bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of an Efficient Solution Method for Solving the Radiative Transfer Equation
Authors: Ouyang Xing , Minardi Antonio , Kassab Alain 
Published: July 2023

Abstract
The radiative heat transfer equation in a participating medium is a Fredholm integral equation of the second kind whose kernels are formally singular at the position where the incident radiation is to be determined. A general method is developed to remove this singularity by capitalizing on the mutual interactions between the source function and the exponential integral appearing in the kernel. The method is based on an interpolation of the unknown source functions, and the analytical integration of the resulting product in the integrand (source function expansion multiplied by the known exponential integral). As such, the method is considered semi-analytical. The method is superior to traditional solution techniques which employ quadratures approximating both the unknown and known functions appearing in the integrand, and which consequently, have numerical difficulties in addressing singularities. The general approach is presented in detail for one-dimensional problems, and extensions to two-dimensional enclosures are also given. One and two-dimensional numerical examples are considered, comparing our predictions to benchmark work. The method is shown to be computationally efficient and highly accurate. In comparison with traditional quadrature based techniques, our method readily handles the singularity of the exponential integral of first order at zero, converges rapidly under grid refinement, and provides superior prediction for radiative heat transfer. The technique is shown to be valid for a wide range of values of the scattering albedo and optical thickness. The proposed technique could be applied to a wide range of conservation problems which lend themselves to an integral formulation.
Wavelets in the Solution of Nongray Radiative Heat Transfer Equation
Authors: Bayazitoglu Yildiz , Wang Bryan Y. 
Published: July 2023

Abstract
The wavelet basis functions are introduced into the radiative transfer equation in the frequency domain. The intensity of radiation is expanded in terms of Daubechies’ wrapped around wavelet functions. It is shown that the wavelet basis approach to modeling nongrayness can be incorporated into any solution method for the equation of transfer. In this paper the resulting system of equations is solved for the one-dimensional radiative equilibrium problem using the P-N approximation.
Radiation Heat Transfer Modeling in Electrorheological Fluids: Treatment as an Absorbing Medium
Authors: Hargrove Jeffrey B. , Lloyd John R. , Radcliffe Clark J. 
Published: July 2023

Abstract
Radiation heat transfer control utilizing the unique properties of electrorheological (ER) fluids has recently been the subject of considerable interest as an innovative new area of research. While much work has been done to demonstrate the concept and show the potential for radiation transmittance control, little has been done to specifically identify the fundamental radiation transport mechanism involved. This paper identifies particle absorption as the dominant mode for attenuation of radiant energy from the range of 500 nm to 800 nm incident upon an ER fluid made of micron sized zeolite particles. Furthermore, appropriate models are developed based on absorption theory to predict radiation heat transfer through a composite window featuring a layer of ER fluid. The levels of extinction predicted by these models are compared to data obtained by experimental measurement, with excellent agreement shown.
Radiative Heat Transfer Inside a Cylindrical Enclosure With Nonparticipating Media Using a Deterministic Statistical Method
Authors: Sivathanu Yudaya R. , Gore Jay P. 
Published: July 2023

Abstract
The radiative heat transfer inside a cylindrical enclosure is modeled using a discrete probability function method. The discrete probability function method involves solution of the equation of radiative heat transfer using Lagrangian simulations of representative photon trajectories on a discrete spatial grid. The DPF method is applied to radiation exchange in a cylindrical tube which has a hot source at one end and a detector at the other end. The cylindrical wall absorbs and reflects (both diffusely and specularly) the radiation incident on it. The calculations are used to simulate the effect of collimating tubes used in intrusive multi-wavelength emission spectroscopy. Results highlight the effect of surface properties on the apparent source temperature determined by the detector. The calculation procedure has application to the measurements of spectral absorption and reflection coefficient of the cylindrical surface using an inverse method.
Nonaxisymmetric Radiative Transfer in Cylindrical Enclosures
Authors: Moder Jeffrey P. , Chai John C. , Parthasarathy Girija , Lee HaeOk S. , Patankar Suhas V. 
Published: July 2023

Abstract
A finite-volume method for radiative transfer in cylindrical enclosures is presented. Angular redistribution terms in the equation of transfer are avoided by defining radiation directions in terms of angular coordinates measured with respect to Cartesian base vectors; this definition of radiation directions can result in control angles which overlap control-volume faces, depending on the type of spatial and angular grids used in the azimuthal direction. A simple treatment for such control-angle overlaps is presented which is also applicable to nonorthogonal curvilinear spatial-coordinates. A comparison of the present procedure with other similar methods is given. Solutions are presented for axisymmetric transfer through a cylinder and nonaxisymmetric transfer through two- and three-dimensional annular sectors. Results show that the procedure produces reasonable solutions for transparent and participating media in axisymmetric and nonaxisymmetric cylindrical enclosures.
Periodic Techniques for Low Temperature Radiative Property Measurements
Authors: Matteï S. , Especel D. 
Published: July 2023

Abstract
Ordinary steady-state methods lend themselves poorly to low temperature total emissivity and reflectivity measurements because extensive reflected power is superimposed on emissive power. A means of separating emitted and reflected fluxes from each other through periodic radiometry is proposed. This technique consists in modulating either emitted or reflected flux by using either a modulated temperature sample or a modulated temperature source. In both cases, the radiative flux leaving the sample is the sum of two fluxes — a modulated one and a non-modulated one. The former can be isolated from the latter using a Fourier analysis. For a given apparatus, an estimation of the statistical uncertainties can be performed from the temperature amplitude (sample or source), the optical path, the electrical characteristics of the detection system, and the measuring time. On the other hand, the accuracy of a particular result (emissivity or reflectivity) can be obtained by measuring the amount of noise in the FFT spectra. Both calculations are explained in detail, and numerical examples for low temperature measurements are given as well. Several emissivity and reflectivity measurement apparatus are described, their performances are discussed, and examples of experimental results are given.
Measurement of Time Varying Temperature Fields Using Visible Imaging CCD Cameras
Authors: Keanini Russell G. , Allgood Christopher L. 
Published: July 2023

Abstract
A method for measuring time-varying surface temperature distributions using high frame rate visible imaging CCD cameras is described. The technique is based on an ad hoc model relating measured radiance to local surface temperature. This approach is based on the fairly non-restrictive assumptions that atmospheric scattering and absorption, and secondary emission and reflection are negligible. In order to assess performance, both concurrent and non-concurrent calibration and measurement, performed under dynamic thermal conditions, are examined. It is found that measurement accuracy is comparable to the theoretical accuracy predicted for infrared-based systems. In addition, performance tests indicate that in our experimental system, real-time calibration can be achieved while real-time whole-field temperature measurements require relatively course spatial resolution. The principal advantages of the proposed method are its simplicity and low cost. In addition, since independent temperature measurements are used for calibration, emissivity remains unspecified, so that a potentially significant source of error is eliminated.
The Effect of Imprecision in Sensor Location on Optimal Sensor Locations
Authors: Emery Ashley F. , Fadale Tushar D. 
Published: July 2023

Abstract
Optimal sensor locations and the information content obtained when estimating parameters using the inverse method are significantly affected by uncertainties in sensor position and in the presumably known parameters. This paper describes the effect of these uncertainties. It is shown that the effect of sensor location uncertainties can be reduced by placing temperature sensors in locations of minimum heat flux. In transient experiments, the uncertainties in the boundary conditions have greatest effect at points of high heat flux and cause the optimal sensor locations to move from the boundary with the highest convective heat transfer coefficient to the boundary with the lowest in an abrupt manner.
A Numerical Study of the Effect of Interwall Spacing on Turbulent Flow in a Corrugated Duct
Authors: Ergin S. , Ota M. , Yamaguchi H. , Sakamoto M. 
Published: July 2023

Abstract
The effect of varying interwall spacing on periodic fully developed turbulent How in a corrugated duct is studied numerically. The k-ε model is adopted for turbulent closure, and computations are performed for the ratio of the corrugation height to the interwall spacing ranging from 0.45 to 2.0, and for the corrugation angles of 30° and 45°. The Reynolds number ranges from 500 to 7000 while the Prandtl number is 0.7. The numerical procedure and implementation of the k-ε model is validated by comparing numerical results with the experimental data directly. The results are also compared with the numerical values obtained by using a two-layer low-Reynolds number turbulence model. At a given Reynolds number, an increase in the interwall spacing increases the size of the separated region. On the other hand the friction factor first increases with the decreasing interwall spacing, reaches its maximum value, and then decreases.
On Two-Fluid Model of Turbulent Combustion Phenomena
Authors: Ilegbusi Olusegun J. 
Published: July 2023

Abstract
Flow characteristics of turbulent combustion in premixed ducted flames are investigated with a two-fluid model. The fluids are defined as the cold premixed, unburned mixture and the hot burned gas mixture. The model involves solution of separate transport equations for zone-averaged variables of each fluid with allowance for interface transfer of mass, momentum and energy. Combustion is assumed to be controlled by the turbulence transport and a simple Arhenius type of chemical reaction model has been employed. The fragment size which affects interfluid transfer terms and the transport properties is deduced from a transport equation that accounts for growth by entrainment and diminution by shear distortion. The growth and diminution constants of the length-scale equation are parametrically established. Predictions generally agree well with the experimental data. Effects of inlet flow rate and aspect ratio are also investigated.
Heat Transfer in Internal Turbulent Flows Using the PDF Method
Authors: Mazumder Sandip , Modest Michael F. 
Published: July 2023

Abstract
One of the strengths of the velocity-composition joint probability density function (PDF) method lies in its ability to predict scalar fields for reactive turbulent flows. The application of PDF methods to internal flows necessitates appropriate description of near-wall effects, namely, molecular transport, production of turbulence by inhomogeneities, and dissipation of the scalar fluctuations by viscosity. A Lagrangian transport equation has been derived for transport of energy, whereby convection is treated exactly. The temperature fluctuations are modeled by a modified version of a deterministic model, which was originally developed for homogeneous turbulence. The thermal wall-functions were used to incorporate these modifications. The resultant modeled Lagrangian energy transport equation is solved simultaneously with the hydrodynamic equations, for the test case of a thermally developing two-dimensional channel flow (parallel plate geometry). The model has been tested for both constant temperature and constant heat flux boundary conditions. Results obtained have been compared to k-ϵ and algebraic Reynolds stress model (ARSM) finite-volume calculations. Apart from the differences due to turbulence models, it was observed that the finite-volume calculations suffered numerical diffusion, which was completely eliminated in the Lagrangian PDF approach.
A Comparative Study on a Non-Linear Turbulent Heat Transfer Model for Separating and Reattaching Flows
Authors: Jia Shaobo , Chung Benjamin T. F. 
Published: July 2023

Abstract
Based on a previously proposed non-linear turbulence model, a turbulent heat transfer model is formulated in the present study using the concept of Generalized Gradient Diffusion (GGD) hypothesis. Under this hypothesis, an anisotropic thermal diffusivity can be obtained through the proposed non-linear turbulent model which is applied to the turbulent flow and heat transfer in a sudden expansion pipe with a constant heat flux through the pipe wall. The numerical results are compared with the available experimental data for both turbulent and thermal quantities, with an emphasis on the non-linear heat transfer predictions. The improved results are obtained for the bulk temperature distribution showing that the present non-linear heat transfer model is capable of predicting the anisotropic turbulent heat transfer for the pipe expansion flow. Some limits of the proposed model are also identified and discussed.
A Non-Boussinesq Model of Mixing in a 2-D Closed Cavity
Authors: Ilegbusi Olusegun J. , Mat Mahmut D. 
Published: July 2023

Abstract
Mixing of fluids inside a cavity under isothermal and non-isothermal conditions is studied with a two-fluid model. This model involves the solution of separate transport equations for zone-averaged variables of each fluid with allowance for interface transport of momentum and energy. The effects of solutal Grashof number, thermal Grashof number, buoyancy ratio and Prandtl number on the flow field, interface behavior and temporal evolution are considered. The calculations are performed over the parameter range: 1 ≤ Grs ≤ 3.7 × 105, 0 ≤ GrT ≤ 7.4 × 106, 0 ≤ N ≤ ∝ and 1 ≤ Pr ≤ 1000. The material interface is represented by the contour of volume fraction separating the fluids. Solutal buoyancy predominates over thermal buoyancy for comparable Grashof numbers. The system exhibits asymmetric behavior at low buoyancy ratio and low Prandtl number.
Melting Characteristics of a Vertical Ice Layer Immersed in Immiscible Liquid
Authors: Yamada M. , Fukusako S. , Sayed M. Eman-Bellah 
Published: July 2023

Abstract
Melting of a vertical ice layer immersed in immiscible liquid has been investigated experimentally to determine the interaction of melt flow based on ice melting and free convection induced by buoyancy in the liquid. Oil, which was contained in a rectangular vessel, was utilized as a testing liquid. During the melting process the solid-liquid interface behavior as well as the ambient liquid flow patterns were extensively observed. Three distinct flow regimes were identified for the ambient liquid temperatures of 7.6 to 30.0°C covered. Photographs of flow regimes are presented, and dependence of the flow structure on the melting morphology is discussed. The local/average heat transfer coefficient at the melting interface and the melt fraction were determined as a function of the ambient liquid temperature as well as melting time.
Genetic Algorithm Tracking Technique for Particle Image Velocimetry and Comparison With Other Tracking Models
Authors: Yoon Churl , Hassan Yassin A. , Ortiz-Villafuerte Javier , Schmidl William D. 
Published: July 2023

Abstract
Particle Image Velocimetry (PIV) is a non-intrusive measurement technique, which can be used to study the structure of various fluid flows. PIV is a very efficient measurement technique since it can obtain both qualitative and quantitative spatial information about the flow field being studied. This information can be further processed into information such as vorticity and pathlines. Other flow measurement techniques (Laser Doppler Velocimetry, Hot Wire Anemometry, etc..) only provide quantitative information at a single point.
A study on the performance of the Sub-Grid Genetic Tracking Algorithm for use in Particle Image Velocimetry was performed. A comparison with other tracking routines as the Cross Correlation, Spring Model and Neural Network tracking techniques was conducted. All four algorithms were used to track the synthetic data, and the results are compared with those obtained from a Large Eddy Simulation computational fluid dynamics program. The simulated vectors were compared with the results from the four tracking techniques, to determine the yield and reliability of each tracking algorithm.
Modeling of Two-Phase Flow Instabilites During Startup Transients Utilizing RAMONA-4B Methodology
Authors: Paniagua J. C. , Rohatgi U. S. , Prasad V. 
Published: July 2023

Abstract
RAM0NA-4B code is currently under development for simulating thermal hydraulic instabilities that can occur in Boiling Water Reactors (BWRs) and the Simplified Boiling Water Reactor (SBWR). As one of the missions of RAMONA-4B is to simulate SBWR startup transients, where geysering or condensation-induced instability may be encountered, the code needs to be assessed for this application. This paper outlines the results of the assessments of the current version of RAMONA-4B and the modifications necessary for simulating the geysering or condensation-induced instability. The test selected for assessment are the geysering tests performed by Prof. Aritomi (1993).
Scaling of High Heat Flux Flow Boiling Flow Systems
Authors: Castrogiovanni Anthony , Sforza Pasquale M. 
Published: July 2023

Abstract
The scaling of high heat flux boiling flow systems is examined using a computational technique newly developed by the present authors. The current work is an extension of our previously reported two-dimensional scaling technique to include flow development along the axis of a cooling channel. The new approach involves the solution of the energy equation for a pipe flow subjected to a step change in wall heat flux assuming a fully developed turbulent velocity profile at the point of initial heating. A boiling-induced turbulent eddy diffusivity term is used with an adaptive genetic algorithm closure scheme to predict both the transition to, and development of, the partial nucleate boiling regime based on a postulated minimization of the local wall temperature. Examination of the constitutive equations in non-dimensional form in conjunction with the use of previously established fluid-property scaling tools, leads to the development of a scaling procedure. Reasonable similarity between a high heat flux boiling flow system utilizing water, and a lower heat flux boiling flow system using R-12 is demonstrated. A numerical experiment is carried out to illustrate the scaling technique.
Conjugate Thermal and Hydrodynamic Analyses of Saturated Film Boiling From a Horizontal Surface
Authors: Banerjee D. , Son G. , Dhir V. K. 
Published: July 2023

Abstract
Film boiling is characterized by the existence of a continuous vapor layer between a heated solid surface and a liquid layer. The evolution of the vapor-liquid interface during film boiling on a horizontal surface is determined by Rayleigh-Taylor instability. To predict the heat transfer rates in film boiling, many studies have been reported in literature. Early attempts to model this phenomenon had used semi-empirical correlations. Recent work on simulation of the evolution of vapor-liquid interface without assuming any empirical vapor-liquid interface shape and by assuming the solid surface temperature to be constant has shown that the convective heat transfer coefficients, associated with the interface, vary both spatially and temporally. Consequently, the assumption of constant solid surface temperature in film boiling is not strictly valid.
In this work, saturated film boiling on a horizontal surface is simulated numerically. Finite difference method is used to simultaneously solve the equations governing conservation of mass, momentum and energy in the vapor and liquid layers. The equations for the two fluid phases are coupled through matching of normal and tangential stresses and continuity of mass and energy at the liquid vapor interface. Second order projection method is used along with numerical grid generation to construct a grid system which is aligned with the vapor-liquid interface. The heat conduction equation is solved separately in the solid, to obtain the wall temperature.
The results show that for most surfaces little coupling takes place between thermal response of the solid substrate and hydrodynamics of evolution of the interface. However, for thin plate heaters of relatively low thermal conductivity materials, the thermal response of the solid can significantly affect the hydrodynamics of the interface and in turn the local heat transfer.
Void Fraction Fluctuations in Two-Phase Flow at 1-G and μ-G
Authors: Elkow Kenneth J. , Rezkallah Kamiel S. 
Published: July 2023

Abstract
Void fraction measurements for adiabatic, two-phase vertical upward, water-air flow in a 9.53 mm ID tube were obtained using a helical wound capacitance sensor. Comparisons were made between 1-g and μ-g void fraction values by matching the flow rates obtained at μ-g conditions. A Probability Density Function was used to analyze the void fraction signals. It was found that a wider fluctuation in void fraction values occurred for slug flow at 1-g as compared to μ-g. For higher flow rates such as with annular flow, inertia forces become dominant. For these flows it was found that the void fraction fluctuations were similar at 1-g and μ-g conditions.