Combustion Starter Pack
This archive contains data that describes a dummy medium to run htrdr for a combustion application, in the general case of an heterogeneous medium. It also proposes a program to validate htrdr-combustion.
The provided combustion medium is an axis aligned cube of 0.2 m side length. The (x=0, y=0) position is the center of the bottom face of the cube, meaning that x and y coordinates vary in the [-0.1, 0.1] m range, while the z coordinate varies in the [0, 0.2] m range.
The laser sheet is 1 mm thick, is horizontal, and splits the medium at half height: the altitude of the laser sheet therefore varies in the [0.0995, 0.105] m range, while x and y coordinates vary in the [-0.1, 0.1] m range. The laser sheet is emitted from the y=0 plane, and propagates in the direction of positive y. Its wavelength is 532 nm, and its surface power density is 1000 W/m².
The sensor on which the flux will be computed is located in the center of the bottom limit of the combustion medium. It is a square of 5 cm side length: x and y coordinates over the sensor vary in the [-0.025, 0.025] m range, and z=0.
Boundaries of the combustion chamber are black, and the sensor is also a blackbody: whenever radiation reaches a boundary, it is fully absorbed. Only the flux that reaches the sensor is accounted for.
Soot aggregates absorb and scatter radiation within the limits of the combustion chamber. Their optical cross-sections are computed according to the RDG-FA theory, using the following data:
- refraction index: 1.60+0.75.i
- fractal dimension: 1.80
- fractal prefactor: 1.30
- primary particles diameter: 20 nm
- number of primary particles per aggregate: 100
The soot volume fraction follows the following inhomogeneous axisymmetric profile:
fv(x,y,z)=fv_max*(1/2-x/L)*(1-sqrt(2*((y/L-1/2)²+(z/L-1/2)²)))
with fv_max the maximum soot volumic fraction, reached at x=-L/2, y=0, z=L/2,
L the length of the cubic combustion chamber, x and y in [-L/2, L/2] and z in
[0, L]. fv_max is set at 10^-6 m³ of soot per m³.
Content
Dummy medium
The dummy_medium directory contains all the data necessary to describe the
aforementioned medium within htrdr-combustion. The available files are:
tetra_mesh.sth: it stores the tetrahedral mesh that represents the heterogeneous medium (12 millions of tetrahedra).refraction_index.atrri: this file defines the spectrally varying refractive indices of the medium.thermodynamic_conditions.atrtp: it saves the per node physical properties of the tetrahedral mesh.
This directory also contains two Bash scripts that run the htrdr-combustion
program to compute a flux density map on this combustion medium
(compute_flux_density_map.sh) or to draw an image of it (draw_image.sh).
These scripts can be a good starting point to study how to run htrdr for a
combustion application. Assuming that htrdr-combustion is correctly installed
and registered into the current Bash shell, simply run the desired script. You
can finally use htpp to convert the computed images into a PPM image that
can be then displayed with a regular image viewer.
~ $ bash htrdr-Combustion-Starter-Pack-0.0.0/dummy_medium/draw_image.sh
~ $ htpp -vm default -o dummy_image.ppm dummy_image_800x600x128.txt
Validation program
The sw_flux directory contains a simple program, written in Fortran, that was
designed to solve the problem of interest only (fixed geometric configuration
and analytical thermodynamic properties fields). However, two separate
Monte-Carlo algorithms have been implemented in order to compute the required
flux:
- a direct Monte-Carlo algorithm: optical trajectories are followed from the laser emission surface, until they reach the sensor (or are lost).
- a reverse Monte-Carlo algorithm: this is actually the one that was
implemented into
htrdr-combustion. Optical paths start from the sensor, and a first-scattering contribution increases the weight of the realization at each scattering position in the medium.
To compile the executable simply invoke make into the sw_flux directory.
Note that the build procedure assumes that the GNU Fortran compiler
(gfortran) is installed. Once built, run the generated executable named
sw_flux. Both algorithms (direct and reverse) must agree, within the limits
of the statistical uncertainty. Furthermore, these results should also agree
with the flux computed by htrdr-combustion via the script
dummy_medium/compute_flux_density_map.sh.
~ $ cd htrdr-Combustion-Starter-Pack-0.0.0/sw_flux
sw_flux $ make
sw_flux $ ./sw_flux
sw_flux $ cd ../dummy_medium/
dummy_medium $ bash compute_flux_density_map.sh
The result should be, in terms of surface power density:
1.028e-2 +/- 1e-5 W/m²
Copyright notice
Copyright © 2021 |Méso|Star> (contact@meso-star.com)
Copyright © 2021 CNRS/RAPSODEE
License
htrdr: Combustion Starter Pack is released under the GPLv3+ license: GNU GPL
version 3 or later. You can freely study, modify or extend it. You are also
welcome to redistribute it under certain conditions; refer to the
license for details.
