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.

Spatially Resolved Lateral Transmission Measurements to Characterize Changes in the Scattering Coefficient and the Anisotropy Factor

2018 ◽  
Vol 72 (5) ◽  
pp. 757-764
Author(s):  
Sabrina Stocker ◽  
Florian Foschum ◽  
Alwin Kienle
Keyword(s):  
Phase Function ◽  
Light Propagation ◽  
Scattered Light ◽  
Scattering Coefficient ◽  
Polystyrene Microsphere ◽  
Reflectance Measurement ◽  
Scattering Coefficients ◽  
Spatially Resolved ◽  
Scattering Phase ◽  
Scattering Phase Function

A new setup is described to characterize the scattering coefficient and the scattering phase function of liquid media. The setup utilizes the basic idea of a spatially resolved reflectance measurement combined with a sophisticated illumination geometry. The sample is illuminated parallel and close to the interface of the sample and a glass window to get information from single scattered and multiple scattered light. By illuminating the sample with a fiber orientated with the axis parallel to the glass surface, small distances to the source can be examined unimpeded by the illumination beam. The derived information is, for example, not only sensitive to the concentration of the scatterers but also to the size of the scattering particles. We present the setup including the theory to describe the light propagation in the whole configuration using Monte Carlo simulations. The validation has been done with polystyrene microsphere dispersions with different scattering coefficients. As application for the developed setup, we show measurements of different milk samples which vary in concentration of fat, protein, and in fat droplet size during homogenization process. By measuring milk, we show the ability of the sensor to determine information about the scattering phase function without diluting the sample. For sensors in the dairy industry, a measurement with no pre-processing and no diluting of the sample is worthwhile, because this can be used to determine the fat and protein concentration on-line.

Monte Carlo Simulation of Radiative Heat Transfer in Coarse Fibrous Media

2003 ◽  
Vol 125 (4) ◽  
pp. 748-752 ◽  
Author(s):  
Eugen Nisipeanu ◽  
Peter D. Jones
Keyword(s):  
Monte Carlo ◽  
Radiative Heat ◽  
Orientation Angle ◽  
Index Of Refraction ◽  
Radiative Properties ◽  
Fibrous Media ◽  
Polar Orientation ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Orientation Bias

Direct Geometric Monte Carlo modeling of a fibrous medium is undertaken. The medium is represented as a monodisperse array, with known solidity, of randomly oriented cylinders of known index of refraction. This technique has the advantage that further radiative properties of the medium (absorption coefficient, scattering albedo, scattering phase function) are not required, and the drawback that its’ Snell- and Fresnel-generated dynamics suggest a limitation to large, smooth fibers. It is found that radiative heat flux results are highly dependent on bias in the polar orientation angle (relative to the boundary planes) of the fibers. Randomly oriented fiber results compare well to both the large (specular radiosity method) and small (radiative transfer equation) limits, while the results of previous experiments lie within the range of simulation results generated using varying degrees of orientation bias.

A Quasidependent Scattering Radiative Properties Model for High Density Fiber Composites

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
Siu-Chun Lee
Keyword(s):  
Near Field ◽  
Incident Radiation ◽  
Fiber Composites ◽  
Mie Scattering ◽  
Radiative Properties ◽  
Field Interaction ◽  
Scattering Approximation ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Spatially Oriented

This paper presents a theoretical model for the radiative properties of fiber composites fabricated of spatially oriented fiber strands that contain closely spaced fibers in the Mie scattering regime. Dependent scattering within the dense fiber strands is accounted for by utilizing the solution of Maxwell’s equations that included the near field interaction of cylindrical waves. Scattering between strands is shown to be uncorrelated due to their macroscopic dimensions compared with the wavelength of the incident radiation. The model is called quasidependent scattering approximation (QDA), as the radiative properties are formulated as the uncorrelated sum of the dependent scattering properties of the constituent fiber strands. The extinction coefficient, scattering coefficient, and scattering phase function are derived for fiber composites of arbitrary internal architecture. The application of the QDA model is demonstrated by means of numerical analyses on two types of fiber composites.

Absorption/Scattering Coefficients and Scattering Phase Functions in Reticulated Porous Ceramics

1996 ◽  
Vol 118 (1) ◽  
pp. 79-87 ◽  
Author(s):  
T. J. Hendricks ◽  
J. R. Howell
Keyword(s):  
Wavelength Range ◽  
Phase Function ◽  
Theoretical Models ◽  
Porous Ceramics ◽  
Physical Structure ◽  
Radiative Properties ◽  
Discrete Ordinates ◽  
Scattering Coefficients ◽  
Scattering Phase ◽  
Phase Functions

Spectral absorption and scattering coefficients and spectral scattering phase functions have been derived for partially stabilized zirconia (PS ZrO2) and oxide-bonded silicon carbide (OB SiC) reticulated porous ceramics (RPCs) across the wavelength range 0.4–5.0 μm. These spectral radiative properties were investigated and quantified for 10 ppi (pores/inch), 20 ppi, and 65 ppi materials. Radiative properties were recovered from spectral hemispherical reflectance and transmittance measurements using inverse analysis techniques based upon discrete ordinates radiative models. Two dual-parameter phase functions were investigated for these materials: one based on the physical structure of reticulated porous ceramics and the other a modified Henyey–Greenstein phase function. The modified Henyey–Greenstein phase function provided the most consistent spectral radiative properties. PS ZrO2 radiative properties exhibited strongly spectrally dependent behavior across the wavelength range studied. OB SiC radiative properties exhibited radiative behavior that was relatively independent of wavelength across the wavelength spectrum studied. OB SiC also demonstrated consistently higher absorption coefficients than PS ZrO2 at all wavelengths. Spectral scattering albedos of PS ZrO2 were discovered to be in the range 0.81–0.999 and increased as ppi rating increased, while those for OB Sic were lower in the range 0.55–0.888 and decreased as ppi rating increased. The average extinction efficiencies for 0.4–5.0 μm were discovered to be 1.45 for Ps ZrO2 and 1.70 for OB SiC. Extinction coefficients were discovered to correlate well with geometric optics theoretical models and electromagnetic wave/fiber interaction models based on independent scattering and absorption mechanisms.

Reduced Models for Radiative Heat Transfer Analysis Through Anisotropic Fibrous Medium

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Hervé Thierry Tagne Kamdem ◽  
Dominique Doermann Baillis
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Phase Function ◽  
Radiative Heat ◽  
Radiative Properties ◽  
Heat Transfer Analysis ◽  
Reduced Models ◽  
Fibrous Medium ◽  
Scattering Phase ◽  
Scattering Phase Function

Reduced models for radiative heat transfer analysis through anisotropic medium are presented and evaluated. The models include two equivalent heat transfer models through isotropic medium using isotropic or Henyey–Greenstein scattering phase functions with arithmetic or weighted means radiative properties calculated over all incident direction and an anisotropic model with directional radiative properties coupled to an isotropic scattering phase function or directional anisotropically scattering phase function. The pertinence of the models is investigated by solving coupled conduction/radiation heat transfer through a slab of anisotropic fibrous medium with fiber randomly oriented in the plan parallel to the boundaries. Good agreements on heat fluxes and thermal conductivity are obtained for reduced anisotropic models and for reduced equivalent isotropic models with weighted mean radiative properties.

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.

A Comparison of Aphelion Cloud Belt Phase Functions Before and After the Mars Year 34 Global Dust Storm

2021 ◽  
Author(s):  
Alex Innanen ◽  
Brittney Cooper ◽  
Charissa Campbell ◽  
Scott Guzewich ◽  
Jacob Kloos ◽  
...  
Keyword(s):  
Dust Storm ◽  
Phase Function ◽  
Dust Storms ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Water Ice ◽  
Ice Cloud ◽  
Sky Survey ◽  
Scattering Phase ◽  
Scattering Phase Function

<p>1. INTRODUCTION</p><p>The Mars Science Laboratory (MSL) is located in Gale Crater (4.5°S, 137.4°E), and has been performing cloud observations for the entirety of its mission, since its landing in 2012 [eg. 1,2,3]. One such observation is the Phase Function Sky Survey (PFSS), developed by Cooper et al [3] and instituted in Mars Year (MY) 34 to determine the scattering phase function of Martian water-ice clouds. The clouds of interest form during the Aphelion Cloud Belt (ACB) season (L<sub>s</sub>=50°-150°), a period of time during which there is an increase in the formation of water-ice clouds around the Martian equator [4]. The PFSS observation was also performed during the MY 35 ACB season and the current MY 36 ACB season.</p><p>Following the MY 34 ACB season, Mars experienced a global dust storm which lasted from L<sub>s</sub>~188° to L<sub>s</sub>~250° of that Mars year [5]. Global dust storms are planet-encircling storms which occur every few Mars years and can significantly impact the atmosphere leading to increased dust aerosol sizes [6], an increase in middle atmosphere water vapour [7], and the formation of unseasonal water-ice clouds [8]. While the decrease in visibility during the global dust storm itself made cloud observation difficult, comparing the scattering phase function prior to and following the global dust storm can help to understand the long-term impacts of global dust storms on water-ice clouds.</p><p>2. METHODS</p><p>The PFSS consists of 9 cloud movies of three frames each, taken using MSL’s navigation cameras, at a variety of pointings in order to observe a large range of scattering angles. The goal of the PFSS is to characterise the scattering properties of water-ice clouds and to determine ice crystal geometry.  In each movie, clouds are identified using mean frame subtraction, and the phase function is computed using the formula derived by Cooper et al [3]. An average phase function can then be computed for the entirety of the ACB season.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.eda718c85da062913791261/sdaolpUECMynit/1202CSPE&app=m&a=0&c=67584351a5c2fde95856e0760f04bbf3&ct=x&pn=gnp.elif&d=1" alt="Figure 1 – Temporal Distribution of Phase Function Sky Survey Observations for Mars Years 34 and 35" width="800" height="681"></p><p>Figure 1 shows the temporal distributions of PFSS observations taken during MYs 34 and 35. We aim to capture both morning and afternoon observations in order to study any diurnal variability in water-ice clouds.</p><p>3. RESULTS AND DISCUSSION</p><p>There were a total of 26 PFSS observations taken in MY 35 between L<sub>s</sub>~50°-160°, evenly distributed between AM and PM observations. Typically, times further from local noon (i.e. earlier in the morning or later in the afternoon) show stronger cloud features, and run less risk of being obscured by the presence of the sun. In all movies in which clouds are detected, a phase function can be calculated, and an average phase function determined for the whole ACB season.  </p><p>Future work will look at the water-ice cloud scattering properties for the MY 36 ACB season, allowing us to get more information about the interannual variability of the ACB and to further constrain the ice crystal habit. The PFSS observations will not only assist in our understanding of the long-term atmospheric impacts of global dust storms but also add to a more complete image of time-varying water-ice cloud properties.</p>

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