sln-slab.1 (5754B)
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If not, see <http://www.gnu.org/licenses/>. 18 .Dd March 19, 2026 19 .Dt SLN-SLAB 1 20 .Os 21 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 22 .Sh NAME 23 .Nm sln-slab 24 .Nd computations of radiative transfer in a 1D homogeneous slab 25 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 26 .Sh SYNOPSIS 27 .Nm 28 .Op Fl hsv 29 .Op Fl n Ar nrealisations 30 .Op Fl T Ar thickness 31 .Op Fl t Ar threads 32 .Fl S Ar nu_min , Ns Ar nu_max 33 .Fl a Ar accel_struct 34 .Fl m Ar molparams 35 .Fl l Ar lines 36 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 37 .Sh DESCRIPTION 38 .Nm 39 calculates the transmittance in a one-dimensional homogeneous slab of 40 arbitrary thickness using a Monte Carlo algorithm that samples the 41 spectral lines that make up the gas mixture. 42 This computation is accelerated by sampling the lines based on the 43 magnitude of their contribution to the mixture’s spectrum, so that few 44 Monte Carlo runs are required to estimate the transmissivity with a high 45 degree of confidence. 46 The core of the proposal rests on this sampling strategy, made possible 47 by constructing an acceleration structure from the set of lines in the 48 mixture. 49 A structure built using the 50 .Xr sln-build 1 51 utility and provided as input to the program. 52 .Pp 53 More than just a numerical simulation tool, 54 .Nm 55 is primarily designed to validate the aforementioned acceleration 56 structure in relation to its intended use, namely radiative transfer 57 calculations. 58 Thus, not only could an error be returned in the event of a problem with 59 the structure or its use, but the computed value can also contribute to 60 this validation through its comparison with the result of a calculation 61 of the same quantity performed by another radiative transfer code. 62 .Pp 63 The output of 64 .Nm 65 displays the estimated transmittance, its standard deviation, and the 66 number of Monte Carlo realisations rejected due to issues encountered 67 during the computation, such as numerical uncertainty. 68 The displayed values are presented as follows: 69 .Bd -literal -offset Ds 70 "%e %e %lu\en", transmittance, std_err, rejects_count 71 .Ed 72 .Pp 73 The options are as follows: 74 .Bl -tag -width Ds 75 .\"""""""""""""""""""""""""""""""""" 76 .It Fl a Ar accel_struct 77 An acceleration structure corresponding to the input 78 .Ar lines , 79 used to accelerate their sampling based on their importance. 80 This structure is generated by the 81 .Xr sln-build 1 82 tool. 83 .\"""""""""""""""""""""""""""""""""" 84 .It Fl h 85 Display short help and exit. 86 .It Fl l Ar lines 87 List of lines from which the tree was built. 88 This list is in binary format as generated by the 89 .Xr shtr 1 90 binary, or in plain text HITRAN format, depending on whether the 91 .Fl s 92 option is set or not, respectively. 93 .\"""""""""""""""""""""""""""""""""" 94 .It Fl m Ar molparams 95 Isotopologue metadata in HITRAN format. 96 .\"""""""""""""""""""""""""""""""""" 97 .It Fl n Ar nrealisations 98 Number of Monte Carlo realisations. 99 By default the number of realisations is 10000. 100 .\"""""""""""""""""""""""""""""""""" 101 .It Fl S Ar nu_min , Ns Ar nu_max 102 The spectral range, in cm^-1, over which the computations are performed. 103 .\"""""""""""""""""""""""""""""""""" 104 .It Fl s 105 Specifies that input lines are formatted according to the binary format 106 as written by the 107 .Xr shtr 1 108 utility, and not according to the HITRAN format. 109 This format is more compact, allowing for faster loading of line data. 110 .\"""""""""""""""""""""""""""""""""" 111 .It Fl T Ar thickness 112 Slab thickness. 113 The default value is 1. 114 .\"""""""""""""""""""""""""""""""""" 115 .It Fl t Ar threads 116 Advice on the number of threads to use. 117 By default, 118 .Nm 119 uses as many threads as processor cores. 120 .\"""""""""""""""""""""""""""""""""" 121 .It Fl v 122 Make 123 .Nm 124 verbose. 125 Multiple 126 .Fl v 127 options increase the verbosity. 128 The maximum is 3. 129 .El 130 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 131 .Sh EXIT STATUS 132 .Ex -std 133 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 134 .Sh EXAMPLES 135 Estimate the transmittance between 100 and 2500 cm^-1 for a slab 2 136 meters thick. 137 The slab consists of a homogeneous gas mixture of H2O, CO2 and CO 138 molecules. 139 The thermodynamic properties of the mixture, such as its pressure, 140 temperature and molecular concentrations, correspond to those used to 141 construct the acceleration structures with sln-build, provided as input 142 arguments 143 .Pq option Fl a . 144 The isotopic metadata 145 .Pq option Fl m 146 and the list of lines 147 .Pq option Fl l 148 partitioned by the acceleration structure, complete the list of input 149 data. 150 The latter is encoded in the format generated by the 151 .Xr shtr 1 152 tool 153 .Pq option Fl s . 154 The isotopes are in HITRAN format. 155 Finally, make the program as verbose as possible 156 .Pq options Fl vvv . 157 .Bd -literal -offset Ds 158 sln-slab -S 100,2500 -T2 -a tree_H2O_CO2_CO_1atm_600K.sln \e 159 -m molparam.txt -sl H2O_CO2_CO_100-2500cm-1.shtr -vvv 160 .Ed 161 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 162 .Sh SEE ALSO 163 .Xr shtr 1 , 164 .Xr sln-build 1