bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Stagnation Flow Analysis of Keyhole Formation in Laser Drilling
Authors: Batteh John J. , Chen Michael M. , Mazumder Jyoti 
Published: January 2022

Abstract
This paper presents a quasi-steady stagnation flow analysis for keyhole initiation processes in high intensity laser materials processing, such as laser drilling. The governing stagnation flow equations are normalized, and the important problem parameters are identified. The simple model accounts for conduction in the solid, conduction and convection in the melt layer, and the latent heats of melting and vaporization. The stagnation flow governing equations and boundary conditions are appropriately normalized and solved, and the important combinations of material properties and independent laser parameters are identified. This semi-quantitative analysis yields quasi-steady estimates for the penetration velocity, the thickness of the melt layer, the velocity profiles in the melt layer, and the fraction of melt that is vaporized for varying absorbed laser power and beam radii. Results from inviscid stagnation flow analyses are shown and compared for four different materials: aluminum, low carbon steel, stainless steel, and titanium.
A Fuzzy-Neural Controller for Film Extruding Processes
Authors: Andersh Jonathan , Axelrod Anthony , Stachowicz Marian 
Published: January 2022

Abstract
This paper presents a new method for controlling thickness in film extruding processes. The proposed architecture uses fuzzy logic and neural network techniques to achieve a MIMO controller that accounts for strong interactions between the thickness in different lanes and for the time delay between the actuators and the sensor. Experimental results demonstrate the performance of the controller.
An Approximate Analysis of the Melt Flow and Heat Transfer in Deep Penetration Laser Welding
Authors: Bos Jeannine A. , Chen Michael M. 
Published: January 2022

Abstract
Deep penetration welding, also called Keyhole welding, is one of the most interesting flow and heat transfer phenomena in laser welding. Once a threshold power density is reached a small diameter vapor cavity, which is characteristic of keyhole welding, is formed. Understanding the fundamental aspects of deep penetration welding will aid in the design and control of welding processes. Of particular interest is the prediction of penetration depths given certain process parameters such as material velocity and laser power.
The present investigation focuses attention on the lower portion of the keyhole where the essential features of the flow are primarily two-dimensional in the plane perpendicular to the axis of the laser. Further it is proposed that by focusing on the stagnation region an approximate solution can be obtained which would capture the essential features of the problem for large Peclet numbers. This work can later be used as a basis for more exact methods of solving the Navier-Stokes equations.
Modeling of Powder Particle Heating, Melting and Evaporation in Plasma Spraying Processes
Authors: Wan Y. P. , Prasad V. , Wang G.-X. , Sampath S. , Fincke J. R. 
Published: January 2022

Abstract
A comprehensive model is developed to study the heating, melting and evaporation of powder particles in plasma flames. The well-established LAVA code, a CFD software specially designed for plasma flame simulation, is used to predict the plasma gas field under given power conditions, and provide inputs to the particle model. The particle is assumed to be spherical and one-dimensional heat conduction equation with phase change within the particle is solved numerically using an appropriate coordinate transformation and finite difference method. Melting and vaporization interfaces are tracked and the particle vaporization is accounted for by the mass diffusion of vapor through the boundary layer around the particle. The model also takes into account of both the convective and radiative heat transfer between the particle and the plasma. The effect of mass transfer on convective heat transfer is also included. Calculations have been carried out for a single particle injected into an Ar-H2 plasma jet from outside the DC-plasma gun. Zirconia and nickel are selected as solid particles because of their widespread industrial applications as well as the apparent difference in their thermal properties. Numerical results show strong non-isothermal effect of heating, especially for materials with low thermal conductivity, such as Zirconia. The model also predicts strong evaporation of the material at high temperatures. A parametric study has been performed to examine the physical mechanisms of particle melting and evaporation in plasma and the effect of vaporization on convective heat transfer.
Heat Transfer Enhancement by Fins in the Microscale Regime
Authors: Chou Fu-Chu , Lukes Jennifer R. , Tien Chang-Lin 
Published: January 2022

Abstract
The current literature contains many studies of microchannel and micro-pin-fin heat exchangers, but none of them considers the size effect on the thermal conductivity of channel and fin walls. The present study analyzes the effect of size (i.e., the microscale effect) on the microfin performance, particularly in the cryogenic region where the microscale effect is often appreciable. Due to the size effect, the thermal conductivity of microchannel and microfin walls is reduced, so is the heat transfer rate. The heat transfer enhancement becomes even more important. This study resolves three basic issues. First, it is found that the heat flow choking can occur even in the case of simple plate fins or pin fins in the microscale regime, although choking is usually caused by the accommodation of a cluster of fins at the fin tip. Second, this paper shows that the use of micro-plate-fin arrays yields a higher heat transfer enhancement ratio than the use of the micro-pin-fin arrays due to the stronger reduction of thermal conductivity in micro-pin-fins. The third issue is how the size effect influences the fin thickness optimization. For convenience in design applications, an equation for the optimum fin thickness is established which generalizes the case without the size effect as first reported by Tuckerman and Pease.
Anisotropic Thermal Conductivity of Si/SiGe Superlattice
Authors: Zhou S. Q. , Chen G. , Liu J. L. , Zheng X. Y. , Wang K. L. 
Published: January 2022

Abstract
Recent experimental and theoretical studies demonstrate that the thermal conductivity of superlattices can be significantly reduced due to the interface phonon scattering. These studies raise the interesting possibility of phonon engineering to control the thermal conductivity of nanostructures for thermoelectric, thermionic, and microelectronic applications. Experimental evidences of a significant thermal conductivity reduction have been reported for GaAs/AlAs, Si/Ge, and Bi2Te3/Sb2Te3 superlattices. In this work, we present experimental results on the anisotropic thermal conductivity of a Si/Si0.71Ge0.29 (50Å/10Å) superlattice measured by a 2-wire 3ω method. The experimental results show that both the cross-plane and the in-plane thermal conductivities of the Si/Si0.71Ge0.29 superlattice are reduced by a factor of three compared to the predictions of the Fourier heat conduction theory. These reductions are not as large as that observed in pure Si/Ge superlattices of comparable thickness, which can be explained by the smaller mismatch in material properties between Si and Si0.71Ge0.29 than those between Si and Ge. This work provides preliminary experimental evidence supporting the idea of controlling the thermophysical properties of low-dimensional structures through phonon engineering.
Grain Growth Following Recrystallization in Reactive Spray Deposited Al-Mg-Mn Alloys
Authors: Dai Shenlong L. , Delplanque Jean-Pierre , Lavernia Enrique J. 
Published: January 2022

Abstract
This paper focuses on the quantitative investigation of grain growth at 500, 530, and 560 °C in reactive spray deposited Al-Mg-Mn alloys after thermo-mechanical processing and recrystallization. Results show that reactive spray deposited 5083 alloy processed using N2-5%O2, in which no significant volume fraction of oxide particles was found, experienced significant grain growth when annealed at 500, 530 and 560°C following recrystallization. On the other hand, the reactive spray deposited 5083 alloy atomized with N2-10% O2 and the 5083+Zr alloy atomized with N2-5% O2 exhibit very slow grain growth below 530°C and limited grain growth at 560°C. This behavior is attributed to the retardation effect of the second phase particles that were formed in these alloys. The grain growth exponent of the two alloys are found to depend on the annealing temperature, with a value of n = 6 at 530°C and n = 5 at 560°C. The retardation effect of the oxide particle and the grain growth kinetics are analyzed in the context of the model developed by Anderson and Grong (Acta Met., 43:2678, 1995).
An Eulerian-Lagrangian Front Tracking Method for Immersed Boundaries
Authors: Udaykumar H. S. , Mittal R. , Shyy Wei 
Published: January 2022

Abstract
In tracking moving boundaries that arise in several flow problems, a mixed Eulerian-Lagrangian algorithm can prove quite useful. In such a method, the grid on which the flow computations are performed remains stationary, while the interface is immersed in and moves through the grid. In this report we present a finite-difference based formulation for a scalar transport equation, which will be designed to alleviate some of the concerns associated with interface tracking on a fixed underlying grid. By performing truncation error analysis, the presentation of the method also sheds light on the expected accuracy of the solutions. The finite-difference operations are performed to maintain nominal global second-order accuracy. To demonstrate the second-order accuracy of the solutions, we present grid refinement studies preformed for some test problems.
Utilization of Sensitivity Coefficients to Guide the Design of a Thermal Battery
Authors: Blackwell Ben F. , Dowding Kevin J. , Cochran Robert J. , Dobranich Dean 
Published: January 2022

Abstract
Equations are presented to describe the sensitivity of the temperature field in a heat conducting body to changes in the volumetric heat source and volumetric heat capacity. These sensitivity equations, along with others not presented, are applied to a thermal battery problem to compute the sensitivity of the temperature field to 19 model input parameters. Sensitivity coefficients, along with assumed standard deviation in these parameters, are used to estimate the uncertainty in the temperature prediction. From the 19 parameters investigated, the battery cell heat source and volumetric heat capacity were clearly identified as being the major contributors to the overall uncertainty in the temperature predictions. The predicted operational life of the thermal battery was shown to be very sensitive to uncertainty in these parameters.
Determination of Interfacial Heat Fluxes During Casting of Aluminum in Resin-Bonded Sand Molds
Authors: Woodbury Keith A. , Chen Yuhui , Ke Quanpeng 
Published: January 2022

Abstract
This paper presents the results from an experiment to determine the heat transfer from aluminum castings during solidification. An aluminum plate (alloy A356 600 mm by 600 mm) was cast in two different thicknesses (6.25 mm and 25 mm) in a horizontal configuration. An inverse analysis, using a sequential function specification method, was used to compute the surface fluxes from the solidifying metal to the mold. The inverse analysis accounted for temperature-dependent thermal properties of the mold sand. Special attention is devoted in this paper to selection of the appropriate value of regularization parameter and suitable error estimation for thermal experiments utilizing measurements from off-the-shelf thermocouples in an inverse estimation procedure.
Numerical Estimation of Heat Transfer and Thermal Stresses in Water Cooling of Shipbuilding Profiles
Authors: Sørli Karstein , Olden Vigdis 
Published: January 2022

Abstract
In this paper a numerical procedure for estimation of heat transfer coefficients based on temperature measurements during the cooling of ship building profiles is described. Results on running a software implementation of the procedure for selected time series of laboratory measurements are presented. The paper also includes computational results of thermal stresses based on the established heat transfer coefficients.
Electrical Capacitance Tomography of Horizontal Two-Phase Flow
Authors: Moura Luiz F. M. , Tambellini Flavio , Belo Francisco A. 
Published: January 2022

Abstract
This paper describes an electrical capacitance tomography (ECT) system for imaging of two-phase flows. The capacitance sensor was built with eight electrodes around an insulating pipe. In the proposed capacitance measurement system, when an electrode is an emitter, the seven other electrodes are receivers, leading to a parallel reading tomography type. For a 8-electrode sensor, there are 28 independent readings. In order to improve the measurement system time response, a new electronic transducer was developed that supports excitation frequency up to 16 MHz. The proposed ECT system was tested for stratified air-water flows, with void fraction ranging from 0.1 to 0.9. A linear back projection algorithm was used to reconstruct the cross section image of the two-phase flow from the measured capacitance values. The reconstructed flow images obtained using this algorithm were compared to the real two-phase distributions. Filtering techniques were applied to the back projection algorithm in order to improve the reconstructed flow image quality. Limitations and possible future improvements of this technique are also discussed.
Characteristics of the Liquid Slug and the Taylor Bubble in a Vertical Slug Flow
Authors: Pedroso Daniel C. , França Fernando A. , Rosa Eugenio S. 
Published: January 2022

Abstract
Measurements in vertical upward concurrent slug flows are presented. The experiments, carried with mixtures of air and water and a viscous aqueous solution, were aimed to the characterization of the structures that form the slug flow. Double-wire conductive probes were carefully designed and calibrated to identify and to measure the slug flow and the structures that constitute the so-called slug-cell model. The variables measured were: the frequency of the slug-cell, the length of the liquid slug, the velocity and the length of the elongated bubble, the thickness of the liquid film surrounding the elongated bubble and the void fraction in the liquid slug. Comparisons between these measured quantities and results of correlation frequently adopted in the literature are presented and discussed.
Flow Regimes and Equations for Predicting Capsule Flow Through Pipe
Authors: Liu Henry , Gao Xiang , Xu Wenwei 
Published: January 2022

Abstract
The motion of cylindrical capsules in pipe can be classified into four regimes. The characteristics of each regime are described and analyzed in this paper. In each of the four regimes, the pressure drop across a capsule or capsule train (comprising a number of capsules with zero spacing or very small spacing between neighboring capsules) can be predicted by using the one-dimensional energy, momentum and continuity equations with proper consideration for the headloss including entrance and exit effects. The effect of eccentric annulus is taken into account. In predicting the capsule velocity, equations are derived by applying the overall force balance to both the capsule train and the annular flow surrounding the capsule train. Comparison with experimental data shows the incipient velocity, the capsule velocity, and the drag coefficient can be determined accurately from the theory.
Annular Flow of R-134A in a Vertical Duct: Local Void Fraction, Droplet Velocity and Droplet Size Measurements
Authors: Trabold Thomas A. , Kumar Ranganathan , Vassallo Peter F. 
Published: January 2022

Abstract
Local measurements were made in annular flow of R-134a through a high aspect ratio vertical duct. Using a gamma densitometer, hot-film anemometer and laser Doppler velocimeter, profiles of void fraction, liquid droplet frequency and droplet velocity were acquired across the narrow test section dimension. Based upon these results, data for liquid droplet size were obtained and compared to previous experimental results from the literature. These data are useful for developing an improved understanding of practical two-phase refrigerant flows, and for assessment of advanced two-fluid computer codes.
Three Phase Air-Oil-Water Flow Patterns
Authors: Odozi Utomi A. , Mendes-Tatsis Maria A. , Hewitt Geoff F. 
Published: January 2022

Abstract
In this paper, the flow patterns observed during three-phase (air/oil/water) flow experiments are described. These experiments have been carried out in the Imperial College WASP High Pressure Facility with the test section (77.92 mm I.D) downwardly inclined at an angle of 1.5° to the horizontal at system pressures of 0, 5 and 10 bar(g).
The results for the flow pattern have been plotted on three-phase horizontal flow pattern maps and these comparisons show that the small downward inclination angle has a pronounced effect on the flow regimes. The system pressure also has a strong effect on the flow pattern transitions. In addition to these, no complete separation was observed between the oil and water layers. The flow pattern transitions were compared with the theoretical predictions of Taitel and Dukler (1976) and this was revealed to be inadequate in predicting the three-phase flow patterns and the effect of pressure.
An Experimental Study of Droplets Impacting on Horizontal Screens
Authors: Hung L. S. , Yao S. C. 
Published: January 2022

Abstract
An experimental investigation of the water droplets impacting on horizontal wire screens at isothermal condition was conducted Mono-size droplets of 350 μm in diameter were generated using a piezoelectric droplet generator. For droplets impacting on coarse screens, they wetted the wires by forming thin liquid lumps. As these lumps of water film accumulated around the wires, dripping drops were produced on the bottom side of the wire. This phenomenon was very similar to the dripping drops from a single wire situation. For finer screens, the liquid film on the top surface permeated through the fine mesh openings and formed liquid ligaments at the bottom side of the screen. This ligament continued to grow in the form of a pendant drop. This situation resembled a dripping phenomenon from the bottom side of a flat surface. Eventually, when the weight of the pendant drop was large enough to overcome the surface tension effect associated with the contact surface of the screen, the drop detached from the wire and dripped off.
Experimental Study of Large Steam-Air Bubbles Condensing in a Suppression Pool
Authors: Meier Markus , Andreani Michele , Yadigaroglu George 
Published: January 2022

Abstract
The injection of air and of a steam-air mixture into water at 60 to 90°C through a downward tube of 50 mm diameter is investigated. Steam at up to 40 l/s and air at up to 24 l/s were injected, leading to the formation and break-up of large bubbles. Instrumentation included video, high-speed video, high-frequency pressure measurement and resistance probes for phase detection.
Air tests show a strong dependence of bubble-formation frequency and thus bubble size on the capacitance or length of the piping. Only at higher flow rates, the equation of Davidson and Schüler (1960) predicts bubble frequency and size well.
For steam-air experiments, total flow-rate, and a maximum-volume-reduction factor are used for defining a test matrix. These parameters effectively describe the fluid dynamics of bubble formation and after break-up, and are useful for visual volume estimations. The pool temperature also has some influence.
Experiments show a very irregular, chaotic, turbulent flow. For some cases, bubble volumes at detachment could be estimated and compared with the given parameters. These tests show that condensation is very strong even before bubble detachment and break-up. The height of complete break-up could be approximately correlated. After complete break-up, uncondensed steam is virtually impossible.
Tomographic Interpretation of Visible Emission From the Fuel-Rich Premixed Flame
Authors: Ha Kwangsoon , Choi Sangmin 
Published: January 2022

Abstract
Visible emission characteristics of a fuel-rich methane/air flame with both the luminous and non-luminous zones have been investigated. An optical train with a two-axis scanning mirror system was used to record the two-dimensional emission data from the flame. A spectrograph with an intensified detector array produced spectrum data for each spatial location. The CH radical and broad band soot emission was separated for the wavelength region of 400–500 nm after confirming the gray behavior of the soot. The line of sight integrated emission data from the axi-symmetric flame was further processed tomographically to provide local intensities. Cross-sectional structure of the flame was discussed based on the tomographically reconstructed spectral emission data.
Development of Liquid Crystal Thermometry for Three-Dimensional Temperature Measurement and its Application to Thermal Convection Phenomena
Authors: Fujisawa N. , Saito R. , Matsuura T. , Nakabayashi T. 
Published: January 2022

Abstract
Field temperature measurement technique using the flow visualization with the liquid crystal has been investigated and is applied to the three-dimensional temperature measurement by scanning the thermometry. The color to temperature calibration of the liquid crystal is carried out using the neural networks, where the effect of view angle relative to the light sheet is considered by distributing the networks over the image plane and with an optimum smoothing technique. The calibration error of temperature due to the view angle is much reduced by the present technique and is proved to be useful by application to the temperature measurement of the thermal convection over a heated surface. The three-dimensional temperature distributions of the thermal convection is reconstructed from the measured temperature field and the structure of thermal plumes is examined.
A Study of Characteristic Length for Natural Convection Heat Transfer to Ice Spheres Melting in Air
Authors: Janna William S. , Jakubowski Gerald S. 
Published: January 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.
The objective of this study is to relate Nusselt number to Rayleigh number, as is done in the literature. Characteristic length is needed to find the Nusselt and Rayleigh numbers, but because of the changing geometry of the melting ice spheres, defining characteristic length to appropriately correlate the data becomes difficult.
A number of researchers have proposed equations for characteristic length for melting ice objects. Three different characteristic lengths were determined based on previous work with melting ice spheres, 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. Three different Nusselt vs Rayleigh number graphs resulted, which are contrasted and compared.
A fourth characteristic length was proposed for the data of this study, 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