
118	!-- Averaging over the entire model domain.
119	uv_gtrans_l = 0.0
120	DO i = nxl, nxr
121	DO j = nys, nyn
122	DO k = nzb+1, nzt
123	uv_gtrans_l(1) = uv_gtrans_l(1) + u(k,j,i)
124	uv_gtrans_l(2) = uv_gtrans_l(2) + v(k,j,i)
125	ENDDO
126	ENDDO
127	ENDDO
128	uv_gtrans_l = uv_gtrans_l / REAL( (nxr-nxl+1)(nyn-nys+1)(nzt-nzb) )
129	#if defined( __parallel )
130	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
131	CALL MPI_ALLREDUCE( uv_gtrans_l, uv_gtrans, 2, MPI_REAL, MPI_SUM, &
132	comm2d, ierr )
133	u_gtrans = uv_gtrans(1) / REAL( numprocs )
134	v_gtrans = uv_gtrans(2) / REAL( numprocs )
135	#else
136	u_gtrans = uv_gtrans_l(1)
137	v_gtrans = uv_gtrans_l(2)
138	#endif
139	ENDIF
140	ENDIF
141
142	IF ( .NOT. dt_fixed ) THEN
143	!
144	!-- Variable time step:
145	!
146	!-- For each component, compute the maximum time step according to the
147	!-- FCL-criterion.
148	dt_u = dx / ( ABS( u_max - u_gtrans ) + 1.0E-10 )
149	dt_v = dy / ( ABS( v_max - v_gtrans ) + 1.0E-10 )
150	dt_w = dzu(MAX( 1, w_max_ijk(1) )) / ( ABS( w_max ) + 1.0E-10 )
151
152	!
153	!-- Compute time step according to the diffusion criterion.
154	!-- First calculate minimum grid spacing which only depends on index k
155	!-- Note: also at k=nzb+1 a full grid length is being assumed, although
156	!-- in the Prandtl-layer friction term only dz/2 is used.
157	!-- Experience from the old model seems to justify this.
158	dt_diff_l = 999999.0
159
160	DO k = nzb+1, nzt
161	dxyz2_min(k) = MIN( dx2, dy2, dzw(k)dzw(k) ) 0.125
162	ENDDO
163
164	!$OMP PARALLEL private(i,j,k,value) reduction(MIN: dt_diff_l)
165	!$OMP DO
166	DO i = nxl, nxr
167	DO j = nys, nyn
168	DO k = nzb+1, nzt
169	value = dxyz2_min(k) / ( MAX( kh(k,j,i), km(k,j,i) ) + 1E-20 )
170
171	dt_diff_l = MIN( value, dt_diff_l )
172	ENDDO
173	ENDDO
174	ENDDO
175	!$OMP END PARALLEL
176	#if defined( __parallel )
177	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
178	CALL MPI_ALLREDUCE( dt_diff_l, dt_diff, 1, MPI_REAL, MPI_MIN, comm2d, &
179	ierr )
180	#else
181	dt_diff = dt_diff_l
182	#endif
183
184	!
185	!-- In case of non-cyclic lateral boundaries, the diffusion time step
186	!-- may be further restricted by the lateral damping layer (damping only
187	!-- along x and y)
188	IF ( bc_lr /= 'cyclic' ) THEN
189	dt_diff = MIN( dt_diff, 0.125 * dx2 / ( km_damp_max + 1E-20 ) )
190	ELSEIF ( bc_ns /= 'cyclic' ) THEN
191	dt_diff = MIN( dt_diff, 0.125 * dy2 / ( km_damp_max + 1E-20 ) )
192	ENDIF
193
194	!
195	!-- Additional timestep criterion with plant canopies:
196	!-- it is not allowed to extract more than the available momentum
197	IF ( plant_canopy ) THEN
198
199	dt_plant_canopy_l = 0.0
200	DO i = nxl, nxr
201	DO j = nys, nyn
202	DO k = nzb+1, nzt
203	dt_plant_canopy_u = cdc(k,j,i) * lad_u(k,j,i) * &
204	SQRT( u(k,j,i)**2 + &
205	( ( v(k,j,i-1) + &
206	v(k,j,i) + &
207	v(k,j+1,i) + &
208	v(k,j+1,i-1) ) &
209	/ 4.0 )**2 + &
210	( ( w(k-1,j,i-1) + &
211	w(k-1,j,i) + &
212	w(k,j,i-1) + &
213	w(k,j,i) ) &
214	/ 4.0 )**2 )
215	IF ( dt_plant_canopy_u > dt_plant_canopy_l ) THEN
216	dt_plant_canopy_l = dt_plant_canopy_u
217	ENDIF
218	dt_plant_canopy_v = cdc(k,j,i) * lad_v(k,j,i) * &
219	SQRT( ( ( u(k,j-1,i) + &
220	u(k,j-1,i+1) + &
221	u(k,j,i) + &
222	u(k,j,i+1) ) &
223	/ 4.0 )**2 + &
224	v(k,j,i)**2 + &
225	( ( w(k-1,j-1,i) + &
226	w(k-1,j,i) + &
227	w(k,j-1,i) + &
228	w(k,j,i) ) &
229	/ 4.0 )**2 )
230	IF ( dt_plant_canopy_v > dt_plant_canopy_l ) THEN
231	dt_plant_canopy_l = dt_plant_canopy_v
232	ENDIF
233	dt_plant_canopy_w = cdc(k,j,i) * lad_w(k,j,i) * &
234	SQRT( ( ( u(k,j,i) + &
235	u(k,j,i+1) + &
236	u(k+1,j,i) + &
237	u(k+1,j,i+1) ) &
238	/ 4.0 )**2 + &
239	( ( v(k,j,i) + &
240	v(k,j+1,i) + &
241	v(k+1,j,i) + &
242	v(k+1,j+1,i) ) &
243	/ 4.0 )**2 + &
244	w(k,j,i)**2 )
245	IF ( dt_plant_canopy_w > dt_plant_canopy_l ) THEN
246	dt_plant_canopy_l = dt_plant_canopy_w
247	ENDIF
248	ENDDO
249	ENDDO
250	ENDDO
251
252	IF ( dt_plant_canopy_l > 0.0 ) THEN
253	!
254	!-- Invert dt_plant_canopy_l and apply a security timestep factor 0.1
255	dt_plant_canopy_l = 0.1 / dt_plant_canopy_l
256	ELSE
257	!
258	!-- In case of inhomogeneous plant canopy, some processors may have no
259	!-- canopy at all. Then use dt_max as dummy instead.
260	dt_plant_canopy_l = dt_max
261	ENDIF
262
263	!
264	!-- Determine the global minumum
265	#if defined( __parallel )
266	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
267	CALL MPI_ALLREDUCE( dt_plant_canopy_l, dt_plant_canopy, 1, MPI_REAL, &
268	MPI_MIN, comm2d, ierr )
269	#else
270	dt_plant_canopy = dt_plant_canopy_l
271	#endif
272
273	ELSE
274	!
275	!-- Use dt_diff as dummy value to avoid extra IF branches further below
276	dt_plant_canopy = dt_diff
277
278	ENDIF
279
280	!
281	!-- The time step is the minimum of the 3-4 components and the diffusion time
282	!-- step minus a reduction to be on the safe side. Factor 0.5 is necessary
283	!-- since the leap-frog scheme always progresses by 2 * delta t.
284	!-- The user has to set the cfl_factor small enough to ensure that the
285	!-- divergences do not become too large.
286	!-- The time step must not exceed the maximum allowed value.
287	IF ( timestep_scheme(1:5) == 'runge' ) THEN
288	dt_3d = cfl_factor * MIN( dt_diff, dt_plant_canopy, dt_u, dt_v, dt_w )
289	ELSE
290	dt_3d = cfl_factor * 0.5 * &
291	MIN( dt_diff, dt_plant_canopy, dt_u, dt_v, dt_w )
292	ENDIF
293	dt_3d = MIN( dt_3d, dt_max )
294
295	!
296	!-- Remember the restricting time step criterion for later output.
297	IF ( MIN( dt_u, dt_v, dt_w ) < MIN( dt_diff, dt_plant_canopy ) ) THEN
298	timestep_reason = 'A'
299	ELSEIF ( dt_plant_canopy < dt_diff ) THEN
300	timestep_reason = 'C'
301	ELSE
302	timestep_reason = 'D'
303	ENDIF
304
305	!
306	!-- Set flag if the time step becomes too small.
307	IF ( dt_3d < ( 0.00001 * dt_max ) ) THEN
308	stop_dt = .TRUE.
309
310	WRITE( message_string, * ) 'Time step has reached minimum limit.', &
311	'&dt = ', dt_3d, ' s Simulation is terminated.', &
312	'&old_dt = ', old_dt, ' s', &
313	'&dt_u = ', dt_u, ' s', &
314	'&dt_v = ', dt_v, ' s', &
315	'&dt_w = ', dt_w, ' s', &
316	'&dt_diff = ', dt_diff, ' s', &
317	'&dt_plant_canopy = ', dt_plant_canopy, ' s', &
318	'&u_max = ', u_max, ' m/s k=', u_max_ijk(1), &
319	' j=', u_max_ijk(2), ' i=', u_max_ijk(3), &
320	'&v_max = ', v_max, ' m/s k=', v_max_ijk(1), &
321	' j=', v_max_ijk(2), ' i=', v_max_ijk(3), &
322	'&w_max = ', w_max, ' m/s k=', w_max_ijk(1), &
323	' j=', w_max_ijk(2), ' i=', w_max_ijk(3)
324	CALL message( 'timestep', 'PA0312', 0, 1, 0, 6, 0 )
325	!
326	!-- In case of coupled runs inform the remote model of the termination
327	!-- and its reason, provided the remote model has not already been
328	!-- informed of another termination reason (terminate_coupled > 0) before.
329	#if defined( __parallel )
330	IF ( coupling_mode /= 'uncoupled' .AND. terminate_coupled == 0 ) THEN
331	terminate_coupled = 2
332	IF ( myid == 0 ) THEN
333	CALL MPI_SENDRECV( &
334	terminate_coupled, 1, MPI_INTEGER, target_id, 0, &
335	terminate_coupled_remote, 1, MPI_INTEGER, target_id, 0, &
336	comm_inter, status, ierr )
337	ENDIF
338	CALL MPI_BCAST( terminate_coupled_remote, 1, MPI_INTEGER, 0, comm2d, ierr)
339	ENDIF
340	#endif
341	ENDIF
342
343	!
344	!-- Ensure a smooth value (two significant digits) of the timestep. For
345	!-- other schemes than Runge-Kutta, the following restrictions appear:
346	!-- The current timestep is only then changed, if the change relative to
347	!-- its previous value exceeds +5 % or -2 %. In case of a timestep
348	!-- reduction, at least 30 iterations have to be performed before a timestep
349	!-- enlargement is permitted again.
350	percent_change = dt_3d / old_dt - 1.0
351	IF ( percent_change > 0.05 .OR. percent_change < -0.02 .OR. &
352	timestep_scheme(1:5) == 'runge' ) THEN
353
354	!
355	!-- Time step enlargement by no more than 2 %.
356	IF ( percent_change > 0.0 .AND. simulated_time /= 0.0 .AND. &
357	timestep_scheme(1:5) /= 'runge' ) THEN
358	dt_3d = 1.02 * old_dt
359	ENDIF
360
361	!
362	!-- A relatively smooth value of the time step is ensured by taking
363	!-- only the first two significant digits.
364	div = 1000.0
365	DO WHILE ( dt_3d < div )
366	div = div / 10.0
367	ENDDO
368	dt_3d = NINT( dt_3d * 100.0 / div ) * div / 100.0
369
370	!
371	!-- Now the time step can be adjusted.
372	IF ( percent_change < 0.0 .OR. timestep_scheme(1:5) == 'runge' ) &
373	THEN
374	!
375	!-- Time step reduction.
376	old_dt = dt_3d
377	dt_changed = .TRUE.
378	ELSE
379	!
380	!-- For other timestep schemes , the time step is only enlarged
381	!-- after at least 30 iterations since the previous time step
382	!-- change or, of course, after model initialization.
383	IF ( current_timestep_number >= last_dt_change + 30 .OR. &
384	simulated_time == 0.0 ) THEN
385	old_dt = dt_3d
386	dt_changed = .TRUE.
387	ELSE
388	dt_3d = old_dt
389	dt_changed = .FALSE.
390	ENDIF
391
392	ENDIF
393	ELSE
394	!
395	!-- No time step change since the difference is too small.
396	dt_3d = old_dt
397	dt_changed = .FALSE.
398	ENDIF
399
400	IF ( dt_changed ) last_dt_change = current_timestep_number
401
402	ENDIF
403	CALL cpu_log( log_point(12), 'calculate_timestep', 'stop' )
404
405	END SUBROUTINE timestep

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source: palm/trunk/SOURCE/timestep.f90 @ 667

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