Numerical Study on the Influence of Radiative Properties in Porous Media Combustion

2001 ◽  
Vol 123 (5) ◽  
pp. 951-957 ◽  
Author(s):  
Isabel Malico ◽  
Jose´ Carlos F. Pereira
Keyword(s):  
Porous Media ◽  
Numerical Study ◽  
Species Conservation ◽  
Radiative Properties ◽  
Isotropic Scattering ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Experimental Values ◽  
Phase Functions ◽  
Porous Media Combustion

The importance of radiation and of radiative properties (extinction coefficient, scattering albedo and scattering phase function) in inert porous media combustion was numerically assessed. The two-dimensional mass, momentum, solid and gas energy, and species conservation equations were solved. Emission, absorption and scattering by the porous media were taken into consideration and the S6 approximation was used to solve the radiative transfer equation. The temperature profiles are very sensitive to a perturbation in the radiative coefficients, particularly when the scattering albedo is increased. When compared to the isotropic scattering assumption, using zero, large diffuse spheres’, linear-anisotropic and modified Henyey–Greenstein phase functions leads to an average temperature difference no bigger than 7 percent. When radiation is neglected, the predicted temperature profile is not in agreement with the available experimental values.

scholarly journals Assessing the Role of Particles in Radiative Heat Transfer during Oxy-Combustion of Coal and Biomass Blends

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Gautham Krishnamoorthy ◽  
Caitlyn Wolf
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Radiative Properties ◽  
Test Facility ◽  
Biomass Combustion ◽  
Radiative Fluxes ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Fuel Fragmentation

This study assesses the required fidelities in modeling particle radiative properties and particle size distributions (PSDs) of combusting particles in Computational Fluid Dynamics (CFD) investigations of radiative heat transfer during oxy-combustion of coal and biomass blends. Simulations of air and oxy-combustion of coal/biomass blends in a 0.5 MW combustion test facility were carried out and compared against recent measurements of incident radiative fluxes. The prediction variations to the combusting particle radiative properties, particle swelling during devolatilization, scattering phase function, biomass devolatilization models, and the resolution (diameter intervals) employed in the fuel PSD were assessed. While the wall incident radiative flux predictions compared reasonably well with the experimental measurements, accounting for the variations in the fuel, char and ash radiative properties were deemed to be important as they strongly influenced the incident radiative fluxes and the temperature predictions in these strongly radiating flames. In addition, particle swelling and the diameter intervals also influenced the incident radiative fluxes primarily by impacting the particle extinction coefficients. This study highlights the necessity for careful selection of particle radiative property, and diameter interval parameters and the need for fuel fragmentation models to adequately predict the fly ash PSD in CFD simulations of coal/biomass combustion.

scholarly journals A Method for Deriving the Mean Volume Scattering Phase Function for Zodiacal Dust

1985 ◽  
Vol 85 ◽  
pp. 215-218
Author(s):  
S.S. Hong
Keyword(s):  
Linear Combination ◽  
Phase Function ◽  
Dust Particles ◽  
Zodiacal Light ◽  
Volume Scattering ◽  
Zodiacal Dust ◽  
Scattering Phase ◽  
The Mean ◽  
Scattering Phase Function ◽  
Phase Functions

AbstractA linear combination of 3 Henyey-Greenstein phase functions is substituted for the mean volume scattering phase function in the zodiacal light brightness integral. Results of the integral are then compared with the observed brightness to form residuals. Minimization of the residuals provides us with the best combination of Henyey-Greenstein functions for the scattering phase function of zodiacal dust particles.

scholarly journals Pyramidal ice crystal scattering phase functions and concentric halos

1996 ◽  
Vol 14 (11) ◽  
pp. 1192-1197 ◽  
Author(s):  
C. Liu ◽  
P. R. Jonas ◽  
C. P. R. Saunders
Keyword(s):  
Three Dimensional ◽  
Ice Crystals ◽  
Ice Crystal ◽  
Three Dimensional Model ◽  
Model Calculations ◽  
Scattering Phase ◽  
The Common ◽  
Scattering Phase Function ◽  
Phase Functions ◽  
Solar Angle

Abstract. Phase functions have been calculated using the Monte Carlo/geometric ray tracing method for single hexagonal pyramidal ice crystals (such as solid and hollow bullets) randomly oriented in space and horizontal plane, in order to study the concentric halo formations. Results from three dimensional model calculations show that 9° halo can be as bright as the common 22° halo for pyramidal angle of 28°, and the 18°, 20°, 24° and 35° halos cannot be seen due to the strong 22° halo domination in the scattering phase function between 18° and 35°. For solid pyramidal ice crystals randomly oriented horizontally, the 35° arc can be produced and its intensity depends on the incident ray solar angle and the particle aspect ratio.

Radiative Transfer in Axisymmetric, Finite Cylindrical Enclosures

1986 ◽  
Vol 108 (2) ◽  
pp. 271-276 ◽  
Author(s):  
M. P. Mengu¨c¸ ◽  
R. Viskanta
Keyword(s):  
Finite Element ◽  
Radiative Transfer ◽  
Numerical Solutions ◽  
Radiative Transfer Equation ◽  
Radiative Properties ◽  
Radiation Characteristics ◽  
Scattering Phase ◽  
Model Equations ◽  
Scattering Phase Function ◽  
Finite Element Schemes

A solution of the radiative transfer equation for an axisymmetric cylindrical enclosure containing radiatively participating gases and particles is presented. Nonhomogeneities of the radiative properties of the medium as well as of the radiation characteristics of the boundaries are allowed for, and the boundaries are assumed to be diffusely emitting and reflecting. The scattering phase function is represented by the delta-Eddington approximation to account for highly forward scattering by particulates. The model for radiative transfer is based on the P1 and P3-spherical harmonics approximations. Numerical solutions of model equations are obtained using finite-difference as well as finite-element schemes.

Modeling of Spectral Properties and the Scattering Phase Function for Lightweight Heat Protection Spacecraft Materials

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Valery V. Cherepanov ◽  
Oleg M. Alifanov
Keyword(s):  
Optical Properties ◽  
Spectral Properties ◽  
Material Structure ◽  
Scattering Pattern ◽  
High Temperature Materials ◽  
Heat Protection ◽  
Angular Scattering ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Phase Functions

This work gives a brief description of the statistical model that takes into account when calculating the physical, in particular, the optical properties of some ultraporous nonmetallic high-temperature materials, the real regularities of the material structure, and the physical properties of substances constituting the material. For the spectral part of the model, some tests are presented, confirming its adequacy. The simulation of the spectra and the scattering of monochromatic radiation pattern by using the representative elements of the model and the material as a whole are carried out. It is found that despite the fact that the scattering pattern based on the use of representative elements of a material can be approximated by the classical distributions, this is not true for the material as a whole. Calculations of the angular scattering probability density of the materials are carried out, and the approximations of obtained distributions that extend the class of modeling scattering phase functions (SPF) are proposed.

scholarly journals New Treatment of Strongly Anisotropic Scattering Phase Functions: The Delta-M+ Method

2018 ◽  
Vol 75 (1) ◽  
pp. 327-336 ◽  
Author(s):  
Zhenyi Lin ◽  
Nan Chen ◽  
Yongzhen Fan ◽  
Wei Li ◽  
Knut Stamnes ◽  
...  
Keyword(s):  
Delta Function ◽  
Anisotropic Scattering ◽  
Dirac Delta ◽  
Scattering Phase ◽  
New Treatment ◽  
Scattering Phase Function ◽  
Legendre Expansion ◽  
Phase Functions ◽  
Accuracy And Stability ◽  
Modified Moments

The treatment of strongly anisotropic scattering phase functions is still a challenge for accurate radiance computations. The new delta- M+ method resolves this problem by introducing a reliable, fast, accurate, and easy-to-use Legendre expansion of the scattering phase function with modified moments. Delta- M+ is an upgrade of the widely used delta- M method that truncates the forward scattering peak with a Dirac delta function, where the “+” symbol indicates that it essentially matches moments beyond the first M terms. Compared with the original delta- M method, delta- M+ has the same computational efficiency, but for radiance computations, the accuracy and stability have been increased dramatically.

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 On the relationship between the scattering phase function of cirrus and the atmospheric state

2014 ◽  
Vol 14 (10) ◽  
pp. 14109-14157 ◽  
Author(s):  
A. J. Baran ◽  
K. Furtado ◽  
L.-C. Labonnote ◽  
S. Havemann ◽  
J.-C. Thelen ◽  
...  
Keyword(s):  
Model Prediction ◽  
Phase Function ◽  
Weather Prediction ◽  
Ice Crystals ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Nwp Model ◽  
Phase Functions ◽  
The Relationship ◽  
Good Agreement

Abstract. This is the first paper to investigate the relationship between the scattering phase function of cirrus and the relative humidity with respect to ice (RHi), using space-based solar radiometric angle-dependent measurements. The relationship between RHi, and the complexity of ice crystals has been previously studied using data from aircraft field campaigns and laboratory cloud chambers. However, to the best of our knowledge, there have been no studies to date that explore this relationship, through the use of remotely sensed space-based angle-dependent solar radiometric measurements. In this paper, a case study of semi-transparent cirrus is used to explore the possibility of such a relationship. Moreover, for the first time, RHi fields predicted by a high-resolution numerical weather prediction (NWP) model are combined with satellite retrievals of ice crystal complexity. The NWP model was initialised at midnight, on the 25 January 2010, and the mid-latitude RHi field was extracted from the NWP model at 13:00 UTC. At about the same time, there was a Polarization and Anisotropy of Reflectance for Atmospheric science coupled with Observations from a Lidar (PARASOL) overpass, and the PARASOL swath covered the NWP model predicted RHi field. The cirrus case was located over Scotland, and over the North Sea. From the satellite channel based at 0.865 μm, the directionally averaged and directional spherical albedos were retrieved between the scattering angles of about 80° and 130°. An ensemble model of cirrus ice crystals is used to predict phase functions that vary between phase functions that exhibit optical features (called pristine), to featureless phase functions. For each of the PARASOL pixels, the phase function that best minimised differences between the spherical albedos was selected. This paper reports a positive correlation between the scattering phase function and RHi. That is, the pristine and completely featureless phase functions are found to be correlated with RHi < 100%, and RHi> 100%, respectively. Moreover, it is demonstrated that the NWP model prediction of the vertical profile of RHi is in good agreement with independent aircraft-based physical retrievals of RHi. Furthermore, the NWP model prediction of the cirrus cloud-top height and its vertical extent is also found to be in good agreement with aircraft-based lidar measurements.

Statistical estimates of the effect of the sea water scattering phase function on the characteristics of airborne hydrooptical lidar signals

2021 ◽  
pp. 171-177
Author(s):  
A.A. Lisenko ◽  
◽  
V.S. Shamanaev ◽  
Keyword(s):  
Sea Water ◽  
Water Layer ◽  
Single Scattering ◽  
Airborne Lidar ◽  
Statistical Estimates ◽  
Scattering Approximation ◽  
Coastal Sea ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Phase Functions

The effect of the scattering phase functions of sea water types by the Petzold classification on the characteristics of signals of an airborne lidar is investigated using the Monte Carlo method. It is shown that for pure and coastal waters, the single scattering approximation is applicable for solving the laser sensing equation. Based on the analysis of the results obtained in the closed numerical experiment, the method of reconstruction of the extinction coefficient of lidar signals by pure and coastal sea waters in the mixing water layer is proposed and substantiated. The obtained results can be used to expand the possibilities of lidar signal interpretation, especially in complex and ambiguous situations.

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