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source: palm/trunk/SOURCE/lpm_boundary_conds.f90 @ 2698

Last change on this file since 2698 was 2698, checked in by suehring, 6 years ago
Particle reflections at downward-facing walls; revision of particle speed interpolations at walls; bugfixes in get_topography_index and in date constants
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1	!> @file lpm_boundary_conds.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 1997-2017 Leibniz Universitaet Hannover
18	!------------------------------------------------------------------------------!
19	!
20	! Current revisions:
21	! -----------------
22	! Particle reflections at downward-facing walls implemented. Moreover,
23	! reflections are adjusted to revised particle grid box location.
24	! (responsible Philipp Thiele)
25	!
26	! Former revisions:
27	! -----------------
28	! $Id: lpm_boundary_conds.f90 2698 2017-12-14 18:46:24Z suehring $
29	! Changed particle box locations: center of particle box now coincides
30	! with scalar grid point of same index.
31	! Renamed module and subroutines: lpm_pack_arrays_mod -> lpm_pack_and_sort_mod
32	! lpm_pack_all_arrays -> lpm_sort_in_subboxes, lpm_pack_arrays -> lpm_pack
33	! lpm_sort -> lpm_sort_timeloop_done
34	!
35	! 2318 2017-07-20 17:27:44Z suehring
36	! Get topography top index via Function call
37	!
38	! 2317 2017-07-20 17:27:19Z suehring
39	!
40	! 2232 2017-05-30 17:47:52Z suehring
41	! Adjustments to new topography and surface concept
42	! Rename character range into location, as range is an intrinsic.
43	!
44	! 2000 2016-08-20 18:09:15Z knoop
45	! Forced header and separation lines into 80 columns
46	!
47	! 1929 2016-06-09 16:25:25Z suehring
48	! Rewritten wall reflection
49	!
50	! 1822 2016-04-07 07:49:42Z hoffmann
51	! Tails removed. Unused variables removed.
52	!
53	! 1682 2015-10-07 23:56:08Z knoop
54	! Code annotations made doxygen readable
55	!
56	! 1359 2014-04-11 17:15:14Z hoffmann
57	! New particle structure integrated.
58	! Kind definition added to all floating point numbers.
59	!
60	! 1320 2014-03-20 08:40:49Z raasch
61	! ONLY-attribute added to USE-statements,
62	! kind-parameters added to all INTEGER and REAL declaration statements,
63	! kinds are defined in new module kinds,
64	! revision history before 2012 removed,
65	! comment fields (!:) to be used for variable explanations added to
66	! all variable declaration statements
67	!
68	! 1036 2012-10-22 13:43:42Z raasch
69	! code put under GPL (PALM 3.9)
70	!
71	! 849 2012-03-15 10:35:09Z raasch
72	! routine renamed lpm_boundary_conds, bottom and top boundary conditions
73	! included (former part of advec_particles)
74	!
75	! 824 2012-02-17 09:09:57Z raasch
76	! particle attributes speed_x\|y\|z_sgs renamed rvar1\|2\|3
77	!
78	! Initial version (2007/03/09)
79	!
80	! Description:
81	! ------------
82	!> Boundary conditions for the Lagrangian particles.
83	!> The routine consists of two different parts. One handles the bottom (flat)
84	!> and top boundary. In this part, also particles which exceeded their lifetime
85	!> are deleted.
86	!> The other part handles the reflection of particles from vertical walls.
87	!> This part was developed by Jin Zhang during 2006-2007.
88	!>
89	!> To do: Code structure for finding the t_index values and for checking the
90	!> ----- reflection conditions is basically the same for all four cases, so it
91	!> should be possible to further simplify/shorten it.
92	!>
93	!> THE WALLS PART OF THIS ROUTINE HAS NOT BEEN TESTED FOR OCEAN RUNS SO FAR!!!!
94	!> (see offset_ocean_*)
95	!------------------------------------------------------------------------------!
96	SUBROUTINE lpm_boundary_conds( location , i, j, k )
97
98
99	USE arrays_3d, &
100	ONLY: zu, zw
101
102	USE control_parameters, &
103	ONLY: dz, message_string, particle_maximum_age
104
105	USE cpulog, &
106	ONLY: cpu_log, log_point_s
107
108	USE grid_variables, &
109	ONLY: ddx, dx, ddy, dy
110
111	USE indices, &
112	ONLY: nxl, nxr, nyn, nys, nz, nzb, wall_flags_0,nyng,nysg
113
114	USE kinds
115
116	USE particle_attributes, &
117	ONLY: deleted_particles, ibc_par_b, ibc_par_t, number_of_particles, &
118	particles, particle_type, offset_ocean_nzt_m1, &
119	use_sgs_for_particles
120
121	USE pegrid
122
123	IMPLICIT NONE
124
125	CHARACTER (LEN=*) :: location !<
126
127	INTEGER(iwp), INTENT(IN) :: i !<
128	INTEGER(iwp), INTENT(IN) :: j !<
129	INTEGER(iwp), INTENT(IN) :: k !<
130
131	INTEGER(iwp) :: inc !< dummy for sorting algorithmus
132	INTEGER(iwp) :: ir !< dummy for sorting algorithmus
133	INTEGER(iwp) :: i1 !< grid index (x) of old particle position
134	INTEGER(iwp) :: i2 !< grid index (x) of current particle position
135	INTEGER(iwp) :: i3 !< grid index (x) of intermediate particle position
136	INTEGER(iwp) :: jr !< dummy for sorting algorithmus
137	INTEGER(iwp) :: j1 !< grid index (y) of old particle position
138	INTEGER(iwp) :: j2 !< grid index (y) of current particle position
139	INTEGER(iwp) :: j3 !< grid index (y) of intermediate particle position
140	INTEGER(iwp) :: k1 !< grid index (z) of old particle position
141	INTEGER(iwp) :: k2 !< grid index (z) of current particle position
142	INTEGER(iwp) :: k3 !< grid index (z) of intermediate particle position
143	INTEGER(iwp) :: n !< particle number
144	INTEGER(iwp) :: t_index !< running index for intermediate particle timesteps in reflection algorithmus
145	INTEGER(iwp) :: t_index_number !< number of intermediate particle timesteps in reflection algorithmus
146	INTEGER(iwp) :: tmp_x !< dummy for sorting algorithm
147	INTEGER(iwp) :: tmp_y !< dummy for sorting algorithm
148	INTEGER(iwp) :: tmp_z !< dummy for sorting algorithm
149
150	INTEGER(iwp), DIMENSION(0:10) :: x_ind(0:10) = 0 !< index array (x) of intermediate particle positions
151	INTEGER(iwp), DIMENSION(0:10) :: y_ind(0:10) = 0 !< index array (y) of intermediate particle positions
152	INTEGER(iwp), DIMENSION(0:10) :: z_ind(0:10) = 0 !< index array (z) of intermediate particle positions
153
154	LOGICAL :: cross_wall_x !< flag to check if particle reflection along x is necessary
155	LOGICAL :: cross_wall_y !< flag to check if particle reflection along y is necessary
156	LOGICAL :: cross_wall_z !< flag to check if particle reflection along z is necessary
157	LOGICAL :: reflect_x !< flag to check if particle is already reflected along x
158	LOGICAL :: reflect_y !< flag to check if particle is already reflected along y
159	LOGICAL :: reflect_z !< flag to check if particle is already reflected along z
160	LOGICAL :: tmp_reach_x !< dummy for sorting algorithmus
161	LOGICAL :: tmp_reach_y !< dummy for sorting algorithmus
162	LOGICAL :: tmp_reach_z !< dummy for sorting algorithmus
163	LOGICAL :: x_wall_reached !< flag to check if particle has already reached wall
164	LOGICAL :: y_wall_reached !< flag to check if particle has already reached wall
165	LOGICAL :: z_wall_reached !< flag to check if particle has already reached wall
166
167	LOGICAL, DIMENSION(0:10) :: reach_x !< flag to check if particle is at a yz-wall
168	LOGICAL, DIMENSION(0:10) :: reach_y !< flag to check if particle is at a xz-wall
169	LOGICAL, DIMENSION(0:10) :: reach_z !< flag to check if particle is at a xy-wall
170
171	REAL(wp) :: dt_particle !< particle timestep
172	REAL(wp) :: dum !< dummy argument
173	REAL(wp) :: eps = 1E-10_wp !< security number to check if particle has reached a wall
174	REAL(wp) :: pos_x !< intermediate particle position (x)
175	REAL(wp) :: pos_x_old !< particle position (x) at previous particle timestep
176	REAL(wp) :: pos_y !< intermediate particle position (y)
177	REAL(wp) :: pos_y_old !< particle position (y) at previous particle timestep
178	REAL(wp) :: pos_z !< intermediate particle position (z)
179	REAL(wp) :: pos_z_old !< particle position (z) at previous particle timestep
180	REAL(wp) :: prt_x !< current particle position (x)
181	REAL(wp) :: prt_y !< current particle position (y)
182	REAL(wp) :: prt_z !< current particle position (z)
183	REAL(wp) :: t_old !< previous reflection time
184	REAL(wp) :: tmp_t !< dummy for sorting algorithmus
185	REAL(wp) :: xwall !< location of wall in x
186	REAL(wp) :: ywall !< location of wall in y
187	REAL(wp) :: zwall !< location of wall in z
188
189	REAL(wp), DIMENSION(0:10) :: t !< reflection time
190
191
192	IF ( location == 'bottom/top' ) THEN
193
194	!
195	!-- Apply boundary conditions to those particles that have crossed the top or
196	!-- bottom boundary and delete those particles, which are older than allowed
197	DO n = 1, number_of_particles
198
199	!
200	!-- Stop if particles have moved further than the length of one
201	!-- PE subdomain (newly released particles have age = age_m!)
202	IF ( particles(n)%age /= particles(n)%age_m ) THEN
203	IF ( ABS(particles(n)%speed_x) > &
204	((nxr-nxl+2)*dx)/(particles(n)%age-particles(n)%age_m) .OR. &
205	ABS(particles(n)%speed_y) > &
206	((nyn-nys+2)*dy)/(particles(n)%age-particles(n)%age_m) ) THEN
207
208	WRITE( message_string, * ) 'particle too fast. n = ', n
209	CALL message( 'lpm_boundary_conds', 'PA0148', 2, 2, -1, 6, 1 )
210	ENDIF
211	ENDIF
212
213	IF ( particles(n)%age > particle_maximum_age .AND. &
214	particles(n)%particle_mask ) &
215	THEN
216	particles(n)%particle_mask = .FALSE.
217	deleted_particles = deleted_particles + 1
218	ENDIF
219
220	IF ( particles(n)%z >= zu(nz) .AND. particles(n)%particle_mask ) THEN
221	IF ( ibc_par_t == 1 ) THEN
222	!
223	!-- Particle absorption
224	particles(n)%particle_mask = .FALSE.
225	deleted_particles = deleted_particles + 1
226	ELSEIF ( ibc_par_t == 2 ) THEN
227	!
228	!-- Particle reflection
229	particles(n)%z = 2.0_wp * zu(nz) - particles(n)%z
230	particles(n)%speed_z = -particles(n)%speed_z
231	IF ( use_sgs_for_particles .AND. &
232	particles(n)%rvar3 > 0.0_wp ) THEN
233	particles(n)%rvar3 = -particles(n)%rvar3
234	ENDIF
235	ENDIF
236	ENDIF
237
238	IF ( particles(n)%z < zw(0) .AND. particles(n)%particle_mask ) THEN
239	IF ( ibc_par_b == 1 ) THEN
240	!
241	!-- Particle absorption
242	particles(n)%particle_mask = .FALSE.
243	deleted_particles = deleted_particles + 1
244	ELSEIF ( ibc_par_b == 2 ) THEN
245	!
246	!-- Particle reflection
247	particles(n)%z = 2.0_wp * zw(0) - particles(n)%z
248	particles(n)%speed_z = -particles(n)%speed_z
249	IF ( use_sgs_for_particles .AND. &
250	particles(n)%rvar3 < 0.0_wp ) THEN
251	particles(n)%rvar3 = -particles(n)%rvar3
252	ENDIF
253	ENDIF
254	ENDIF
255	ENDDO
256
257	ELSEIF ( location == 'walls' ) THEN
258
259
260	CALL cpu_log( log_point_s(48), 'lpm_wall_reflect', 'start' )
261
262	DO n = 1, number_of_particles
263	!
264	!-- Recalculate particle timestep
265	dt_particle = particles(n)%age - particles(n)%age_m
266	!
267	!-- Obtain x/y indices for current particle position
268	i2 = particles(n)%x * ddx
269	j2 = particles(n)%y * ddy
270	IF (zw(k) < particles(n)%z ) k2 = k + 1
271	IF (zw(k-1) > particles(n)%z ) k2 = k - 1
272	!
273	!-- Save current particle positions
274	prt_x = particles(n)%x
275	prt_y = particles(n)%y
276	prt_z = particles(n)%z
277	!
278	!-- Recalculate old particle positions
279	pos_x_old = particles(n)%x - particles(n)%speed_x * dt_particle
280	pos_y_old = particles(n)%y - particles(n)%speed_y * dt_particle
281	pos_z_old = particles(n)%z - particles(n)%speed_z * dt_particle
282	!
283	!-- Obtain x/y indices for old particle positions
284	i1 = i
285	j1 = j
286	k1 = k
287	!
288	!-- Determine horizontal as well as vertical walls at which particle can
289	!-- be potentially reflected.
290	!-- Start with walls aligned in yz layer.
291	!-- Wall to the right
292	IF ( prt_x > pos_x_old ) THEN
293	xwall = ( i1 + 1 ) * dx
294	!
295	!-- Wall to the left
296	ELSE
297	xwall = i1 * dx
298	ENDIF
299	!
300	!-- Walls aligned in xz layer
301	!-- Wall to the north
302	IF ( prt_y > pos_y_old ) THEN
303	ywall = ( j1 +1 ) * dy
304	!-- Wall to the south
305	ELSE
306	ywall = j1 * dy
307	ENDIF
308
309	IF ( prt_z > pos_z_old ) THEN
310	zwall = zw(k)
311	ELSE
312	zwall = zw(k-1)
313	ENDIF
314	!
315	!-- Initialize flags to check if particle reflection is necessary
316	cross_wall_x = .FALSE.
317	cross_wall_y = .FALSE.
318	cross_wall_z = .FALSE.
319	!
320	!-- Initialize flags to check if a wall is reached
321	reach_x = .FALSE.
322	reach_y = .FALSE.
323	reach_z = .FALSE.
324	!
325	!-- Initialize flags to check if a particle was already reflected
326	reflect_x = .FALSE.
327	reflect_y = .FALSE.
328	reflect_z = .FALSE.
329	!
330	!-- Initialize flags to check if a wall is already crossed.
331	!-- ( Required to obtain correct indices. )
332	x_wall_reached = .FALSE.
333	y_wall_reached = .FALSE.
334	z_wall_reached = .FALSE.
335	!
336	!-- Initialize time array
337	t = 0.0_wp
338	!
339	!-- Check if particle can reach any wall. This case, calculate the
340	!-- fractional time needed to reach this wall. Store this fractional
341	!-- timestep in array t. Moreover, store indices for these grid
342	!-- boxes where the respective wall belongs to.
343	!-- Start with x-direction.
344	t_index = 1
345	t(t_index) = ( xwall - pos_x_old ) &
346	/ MERGE( MAX( prt_x - pos_x_old, 1E-30_wp ), &
347	MIN( prt_x - pos_x_old, -1E-30_wp ), &
348	prt_x > pos_x_old )
349	x_ind(t_index) = i2
350	y_ind(t_index) = j1
351	z_ind(t_index) = k1
352	reach_x(t_index) = .TRUE.
353	reach_y(t_index) = .FALSE.
354	reach_z(t_index) = .FALSE.
355	!
356	!-- Store these values only if particle really reaches any wall. t must
357	!-- be in a interval between [0:1].
358	IF ( t(t_index) <= 1.0_wp .AND. t(t_index) >= 0.0_wp ) THEN
359	t_index = t_index + 1
360	cross_wall_x = .TRUE.
361	ENDIF
362	!
363	!-- y-direction
364	t(t_index) = ( ywall - pos_y_old ) &
365	/ MERGE( MAX( prt_y - pos_y_old, 1E-30_wp ), &
366	MIN( prt_y - pos_y_old, -1E-30_wp ), &
367	prt_y > pos_y_old )
368	x_ind(t_index) = i1
369	y_ind(t_index) = j2
370	z_ind(t_index) = k1
371	reach_x(t_index) = .FALSE.
372	reach_y(t_index) = .TRUE.
373	reach_z(t_index) = .FALSE.
374	IF ( t(t_index) <= 1.0_wp .AND. t(t_index) >= 0.0_wp ) THEN
375	t_index = t_index + 1
376	cross_wall_y = .TRUE.
377	ENDIF
378	!
379	!-- z-direction
380	t(t_index) = (zwall - pos_z_old ) &
381	/ MERGE( MAX( prt_z - pos_z_old, 1E-30_wp ), &
382	MIN( prt_z - pos_z_old, -1E-30_wp ), &
383	prt_z > pos_z_old )
384
385	x_ind(t_index) = i1
386	y_ind(t_index) = j1
387	z_ind(t_index) = k2
388	reach_x(t_index) = .FALSE.
389	reach_y(t_index) = .FALSE.
390	reach_z(t_index) = .TRUE.
391	IF( t(t_index) <= 1.0_wp .AND. t(t_index) >= 0.0_wp) THEN
392	t_index = t_index + 1
393	cross_wall_z = .TRUE.
394	ENDIF
395
396	t_index_number = t_index - 1
397	!
398	!-- Carry out reflection only if particle reaches any wall
399	IF ( cross_wall_x .OR. cross_wall_y .OR. cross_wall_z ) THEN
400	!
401	!-- Sort fractional timesteps in ascending order. Also sort the
402	!-- corresponding indices and flag according to the time interval a
403	!-- particle reaches the respective wall.
404	inc = 1
405	jr = 1
406	DO WHILE ( inc <= t_index_number )
407	inc = 3 * inc + 1
408	ENDDO
409
410	DO WHILE ( inc > 1 )
411	inc = inc / 3
412	DO ir = inc+1, t_index_number
413	tmp_t = t(ir)
414	tmp_x = x_ind(ir)
415	tmp_y = y_ind(ir)
416	tmp_z = z_ind(ir)
417	tmp_reach_x = reach_x(ir)
418	tmp_reach_y = reach_y(ir)
419	tmp_reach_z = reach_z(ir)
420	jr = ir
421	DO WHILE ( t(jr-inc) > tmp_t )
422	t(jr) = t(jr-inc)
423	x_ind(jr) = x_ind(jr-inc)
424	y_ind(jr) = y_ind(jr-inc)
425	z_ind(jr) = z_ind(jr-inc)
426	reach_x(jr) = reach_x(jr-inc)
427	reach_y(jr) = reach_y(jr-inc)
428	reach_z(jr) = reach_z(jr-inc)
429	jr = jr - inc
430	IF ( jr <= inc ) EXIT
431	ENDDO
432	t(jr) = tmp_t
433	x_ind(jr) = tmp_x
434	y_ind(jr) = tmp_y
435	z_ind(jr) = tmp_z
436	reach_x(jr) = tmp_reach_x
437	reach_y(jr) = tmp_reach_y
438	reach_z(jr) = tmp_reach_z
439	ENDDO
440	ENDDO
441	!
442	!-- Initialize temporary particle positions
443	pos_x = pos_x_old
444	pos_y = pos_y_old
445	pos_z = pos_z_old
446	!
447	!-- Loop over all times a particle possibly moves into a new grid box
448	t_old = 0.0_wp
449	DO t_index = 1, t_index_number
450	!
451	!-- Calculate intermediate particle position according to the
452	!-- timesteps a particle reaches any wall.
453	pos_x = pos_x + ( t(t_index) - t_old ) * dt_particle &
454	* particles(n)%speed_x
455	pos_y = pos_y + ( t(t_index) - t_old ) * dt_particle &
456	* particles(n)%speed_y
457	pos_z = pos_z + ( t(t_index) - t_old ) * dt_particle &
458	* particles(n)%speed_z
459	!
460	!-- Obtain x/y grid indices for intermediate particle position from
461	!-- sorted index array
462	i3 = x_ind(t_index)
463	j3 = y_ind(t_index)
464	k3 = z_ind(t_index)
465	!
466	!-- Check which wall is already reached
467	IF ( .NOT. x_wall_reached ) x_wall_reached = reach_x(t_index)
468	IF ( .NOT. y_wall_reached ) y_wall_reached = reach_y(t_index)
469	IF ( .NOT. z_wall_reached ) z_wall_reached = reach_z(t_index)
470	!
471	!-- Check if a particle needs to be reflected at any yz-wall. If
472	!-- necessary, carry out reflection. Please note, a security
473	!-- constant is required, as the particle position does not
474	!-- necessarily exactly match the wall location due to rounding
475	!-- errors.
476	IF ( reach_x(t_index) .AND. &
477	ABS( pos_x - xwall ) < eps .AND. &
478	.NOT. BTEST(wall_flags_0(k3,j3,i3),0) .AND. &
479	.NOT. reflect_x ) THEN
480	!
481	!
482	!-- Reflection in x-direction.
483	!-- Ensure correct reflection by MIN/MAX functions, depending on
484	!-- direction of particle transport.
485	!-- Due to rounding errors pos_x does not exactly match the wall
486	!-- location, leading to erroneous reflection.
487	pos_x = MERGE( MIN( 2.0_wp * xwall - pos_x, xwall ), &
488	MAX( 2.0_wp * xwall - pos_x, xwall ), &
489	particles(n)%x > xwall )
490	!
491	!-- Change sign of particle speed
492	particles(n)%speed_x = - particles(n)%speed_x
493	!
494	!-- Also change sign of subgrid-scale particle speed
495	particles(n)%rvar1 = - particles(n)%rvar1
496	!
497	!-- Set flag that reflection along x is already done
498	reflect_x = .TRUE.
499	!
500	!-- As the particle does not cross any further yz-wall during
501	!-- this timestep, set further x-indices to the current one.
502	x_ind(t_index:t_index_number) = i1
503	!
504	!-- If particle already reached the wall but was not reflected,
505	!-- set further x-indices to the new one.
506	ELSEIF ( x_wall_reached .AND. .NOT. reflect_x ) THEN
507	x_ind(t_index:t_index_number) = i2
508	ENDIF !particle reflection in x direction done
509
510	!
511	!-- Check if a particle needs to be reflected at any xz-wall. If
512	!-- necessary, carry out reflection. Please note, a security
513	!-- constant is required, as the particle position does not
514	!-- necessarily exactly match the wall location due to rounding
515	!-- errors.
516	WRITE(9,*) 'wall_test_y nysg:',nysg ,' y: ',particles(n)%y,' j3: ',j3,'nyng:', nyng
517	FLUSH(9)
518	WRITE(9,*) BTEST(wall_flags_0(k3,j3,i3),0)
519	FLUSH(9)
520	IF ( reach_y(t_index) .AND. &
521	ABS( pos_y - ywall ) < eps .AND. &
522	.NOT. BTEST(wall_flags_0(k3,j3,i3),0) .AND. &
523	.NOT. reflect_y ) THEN
524	!
525	!
526	!-- Reflection in y-direction.
527	!-- Ensure correct reflection by MIN/MAX functions, depending on
528	!-- direction of particle transport.
529	!-- Due to rounding errors pos_y does not exactly match the wall
530	!-- location, leading to erroneous reflection.
531	pos_y = MERGE( MIN( 2.0_wp * ywall - pos_y, ywall ), &
532	MAX( 2.0_wp * ywall - pos_y, ywall ), &
533	particles(n)%y > ywall )
534	!
535	!-- Change sign of particle speed
536	particles(n)%speed_y = - particles(n)%speed_y
537	!
538	!-- Also change sign of subgrid-scale particle speed
539	particles(n)%rvar2 = - particles(n)%rvar2
540	!
541	!-- Set flag that reflection along y is already done
542	reflect_y = .TRUE.
543	!
544	!-- As the particle does not cross any further xz-wall during
545	!-- this timestep, set further y-indices to the current one.
546	y_ind(t_index:t_index_number) = j1
547	!
548	!-- If particle already reached the wall but was not reflected,
549	!-- set further y-indices to the new one.
550	ELSEIF ( y_wall_reached .AND. .NOT. reflect_y ) THEN
551	y_ind(t_index:t_index_number) = j2
552	ENDIF !particle reflection in y direction done
553
554	!
555	!-- Check if a particle needs to be reflected at any xy-wall. If
556	!-- necessary, carry out reflection. Please note, a security
557	!-- constant is required, as the particle position does not
558	!-- necessarily exactly match the wall location due to rounding
559	!-- errors.
560	IF ( reach_z(t_index) .AND. &
561	ABS( pos_z - zwall ) < eps .AND. &
562	.NOT. BTEST(wall_flags_0(k3,j3,i3),0) .AND. &
563	.NOT. reflect_z ) THEN
564	!
565	!
566	!-- Reflection in z-direction.
567	!-- Ensure correct reflection by MIN/MAX functions, depending on
568	!-- direction of particle transport.
569	!-- Due to rounding errors pos_z does not exactly match the wall
570	!-- location, leading to erroneous reflection.
571	pos_z = MERGE( MIN( 2.0_wp * zwall - pos_z, zwall ), &
572	MAX( 2.0_wp * zwall - pos_z, zwall ), &
573	particles(n)%z > zwall )
574	!
575	!-- Change sign of particle speed
576	particles(n)%speed_z = - particles(n)%speed_z
577	!
578	!-- Also change sign of subgrid-scale particle speed
579	particles(n)%rvar3 = - particles(n)%rvar3
580	!
581	!-- Set flag that reflection along z is already done
582	reflect_z = .TRUE.
583	!
584	!-- As the particle does not cross any further xy-wall during
585	!-- this timestep, set further z-indices to the current one.
586	z_ind(t_index:t_index_number) = k1
587	!
588	!-- If particle already reached the wall but was not reflected,
589	!-- set further z-indices to the new one.
590	ELSEIF ( z_wall_reached .AND. .NOT. reflect_z ) THEN
591	z_ind(t_index:t_index_number) = k2
592	ENDIF !particle reflection in z direction done
593
594	!
595	!-- Swap time
596	t_old = t(t_index)
597
598	ENDDO
599	!
600	!-- If a particle was reflected, calculate final position from last
601	!-- intermediate position.
602	IF ( reflect_x .OR. reflect_y .OR. reflect_z ) THEN
603
604	particles(n)%x = pos_x + ( 1.0_wp - t_old ) * dt_particle &
605	* particles(n)%speed_x
606	particles(n)%y = pos_y + ( 1.0_wp - t_old ) * dt_particle &
607	* particles(n)%speed_y
608	particles(n)%z = pos_z + ( 1.0_wp - t_old ) * dt_particle &
609	* particles(n)%speed_z
610
611	ENDIF
612
613	ENDIF
614
615	ENDDO
616
617	CALL cpu_log( log_point_s(48), 'lpm_wall_reflect', 'stop' )
618
619	ENDIF
620
621	END SUBROUTINE lpm_boundary_conds

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