bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Freestream Vortical Structures on Stagnation Region Heat Transfer
Authors: Oo Aung N. , Ching Chan Y. 
Published: November 2021

Abstract
An experimental study was performed to investigate the influence of freestream vortical structures on stagnation region heat transfer. A heat transfer model with a cylindrical leading edge was tested in a low speed wind tunnel at Reynolds numbers ranging from 67,750 to 142,250 based on leading edge diameter of the model. Turbulence generating grids of parallel rods of diameter, 2.86 cm, 1.59 cm and 0.95 cm, were placed upstream of the heat transfer model in horizontal and vertical orientations to generate freestream turbulence with different orientations of vortical structures. The rods in horizontal orientation were perpendicular to the stagnation line and those in vertical orientation were parallel to the stagnation line of the heat transfer model. The distance between the grid and heat transfer model was varied from 25 to 125 rod diameters. The grids with rods in the horizontal orientation, where the primary vortical structures are expected to be perpendicular to the stagnation line, result in higher heat transfer than with the grids where the rods are in the vertical orientation. The difference in heat transfer with the two grid orientations decreases with increasing grid-to-model distance for a given rod-grid. The difference also decreases with decreasing rod size for a given normalized grid-to-model distance. For the 2.86 cm rod-grid, the difference in heat transfer augmentation between horizontal and vertical grid-orientations is highest at the stagnation line and decreases with streamwise distance. This difference, however, remains fairly constant over the whole stagnation region for the 1.59 cm and 0.95 cm rod-grids.
Femtosecond Laser Ablation of Titanium and Silicon
Authors: Ye Mengqi , Grigoropoulos Costas P. 
Published: November 2021

Abstract
Femtosecond laser ablation of titanium and silicon samples has been studied via time-of-flight (TOF), emission spectroscopy and microscopy measurement. Laser pulses of around 100 fs (FWHM) at λ = 800 nm were delivered by a Ti:sapphire femtosecond laser system. A vacuum chamber with a base pressure of 10−7 torr was built for ion TOF measurement. These ion TOF spectra were utilized to determine the velocity distribution of the ejected ions. While nanosecond laser ablation typically generates ions of a few tens of eV, femtosecond laser irradiation even at moderate energy densities can produce energetic ions with energies of up to a few keV. The most probable energy of these fast ions is proportional to the laser fluence. The structure and number of peaks of the TOF spectra varies with the laser fluence. Images of plume emission were captured by an intensified CCD (ICCD) camera. The plume emission spectrum was analyzed by a spectrometer. Laser ablated craters were measured by an interferometric microscope and a scanning electron microscope (SEM). Ablation yield was expressed as a function of laser fluence, and number of shots.
A Parametric Study of the Quasi-Steady State Temperature Field by a Moving Heat Source for Surface Treating
Authors: Bianco Nicola , Manca Oronzio 
Published: November 2021

Abstract
A three dimensional numerical analysis of a solid irradiated by a moving laser heat source in a quasi-steady state is carried out. The thermophysical properties of the material are considered to be temperature dependent. The dependence of the solution on the radiative and convective heat losses, the latter due to an impinging jet on the upper surface, is highlighted; the dependence of the temperature distribution on the Reynolds number of the jet is also presented. Different thicknesses and widths are shown to have discrepant influences on the induced thermal fields for a Gaussian laser source. The parametric analysis shows the thermal profiles to be strongly dependent on the jet Reynolds number. The thermal field is almost symmetric with respect to the spot center for a Peclet number equal to 0.1. The thermal penetration decreases as the Peclet number increases.
Numerical Modeling of Diffusion Boundary Layer in Strip Casting Process of Carbon Steel
Authors: Kuznetsov A. V. 
Published: November 2021

Abstract
This paper is aimed at the investigation of the diffusion boundary layer near the cooled casting surface encountered in the horizontal continuous casting process of carbon steel. The strip casting process is a relatively new continuous casting process. This process makes it possible to produce high-quality flat steel products directly, without using hot rolling. This explains why this process is very attractive for industry. Extensive numerical simulations under equilibrium and nonequilibrium assumptions provide valuable insight into the physics of diffusion boundary layer.
Technical Feasibility of a New Solventless Approach to Manufacture Pre-Pregs and Laminates for Electronic Applications
Authors: Dehnke Lynnette M. , Hogade Ranjeet R. , Castro Jose M. 
Published: November 2021

Abstract
This study refers to the technical feasibility of a continuous process for manufacturing pre-pregs and copper-clad laminates for electronic applications, with the aim to overcome three critical technological challenges, the elimination of environmentally detrimental solvents, elimination of voids and elimination of cure/temperature history variability between laminates. The new approach is based on the concept of injection pultrusion or continuous RTM. The centerpiece of the process is the impregnation die. Glass fabric and resin are fed into the die where impregnation and depending of the design, partial reaction occurs. The B-staging, if not finished in the die, will be done in an oven located immediately after. The final cure and lamination occurs in a continuous belt clamp. In the present paper, we discuss the chemo-rheology of a potential resin system and use it to establish the technical feasibility of the process.
Micro-Scale Aspects of Spray Deposition Processing: A Semi-Analytical Model for Droplet Spreading and Solidification at Off-Normal Impact Angles
Authors: Johnson S. B. , Delplanque J.-P. 
Published: November 2021

Abstract
Droplet impacts are rarely normal to the target substrate during thermal spray processing because of droplet dispersion in the spray cone or because the substrate is moving. A model for droplet spreading and solidification after off-normal impact on a cold substrate was developed. This model is based on Madejski’s energy conservation model but uses a three-dimensional velocity field, which satisfies the no slip condition at the solid front, the no shear condition at the free surface as well as the continuity equation. Furthermore, the present model assumes the shape of the spreading droplet to have a non-axisymmetric shape (limaçon perimeter and a uniform height). Stefan solidification is assumed. A mechanical energy balance is used to describe the deformation of the spreading droplet. The resulting integro-differential equation is solved numerically using a modified Euler predictor-corrector method. This model was validated by comparison with existing energy-conservation models in the case of normal impact. The results indicate both a decrease in the final splat diameter and a decrease in the expansion rate of the spreading droplet as the impact angle increases, as measured from the normal axis. The resulting impacts are therefore less efficient as the impact angle increases.
Theoretically-Based Leidenfrost Point Model
Authors: Bernardin John D. , Mudawar Issam 
Published: November 2021

Abstract
This study presents a theoretically-based model of the Leidenfrost point (LFP); the minimum liquid/solid interface temperature required to support film boiling on a smooth surface. The model is structured around bubble nucleation, growth, and merging criteria, as well as surface cavity size characterization. It is postulated that for liquid/solid interface temperatures at and above the LFP, a sufficient number of cavities (about 20%) are activated and the bubble growth rates are sufficiently fast that a continuous vapor layer is established nearly instantaneously between the liquid and the solid. The model is applicable to both pools of liquid and sessile droplets. The effect of surface cavity distribution on the LFP predicted by the model is verified for boiling on aluminum, nickel and silver surfaces, as well as on a liquid gallium surface. The model exhibits good agreement with experimental sessile droplet data for water, FC-72, and acetone. While the model was developed for smooth surfaces on which the roughness asperities are of the same magnitude as the cavity radii (0.1–1.0 μm), it is capable of predicting the boundary or limiting Leidenfrost temperature for rougher surfaces with good accuracy.
Boiling Incipience in Narrow Channels
Authors: Lakshminarasimhan M. S. , Hollingsworth D. K. , Witte Larry C. 
Published: November 2021

Abstract
Experiments were performed to investigate nucleate flow boiling and incipience in a flow channel, 1 mm high × 20 mm wide × 357 mm long, vertical, with one wall heated uniformly and others approximately adiabatic. Subcooled R-11 flowed upward through the channel; the mass flux varied from 60 to 4586 kg/(m2s). The inlet subcooling varied from 3.0 to 15.3 °C, and the inlet pressure ranged up to 0.20 MPa. Liquid crystal thermography was used to measure distributions of surface temperature from which the heat transfer coefficients on the heated surface were calculated. Observations of the boiling incipience superheat excursion and the hysteresis phenomenon are presented and discussed.
In laminar flow, a boiling front was observed that clearly separated the region cooled by single-phase convection from the region experiencing nucleate boiling. A prediction for the wall temperature and heat flux at boiling incipience based on nucleation theory compared favorably with the data. An incipience turning angle was defined to describe the transition process from the point of incipience to fully developed nucleate boiling. Fully developed saturated nucleate boiling was correlated well by Kandlikar’s technique.
Experimental Investigation of Condensation Heat Transfer of Refrigerant R-134A in Helicoidal Pipes
Authors: Han J. T. , Lin C. X. , Ebadian M. A. 
Published: November 2021

Abstract
Alternative refrigerant R-134a is considered to be ozone-friendly and a potential candidate for replacing the refrigerant CFC-12 in refrigeration and air-conditioning applications. This paper presents the experimental investigation of condensation heat transfer characteristics of superheated R-134a vapor flowing inside helicoidal pipes with the cooling water flowing through the annular helicoidal passage in a counter-flow direction. The heat transfer experiment was performed for R-134a mass flow flux ranging from 100 to 420 kg/m2s with the superheat of the inlet vapor of 2.8°C and 8.3°C, respectively. The cooling water flow Reynolds Rew ranges from 1500 to 12000. The Nusselt numbers were experimentally determined for a helicoidal pipe with the helix axis of vertical direction. The correlations for Nusselt numbers are developed based on the experimental results, which can be used as a reference in the design of helicoidal pipe condensers.
Analysis and Prediction of Condensation Heat Transfer of the Zeotropic Mixture R-125/236ea
Authors: Cavallini Alberto , Censi Giuseppe , Del Col Davide , Doretti Luca , Rossetto Luisa , Zilio Claudio , Longo Giovanni A. 
Published: November 2021

Abstract
The high temperature glide mixture R-125/236ea at three mass compositions (28/72%, 46/54%, 63/37%) is tested during condensation against water in a tube-in-tube heat exchanger. The experimental runs to measure the heat transfer coefficients are carried out at saturation temperature ranging from 40°C to 60°C and mass velocities ranging from 100 to 750 kg/(m2 s). A gas chromatograph is used for on-line concentration measurements. By comparing the heat transfer performances of the three compositions to the condensation coefficients previously measured for the two pure components inside a smooth horizontal tube [Cavallini et al. (2000)], the dependence of the heat transfer performance on composition during condensation for a non-azeotropic mixture is investigated.
The film method by Colburn and Drew (1937) is applied to predict the experimental coefficients and it is found to underestimate the heat transfer rate, with more conservative results as compared to the equilibrium method by Silver (1947), Bell and Ghaly (1973).
Heat Transfer Characteristics for a Single Fin in a Boiling Liquid
Authors: Bu Yingzong , Kraus Allan D. , Chung Benjamin T. F. 
Published: November 2021

Abstract
This work utilizes the cascade algorithm to predict the heat transfer characteristics of a one-dimensional longitudinal fin of rectangular profile in a boiling liquid. In this analysis, the geometric parameters of the fin, the temperature at the fin base and the saturation temperature of the boiling liquid are assumed. With the utilization of experimental boiling heat transfer coefficient curves, the heat flux, temperature profile, and boiling heat transfer coefficient of each point on the fin are obtained. The effectiveness of the fin in a boiling liquid is plotted for different fin thicknesses. It is found that the fin conductivity, boiling liquid, fin geometry and fin base temperature all affect the effectiveness of the fin in boiling. The effectiveness curves clearly indicate whether a fin should be used or when it is advantageous to use a fin in boiling liquid.
An Analytical and Experimental Model for a Thermosyphon That Employs Solid/Liquid Phase Change Materials
Authors: Nnanna A. G. Agwu , Harris Kendall T. , Haji-Sheikh A. 
Published: November 2021

Abstract
Application of solid/liquid phase change material (PCM) for passive cooling of electronic modules is on the increase. A simplified method of predicting the thermal performance of passive cooling systems is needed for efficient design of thermal storage systems. This paper presents an experimental and approximate analytical method for quick estimation of the rate of thermal transport in solid/liquid PCM during and after the melting process. However, the emphasis of this paper is on the transport phenomena after the melting process is completed. This research is motivated in part by the need for a simplified analytical method of predicting the rate of heat transfer in buoyancy-driven fluids within a partitioned enclosure, and the need for a fundamental understanding of the rate of heat transfer in liquid melt after the phase change phenomena. These needs are of practical importance for efficient design of a thermal energy storage system. The approximate analytical model serves as a quick method of studying the performance of a thermosyphon system.
Modeling and Simulation of Subcooled Turbulent Boiling Flow
Authors: Zarate J. A. , Roy R. P. , Kang S. , Laporta Andre 
Published: November 2021

Abstract
Modeling and numerical simulation of turbulent sub-cooled boiling flow of refrigerant-113 through a vertical concentric annular channel with its inner wall heated are reported. The two-fluid model conservation equations were solved. The Reynolds stresses in the liquid phase momentum equation were closed using the gradient transport approximation. The turbulent viscosity was considered to be comprised of shear-induced and bubble-induced components. Boiling at the inner wall was described by a wall heat transfer model which splits the wall heat flux into convective, quenching, and vaporization heat flux components. This model was modified to reflect our measurement of the radial turbulent heat flux in the liquid phase near the wall. In addition, new wall laws for the liquid phase mean temperature and axial velocity were used. The computational results are compared with our measurements wherever possible.
Methodology for Designing a Hybrid Thermal Energy Storage Heat Sink
Authors: Zheng Ning , Wirtz R. A. 
Published: November 2021

Abstract
A thermal response model for designing a hybrid thermal energy storage (TES) heat sink is developed. The stabilization time and maximum operating (hot side) temperature-to-transition temperature difference are used to characterize the performance of the heat sink. The thermal properties of the PCM employed in the design are investigated. Integration of a design optimization algorithm into a thermal performance model of the TES-hybrid heat sink results in determination of a best design subject to geometric and heat loading constraints. A prototype based on this best design is build and used to benchmark the performance model. The performance measured is consistent with the simulation model predictions of performance.
Structure and Mixing Properties of Unsteady Round Nonbuoyant Turbulent Jets and Puffs in Still Gases
Authors: Sangras R. , Faeth G. M. 
Published: November 2021

Abstract
A theoretical and experimental study of the temporal development of unsteady round nonbuoyant turbulent jets (starting jets) and puffs (interrupted jets) is described, limited to sources in still and unstratified environments. The experiments involved dye-containing fresh water sources injected vertically downward into fresh water within a large windowed tank with injector passage length/diameter ratios of 50. Time-resolved video images of the flows were obtained using a CCD camera. Test conditions were as follows: jet exit diameters of 3.2–12.7 mm, jet exit Reynolds numbers of 1450–11700, volume of injected fluid for puffs up to 80 passage diameters long, and penetration lengths up to 100 source diameters. Near-source behavior varied significantly with source properties but the flows generally became turbulent near the jet exit with self-preserving behavior observed at distances greater than 20–30 source diameters from the source. Within the self-preserving region, both the normalized streamwise penetration distance and the normalized maximum flow radius varied as functions of time to the following powers, in agreement with estimates for self-preserving turbulent flows: 1/2 for starting nonbuoyant jets and 1/4 for nonbuoyant puffs.
Thermal Modeling of the Cavity in Pulsed Excimer Laser Calorimeters
Authors: Chen D. H. , Zhang Z. M. 
Published: November 2021

Abstract
A simplified finite element model is built to study the thermal response of the 193-nm pulsed-laser calorimeter. The nonequivalence between pulsed-laser heating and electrical heating is estimated to be 0.46% at the thermocouple locations by comparing the calibration factors for average-power laser heating and electrical heating. This study should help the development of calibration and measurement standards in pulsed energy measurements for deep ultraviolet excimer lasers that are important for photolithographic and materials processing applications.
The Effect of Wave Number on the Performance of BGT Absorbing Boundary Conditions for Acoustic Scattering
Authors: Harari Isaac , Djellouli Rabia 
Published: November 2021

Abstract
The computation of exterior wave problems at low wave numbers can become prohibitively expensive when higher circumferential modes are significant. An analysis of the effect of wave number on scattering problems, with local absorbing boundary conditions specified on simple shapes as on-surface radiation conditions, provides guidelines for satisfactory performance. Excessive computational cost may be avoided for most practical applications.
Newton-Like Method for Solving Inverse Obstacle Acoustic Scattering Problems
Authors: Djellouli Rabia , Farhat Charbel , Tezaur Radek 
Published: November 2021

Abstract
A Newton-like method is designed for determining the shape or sought-after shape modifications of a scatterer from the knowledge of acoustic far-field patterns at a given number of observation points. This method distinguishes itself from existing numerical procedures by the following features: (a) exact Jacobian matrices for the linearized problems rather than approximate ones, (b) a fast numerical procedure for computing these Jacobian matrices, (c) a computationally efficient absorbing boundary condition for the finite element discretization, and (d) a numerically scalable domain decomposition methods for the fast solution of high-frequency direct acoustic scattering problems.
Time-Dependent Calculation of Acoustic Radiation From Finite Wings Using BEM
Authors: Wood Trevor H. , Grace Sheryl M. 
Published: November 2021

Abstract
The calculation of acoustic radiation from finite wings using a 3D, time-domain Boundary Element Method (BEM) was investigated. Numerical convergence was studied and solutions obtained using an extrapolated convergence method were used to compare to 2D analytical solutions. Frequency-domain lift solutions were found to be accurate to less than 5% using relatively coarse grids (Δx ∼ 0.1) for reduced frequencies above 0.1 and less than approximately 3. The acoustic responses for high aspect ratio wings were found to agree well qualitatively with the 2D results. As an illustration of the capabilities of the method, a full-span, flapped wing configuration undergoing oscillatory motion was considered with a preliminary quantification of the aeroacoustic influence of the flap.
Ultrasound Modulation of Diffusive Optical Waves for Medical Imaging
Authors: Townsend Daniel J. , Stott Jonathan J. , Roy Ronald A. , DiMarzio Charles A. 
Published: November 2021

Abstract
Diffusive optical tomography [DOT] is a technique for imaging within the body. While DOT provides excellent results under good conditions, there are many situations (due to anatomy or other physical limitation) in which it suffers from a “limited view” problem. In this paper we discuss our work on a new technique for combining DOT with focused ultrasound to generate virtual sources of illumination. These virtual sources help overcome the limited view problem. We present our experimental results using laboratory tissue phantoms.
Vibration and Acoustic Evaluation of a Large Centrifugal Wastewater Pump, Part 1: Background and Experiment
Authors: Abbot Philip , Gedney Charles , Morton David , Celuzza Stephen , Dyer Ira , Ehlers Peter , Vaicaitis Rimas , Brown James , Guinzburg Adiel , Hodgson William 
Published: November 2021

Abstract
An extensive series of vibration and acoustic measurements has been conducted on a large (63 inch diameter three-vane impeller) centrifugal wastewater pump at a municipal pump station. Vibration measurements on the pump bearing housing exceeded the design specification at most operating blade-passing frequencies (BPF). The purpose of the testing was to determine the primary mechanisms of the vibration, including contributions from an acoustic resonance (within the piping system) and the pump’s hydrodynamic near-field. In Part 1, the physical mechanisms of pump vibration and overall experimental results are presented.
Sensitivity of Stiffness and Damping to Various Aspects of Material and Structural Behavior
Authors: Gibson Ronald F. 
Published: November 2021

Abstract
This paper reviews research which has demonstrated the use of nondestructive measurements of stiffness and damping to characterize some interesting aspects of both micromechanical and macromechanical behavior in materials and structures. The sensitivity of stiffness and damping to material microstructural detail, macroscopic defects and damage, degradation due to environmental conditions such as temperature and moisture, and other mechanical properties is examined. Observed changes in stiffness and damping can be particularly useful when measured by using nondestructive vibration tests, and there are potential applications of such measurements in both manufacturing quality control and in-service evaluation of materials and structures. A particularly attractive method for fast, low cost nondestructive measurement of stiffness and damping is based on the use of impulsive excitation, non-contacting response measurement, and data analysis with PC-based virtual instruments.