Optical Diagnostics and Radiative Properties of Simulated Soot Agglomerates

1991 ◽  
Vol 113 (4) ◽  
pp. 953-958 ◽  
Author(s):  
J. C. Ku ◽  
K.-H. Shim
Keyword(s):  
Optical Diagnostics ◽  
Forward Scattering ◽  
Radiative Properties ◽  
Weak Effect ◽  
Radiative Transport ◽  
Fractal Aggregates ◽  
Scattering Coefficients ◽  
Primary Particles ◽  
Accurate Relation ◽  
Number Of Particles

The effect of agglomeration on the optical diagnostics and radiative properties of simulated soot agglomerates is investigated, using results from the Jones solution. It is found that agglomeration has a very strong effect on scattering, but only a weak effect on extinction (≅ absorption). An accurate relation has been developed, based on near-forward scattering coefficients, for inferring the number of primary particles in soot agglomerates. General models for both total and differential scattering coefficients have also been established. These results are in general agreement with those predicted for fractal aggregates having a large number of particles. Because of the effect of agglomeration, scattering may not be negligible in treating radiative transport from soot agglomerates.

Radiative Properties of Numerically Generated Fractal Soot Aggregates: The Importance of Configuration Averaging

2009 ◽  
Author(s):  
Fengshan Liu ◽  
Gregory J. Smallwood
Keyword(s):  
Primary Particle ◽  
Particle Diameter ◽  
Practical Interest ◽  
Aggregate Size ◽  
Small Variation ◽  
Radiative Properties ◽  
Fractal Aggregates ◽  
Cluster Aggregation ◽  
Fractal Parameters ◽  
Primary Particles

The radiative properties of numerically generated fractal soot aggregates were studied using the numerically accurate generalized multi-sphere Mie-solution method. The fractal aggregates investigated in this study contain from 10 to 600 primary particles of 30 nm in diameter. These fractal aggregates were numerically generated using a combination of the particle-cluster and cluster-cluster aggregation algorithms with fractal parameters representing flame generated soot. Ten different realizations were obtained for a given aggregate size measured by the number of primary particles. The wavelength considered is 532 nm and the corresponding size parameter of primary particle is 0.177. Attention is paid to the effect of different realizations of a fractal aggregate with identical fractal dimension, prefactor, primary particle diameter, and the number of primary particles on its orientation-averaged radiative properties. Most properties of practical interest exhibit relatively small variation with aggregate realization. However, other scattering properties, especially the vertical-horizontal differential scattering cross section, are very sensitive to the variation in geometrical configuration of primary particles. Orientation-averaged radiative properties of a single aggregate realization are not always sufficient to represent the properties of random-oriented ensemble of fractal aggregates.

scholarly journals Radiative Properties of Numerically Generated Fractal Soot Aggregates: The Importance of Configuration Averaging

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
Fengshan Liu ◽  
Gregory J. Smallwood
Keyword(s):  
Primary Particle ◽  
Particle Diameter ◽  
Practical Interest ◽  
Aggregate Size ◽  
Small Variation ◽  
Radiative Properties ◽  
Fractal Aggregates ◽  
Cluster Aggregation ◽  
Fractal Parameters ◽  
Primary Particles

The radiative properties of numerically generated fractal soot aggregates were studied using the numerically accurate generalized multisphere Mie-solution method. The fractal aggregates investigated in this study contain 10–600 primary particles of 30 nm in diameter. These fractal aggregates were numerically generated using a combination of the particle-cluster and cluster-cluster aggregation algorithms with fractal parameters representing flame-generated soot. Ten different realizations were obtained for a given aggregate size measured by the number of primary particles. The wavelength considered is 532 nm, and the corresponding size parameter of primary particle is 0.177. Attention is paid to the effect of different realizations of a fractal aggregate with identical fractal dimension, prefactor, primary particle diameter, and the number of primary particles on its orientation-averaged radiative properties. Most properties of practical interest exhibit relatively small variation with aggregate realization. However, other scattering properties, especially the vertical-horizontal differential scattering cross section, are very sensitive to the variation in geometrical configuration of primary particles. Orientation-averaged radiative properties of a single aggregate realization are not always sufficient to represent the properties of random-oriented ensemble of fractal aggregates.

Effect of Configuration on the Radiative Properties of High Density Fiber Composites

2009 ◽  
Author(s):  
Siu-Chun Lee
Keyword(s):  
Phase Function ◽  
Fiber Composites ◽  
High Density ◽  
Radiative Properties ◽  
Numerical Analyses ◽  
Fiber Bundles ◽  
Scattering Coefficients ◽  
Polar Orientation ◽  
Scattering Phase ◽  
Scattering Phase Function

The influence of the geometric arrangement of fiber bundles on the radiative properties of high density woven fiber composites are examined in this paper. Of particular interest is the effect of the polar orientation of fiber bundles on the angular variation of the extinction and scattering coefficients and scattering phase function. The configuration effect is examined by numerical analyses on four types of cross-ply composites with fiber bundles at specific polar inclinations. The numerical analyses utilized the theoretical model that accounts for dependent scattering within, and uncorrelated scattering between, the dense fiber bundles. The extinction and scattering coefficients and scattering phase function are shown to depend strongly on the spatial orientation of the fiber bundles. These results indicate the feasibility of customizing the radiative properties and thus radiative transport by tailoring the geometric configuration of the fiber bundles.

scholarly journals Spectral Radiative Properties of a Liquid n-Octane Droplet in the Midinfrared Region

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Liang Zhao ◽  
Chaoyu Jing ◽  
Yu Jin ◽  
Jiangping Chen ◽  
Ke Yin ◽  
...  
Keyword(s):  
Refractive Index ◽  
Wavelength Range ◽  
Optical Constants ◽  
Absorption Efficiency ◽  
Efficiency Factor ◽  
Radiative Properties ◽  
Droplet Radius ◽  
Scattering Efficiency ◽  
Scattering Coefficients ◽  
Increasing Temperature

The optical constants of a liquid hydrocarbon such as liquid n-octane are basic material properties that may be used to evaluate their thermal radiation transfer capabilities. In this study, the ellipsometry method was used to measure the optical constants of liquid n-octane in the midinfrared wavelength range of 2.0–16.0 μm at temperatures of 20, 50, and 80°C. Experimental analyses indicate the significant effect of temperature on the refractive index, although it has little effect on the absorption index. With increasing temperature, the refractive index shows a linear decrease, and reduced density leads to weaker absorption intensities. The radiative properties of n-octane droplets, including the absorption and scattering efficiency factors of single droplets with droplet radii r = 10, 20, 50, and 100 μm and the absorption and scattering coefficients in a droplets-air system of droplet volume fractions fv = 2%, 3%, and 4%, were calculated using Mie theory. The numerical results indicate that, with increasing temperature, the absorption efficiency factor slightly decreases, and the variation trend of the scattering efficiency factor is more complicated. With increasing droplet radius, the absorption efficiency factor increases within the studied wavelength range, except for certain absorption peaks, but the scattering efficiency factor tends to decrease. While the absorption is greater, the scattering is weaker for a given droplet radius. With an increasing volume fraction of n-octane droplets, the absorption and scattering coefficients increase linearly within the studied wavelength range.

Predicting the Optical Properties of Arbitrarily Shaped Black Carbon Aerosols with Graph Neural Networks

2021 ◽  
Author(s):  
Kara D. Lamb ◽  
Pierre Gentine
Keyword(s):  
Remote Sensing ◽  
Optical Properties ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Training Data ◽  
Radiative Properties ◽  
Training Dataset ◽  
Small Scale ◽  
Atmospheric Models ◽  
Fractal Aggregates

<p>Aerosols sourced from combustion such as black carbon (BC) are important short-lived climate forcers whose direct radiative forcing and atmospheric lifetime depend on their morphology. These aerosols are typically fractal aggregates consisting of ~20-80 nm spheres. This complex morphology makes modeling their optical properties difficult, contributing to uncertainty in both their direct and indirect climate effects. Accurate and fast calculations of BC optical properties are needed for remote sensing inversions and for radiative forcing calculations in atmospheric models, but current methods to accurately calculate the optical properties of these aerosols such as the multi-sphere T-matrix method or generalized multiple-particle Mie Theory are computationally expensive and must be compiled in extensive data-bases off-line and then used as a look-up table. Recent advances in machine learning approaches have applied the graph convolutional neural network (GCN) to various physical science applications, demonstrating skill in generalizing beyond initial training data by exploiting and learning internal properties and interactions inherent to the larger system. Here we demonstrate for the first time that a GCN trained to predict the optical properties of numerically-generated BC fractal aggregates can accurately generalize to arbitrarily shaped aerosol particles, even over much larger aggregates than in the training dataset, providing a fast and accurate method to calculate aerosol optical properties in atmospheric models and for observational retrievals. This approach could be integrated into atmospheric models or remote sensing inversions to more realistically predict the physical properties of arbitrarily-shaped aerosol and cloud particles. In addition, GCN’s can be used to gain physical intuition on the relationship between large-scale properties (here of the radiative properties of aerosols) and small-scale interactions (here of the spheres’ positions and their interactions).</p>

Effects of multiple scattering on radiative properties of soot fractal aggregates

2014 ◽  
Vol 133 ◽  
pp. 374-381 ◽  
Author(s):  
Jérôme Yon ◽  
Fengshan Liu ◽  
Alexandre Bescond ◽  
Chloé Caumont-Prim ◽  
Claude Rozé ◽  
...  
Keyword(s):  
Multiple Scattering ◽  
Radiative Properties ◽  
Fractal Aggregates

scholarly journals MOLECULAR ASSOCIATION OF HEMOCYANIN PRODUCED BY X-RAYS AS OBSERVED IN THE ULTRACENTRIFUGE

1946 ◽  
Vol 30 (2) ◽  
pp. 83-99 ◽  
Author(s):  
Edward G. Pickels ◽  
Rubert S. Anderson
Keyword(s):  
Oxygen Tension ◽  
Horse Serum ◽  
Molecular Association ◽  
Vanishing Point ◽  
X Rays ◽  
Egg Albumin ◽  
Primary Particles ◽  
Theoretical Significance ◽  
Absolute Effect ◽  
Number Of Particles

1. When normal, monodisperse hemocyanin (60.5S) from Limulus Rolyphemus was irradiated in neutral buffer with x-rays, several new, more rapidly sedimenting ultracentrifugal components (86S, 107S, 122S) were produced, with a corresponding loss in the amount of the unaffected protein. The amount of the effect was roughly proportional to the amount of irradiation. 2. The new resolvable components apparently represented an association of the primary particles into aggregates of 2, 3, and 4 primary particles respectively. 3. The proportional amount of hemocyanin affected decreased almost to the vanishing point as the concentration of the protein was raised to high levels. 4. The absolute effect, i.e. the total number of particles affected in a given volume, increased with the concentration of hemocyanin, at least for concentrations below 15 per cent. 5. The presence of 33 per cent horse serum during irradiation inhibited the effect on the hemocyanin almost completely, with hemocyanin concentrations of both 0.8 and 14 per cent. 6. The presence of 2.8 per cent egg albumin during irradiation lowered the effect by about 70 per cent in the case of dilute preparations (0.8 per cent hemocyanin), but by only about 25 per cent in the case of 14 per cent solutions. 7. A lowering of the solution's oxygen tension during irradiation enhanced the effect, almost doubling it in some cases. 8. The probable theoretical significance of these and other observations are discussed in the text.

Heat Transfer in Open Cell Foam Insulation

1996 ◽  
Vol 118 (1) ◽  
pp. 88-93 ◽  
Author(s):  
D. Doermann ◽  
J. F. Sacadura
Keyword(s):  
Heat Transfer ◽  
Extinction Coefficient ◽  
Solid Material ◽  
Diffraction Theory ◽  
Radiative Properties ◽  
Cell Interior ◽  
Open Cell ◽  
Scattering Coefficients ◽  
Open Cell Foam ◽  
Cell Foam

Heat transfer in open cell foam insulation occurs by conduction through the solid material and through the gas in the cell interior and by thermal radiation, which propagates through the structure. The conductive process within these media is described using a simple parallel-series model. Spectral volumetric absorption and scattering coefficients as well as the spectral phase function are predicted using a combination of geometric optics laws and diffraction theory to model the interaction of radiation with the particles forming the foam. The particles considered are both struts formed at the juncture of three cells and strut junctures. The radiative properties can then be utilized to obtain a weighted extinction coefficient, which can be used in the Rosseland equation to obtain the radiative flux. The innovative part of the work lies in the radiative properties predictive model. This new model is compared with simpler ones.

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