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source: palm/trunk/SOURCE/lpm_droplet_collision.f90 @ 1822

Last change on this file since 1822 was 1822, checked in by hoffmann, 8 years ago
changes in LPM and bulk cloud microphysics
Property svn:keywords set to `Id`
File size: 22.5 KB

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

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