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source: palm/trunk/SOURCE/lpm_droplet_collision.f90 @ 1858

Last change on this file since 1858 was 1823, checked in by hoffmann, 9 years ago
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[1682]	1	!> @file lpm_droplet_collision.f90
[1036]	2	!--------------------------------------------------------------------------------!
	3	! This file is part of PALM.
	4	!
	5	! PALM is free software: you can redistribute it and/or modify it under the terms
	6	! of the GNU General Public License as published by the Free Software Foundation,
	7	! either version 3 of the License, or (at your option) any later version.
	8	!
	9	! PALM is distributed in the hope that it will be useful, but WITHOUT ANY
	10	! WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
	11	! A PARTICULAR PURPOSE. See the GNU General Public License for more details.
	12	!
	13	! You should have received a copy of the GNU General Public License along with
	14	! PALM. If not, see <http://www.gnu.org/licenses/>.
	15	!
[1818]	16	! Copyright 1997-2016 Leibniz Universitaet Hannover
[1036]	17	!--------------------------------------------------------------------------------!
	18	!
[849]	19	! Current revisions:
	20	! ------------------
[1823]	21	!
	22	!
[1321]	23	! Former revisions:
	24	! -----------------
	25	! $Id: lpm_droplet_collision.f90 1823 2016-04-07 08:57:52Z hoffmann $
	26	!
[1823]	27	! 1822 2016-04-07 07:49:42Z hoffmann
	28	! Integration of a new collision algortithm based on Shima et al. (2009) and
	29	! Soelch and Kaercher (2010) called all_or_nothing. The previous implemented
	30	! collision algorithm is called average_impact. Moreover, both algorithms are
	31	! now positive definit due to their construction, i.e., no negative weighting
	32	! factors should occur.
	33	!
[1683]	34	! 1682 2015-10-07 23:56:08Z knoop
	35	! Code annotations made doxygen readable
	36	!
[1360]	37	! 1359 2014-04-11 17:15:14Z hoffmann
	38	! New particle structure integrated.
	39	! Kind definition added to all floating point numbers.
	40	!
[1323]	41	! 1322 2014-03-20 16:38:49Z raasch
	42	! REAL constants defined as wp_kind
	43	!
[1321]	44	! 1320 2014-03-20 08:40:49Z raasch
[1320]	45	! ONLY-attribute added to USE-statements,
	46	! kind-parameters added to all INTEGER and REAL declaration statements,
	47	! kinds are defined in new module kinds,
	48	! revision history before 2012 removed,
	49	! comment fields (!:) to be used for variable explanations added to
	50	! all variable declaration statements
[1072]	51	!
[1093]	52	! 1092 2013-02-02 11:24:22Z raasch
	53	! unused variables removed
	54	!
[1072]	55	! 1071 2012-11-29 16:54:55Z franke
[1071]	56	! Calculation of Hall and Wang kernel now uses collision-coalescence formulation
	57	! proposed by Wang instead of the continuous collection equation (for more
	58	! information about new method see PALM documentation)
	59	! Bugfix: message identifiers added
[849]	60	!
[1037]	61	! 1036 2012-10-22 13:43:42Z raasch
	62	! code put under GPL (PALM 3.9)
	63	!
[850]	64	! 849 2012-03-15 10:35:09Z raasch
	65	! initial revision (former part of advec_particles)
[849]	66	!
[850]	67	!
[849]	68	! Description:
	69	! ------------
[1682]	70	!> Calculates change in droplet radius by collision. Droplet collision is
	71	!> calculated for each grid box seperately. Collision is parameterized by
[1822]	72	!> using collision kernels. Two different kernels are available:
[1682]	73	!> Hall kernel: Kernel from Hall (1980, J. Atmos. Sci., 2486-2507), which
	74	!> considers collision due to pure gravitational effects.
	75	!> Wang kernel: Beside gravitational effects (treated with the Hall-kernel) also
	76	!> the effects of turbulence on the collision are considered using
	77	!> parameterizations of Ayala et al. (2008, New J. Phys., 10,
	78	!> 075015) and Wang and Grabowski (2009, Atmos. Sci. Lett., 10,
	79	!> 1-8). This kernel includes three possible effects of turbulence:
	80	!> the modification of the relative velocity between the droplets,
	81	!> the effect of preferential concentration, and the enhancement of
	82	!> collision efficiencies.
[849]	83	!------------------------------------------------------------------------------!
[1682]	84	SUBROUTINE lpm_droplet_collision (i,j,k)
	85
[849]	86
[1359]	87
[1320]	88	USE arrays_3d, &
[1822]	89	ONLY: diss, ql_v, ql_vp
[849]	90
[1320]	91	USE cloud_parameters, &
[1822]	92	ONLY: rho_l
[1320]	93
	94	USE constants, &
	95	ONLY: pi
	96
	97	USE control_parameters, &
[1822]	98	ONLY: dt_3d, message_string, dz
[1320]	99
	100	USE cpulog, &
	101	ONLY: cpu_log, log_point_s
	102
	103	USE grid_variables, &
[1822]	104	ONLY: dx, dy
[1320]	105
	106	USE kinds
	107
	108	USE lpm_collision_kernels_mod, &
[1822]	109	ONLY: ckernel, recalculate_kernel
[1320]	110
	111	USE particle_attributes, &
[1822]	112	ONLY: all_or_nothing, average_impact, dissipation_classes, &
	113	hall_kernel, iran_part, number_of_particles, particles, &
	114	particle_type, prt_count, use_kernel_tables, wang_kernel
[1320]	115
[1822]	116	USE random_function_mod, &
	117	ONLY: random_function
	118
[1359]	119	USE pegrid
	120
[849]	121	IMPLICIT NONE
	122
[1682]	123	INTEGER(iwp) :: eclass !<
	124	INTEGER(iwp) :: i !<
	125	INTEGER(iwp) :: j !<
	126	INTEGER(iwp) :: k !<
	127	INTEGER(iwp) :: n !<
[1822]	128	INTEGER(iwp) :: m !<
[1682]	129	INTEGER(iwp) :: rclass_l !<
	130	INTEGER(iwp) :: rclass_s !<
[849]	131
[1822]	132	REAL(wp) :: collection_probability !< probability for collection
	133	REAL(wp) :: ddV !< inverse grid box volume
	134	REAL(wp) :: epsilon !< dissipation rate
	135	REAL(wp) :: factor_volume_to_mass !< 4.0 / 3.0 * pi * rho_l
	136	REAL(wp) :: xm !< mean mass of droplet m
	137	REAL(wp) :: xn !< mean mass of droplet n
[1359]	138
[1822]	139	REAL(wp), DIMENSION(:), ALLOCATABLE :: weight !< weighting factor
	140	REAL(wp), DIMENSION(:), ALLOCATABLE :: mass !< total mass of super droplet
[1359]	141
[849]	142	CALL cpu_log( log_point_s(43), 'lpm_droplet_coll', 'start' )
	143
[1822]	144	number_of_particles = prt_count(k,j,i)
	145	factor_volume_to_mass = 4.0_wp / 3.0_wp * pi * rho_l
	146	ddV = 1 / ( dx * dy * dz )
[849]	147	!
[1822]	148	!-- Collision requires at least one super droplet inside the box
	149	IF ( number_of_particles > 0 ) THEN
[849]	150
	151	!
[1359]	152	!-- Now apply the different kernels
[1822]	153	IF ( use_kernel_tables ) THEN
[849]	154	!
[1822]	155	!-- Fast method with pre-calculated collection kernels for
[1359]	156	!-- discrete radius- and dissipation-classes.
	157	!--
	158	!-- Determine dissipation class index of this gridbox
	159	IF ( wang_kernel ) THEN
	160	eclass = INT( diss(k,j,i) * 1.0E4_wp / 1000.0_wp * &
	161	dissipation_classes ) + 1
	162	epsilon = diss(k,j,i)
	163	ELSE
	164	epsilon = 0.0_wp
	165	ENDIF
	166	IF ( hall_kernel .OR. epsilon * 1.0E4_wp < 0.001_wp ) THEN
	167	eclass = 0 ! Hall kernel is used
	168	ELSE
	169	eclass = MIN( dissipation_classes, eclass )
	170	ENDIF
	171
[849]	172	!
[1359]	173	!-- Droplet collision are calculated using collision-coalescence
	174	!-- formulation proposed by Wang (see PALM documentation)
[1822]	175	!-- Temporary fields for total mass of super-droplet and weighting factors
	176	!-- are allocated.
	177	ALLOCATE(mass(1:number_of_particles), weight(1:number_of_particles))
[849]	178
[1822]	179	mass(1:number_of_particles) = particles(1:number_of_particles)%weight_factor * &
	180	particles(1:number_of_particles)%radius*3 &
	181	factor_volume_to_mass
	182	weight(1:number_of_particles) = particles(1:number_of_particles)%weight_factor
[849]	183
[1822]	184	IF ( average_impact ) THEN ! select collision algorithm
[1071]	185
[1822]	186	DO n = 1, number_of_particles
[1071]	187
[1822]	188	rclass_l = particles(n)%class
	189	xn = mass(n) / weight(n)
[849]	190
[1822]	191	DO m = n, number_of_particles
[849]	192
[1822]	193	rclass_s = particles(m)%class
	194	xm = mass(m) / weight(m)
[849]	195
[1822]	196	IF ( xm .LT. xn ) THEN
	197
	198	!
	199	!-- Particle n collects smaller particle m
	200	collection_probability = ckernel(rclass_l,rclass_s,eclass) * &
	201	weight(n) * ddV * dt_3d
[849]	202
[1822]	203	mass(n) = mass(n) + mass(m) * collection_probability
	204	weight(m) = weight(m) - weight(m) * collection_probability
	205	mass(m) = mass(m) - mass(m) * collection_probability
	206	ELSEIF ( xm .GT. xn ) THEN
[849]	207	!
[1822]	208	!-- Particle m collects smaller particle n
	209	collection_probability = ckernel(rclass_l,rclass_s,eclass) * &
	210	weight(m) * ddV * dt_3d
[849]	211
[1822]	212	mass(m) = mass(m) + mass(n) * collection_probability
	213	weight(n) = weight(n) - weight(n) * collection_probability
	214	mass(n) = mass(n) - mass(n) * collection_probability
	215	ELSE
[1071]	216	!
[1822]	217	!-- Same-size collections. If n = m, weight is reduced by the
	218	!-- number of possible same-size collections; the total mass
	219	!-- is not changed during same-size collection.
	220	!-- Same-size collections of different
	221	!-- particles ( n /= m ) are treated as same-size collections
	222	!-- of ONE partilce with weight = weight(n) + weight(m) and
	223	!-- mass = mass(n) + mass(m).
	224	!-- Accordingly, each particle loses the same number of
	225	!-- droplets to the other particle, but this has no effect on
	226	!-- total mass mass, since the exchanged droplets have the
	227	!-- same radius.
[849]	228
[1822]	229	!-- Note: For m = n this equation is an approximation only
	230	!-- valid for weight >> 1 (which is usually the case). The
	231	!-- approximation is weight(n)-1 = weight(n).
	232	weight(n) = weight(n) - 0.5_wp * weight(n) * &
	233	ckernel(rclass_l,rclass_s,eclass) * &
	234	weight(m) * ddV * dt_3d
	235	IF ( n .NE. m ) THEN
	236	weight(m) = weight(m) - 0.5_wp * weight(m) * &
	237	ckernel(rclass_l,rclass_s,eclass) * &
	238	weight(n) * ddV * dt_3d
	239	ENDIF
	240	ENDIF
[1071]	241
[1822]	242	ENDDO
[1071]	243
[1822]	244	ql_vp(k,j,i) = ql_vp(k,j,i) + mass(n) / factor_volume_to_mass
	245
[1359]	246	ENDDO
[849]	247
[1822]	248	ELSEIF ( all_or_nothing ) THEN ! select collision algorithm
[849]	249
[1822]	250	DO n = 1, number_of_particles
[849]	251
[1822]	252	rclass_l = particles(n)%class
	253	xn = mass(n) / weight(n) ! mean mass of droplet n
[849]	254
[1822]	255	DO m = n, number_of_particles
[849]	256
[1822]	257	rclass_s = particles(m)%class
	258	xm = mass(m) / weight(m) ! mean mass of droplet m
[849]	259
[1822]	260	IF ( weight(n) .LT. weight(m) ) THEN
	261	!
	262	!-- Particle n collects weight(n) droplets of particle m
	263	collection_probability = ckernel(rclass_l,rclass_s,eclass) * &
	264	weight(m) * ddV * dt_3d
[1071]	265
[1822]	266	IF ( collection_probability .GT. random_function( iran_part ) ) THEN
	267	mass(n) = mass(n) + weight(n) * xm
	268	weight(m) = weight(m) - weight(n)
	269	mass(m) = mass(m) - weight(n) * xm
	270	ENDIF
	271
	272	ELSEIF ( weight(m) .LT. weight(n) ) THEN
[849]	273	!
[1822]	274	!-- Particle m collects weight(m) droplets of particle n
	275	collection_probability = ckernel(rclass_l,rclass_s,eclass) * &
	276	weight(n) * ddV * dt_3d
	277
	278	IF ( collection_probability .GT. random_function( iran_part ) ) THEN
	279	mass(m) = mass(m) + weight(m) * xn
	280	weight(n) = weight(n) - weight(m)
	281	mass(n) = mass(n) - weight(m) * xn
	282	ENDIF
	283	ELSE
[849]	284	!
[1822]	285	!-- Collisions of particles of the same weighting factor.
	286	!-- Particle n collects 1/2 weight(n) droplets of particle m,
	287	!-- particle m collects 1/2 weight(m) droplets of particle n.
	288	!-- The total mass mass changes accordingly.
	289	!-- If n = m, the first half of the droplets coalesces with the
	290	!-- second half of the droplets; mass is unchanged because
	291	!-- xm = xn for n = m.
[849]	292
[1822]	293	!-- Note: For m = n this equation is an approximation only
	294	!-- valid for weight >> 1 (which is usually the case). The
	295	!-- approximation is weight(n)-1 = weight(n).
	296	collection_probability = ckernel(rclass_l,rclass_s,eclass) * &
	297	weight(n) * ddV * dt_3d
[849]	298
[1822]	299	IF ( collection_probability .GT. random_function( iran_part ) ) THEN
	300	mass(n) = mass(n) + 0.5_wp * weight(n) * ( xm - xn )
	301	mass(m) = mass(m) + 0.5_wp * weight(m) * ( xn - xm )
	302	weight(n) = weight(n) - 0.5_wp * weight(m)
	303	weight(m) = weight(n)
	304	ENDIF
	305	ENDIF
[849]	306
[1822]	307	ENDDO
[849]	308
[1822]	309	ql_vp(k,j,i) = ql_vp(k,j,i) + mass(n) / factor_volume_to_mass
[849]	310
[1822]	311	ENDDO
[849]	312
[1822]	313	ENDIF
[849]	314
	315
	316
	317
[1822]	318	IF ( ANY(weight < 0.0_wp) ) THEN
	319	WRITE( message_string, * ) 'negative weighting'
	320	CALL message( 'lpm_droplet_collision', 'PA0028', &
	321	2, 2, -1, 6, 1 )
	322	ENDIF
[849]	323
[1822]	324	particles(1:number_of_particles)%radius = ( mass(1:number_of_particles) / &
	325	( weight(1:number_of_particles) &
	326	* factor_volume_to_mass &
	327	) &
	328	)**0.33333333333333_wp
[849]	329
[1822]	330	particles(1:number_of_particles)%weight_factor = weight(1:number_of_particles)
[849]	331
[1822]	332	DEALLOCATE(weight, mass)
[849]	333
[1822]	334	ELSEIF ( .NOT. use_kernel_tables ) THEN
	335	!
	336	!-- Collection kernels are calculated for every new
	337	!-- grid box. First, allocate memory for kernel table.
	338	!-- Third dimension is 1, because table is re-calculated for
	339	!-- every new dissipation value.
	340	ALLOCATE( ckernel(1:number_of_particles,1:number_of_particles,1:1) )
	341	!
	342	!-- Now calculate collection kernel for this box. Note that
	343	!-- the kernel is based on the previous time step
	344	CALL recalculate_kernel( i, j, k )
	345	!
	346	!-- Droplet collision are calculated using collision-coalescence
	347	!-- formulation proposed by Wang (see PALM documentation)
	348	!-- Temporary fields for total mass of super-droplet and weighting factors
	349	!-- are allocated.
	350	ALLOCATE(mass(1:number_of_particles), weight(1:number_of_particles))
[849]	351
[1822]	352	mass(1:number_of_particles) = particles(1:number_of_particles)%weight_factor * &
	353	particles(1:number_of_particles)%radius*3 &
	354	factor_volume_to_mass
[849]	355
[1822]	356	weight(1:number_of_particles) = particles(1:number_of_particles)%weight_factor
[849]	357
[1822]	358	IF ( average_impact ) THEN ! select collision algorithm
[849]	359
[1822]	360	DO n = 1, number_of_particles
[849]	361
[1822]	362	xn = mass(n) / weight(n) ! mean mass of droplet n
[849]	363
[1822]	364	DO m = n, number_of_particles
[849]	365
[1822]	366	xm = mass(m) / weight(m) !mean mass of droplet m
[849]	367
[1822]	368	IF ( xm .LT. xn ) THEN
[849]	369	!
[1822]	370	!-- Particle n collects smaller particle m
	371	collection_probability = ckernel(n,m,1) * weight(n) * &
	372	ddV * dt_3d
	373
	374	mass(n) = mass(n) + mass(m) * collection_probability
	375	weight(m) = weight(m) - weight(m) * collection_probability
	376	mass(m) = mass(m) - mass(m) * collection_probability
	377	ELSEIF ( xm .GT. xn ) THEN
[849]	378	!
[1822]	379	!-- Particle m collects smaller particle n
	380	collection_probability = ckernel(n,m,1) * weight(m) * &
	381	ddV * dt_3d
[849]	382
[1822]	383	mass(m) = mass(m) + mass(n) * collection_probability
	384	weight(n) = weight(n) - weight(n) * collection_probability
	385	mass(n) = mass(n) - mass(n) * collection_probability
	386	ELSE
[849]	387	!
[1822]	388	!-- Same-size collections. If n = m, weight is reduced by the
	389	!-- number of possible same-size collections; the total mass
	390	!-- mass is not changed during same-size collection.
	391	!-- Same-size collections of different
	392	!-- particles ( n /= m ) are treated as same-size collections
	393	!-- of ONE partilce with weight = weight(n) + weight(m) and
	394	!-- mass = mass(n) + mass(m).
	395	!-- Accordingly, each particle loses the same number of
	396	!-- droplets to the other particle, but this has no effect on
	397	!-- total mass mass, since the exchanged droplets have the
	398	!-- same radius.
	399	!--
	400	!-- Note: For m = n this equation is an approximation only
	401	!-- valid for weight >> 1 (which is usually the case). The
	402	!-- approximation is weight(n)-1 = weight(n).
	403	weight(n) = weight(n) - 0.5_wp * weight(n) * &
	404	ckernel(n,m,1) * weight(m) * &
	405	ddV * dt_3d
	406	IF ( n .NE. m ) THEN
	407	weight(m) = weight(m) - 0.5_wp * weight(m) * &
	408	ckernel(n,m,1) * weight(n) * &
	409	ddV * dt_3d
	410	ENDIF
	411	ENDIF
[849]	412
	413
[1359]	414	ENDDO
[849]	415
[1822]	416	ql_vp(k,j,i) = ql_vp(k,j,i) + mass(n) / factor_volume_to_mass
[849]	417
[1822]	418	ENDDO
[849]	419
[1822]	420	ELSEIF ( all_or_nothing ) THEN ! select collision algorithm
[849]	421
[1822]	422	DO n = 1, number_of_particles
[849]	423
[1822]	424	xn = mass(n) / weight(n) ! mean mass of droplet n
[849]	425
[1822]	426	DO m = n, number_of_particles
[849]	427
[1822]	428	xm = mass(m) / weight(m) !mean mass of droplet m
[849]	429
[1822]	430	IF ( weight(n) .LT. weight(m) ) THEN
	431	!
	432	!-- Particle n collects smaller particle m
	433	collection_probability = ckernel(n,m,1) * weight(m) * &
	434	ddV * dt_3d
[1071]	435
[1822]	436	IF ( collection_probability .GT. random_function( iran_part ) ) THEN
	437	mass(n) = mass(n) + weight(n) * xm
	438	weight(m) = weight(m) - weight(n)
	439	mass(m) = mass(m) - weight(n) * xm
	440	ENDIF
[1359]	441
[1822]	442	ELSEIF ( weight(m) .LT. weight(n) ) THEN
[1071]	443	!
[1822]	444	!-- Particle m collects smaller particle n
	445	collection_probability = ckernel(n,m,1) * weight(n) * &
	446	ddV * dt_3d
[1071]	447
[1822]	448	IF ( collection_probability .GT. random_function( iran_part ) ) THEN
	449	mass(m) = mass(m) + weight(m) * xn
	450	weight(n) = weight(n) - weight(m)
	451	mass(n) = mass(n) - weight(m) * xn
	452	ENDIF
	453	ELSE
	454	!
	455	!-- Collisions of particles of the same weighting factor.
	456	!-- Particle n collects 1/2 weight(n) droplets of particle m,
	457	!-- particle m collects 1/2 weight(m) droplets of particle n.
	458	!-- The total mass mass changes accordingly.
	459	!-- If n = m, the first half of the droplets coalesces with the
	460	!-- second half of the droplets; mass is unchanged because
	461	!-- xm = xn for n = m.
	462	!--
	463	!-- Note: For m = n this equation is an approximation only
	464	!-- valid for weight >> 1 (which is usually the case). The
	465	!-- approximation is weight(n)-1 = weight(n).
	466	collection_probability = ckernel(n,m,1) * weight(n) * &
	467	ddV * dt_3d
[1071]	468
[1822]	469	IF ( collection_probability .GT. random_function( iran_part ) ) THEN
	470	mass(n) = mass(n) + 0.5_wp * weight(n) * ( xm - xn )
	471	mass(m) = mass(m) + 0.5_wp * weight(m) * ( xn - xm )
	472	weight(n) = weight(n) - 0.5_wp * weight(m)
	473	weight(m) = weight(n)
	474	ENDIF
	475	ENDIF
[1071]	476
	477
[1822]	478	ENDDO
[1071]	479
[1822]	480	ql_vp(k,j,i) = ql_vp(k,j,i) + mass(n) / factor_volume_to_mass
[1071]	481
[1822]	482	ENDDO
[1071]	483
[1822]	484	ENDIF
[1071]	485
[1822]	486	IF ( ANY(weight < 0.0_wp) ) THEN
	487	WRITE( message_string, * ) 'negative weighting'
	488	CALL message( 'lpm_droplet_collision', 'PA0028', &
	489	2, 2, -1, 6, 1 )
	490	ENDIF
	491
	492	particles(1:number_of_particles)%radius = ( mass(1:number_of_particles) / &
	493	( weight(1:number_of_particles) &
	494	* factor_volume_to_mass &
	495	) &
	496	)**0.33333333333333_wp
	497
	498	particles(1:number_of_particles)%weight_factor = weight(1:number_of_particles)
	499
	500	DEALLOCATE( weight, mass, ckernel )
	501
	502	ENDIF
	503
[1359]	504	ENDIF
[1822]	505
[849]	506
	507	!
[1822]	508	!-- Check if LWC is conserved during collision process
[1359]	509	IF ( ql_v(k,j,i) /= 0.0_wp ) THEN
[1822]	510	IF ( ql_vp(k,j,i) / ql_v(k,j,i) >= 1.0001_wp .OR. &
[1359]	511	ql_vp(k,j,i) / ql_v(k,j,i) <= 0.9999_wp ) THEN
[1822]	512	WRITE( message_string, * ) ' LWC is not conserved during', &
	513	' collision! ', &
	514	' LWC after condensation: ', ql_v(k,j,i), &
	515	' LWC after collision: ', ql_vp(k,j,i)
	516	CALL message( 'lpm_droplet_collision', 'PA0040', 2, 2, -1, 6, 1 )
[1359]	517	ENDIF
	518	ENDIF
[849]	519
	520	CALL cpu_log( log_point_s(43), 'lpm_droplet_coll', 'stop' )
	521
[1359]	522	END SUBROUTINE lpm_droplet_collision

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