bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parallel Computing of Magnetically-Induced Flows and Microstructure Formation During Solidification Processing
Authors: Govindaraju N. , Li B. Q. 
Published: November 2021

Abstract
Solidification starts with nucleation that comes from the clustering of molecules, followed by deposition of molecules upon the nuclei or grain growth. In materials dynamics, these events are modeled at a spatial scale of microns and a temporal scale of micro seconds. On the other hand, the electrodynamic, fluid flow and heat transfer phenomena in solidifying metals are observable and thus modeled at a scale of millimeters (or sometimes centimeters) and a fraction of a second. An integrated macro/micro model is developed to represent the evolution of complex electrodynamic and transport phenomena and microstructure formation in solidifying metals with electromagnetic stirring applied to affect the solidification micrstructures. The model development is based on the hybrid boundary/finite element solution of the Maxwell equations and the finite element solution of the momentum and thermal transport equations, in combination with the Monte-Carlo-Cellular-Automaton representation of the evolution of solidification microstructure formation. Parallel computing has been applied to speed up the microstruture formation simulation, which is the most time consuming part of the calculations. The model should be useful to further our fundamental understanding of flow and microstructure formation in electromagnetically-assisted processes such as electromagnetic casting, arc welding, and vacuum refining.
Comparison of a Hydraulic Vane Actuator With Oil and Water
Authors: Raneda Albert , Siuko Mikko , Virvalo Tapio 
Published: November 2021

Abstract
The aim of this paper is to compare the performance of a hydraulic vane actuator with oil and water as the pressure medium. If the same performance level can be achieved with water and oil hydraulics, water as the pressure medium is preferred in applications where external oil leakage is not allowed or in applications that need fireproof fluids.
In order to compare the performance, a theoretical analysis of the actuator characteristics is carried out. The analysis includes a linear model of the hydraulic drive and allows identifying which factors should be analyzed in detail. As a result of this study, the parameters that greatly affect the performance of a hydraulic drive are identified (mainly, natural frequency, leakage, friction, damping and servovalve behaviour).
To experimentally verify the influence of these factors on the behaviour of the vane actuator, a set of measurements is designed to be able to identify the critical parameters.
During this study, special attention is paid to friction and leakage effects. Due to the lower water viscosity, sealing of the fluid chambers is difficult and internal leakage is difficult to avoid.
Thermal and Fluid Dynamic Structures of a Laboratory-Scale Fixed-Frame Fire-Whirl
Authors: Hassan Mohamed I. , Helali A. , Saito Kozo 
Published: November 2021

Abstract
Fire whirl is one of the most destructive phenomena in mass fires. To study thermal and fluid dynamic structures of a fire whirl in a laboratory, a fire whirl generator consisting of two vertically oriented split-cylinders were placed in an asymmetric position to form a compartment leaving two open slits in each end. A 5-cm diameter liquid pool fire was placed at the center of the compartment floor, the fire generated buoyancy flow moved upwardly, and fresh air entered to the compartment creating swirl motion. The visible flame height of the generated fire whirl was measured by a video camera, 2-D azimuthal velocity profiles at several different heights by particle image velocimetry (PIV), and the average heat flux input to the fuel surface by a Gardon gauge type heat flux meter.
A Study of Effects of Combustion on the Noise Generated by a Circular Jet Flow
Authors: Singh Kapil K. , Frankel Steven H. , Gore Jay P. 
Published: November 2021

Abstract
The noise generated by the standard Sandia Non-premixed Turbulent Flame Workshop (TNF) DLR-A and DLR-B flames was experimentally studied and compared with the noise generated by a cold air jet from same burner with identical exit Reynolds Numbers (Re). The axial and radial variations were studied for both reacting and non-reacting jets and compared.
Simultaneous Measurements of Droplet Size, Temperature, and Velocity Using an Integrated Phase-Doppler/Rainbow Thermometer
Authors: Donnell Matt O’ , Acharya Sumanta 
Published: November 2021

Abstract
This work summarizes efforts to determine the accuracy and performance characteristics of a new and novel laser diagnostic to measure instantaneous, in flight, droplet temperatures. The instrument uses the location of the rainbow peak to deduce the refractive index of the droplet, which in turn is related to the droplet temperature. Preliminary experiments were undertaken in order to understand the fundamental operating principles and limitations of the instrument. These experiments measured the temperature of an isothermal, single stream of monodisperse droplets. These measurements indicate that the mean refractive index can be measured with a standard deviation as low as 0.0001m.
Once the operation of the refractometer was proved under isothermal conditions, the measurement of droplet temperatures in a swirl-stabilized combustor was performed. These measurements indicate that the strength of the rainbow signal is significantly hampered by the noise induced by the flame. Preliminary temperature measurements with the combustor equipped with 45° vanes showed relatively constant radial temperature profiles (∼55–60°C) at locations less than 2 inches from the nozzle exit. A detailed examination of the temperature correlation with velocity and diameter revealed that larger and faster moving droplets dominate the distributions. Thus, the smaller droplets that are suspected of having the highest temperatures are inadequately represented in the mean droplet temperature.
Extinction Limits of Nonadiabatic, Catalyst-Assisted Flames in Stagnation-Point Flow
Authors: Margolis Stephen B. , Gardner Timothy J. 
Published: November 2021

Abstract
Because combustion is essentially an Arrhenius process, premixed flames generally can only exist within certain parameter ranges, or extinction limits, that correspond to a rate of heat production that is sufficient to sustain the reaction in a given flow geometry. Nonetheless, it is frequently desirable to extend these limits, often for the purpose of increasing fuel efficiency and/or reducing the rate of formation of pollutant species. Another emerging motivation is to allow combustion to be sustained in relatively small volumes, which are characterized by larger surface-to-volume ratios, that would otherwise lead to extinguishing levels of heat loss. Surface catalysts are widely used to achieve such enhancements with respect to efficiency and pollutant formation, and we wish to now consider the role catalysts might play with respect to nonadiabatic flames.
A Two-Phase and Multi-Component Model for the Cathode of PEM Fuel Cells
Authors: You Lixin , Liu Hongtan 
Published: November 2021

Abstract
A two-dimensional, two-phase and multi-component flow and transport model has been developed to simulate the flow and transport phenomena in the cathodes of PEM fuel cells. First, the governing equations based on a “two-phase mixture model” are derived by using a unified approach that describes the flow and transport in the gas channel and gas diffuser simultaneously. Then, the detailed boundary conditions are discussed especially at the gas diffuser/catalyst layer interface, which couples the flow, transport, potential and current density in the anode, the catalyst layer and membrane. Next, the model is validated by comparing the modeling results with experimental data. Further, typical distributions of oxygen and water-mass fraction in the “two-phase mixture,” as well as water vapor mass fraction, liquid saturation and liquid velocity vector are presented. Finally, the model is used to study the influences of two of the most critical issues of PEM fuel cell operation: i.e., the water and the thermal management on the two-phase flow. It was found that the two-phase flow characteristics in the cathode depend on some of the following factors: current density, operating temperature, and cathode and anode humidification temperatures. The dependence of the formation and the distribution of the two-phase flow in the gas diffuser and gas channel on these factors is explored. By studying the effects of these parameters on the two-phase flow and the fuel cell performance, the model can be used to study a water and thermal management scheme.
Ultrafast Deformation in Femtosecond Laser Heating
Authors: Tzou D. Y. , Beraun J. E. , Chen J. K. 
Published: November 2021

Abstract
The hot-electron blasting model is extended in this work to describe the ultrafast deformation in thin metal films in the sub-picosecond to picosecond domain. The driving force depends on both the temperature and temperature gradient in the hot electron gas, while the metal lattices remain thermally undisturbed in this highly non-equilibrium regime. The dominating parameters characterizing the ultrafast deformation are identified. The phonon-electron interaction model is used to describe the electron temperature, while renormalization of elastic moduli is accommodated in the dynamic equation of motion. Method of lines is used to solve the nonlinearly coupled equations describing ultrafast deformation in the sub-picosecond domain.
High-Temperature Electron Emission From Diamond Films
Authors: Shin S. H. , Fisher T. S. , Walker D. G. , Strauss A. M. , Kang W. P. , Davidson J. L. 
Published: November 2021

Abstract
This work examines the electron field emission characteristics of polycrystalline diamond films at high temperatures. Diamond is an excellent material as a field emitter because its high mechanical hardness and chemical inertness enable robust reliability. Diamond is also a wide-band gap semiconductor, increasing the probability for selective emission of higher-energy electrons. In recent years, considerable interest has developed in energy conversion applications of polycrystalline diamond films. However, little work has been considered for the field emission characteristics of diamond at elevated temperatures. The motivation behind this study involves direct energy conversion applications in power generation systems, where high temperatures exist. N-doped polycrystalline diamond films were grown by plasma-enhanced chemical-vapor deposition (PECVD). To investigate the effect of increased temperatures on field emission, current-voltage measurements were taken from the same diamond film at varying temperatures. Results from these measurements indicate a decrease in the turn-on voltage with increasing temperature. Further analysis of the temperature dependency of diamond was achieved through the parameter estimation of the effective emitting area, field enhancement factor, and work function. These results suggest that high-energy electrons are responsible for improved emission at high temperature. The resulting possibilities for direct energy conversion via diamond field emission are considered and discussed.
Numerical Solution of Melting Processes for Fixed and Unfixed Phase Change Material in the Presence of Magnetic Field: Simulation of Low Gravity Environment
Authors: Asako Y. , Gonçalves E. , Faghri M. , Charmchi M. 
Published: November 2021

Abstract
Transport processes associated with melting of an electrically conducting Phase Change Material (PCM), placed inside a rectangular enclosure, under low-gravity environment, and in the presence of a magnetic field is simulated numerically. Electromagnetic forces damp the natural convection as well as the flow induced by sedimentation and/or floatation, and thereby simulating the low gravity environment of outer space. Computational experiments are conducted for both side-wall heating and top-wall heating under horizontal magnetic field. The governing equations are discretized using a control-volume-based finite difference scheme. Numerical solutions are obtained for true low-gravity environment as well as for the simulated-low-gravity conditions resulted by the presence of a horizontal magnetic field. The effects of magnetic field on the natural convection, solid phase floatation/sedimentation, liquid-solid interface location, solid melting rate, and flow patterns are investigated. It is found that the melting under low-gravity environment can reasonably be simulated on earth via applying a strong horizontal magnetic field. However, the flow patterns obtained for the true low-gravity cases are not similar to the corresponding cases solved for the simulated-low-gravity environment.
Effect of Squealer Geometry Arrangement on Gas Turbine Blade Tip Heat Transfer
Authors: Azad Gm Salam , Han Je-Chin , Bunker Ronald S. , Lee C. Pang 
Published: November 2021

Abstract
This study investigates the effect of a squealer tip geometry arrangement on heat transfer coefficient and static pressure distributions on a gas turbine blade tip in a five-bladed stationary linear cascade. A transient liquid crystal technique is used to obtain detailed heat transfer coefficient distribution. The test blade is a linear model of a tip section of the GE E3 high-pressure turbine first stage rotor blade. Six tip geometry cases are studied: 1) squealer on pressure side, 2) squealer on mid camber line, 3) squealer on suction side, 4) squealer on pressure and suction sides, 5) squealer on pressure side plus mid camber line, and 6) squealer on suction side plus mid camber line. The flow condition corresponds to an overall pressure ratio of 1.32 and exit Reynolds number based on axial chord of 1.1 × 106. Results show that squealer geometry arrangement can change the leakage flow and results in different heat transfer coefficients to the blade tip. A squealer on suction side provides a better benefit compared to that on pressure side or mid camber line. A squealer on mid camber line performs better than that on a pressure side.
Heat Transfer Enhancement With Inclined Baffles and Ribs Combined
Authors: Khan Jamil A. , Hinton Jason , Baxter Sarah C. 
Published: November 2021

Abstract
Common heat transfer enhancement techniques are found in many of today’s processes. Devices such as inclined baffles, rib turbulators, jet impingement, etc are all used in order to augment the thermal transfer of a process. Inclined baffles have been studied along with the combination of jet impingement techniques. Inclined baffles enhance heat transfer by enhancing large-scale fluid bulk motion and through tripped boundary layer flow separation. Impinging jets, created by perforating the baffle, create additional heat transfer through flow impingement on the heated surface. Rib turbulators create heat transfer augmentation by disturbing the thermal boundary layer, unlike baffles; ribs enhance heat transfer in areas near the heat transfer surface leaving the core flow largely undisturbed. This investigation investigates experimental heat transfer of turbulent flow in a rectangular channel with inclined solid and perforated baffles combined with rib turbulators for isoflux heating at the top surface of the channel. Combining ribs with baffles yielded an increase in average Nusselt Number, albeit, with a pressure drop penalty. In situations where rate of heat transfer is critical to the performance of a device combining ribs with baffle is a viable solution.
Numerical Solution of Alloy Solidification and Columnar Eutectic Growth Using a Phase-Field Model
Authors: Judson Ward , Paolucci Samuel 
Published: November 2021

Abstract
Near-eutectic alloys freeze with a macroscopically discrete solid-liquid interface at a temperature below the equilibrium eutectic temperature. The velocity dependence of the freezing temperature results from the microscale species diffusion for microstructures with coupled eutectic growth characteristic of a near-eutectic alloy composition. At solidification rates that are representative of gravity permanent mold and die casting processes, consideration of the nonequilibrium conditions at the interface affects the prediction of the macroscale thermal field, and it in turn affects microscale properties.
A phase-field formulation is presented to model the alloy solidification which implicitly links the interface temperature to the interface speed. The utility of the method is well-suited for complex evolving solid-liquid interfaces and the velocity-dependent freezing temperature is satisfied implicitly.
The dimensionless governing equations are solved numerically with a fixed-grid Galerkin finite element method. After demonstrating sufficient numerical accuracy, temperature, phase field, and interface position results are presented for a square domain and three-dimensional casting geometry. Limitations of the phase-field method are discussed, and the conjugate heat transfer problem is studied to address boundary condition issues.
Fundamental and Application of High Precision Laser Micro-Bending
Authors: Zhang X. Richard , Xu Xianfan 
Published: November 2021

Abstract
This paper presents the technique of high precision microscale laser bending and the study of the thermomechanical phenomena involved. The use of pulsed and CW lasers for microscale bending of ceramics, silicon, and stainless steel is demonstrated. Experimental studies are conducted to find out the relation between bending angles and laser operation parameters. Bending results obtained by a pulsed and a CW laser are compared. Changes of surface composition after laser irradiation are analyzed. Numerical calculations based on thermo-elasto-plastic theory are conducted and results are compared with the experimental data Examples of industrial applications of high precision laser bending are given.
Affordable Integrated Helicopter Fuselage Structure — Full-Scale Article (Extended Abstract)
Authors: Burpo Steven J. , Sen Joyanto K. , Renieri Gary D. , Froeschner Neal A. , Kollmansberger Ronald B. 
Published: November 2021

Abstract
The Boeing Company and the US Army Aviation Applied Technology Directorate Missile are working under a cooperative agreement to re-engineer the center fuselage of the Longbow Apache Helicopter using an integrated design and manufacturing approach. The program is aggressively applying advanced composite manufacturing processes to a 14-foot portion of the Longbow fuselage. The goal of the program is to reduce recurring manufacturing labor costs by 25% and structural weight by 15% as compared to a 1994 Composite Baseline Design. This paper presents the accomplishments on the program.
A Model for Nonisothermal Healing of Thermoplastic Polymers During Fusion Bonding
Authors: Yang Fuzheng , Pitchumani Ranga 
Published: November 2021

Abstract
Polymer healing, referring to the intermolecular diffusion across the interfaces of thermoplastic tape layers in intimate contact, is one of the important steps in fusion bonding responsible for the development of interlaminar bond strength, and is strongly influenced by the temperature history. In this paper, a model for the healing process under non-isothermal conditions is developed starting from a fundamental formulation of the reptation of polymer chains. Considering the temperature dependence of the reptation time, the bond strength is described as a function of temperature history. Parametric studies and comparison of the model with available models in the literature are presented.
A Simplified Modeling Scheme for Design Sensitivity Study of Thermal Solution Utilizing Heat Pipe and Vapor Chamber Technology
Authors: Prasher Ravi S. , Shipley James , Devpura Amit 
Published: November 2021

Abstract
This paper introduces a simplified modeling scheme for the prediction of heat transport capability of heat pipes and vapor chambers. The modeling scheme introduced in this paper enables thermal designers to model heat pipes and vapor chambers in commercially available conduction modeling tools such as Ansys™ and IcePak™. This modeling scheme allows thermal designers to perform design sensitivity studies in terms of power dissipation of heat pipes and vapor chambers for different scenarios such as configurations, heat sink resistance for a given temperature drop between the heating source and the ambient. This paper also discusses how thermal designers can specify requirements to heat pipe/vapor chamber suppliers for their thermal design, without delving into the complete thermofluidic modeling of this technology.
Numeric Modeling of Ultrasonic Acoustic Streaming Cooling Effect on IC Chips
Authors: Wan Q. , Kuznetsov A. V. 
Published: November 2021

Abstract
This paper investigates enhancement of cooling of an IC chip by acoustic streaming induced by a PZT-covered vibrating beam, which is placed underneath the chip. Vibration of the beam induces acoustic streaming in the gap between the chip and the beam. The governing equations are asymptotically decomposed into the first order harmonic equations and second order time-independent acoustic streaming equations by the infinite small parameter defined as the ratio of characteristic beam vibration velocity and the local sound speed. The first order harmonic equations are numerically solved in the reduced wave equation form. The steady acoustic streaming equations are driven by the first order harmonic field and are solved by SIMPLER method. The cooling effect on the uniform heat flux from the chip is also analyzed and behavior of the cooling effect on the uniform heat generation within a chip with finite thickness is also estimated.
Design and Development of a Jet Impingement Facility for Experimental Studies
Authors: Allen Jason R. , Anderson Ann M. 
Published: November 2021

Abstract
This paper describes the design and development of a facility for the study of jet impingement heat transfer. The facility was designed to teach undergraduate students about the relation between fluid mechanics and convective heat transfer. It consists of a heated surface mounted perpendicular to a 9.8 by 3.8 cm slot jet nozzle on an adjustable base. A small compact blower serves as the air supply and is also mounted on the base. The jet to surface gap distance can be varied from 0 to 25 cm and the jet velocity can be varied from 2 to 15 m/s. The system uses particle image velocimetry (PIV) to measure the impinging flow velocities and liquid crystal thermography (LCT) to measure the temperatures on the heated surface. This paper will discuss the design constraints, the design options, and several analyses used to size the jet nozzle and the heat transfer surface. The final design will be presented as well as some typical PIV and LC results which illustrate the jet impingement cooling phenomena.