bluuebunny/crossref_metadata_2025_split huggingface dataset:
NAPL Dissolution in Saturated Porous Media: Model Experiments and Pore-Scale Interpretation
Authors: Radilla Giovanni , Quintard Michel , Bertin Henri 
Published: March 2022

Abstract
Predicting the rate of mass transfer in liquid-liquid systems is of crucial importance for the study of ground water contamination by hydrocarbons. Proposed correlations assume that mass transfer is strongly related to the interfacial area between the two immiscible fluids. In this paper, we present results of column experiments on the dissolution of pure hydrocarbons as well as a 1D model. Experiments were conducted for small values of the Peclet number (Pe &lt; 1). The model involves a classical convection-dispersion-mass transfer equation. Mass transfer coefficient was calculated for various periodical simplified porous systems on the basis of theoretical results from the volume averaging theory. Results show that the transport model simulates correctly the shape and dynamics of the dissolution front. It is shown that an average value of the distance between two NAPL blobs can be a key parameter for the estimation of the mass transfer coefficient rather than the interfacial area.
Numerical Analysis of Discrete Phase Influence on Gas Flow in a Two-Phase Turbulent Free Jet
Authors: Stakić Milan B. , Živković Goran S. , Sijerčić Miroslav A. 
Published: March 2022

Abstract
The influence of discrete phase (particles and/or droplets) on gas flow in a two-phase turbulent flow is of particular importance in many fields of chemical engineering. Results of numerical simulation of the two-phase turbulent flow inside a long vertical pipe as well as in a two-phase turbulent free jet formed at the pipe outlet, compared to the previously obtained experimental results, are the scope of this paper. Experimental investigation of gas and particle interaction in a two-phase turbulent free jet formed from a long vertical injection pipe were presented earlier [1].
In all numerical calculations, as well as in the experiments performed, air has been used as a gas phase (mass flow rate ma = 1.25–4.0 g/s), and sand particles of two different size ranges (0.25–0.3 mm, and 0.8–1.0 mm) as a discrete phase, with particles to gas mass flow ratio from 0.72 to 4.08. The cases of vertical downward two-phase flow inside the pipe as well as in a turbulent free jet was studied. Gas-particle interaction has been analyzed on the basis of gas velocity obtained in the particle laden two-phase flow and the clean gas flow at various distances along both the injection pipe and jet axis and radius.
Mathematical model for the continuous phase was based on the models developed for a single phase flows, with corrections due to presence of particles. The simulation model treats the flow as two-phase mixture with Eulerian description of the gas phase and Lagrangian description of the particles movements. In order to close the system of time-averaged equations, as the most reliable, k-ε turbulent model has been used. Phase coupling was achieved on the basis of so-called PSI-CELL concept. Results obtained on the basis of numerical simulation have shown a good agreement with experimental results.
Structural Integrity of Optical Fibers in Connectors
Authors: King Wilton W. , LeFevre Bruce G. , Hardee A. Guy 
Published: March 2022

Abstract
Fracture of fiber in a connector occurs when induced tensile stress exceeds local strength, usually governed by a stripping-related flaw. Stress analyses based upon elementary models from structural mechanics are presented to explore the significance of differential thermal expansion of ferrule and backbone. Results of finite-element analyses are used to suggest an epoxy-driven mechanism for fractures observed after thermal cycling. Implications for reliability are discussed.
Modeling and Stability Analysis of Polymer Sheet Extrusion
Authors: Nizami Javeed , Batur Celal 
Published: March 2022

Abstract
Dimensional stability of thin extruded sheets is analyzed as a function of draw ratio. It is assumed that the sheet keeps its rectangular cross section between the flat die and the chill roll and the flow is Newtonian. Through the analysis of linearized equations it is shown that the system is linearly unstable beyond a critical draw ratio similar to the one observed in experimental studies. The nonlinear model is then analyzed using singular perturbation analysis and simulations to confirm the existence of a stable limit cycle.
Natural Convection Heat Transfer to Ice Spheres Melting in Air
Authors: Janna William S. , Jakubowski Gerald S. 
Published: March 2022

Abstract
Three different diameter ice spheres were formed and allowed to melt in air. Each sphere was suspended by a string from a cantilevered beam, which had strain gages attached. A four active element Wheatstone Bridge was used to measure the output of the strain gages. The output signal was calibrated to measure weight of the sphere at any time during the phase change process. Data on weight versus time were thus obtained using a recorder, and used to calculate values of Nusselt and Rayleigh numbers at various instants in time. The geometry of each sphere changed during the melting process as did surface area and volume. A satisfactory determination of characteristic length was proposed which yielded excellent results. An equation relating Nusselt number to Rayleigh number was derived with a correlation coefficient of 0.975. Rayleigh numbers ranged 1.0 × 104 to 1.2 × 107, while Nusselt number ranged from 4 to 10.2. It was found that the Nusselt number could be predicted with
Nu = 1.45 Ra0.126
Influence of Flow Regime, Heat Flux, and Mass Flux on Electrohydrodynamically Enhanced Convective Boiling
Authors: Bryan James E. , Seyed-Yagoobi Jamal 
Published: March 2022

Abstract
The influence of quality, flow regime, heat flux, and mass flux on the EHD enhancement of convective boiling of R-134a in a horizontal smooth tube was fundamentally investigated. The EHD forces generated significant enhancements in the heat transfer coefficient, but the enhancements were highly dependent on the quality, flow regime, heat flux, and mass flux. The experimental data provided evidence that an optimum EHD enhancement exists for a given set of these variables for a specific electrode design. However, experimental data also provided evidence that the EHD forces can drastically reduce the rate of heat transfer at certain conditions.
Chaos Analysis and Contact Dynamics of Heat Transfer in a Gas-Fluidized Bed
Authors: Pence Deborah V. , Beasley Donald E. 
Published: March 2022

Abstract
The present study examines fundamental aspects of the heat transfer and hydrodynamics in pulse-stabilized fluidization from a chaos perspective. The pulsed atmospheric fluidized bed combustor (PAFBC), a pulsed combustor coupled with an atmospheric bubbling fluidized bed, has technical advantages in energy efficiency and emissions. The flow in the tailpipe of the pulsed combustor was modeled in a laboratory scale fluidized bed by superimposing an oscillating component on a steady mean component. Time-varying local heat transfer was measured from a heated horizontal cylinder to the cold bed.
Contact dynamics and spectral analysis of instantaneous heat flux signals clearly indicate that the bed hydrodynamics were significantly altered by the opposing secondary flow. The purpose of the present paper is to quantify these changes using chaos analysis and fractal measures. Specifically, the effect of the secondary flow on the chaotic dynamics and fractal characteristics of heat transfer were assessed by evaluating the Kolmogorov entropy and Hurst exponents, respectively, at several positions around the cylinder. The relation between chaos measures and contact dynamics was examined.
Scanning Laser Thermoelectric Microscope for Thin Film Thermophysical Property Measurement
Authors: Tasciuc Theodorian Borca , Chen Gang 
Published: March 2022

Abstract
This work presents a new thermal diffusivity measurement technique for thin films as well as bulk materials. In this technique, a modulated laser beam is focused through a transparent substrate onto the film-substrate interface. The generated thermal wave is detected using a fast responding thermocouple formed between the sample surface and the tip of a sharp probe. By scanning the laser beam around the thermocouple, the amplitude and phase distributions of the thermal wave are obtained with micrometer resolution. Thermal diffusivity of the film is determined by fitting the obtained phase signal with a three dimensional heat conduction model. Experimental results are presented for a 150 nm gold film evaporated on a glass substrate.
Optical Properties in the Visible of Soot Emitted From Turbulent Pool Fires
Authors: Krishnan S. S. , Lin K.-C. , Wu J.-S. , Faeth G. M. 
Published: March 2022

Abstract
The optical properties of soot at visible wavelengths (350–800 nm) were measured for soot emitted from liquid-fueled (benzene, toluene, cyclohexane and n-heptane) buoyant turbulent pool fires burning in air in the long residence time regime where soot properties are independent of position in the overfire region and residence time. The measurements were analyzed to find soot fractal dimensions, refractive index functions, refractive indices and dimensionless extinction coefficients, assuming Rayleigh-Debye-Gans scattering for populations of polydisperse mass fractal aggregates (RDG-PFA theory). The measurements yielded results that support recent findings for soot emitted from similar gas-fueled flames (acetylene, propylene, ethylene and propane): RDG-PFA theory is effective for estimating the optical properties of soot for the present range of conditions, soot fractal dimensions are independent of the fuel type and have a mean value of 1.79, soot refractive index properties are independent of the fuel type and are in reasonably good agreement with the often criticized measurements of Dalzell and Sarofim (1969), and dimensionless extinction coefficients are relatively independent of wavelength and fuel type over the present range of conditions and yield a mean value of 5.7, averaged over findings for both gaseous and liquid fuels.
Demonstration of a Continuous Flame Process for Producing Nanosized Silica Particles
Authors: Danczyk Stephen A. , Wu Jianfan , Wooldridge Margaret S. 
Published: March 2022

Abstract
The current work describes a novel laboratory-scale flame process for gas-phase combustion synthesis of nanosized silica (SiO2) particles. Hydrogen (H2) and oxygen (O2) are pre-mixed with argon (Ar) in a flat flame burner to produce a primary flame. Silane (SiH4), dilute in argon, is injected through the center of the cylindrical burner. The SiH4/Ar mixture produces a secondary flame and SiO2 particles are formed in the plume region of this flame. By changing reactant stoichiometries, the particle size distribution and morphology are altered. In an effort to identify the relevant processes controlling particle growth, temperature profiles, digital images and emission spectra are used to characterize the dual flame system. Particle morphology is examined by sampling directly from the secondary flame onto transmission electron microscope (TEM) grids.
Extinguishment Characteristics of Buoyant Liquid and Gas Diffusion Flames With Physical and Chemical Agents
Authors: Babb Michael , Gollahalli Subramanyam R. , Sliepcevich Cedomir M. 
Published: March 2022

Abstract
A comparative study of the extinguishment characteristics of liquid heptane and gaseous propane diffusion flames in a co-flowing stream of air in an apparatus simulating the NFPA standard 2001-cup burner apparatus is presented. A physical agent, carbon dioxide, and a chemical agent Halon 1301 were used as flame extinguishing agents. Results indicate that when the agents were premixed with air, the concentrations of CO2 and Halon 1301 at extinction of propane flames were approximately the same as the corresponding values in heptane flames. Results are substantiated with the measurements of in-flame temperature profiles and exhaust gas composition/temperature measurements in the flames.
Liftoff and Blow Off Characteristics of Laminar Non-Premixed Planar Jets
Authors: Tillman S. T. , Annamalai K. , Caton J. A. 
Published: March 2022

Abstract
The NOx emission from gas burners is essentially due to thermal NOx occuring at temperatures above 1500 K. Lean combustion reduces the flame temperature and hence thermal NOx production. However, operation at leaner mixtures creates problems in flame stability. It is well established that the closer the standoff distance of the flame to the burner, the more stable the flame. In the current paper, the liftoff and blow off characteristics of two dimensional planar jets (width/length ≪ 1) have been analyzed. The equations of mass, momentum, energy, and species have been transformed from compressible to incompressible form, then normalized, and converted into ordinary differential equations using an appropriate similarity variable, η. Explicit mixing solutions are obtained for a range of Schmidt numbers. The mixing solutions for single jets are used to determine flame standoff distance by matching the local axial velocity on the stoichiometric contour with the laminar burning velocity. The blow off velocity is then deduced. It has been verified, but not reported here, that the results are qualitatively similar for circular jets. It is envisioned that this model will be extrapolated to include multiple planar/cluster jets and thus allow the effect of flame interaction on liftoff height and blow off velocity to be studied.
Fractal Properties of Smoke Produced From Smoldering and Flaming Fires
Authors: Litton Charles D. 
Published: March 2022

Abstract
This report presents the initial results of experiments to determine the fractal-like properties of aggregate smoke particles produced from both smoldering and flaming fires. In the experiments, angular intensity data were acquired in order to determine the fractal dimension, Df, radius of gyration, Rg, and albedo, ω, for smoke produced from smoldering coal and wood, flaming coal and wood, a pool fire of No. 2 diesel fuel, and the smoke produced at the exhaust of a diesel engine. This data was combined with simultaneous measurements of current reduction in a calibrated ionization chamber detector and independent measurements of specific extinction for the different types of smoke in order to determine the primary particle diameters for the aggregate smoke particles. Both types of smoldering fires yielded similar fractal properties, and the three types of flaming fires also possessed similar fractal properties, but significant differences exist between the smoldering and flaming properties. The characteristics of smoke from the diesel engine were similar to those of smoke from the flaming fires, yet distinct Smoldering aggregates appear to be composed of a small number (≃ 100) of large primary particles (dp ≃ 0.07 μm), while flaming aggregates are composed of a large number (≃ 1000) of small primary particles (dp ≃ 0.025–0.035 μm). The average ω’s of smoldering aggregates are a factor of 2 to 3 larger than those of the flaming aggregates. In addition, further analysis indicates that the complex component of the index of refraction, i.e., the extinction coefficient, k, is a factor of 2 to 3 lower for the smoldering aggregates compared to the flaming aggregates. The implications of these results are also discussed.
Active Control of Thermoacoustic Instability Using a Model-Based Approach
Authors: Hathout J. P. , Annaswamy A. M. , Fleifil M. , Ghonlem A. F. 
Published: March 2022

Abstract
Recently, active control has been pursued vigorously for combating thermoacoustic instabilities in the combustion process. While many of the reported experiments, with controllers that include filter components determined by trial and error, have demonstrated that the dominant thermoacoustic instability can be suppressed, often the response contains secondary peaks at other frequencies which were not excited in the uncontrolled combustor. In this paper, a physical systematic model-based design of an active controller for suppressing thermoacoustic instability which overcomes many of the drawbacks of the experimental controllers is presented. This model takes into account laminar flame kinematics and linear acoustic dynamics with coupling between the acoustic modes and actuation using an end-mounted loudspeaker. With this model, a model-based controller which results in a distinctly improved performance over the experimental controllers is designed. This controller is based on an optimization strategy and leads to significantly faster settling time of the pressure oscillations, exhibits no secondary peaks, and uses smaller control effort.
Clean Coal Slurries, Their Processing for Burning
Authors: Barsky L. A. , Timnat Y. M. 
Published: March 2022

Abstract
Clean coal slurry is a possible alternative to liquid fuel. The mine problems in use of coal in engines (ash content and particles size) are solved via a novel slurry processing technique consisting in superfine grinding of the coal, selective separation of the coal particles and other inorganic ingredients, and finally combustion of the fine fraction coal in slurry droplets. An experimental rig for column flotation and selective flocculation has been built. A vibroinertial grinding facility reduces the coal particles to 40 microns or less. After addition of appropriate amounts of a suitable oil and water an emulsion flotation step produces coal-water slurry with ash content under 4%, which in turn coal under 20 microns in size with ash content 0.4% by film-flotation.
Turbulent Natural Convection in Enclosures: 1992 Workshop Revisited
Authors: Londino Joseph M. , Yang K. T. 
Published: March 2022

Abstract
The objective of this paper is to provide an improved finite-volume numerical method for turbulent natural convection in a vertical differentially-heated square enclosure for the benchmark problem in the 1992 Workshop (Eurotherm Seminar n° 22). The specific purpose here is to identify difficulties associated with the use of the QUICK scheme in solving all the governing equations, including those for k and ∈, and to demonstrate that our algorithm provides accurate calculations without the observed difficulties. A computational logic has been developed to insure the presence of positive source terms, resulting in very stable results with the use of the QUICK scheme. The present results at Ra = 5(10)10 are directly compared with those from the 1992 Workshop contributors.
Mechanisms of Heat Transfer Enhancement in a Turbulent Boundary Layer Downstream of a Cylinder-Wall Junction
Authors: Wroblewski Donald E. , Xie Qi 
Published: March 2022

Abstract
The wall heat transfer enhancement behind a circular cylinder-wall junction was investigated experimentally for Reynolds numbers ranging from ReD = 21,000 to 54,000 for locations up to 12 diameters downstream of the cylinder leading edge. Surface heat transfer was studied using a fully-heated surface downstream of the cylinder to provide traditional heat transfer coefficients, and thin-film surface sensors flush-mounted on an unheated surface to provide adiabatic heat transfer coefficients. Flow field transport measurements were obtained with a triple-wire Reynolds heat flux probe. The enhancement could be attributed to two effects: (1) a local fluid dynamic effect attributed to increased eddy diffusivity and subsequent increased turbulent transport and (2) an upstream heating effect, caused by reduced wall temperatures in the region directly behind the obstacle, and their effect on the subsequent redevelopment of the boundary layer downstream. The adiabatic heat transfer coefficients obtained from the surface sensors provided misleading results, because of the breakdown in the analogy between heat and momentum transport.
Measurements of the Convection Heat Transfer Coefficient for a Two-Dimensional Wall Jet: Uniform Temperature and Uniform Heat Flux Boundary Conditions
Authors: AbdulNour R. S. , Willenborg K. , McGrath J. J. , Foss J. F. , AbdulNour B. S. 
Published: March 2022

Abstract
The local heat transfer coefficients for isothermal and uniform heat flux boundary conditions for a two-dimensional wall jet have been experimentally determined. Hot wire anemometry surveys were used to quantify the velocity field in the wall jet. A micro thermocouple was used to quantify the temperature field in the wall jet for the isothermal boundary condition. Infrared imaging was applied to measure the wall temperature for the uniform heat flux boundary condition. The difference in the local convection coefficients due to the different thermal boundary conditions was largest at the leading edge of the heated wall and decreased in the stream wise direction. The local convection coefficient was found to be insensitive to the thermal boundary condition in the more turbulent region of the wall jet.
Facility for Calibrating Heat Flux Sensors in a Convective Environment
Authors: Holmberg D. , Steckler K. , Womeldorf C. , Grosshandler W. 
Published: March 2022

Abstract
The National Institute of Standards and Technology (NIST) presently conducts heat flux sensor calibrations using standard radiation methods. In practice, however, many heat flux sensors are used in test environments where convective heat transfer dominates. Equivalent fluxes in radiation or convection can produce different sensor responses due to sensor surface properties (e.g., emissivity, roughness) and near-surface structure (e.g., transmissivity, temperature distribution). These issues are being addressed at NIST by the development of a convective heat flux facility. By extending calibration capabilities to include a primarily convective environment, direct comparisons of sensors in controlled convective and radiative environments will be possible.
This report describes the progress of the convective heat flux calibration facility under development at NIST. A low-speed wind tunnel has been built to produce a boundary layer shear flow above a constant temperature copper plate. Independently controlled heaters and temperature monitoring systems have been designed and installed to provide an isothermal surface with a known reference heat flux. Wind tunnel configuration and test section instrumentation details, as well as characterization of the flow and the temperature distribution in the plate, are described. Initial heat transfer measurements and results from numerical modeling efforts and hot-wire anemometry are reported.
3-D Convection in 2-D Boundary Layers: First Progress Report
Authors: Eaton John K. , Mukerii Debiit , Moffat Robert J. , Batchelder Keith A. 
Published: March 2022

Abstract
Experiments are under way to investigate the effect of spanwise thermal diffusion within the boundary layer on the convective heat transfer rate from a small heated spot under a hydrodynamically two-dimensional boundary layer. If there is a significant effect, this would require a correction to the readings from small heat flux gages whenever the gage temperature differs from the surrounding wall temperature. This correction would be in addition to the known effect of a step change in wall temperature on the local heat transfer rate.
This note describes the hypothesis which underlies the test plan, the apparatus, and some preliminary qualification test results. No definitive data are presented.