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source: palm/trunk/SOURCE/lpm_droplet_collision.f90 @ 1978

Last change on this file since 1978 was 1885, 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	!
[1885]	22	!
[1321]	23	! Former revisions:
	24	! -----------------
	25	! $Id: lpm_droplet_collision.f90 1885 2016-04-21 11:12:26Z maronga $
	26	!
[1885]	27	! 1884 2016-04-21 11:11:40Z hoffmann
	28	! Conservation of mass should only be checked if collisions took place.
	29	!
[1861]	30	! 1860 2016-04-13 13:21:28Z hoffmann
	31	! Interpolation of dissipation rate adjusted to more reasonable values.
	32	!
[1823]	33	! 1822 2016-04-07 07:49:42Z hoffmann
	34	! Integration of a new collision algortithm based on Shima et al. (2009) and
	35	! Soelch and Kaercher (2010) called all_or_nothing. The previous implemented
	36	! collision algorithm is called average_impact. Moreover, both algorithms are
	37	! now positive definit due to their construction, i.e., no negative weighting
	38	! factors should occur.
	39	!
[1683]	40	! 1682 2015-10-07 23:56:08Z knoop
	41	! Code annotations made doxygen readable
	42	!
[1360]	43	! 1359 2014-04-11 17:15:14Z hoffmann
	44	! New particle structure integrated.
	45	! Kind definition added to all floating point numbers.
	46	!
[1323]	47	! 1322 2014-03-20 16:38:49Z raasch
	48	! REAL constants defined as wp_kind
	49	!
[1321]	50	! 1320 2014-03-20 08:40:49Z raasch
[1320]	51	! ONLY-attribute added to USE-statements,
	52	! kind-parameters added to all INTEGER and REAL declaration statements,
	53	! kinds are defined in new module kinds,
	54	! revision history before 2012 removed,
	55	! comment fields (!:) to be used for variable explanations added to
	56	! all variable declaration statements
[1072]	57	!
[1093]	58	! 1092 2013-02-02 11:24:22Z raasch
	59	! unused variables removed
	60	!
[1072]	61	! 1071 2012-11-29 16:54:55Z franke
[1071]	62	! Calculation of Hall and Wang kernel now uses collision-coalescence formulation
	63	! proposed by Wang instead of the continuous collection equation (for more
	64	! information about new method see PALM documentation)
	65	! Bugfix: message identifiers added
[849]	66	!
[1037]	67	! 1036 2012-10-22 13:43:42Z raasch
	68	! code put under GPL (PALM 3.9)
	69	!
[850]	70	! 849 2012-03-15 10:35:09Z raasch
	71	! initial revision (former part of advec_particles)
[849]	72	!
[850]	73	!
[849]	74	! Description:
	75	! ------------
[1682]	76	!> Calculates change in droplet radius by collision. Droplet collision is
	77	!> calculated for each grid box seperately. Collision is parameterized by
[1822]	78	!> using collision kernels. Two different kernels are available:
[1682]	79	!> Hall kernel: Kernel from Hall (1980, J. Atmos. Sci., 2486-2507), which
	80	!> considers collision due to pure gravitational effects.
	81	!> Wang kernel: Beside gravitational effects (treated with the Hall-kernel) also
	82	!> the effects of turbulence on the collision are considered using
	83	!> parameterizations of Ayala et al. (2008, New J. Phys., 10,
	84	!> 075015) and Wang and Grabowski (2009, Atmos. Sci. Lett., 10,
	85	!> 1-8). This kernel includes three possible effects of turbulence:
	86	!> the modification of the relative velocity between the droplets,
	87	!> the effect of preferential concentration, and the enhancement of
	88	!> collision efficiencies.
[849]	89	!------------------------------------------------------------------------------!
[1682]	90	SUBROUTINE lpm_droplet_collision (i,j,k)
	91
[849]	92
[1359]	93
[1320]	94	USE arrays_3d, &
[1822]	95	ONLY: diss, ql_v, ql_vp
[849]	96
[1320]	97	USE cloud_parameters, &
[1822]	98	ONLY: rho_l
[1320]	99
	100	USE constants, &
	101	ONLY: pi
	102
	103	USE control_parameters, &
[1822]	104	ONLY: dt_3d, message_string, dz
[1320]	105
	106	USE cpulog, &
	107	ONLY: cpu_log, log_point_s
	108
	109	USE grid_variables, &
[1822]	110	ONLY: dx, dy
[1320]	111
	112	USE kinds
	113
	114	USE lpm_collision_kernels_mod, &
[1822]	115	ONLY: ckernel, recalculate_kernel
[1320]	116
	117	USE particle_attributes, &
[1822]	118	ONLY: all_or_nothing, average_impact, dissipation_classes, &
	119	hall_kernel, iran_part, number_of_particles, particles, &
	120	particle_type, prt_count, use_kernel_tables, wang_kernel
[1320]	121
[1822]	122	USE random_function_mod, &
	123	ONLY: random_function
	124
[1359]	125	USE pegrid
	126
[849]	127	IMPLICIT NONE
	128
[1682]	129	INTEGER(iwp) :: eclass !<
	130	INTEGER(iwp) :: i !<
	131	INTEGER(iwp) :: j !<
	132	INTEGER(iwp) :: k !<
	133	INTEGER(iwp) :: n !<
[1822]	134	INTEGER(iwp) :: m !<
[1682]	135	INTEGER(iwp) :: rclass_l !<
	136	INTEGER(iwp) :: rclass_s !<
[849]	137
[1822]	138	REAL(wp) :: collection_probability !< probability for collection
	139	REAL(wp) :: ddV !< inverse grid box volume
	140	REAL(wp) :: epsilon !< dissipation rate
	141	REAL(wp) :: factor_volume_to_mass !< 4.0 / 3.0 * pi * rho_l
	142	REAL(wp) :: xm !< mean mass of droplet m
	143	REAL(wp) :: xn !< mean mass of droplet n
[1359]	144
[1822]	145	REAL(wp), DIMENSION(:), ALLOCATABLE :: weight !< weighting factor
	146	REAL(wp), DIMENSION(:), ALLOCATABLE :: mass !< total mass of super droplet
[1359]	147
[849]	148	CALL cpu_log( log_point_s(43), 'lpm_droplet_coll', 'start' )
	149
[1822]	150	number_of_particles = prt_count(k,j,i)
	151	factor_volume_to_mass = 4.0_wp / 3.0_wp * pi * rho_l
	152	ddV = 1 / ( dx * dy * dz )
[849]	153	!
[1822]	154	!-- Collision requires at least one super droplet inside the box
	155	IF ( number_of_particles > 0 ) THEN
[849]	156
	157	!
[1359]	158	!-- Now apply the different kernels
[1822]	159	IF ( use_kernel_tables ) THEN
[849]	160	!
[1822]	161	!-- Fast method with pre-calculated collection kernels for
[1359]	162	!-- discrete radius- and dissipation-classes.
	163	!--
	164	!-- Determine dissipation class index of this gridbox
	165	IF ( wang_kernel ) THEN
[1860]	166	eclass = INT( diss(k,j,i) * 1.0E4_wp / 600.0_wp * &
[1359]	167	dissipation_classes ) + 1
	168	epsilon = diss(k,j,i)
	169	ELSE
	170	epsilon = 0.0_wp
	171	ENDIF
	172	IF ( hall_kernel .OR. epsilon * 1.0E4_wp < 0.001_wp ) THEN
	173	eclass = 0 ! Hall kernel is used
	174	ELSE
	175	eclass = MIN( dissipation_classes, eclass )
	176	ENDIF
	177
[849]	178	!
[1359]	179	!-- Droplet collision are calculated using collision-coalescence
	180	!-- formulation proposed by Wang (see PALM documentation)
[1822]	181	!-- Temporary fields for total mass of super-droplet and weighting factors
	182	!-- are allocated.
	183	ALLOCATE(mass(1:number_of_particles), weight(1:number_of_particles))
[849]	184
[1822]	185	mass(1:number_of_particles) = particles(1:number_of_particles)%weight_factor * &
	186	particles(1:number_of_particles)%radius*3 &
	187	factor_volume_to_mass
	188	weight(1:number_of_particles) = particles(1:number_of_particles)%weight_factor
[849]	189
[1822]	190	IF ( average_impact ) THEN ! select collision algorithm
[1071]	191
[1822]	192	DO n = 1, number_of_particles
[1071]	193
[1822]	194	rclass_l = particles(n)%class
	195	xn = mass(n) / weight(n)
[849]	196
[1822]	197	DO m = n, number_of_particles
[849]	198
[1822]	199	rclass_s = particles(m)%class
	200	xm = mass(m) / weight(m)
[849]	201
[1822]	202	IF ( xm .LT. xn ) THEN
	203
	204	!
	205	!-- Particle n collects smaller particle m
	206	collection_probability = ckernel(rclass_l,rclass_s,eclass) * &
	207	weight(n) * ddV * dt_3d
[849]	208
[1822]	209	mass(n) = mass(n) + mass(m) * collection_probability
	210	weight(m) = weight(m) - weight(m) * collection_probability
	211	mass(m) = mass(m) - mass(m) * collection_probability
	212	ELSEIF ( xm .GT. xn ) THEN
[849]	213	!
[1822]	214	!-- Particle m collects smaller particle n
	215	collection_probability = ckernel(rclass_l,rclass_s,eclass) * &
	216	weight(m) * ddV * dt_3d
[849]	217
[1822]	218	mass(m) = mass(m) + mass(n) * collection_probability
	219	weight(n) = weight(n) - weight(n) * collection_probability
	220	mass(n) = mass(n) - mass(n) * collection_probability
	221	ELSE
[1071]	222	!
[1822]	223	!-- Same-size collections. If n = m, weight is reduced by the
	224	!-- number of possible same-size collections; the total mass
	225	!-- is not changed during same-size collection.
	226	!-- Same-size collections of different
	227	!-- particles ( n /= m ) are treated as same-size collections
	228	!-- of ONE partilce with weight = weight(n) + weight(m) and
	229	!-- mass = mass(n) + mass(m).
	230	!-- Accordingly, each particle loses the same number of
	231	!-- droplets to the other particle, but this has no effect on
	232	!-- total mass mass, since the exchanged droplets have the
	233	!-- same radius.
[849]	234
[1822]	235	!-- Note: For m = n this equation is an approximation only
	236	!-- valid for weight >> 1 (which is usually the case). The
	237	!-- approximation is weight(n)-1 = weight(n).
	238	weight(n) = weight(n) - 0.5_wp * weight(n) * &
	239	ckernel(rclass_l,rclass_s,eclass) * &
	240	weight(m) * ddV * dt_3d
	241	IF ( n .NE. m ) THEN
	242	weight(m) = weight(m) - 0.5_wp * weight(m) * &
	243	ckernel(rclass_l,rclass_s,eclass) * &
	244	weight(n) * ddV * dt_3d
	245	ENDIF
	246	ENDIF
[1071]	247
[1822]	248	ENDDO
[1071]	249
[1822]	250	ql_vp(k,j,i) = ql_vp(k,j,i) + mass(n) / factor_volume_to_mass
	251
[1359]	252	ENDDO
[849]	253
[1822]	254	ELSEIF ( all_or_nothing ) THEN ! select collision algorithm
[849]	255
[1822]	256	DO n = 1, number_of_particles
[849]	257
[1822]	258	rclass_l = particles(n)%class
	259	xn = mass(n) / weight(n) ! mean mass of droplet n
[849]	260
[1822]	261	DO m = n, number_of_particles
[849]	262
[1822]	263	rclass_s = particles(m)%class
	264	xm = mass(m) / weight(m) ! mean mass of droplet m
[849]	265
[1822]	266	IF ( weight(n) .LT. weight(m) ) THEN
	267	!
	268	!-- Particle n collects weight(n) droplets of particle m
	269	collection_probability = ckernel(rclass_l,rclass_s,eclass) * &
	270	weight(m) * ddV * dt_3d
[1071]	271
[1822]	272	IF ( collection_probability .GT. random_function( iran_part ) ) THEN
	273	mass(n) = mass(n) + weight(n) * xm
	274	weight(m) = weight(m) - weight(n)
	275	mass(m) = mass(m) - weight(n) * xm
	276	ENDIF
	277
	278	ELSEIF ( weight(m) .LT. weight(n) ) THEN
[849]	279	!
[1822]	280	!-- Particle m collects weight(m) droplets of particle n
	281	collection_probability = ckernel(rclass_l,rclass_s,eclass) * &
	282	weight(n) * ddV * dt_3d
	283
	284	IF ( collection_probability .GT. random_function( iran_part ) ) THEN
	285	mass(m) = mass(m) + weight(m) * xn
	286	weight(n) = weight(n) - weight(m)
	287	mass(n) = mass(n) - weight(m) * xn
	288	ENDIF
	289	ELSE
[849]	290	!
[1822]	291	!-- Collisions of particles of the same weighting factor.
	292	!-- Particle n collects 1/2 weight(n) droplets of particle m,
	293	!-- particle m collects 1/2 weight(m) droplets of particle n.
	294	!-- The total mass mass changes accordingly.
	295	!-- If n = m, the first half of the droplets coalesces with the
	296	!-- second half of the droplets; mass is unchanged because
	297	!-- xm = xn for n = m.
[849]	298
[1822]	299	!-- Note: For m = n this equation is an approximation only
	300	!-- valid for weight >> 1 (which is usually the case). The
	301	!-- approximation is weight(n)-1 = weight(n).
	302	collection_probability = ckernel(rclass_l,rclass_s,eclass) * &
	303	weight(n) * ddV * dt_3d
[849]	304
[1822]	305	IF ( collection_probability .GT. random_function( iran_part ) ) THEN
	306	mass(n) = mass(n) + 0.5_wp * weight(n) * ( xm - xn )
	307	mass(m) = mass(m) + 0.5_wp * weight(m) * ( xn - xm )
	308	weight(n) = weight(n) - 0.5_wp * weight(m)
	309	weight(m) = weight(n)
	310	ENDIF
	311	ENDIF
[849]	312
[1822]	313	ENDDO
[849]	314
[1822]	315	ql_vp(k,j,i) = ql_vp(k,j,i) + mass(n) / factor_volume_to_mass
[849]	316
[1822]	317	ENDDO
[849]	318
[1822]	319	ENDIF
[849]	320
	321
	322
	323
[1822]	324	IF ( ANY(weight < 0.0_wp) ) THEN
	325	WRITE( message_string, * ) 'negative weighting'
	326	CALL message( 'lpm_droplet_collision', 'PA0028', &
	327	2, 2, -1, 6, 1 )
	328	ENDIF
[849]	329
[1822]	330	particles(1:number_of_particles)%radius = ( mass(1:number_of_particles) / &
	331	( weight(1:number_of_particles) &
	332	* factor_volume_to_mass &
	333	) &
	334	)**0.33333333333333_wp
[849]	335
[1822]	336	particles(1:number_of_particles)%weight_factor = weight(1:number_of_particles)
[849]	337
[1822]	338	DEALLOCATE(weight, mass)
[849]	339
[1822]	340	ELSEIF ( .NOT. use_kernel_tables ) THEN
	341	!
	342	!-- Collection kernels are calculated for every new
	343	!-- grid box. First, allocate memory for kernel table.
	344	!-- Third dimension is 1, because table is re-calculated for
	345	!-- every new dissipation value.
	346	ALLOCATE( ckernel(1:number_of_particles,1:number_of_particles,1:1) )
	347	!
	348	!-- Now calculate collection kernel for this box. Note that
	349	!-- the kernel is based on the previous time step
	350	CALL recalculate_kernel( i, j, k )
	351	!
	352	!-- Droplet collision are calculated using collision-coalescence
	353	!-- formulation proposed by Wang (see PALM documentation)
	354	!-- Temporary fields for total mass of super-droplet and weighting factors
	355	!-- are allocated.
	356	ALLOCATE(mass(1:number_of_particles), weight(1:number_of_particles))
[849]	357
[1822]	358	mass(1:number_of_particles) = particles(1:number_of_particles)%weight_factor * &
	359	particles(1:number_of_particles)%radius*3 &
	360	factor_volume_to_mass
[849]	361
[1822]	362	weight(1:number_of_particles) = particles(1:number_of_particles)%weight_factor
[849]	363
[1822]	364	IF ( average_impact ) THEN ! select collision algorithm
[849]	365
[1822]	366	DO n = 1, number_of_particles
[849]	367
[1822]	368	xn = mass(n) / weight(n) ! mean mass of droplet n
[849]	369
[1822]	370	DO m = n, number_of_particles
[849]	371
[1822]	372	xm = mass(m) / weight(m) !mean mass of droplet m
[849]	373
[1822]	374	IF ( xm .LT. xn ) THEN
[849]	375	!
[1822]	376	!-- Particle n collects smaller particle m
	377	collection_probability = ckernel(n,m,1) * weight(n) * &
	378	ddV * dt_3d
	379
	380	mass(n) = mass(n) + mass(m) * collection_probability
	381	weight(m) = weight(m) - weight(m) * collection_probability
	382	mass(m) = mass(m) - mass(m) * collection_probability
	383	ELSEIF ( xm .GT. xn ) THEN
[849]	384	!
[1822]	385	!-- Particle m collects smaller particle n
	386	collection_probability = ckernel(n,m,1) * weight(m) * &
	387	ddV * dt_3d
[849]	388
[1822]	389	mass(m) = mass(m) + mass(n) * collection_probability
	390	weight(n) = weight(n) - weight(n) * collection_probability
	391	mass(n) = mass(n) - mass(n) * collection_probability
	392	ELSE
[849]	393	!
[1822]	394	!-- Same-size collections. If n = m, weight is reduced by the
	395	!-- number of possible same-size collections; the total mass
	396	!-- mass is not changed during same-size collection.
	397	!-- Same-size collections of different
	398	!-- particles ( n /= m ) are treated as same-size collections
	399	!-- of ONE partilce with weight = weight(n) + weight(m) and
	400	!-- mass = mass(n) + mass(m).
	401	!-- Accordingly, each particle loses the same number of
	402	!-- droplets to the other particle, but this has no effect on
	403	!-- total mass mass, since the exchanged droplets have the
	404	!-- same radius.
	405	!--
	406	!-- Note: For m = n this equation is an approximation only
	407	!-- valid for weight >> 1 (which is usually the case). The
	408	!-- approximation is weight(n)-1 = weight(n).
	409	weight(n) = weight(n) - 0.5_wp * weight(n) * &
	410	ckernel(n,m,1) * weight(m) * &
	411	ddV * dt_3d
	412	IF ( n .NE. m ) THEN
	413	weight(m) = weight(m) - 0.5_wp * weight(m) * &
	414	ckernel(n,m,1) * weight(n) * &
	415	ddV * dt_3d
	416	ENDIF
	417	ENDIF
[849]	418
	419
[1359]	420	ENDDO
[849]	421
[1822]	422	ql_vp(k,j,i) = ql_vp(k,j,i) + mass(n) / factor_volume_to_mass
[849]	423
[1822]	424	ENDDO
[849]	425
[1822]	426	ELSEIF ( all_or_nothing ) THEN ! select collision algorithm
[849]	427
[1822]	428	DO n = 1, number_of_particles
[849]	429
[1822]	430	xn = mass(n) / weight(n) ! mean mass of droplet n
[849]	431
[1822]	432	DO m = n, number_of_particles
[849]	433
[1822]	434	xm = mass(m) / weight(m) !mean mass of droplet m
[849]	435
[1822]	436	IF ( weight(n) .LT. weight(m) ) THEN
	437	!
	438	!-- Particle n collects smaller particle m
	439	collection_probability = ckernel(n,m,1) * weight(m) * &
	440	ddV * dt_3d
[1071]	441
[1822]	442	IF ( collection_probability .GT. random_function( iran_part ) ) THEN
	443	mass(n) = mass(n) + weight(n) * xm
	444	weight(m) = weight(m) - weight(n)
	445	mass(m) = mass(m) - weight(n) * xm
	446	ENDIF
[1359]	447
[1822]	448	ELSEIF ( weight(m) .LT. weight(n) ) THEN
[1071]	449	!
[1822]	450	!-- Particle m collects smaller particle n
	451	collection_probability = ckernel(n,m,1) * weight(n) * &
	452	ddV * dt_3d
[1071]	453
[1822]	454	IF ( collection_probability .GT. random_function( iran_part ) ) THEN
	455	mass(m) = mass(m) + weight(m) * xn
	456	weight(n) = weight(n) - weight(m)
	457	mass(n) = mass(n) - weight(m) * xn
	458	ENDIF
	459	ELSE
	460	!
	461	!-- Collisions of particles of the same weighting factor.
	462	!-- Particle n collects 1/2 weight(n) droplets of particle m,
	463	!-- particle m collects 1/2 weight(m) droplets of particle n.
	464	!-- The total mass mass changes accordingly.
	465	!-- If n = m, the first half of the droplets coalesces with the
	466	!-- second half of the droplets; mass is unchanged because
	467	!-- xm = xn for n = m.
	468	!--
	469	!-- Note: For m = n this equation is an approximation only
	470	!-- valid for weight >> 1 (which is usually the case). The
	471	!-- approximation is weight(n)-1 = weight(n).
	472	collection_probability = ckernel(n,m,1) * weight(n) * &
	473	ddV * dt_3d
[1071]	474
[1822]	475	IF ( collection_probability .GT. random_function( iran_part ) ) THEN
	476	mass(n) = mass(n) + 0.5_wp * weight(n) * ( xm - xn )
	477	mass(m) = mass(m) + 0.5_wp * weight(m) * ( xn - xm )
	478	weight(n) = weight(n) - 0.5_wp * weight(m)
	479	weight(m) = weight(n)
	480	ENDIF
	481	ENDIF
[1071]	482
	483
[1822]	484	ENDDO
[1071]	485
[1822]	486	ql_vp(k,j,i) = ql_vp(k,j,i) + mass(n) / factor_volume_to_mass
[1071]	487
[1822]	488	ENDDO
[1071]	489
[1822]	490	ENDIF
[1071]	491
[1822]	492	IF ( ANY(weight < 0.0_wp) ) THEN
	493	WRITE( message_string, * ) 'negative weighting'
	494	CALL message( 'lpm_droplet_collision', 'PA0028', &
	495	2, 2, -1, 6, 1 )
	496	ENDIF
	497
	498	particles(1:number_of_particles)%radius = ( mass(1:number_of_particles) / &
	499	( weight(1:number_of_particles) &
	500	* factor_volume_to_mass &
	501	) &
	502	)**0.33333333333333_wp
	503
	504	particles(1:number_of_particles)%weight_factor = weight(1:number_of_particles)
	505
	506	DEALLOCATE( weight, mass, ckernel )
	507
	508	ENDIF
	509
[849]	510	!
[1884]	511	!-- Check if LWC is conserved during collision process
	512	IF ( ql_v(k,j,i) /= 0.0_wp ) THEN
	513	IF ( ql_vp(k,j,i) / ql_v(k,j,i) >= 1.0001_wp .OR. &
	514	ql_vp(k,j,i) / ql_v(k,j,i) <= 0.9999_wp ) THEN
	515	WRITE( message_string, * ) ' LWC is not conserved during', &
	516	' collision! ', &
	517	' LWC after condensation: ', ql_v(k,j,i), &
	518	' LWC after collision: ', ql_vp(k,j,i)
	519	CALL message( 'lpm_droplet_collision', 'PA0040', 2, 2, -1, 6, 1 )
	520	ENDIF
[1359]	521	ENDIF
[1884]	522
[1359]	523	ENDIF
[1884]	524
[849]	525	CALL cpu_log( log_point_s(43), 'lpm_droplet_coll', 'stop' )
	526
[1359]	527	END SUBROUTINE lpm_droplet_collision

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