bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling of Interphase Formation on Unsized Fibers in Thermosetting Composites
Authors: Yang Fuzheng , Pitchumani Ranga 
Published: November 2021

Abstract
The interphase is the region between the fiber and matrix whose properties strongly influence the overall composite behavior in terms of mechanical strength, chemical and thermal durability. The composition and thickness of the interphase region is governed by the processing conditions, in addition to the fiber surface treatments and other characteristics of the fiber and the resin materials. One of the strong contributing mechanisms to interphase formation is the preferential adsorption of matrix components onto the fiber surface, which takes place on the order of molecular scales. Chemical reaction in the matrix also happens simultaneously with the adsorption process. In this paper, a multi-layer adsorption-desorption-reaction model for a binary fluid mixture in contact with a solid surface is implemented to study the kinetics of interphase formation near bare fiber surfaces in thermosetting composite systems. Composition and thickness evolution of the interphase are predicted as functions of time. Conditions that lead to interphase formation upon vitrification are identified. Parametric studies are presented to investigate the effects of various nondimensional groups on the interphase region development.
Splashing of a Small Droplet Impinging on a Solid Surface at High Velocity
Authors: Mehdizadeh N. Z. , Chandra S. , Mostaghimi J. 
Published: November 2021

Abstract
We photographed water droplets (550 μm diameter) as they impacted on a stainless steel surface. We varied droplet impact velocity (10–40 m/s) and the average surface roughness (0.03–0.23 μm) of the steel plates used as test surfaces in our experiments. A piezoelectric droplet generator was used to produce water droplets. The stainless steel substrate was mounted on the end of a rotating arm, giving linear velocities of up to 40 m/s. A CCD video camera was used to photograph droplets impinging on the substrate. By synchronizing the ejection of a single droplet with the position of the rotating arm and triggering of the camera, different stages of droplet impact were photographed. From these photographs we measured the size of droplets as they spread. It was observed that as the impact velocity increased, finger-shape perturbations around the spreading droplet became longer and narrower. At sufficiently high velocities the tips of these fingers detached, producing satellite droplets. Increasing surface roughness was found to promote splashing and reduce the velocity at which splashing was first observed. By increasing surface roughness, both the number of fingers and the maximum extent of spreading were decreased. At high impact velocities the spreading liquid film became so thin that it ruptured in several places.
Saturated Pool Boiling Mechanisms During Single Bubble Heat Transfer: Comparison at Two Wall Superheats
Authors: Kim Jungho , Demiray Fatih , Yaddanapudi Nagaraja 
Published: November 2021

Abstract
A study of single bubbles growing on a microscale heater array kept at nominally constant temperature was performed. The behavior of bubbles nucleating at a single site at two different temperatures (22.5 K and 27.5 K superheat) is compared for saturated pool boiling of FC-72 at 1 atm. It is concluded that energy is transferred from the surface through similar heat transfer mechanisms at both superheats. Microlayer evaporation was observed to play a minor role in the overall heat transfer, with microconvection/transient conduction being the dominant mechanism. Evaluation of various heat transfer models are made.
Numerical Solution of Thermal and Fluid Flow With Phase Change by VOF Method
Authors: Shirakawa Hidemi , Takata Yasuyuki , Ito Takehiro , Satonaka Shinobu 
Published: November 2021

Abstract
Numerical method for thermal and fluid flow with free surface and phase change has been developed. The calculation result of one-dimensional solidification problem agrees with Neumann’s theoretical value. We applied it to a bubble growth in superheated liquid and obtained the result that a bubble grows with spherical shape. The present method can be applicable to various phase change problems.
Numerical Investigation of Marangoni Convection Around a Vapor Bubble in Aqueous Surfactant Solutions
Authors: Wasekar Vivek M. , Manglik Raj M. , Jog Milind A. 
Published: November 2021

Abstract
The effect of surfactant concentration on the Marangoni convection around vapor bubbles has been numerically investigated. The model consists of an adiabatic, hemispherical bubble on a downward facing constant temperature heated wall, in a fluid pool with an initial uniform temperature gradient. The time-dependent liquid mass, momentum, energy, surfactant bulk and surface transport, and adsorption kinetic rate equations are solved simultaneously. Conditions for bubble sizes varying from boiling nuclei to growing bubbles, and different surfactant bulk concentrations and wall heat flux levels are represented by a range of Marangoni and Rayleigh numbers: 100 ≤ MaT ≤ 6000, 0 ≤ MaS ≤ 2.2×106, 0 ≤ Ra ≤ 2.2. In the early transients, liquid motion is found to be induced by the temperature non-uniformity over the bubble surface, which along with self-diffusion, transports surfactant molecules from the bulk liquid towards the bubble surface. Consequently, the surface excess concentration is higher at the bubble base and decreases along the interface towards the bubble crown. The resulting concentration gradients promote diffusocapillary flows, which act in the same direction as the temperature-gradient induced thermocapillary flows, thereby enhancing the convection significantly. Also, for conditions representing boiling nuclei (in both partially and fully developed boiling regimes), the initial time transients appear to be heat flux independent.
Buoyancy-Induced Convection in Metal Foam and Finned Metal Foam Heat Sinks©
Authors: Bhattacharya A. , Mahajan Roop L. 
Published: November 2021

Abstract
In this paper, we present our recent experimental results on buoyancy induced convection in metal foams of different pore densities (corresponding to 5, 10, 20 and 40 pores per inch) and porosities (0.89–0.96). The results show that compared to a hot surface facing up, the heat transfer coefficients in these heat sinks are 5 to 6 times higher. However, when compared to commercially available heat sinks of similar dimensions, the enhancement is found to be marginal. The experimental results also show that for a given pore size, the heat transfer rate increases with porosity suggesting the dominant role played by conduction in enhancing heat transfer. On the other hand, if the porosity is held constant, the heat transfer rate is found to be lower at higher pore densities. This can be attributed to the higher permeability with the larger pores, which allows higher entrainment of air through the porous medium. An empirical correlation, developed for the estimation of Nusselt number in terms of Rayleigh and Darcy numbers, is found to be in good agreement with the experimental data with a maximum error of 10%.
We also report our results on novel finned metal foam heat sinks© in natural convection. Experiments were conducted on aluminum foams of 90% porosity with 5 and 20 PPI (pores per inch) with one, two, and four aluminum fins inserted in the foam. All these heat sinks were fabricated in-house. The results show that the finned metal foam heat sinks© are superior in thermal performance compared to the normal metal foam and conventional finned heat sinks. The heat transfer increases with increase in the number of fins. However, the relative enhancement is found to decrease with each additional fin. The indication is that there exists an optimum number of fins beyond which the enhancement in heat transfer due to increased surface area is offset by the retarding effect of overlapping thermal boundary layers. Similar to normal metal foams, the 5 PPI samples are found to give higher values of the heat transfer coefficient compared to the 20 PPI samples due to higher permeability of the porous medium. Future work is planned to arrive at the optimal heat sink configuration for even larger enhancement in heat transfer.
Cooling of Thermal Enhanced BGA Package Using Foam Metal Heat Sinks
Authors: Hwang Jenn-Jiang , Chao Chung-Hsing 
Published: November 2021

Abstract
This study reported thermal performance of a thermally enhanced plastic ball grid array (PBGA), namely T2-BGA™ which incorporates a heat slug in package, with a foam-metal heat sink on the top of this package. Experimental measurement of junction-to-ambient thermal resistance is performed in accordance with the SEMI standards of G38-0996 and G42-0996 for thermal characterization of BGA packages. Allowable power dissipation is subject to the constraint of junction temperature (Tj) at 95°C and ambient temperature (Ta) in chassis at 35 °C under free and forced air (0 ∼ 3 m/s) conditions. Based on this constraint, allowable power dissipation of a regular PBGA with a commercial pin fin heat sink under free and 3 m/s forced air is 5.45 W and 9.17 W compared with those of T2-BGA with a foam heat sink of 6.80 W and 19.6 W respectively. This results show that T2-BGA™ with a foam heat sink offers enormous potential to high power package applications.
Numerical Investigation of the Steady State Operation of a Cylindrical Capillary Pumped Loop Evaporator
Authors: Yan Y. H. , Ochterbeck J. M. 
Published: November 2021

Abstract
A two-dimensional numerical model was established to study the behavior of a cylindrical capillary pumped loop evaporator under steady-state operations. The influence of heat load, liquid subcooling and effective thermal conductivity of the wick structure on the evaporator performance were studied. It was found that increasing the applied heat flux and degree of liquid subcooling resulted in a decrease the temperature in the liquid core. This helped to prevent the vapor from generating in the liquid core and decreased the length of the two phase region in the wick structure. Decreasing the effective thermal conductivity also decreases the temperature in the liquid core as related to the back wick condition. It was observed that for a given liquid subcooling, a minimum heat flux exists below which vapor will generate in the liquid core and render the evaporator non-operational. It was also observed that for a given heat flux, a minimum required liquid subcooling exists. Vapor may form in the liquid core when the liquid subcooling is less than the minimum value.
Numerical Modeling of Steam Injection Into Saturated Porous Media
Authors: Kaslusky Scott F. , Udell Kent S. , McCreery Glenn E. 
Published: November 2021

Abstract
The Steam Enhanced Extraction (SEE) process is being considered for removal of volatile organic contaminants contained in the fractured basalt rocks which lie above the Snake River aquifer at the Idaho National Engineering and Environmental Laboratory (INEEL). In this work the computer code M2NOTS (Multiphase Multi-component Non-isothermal Organic Transport Simulator) was used to simulate an experiment which tracked the movement of a steam condensation front through glass blocks separated by glass beads. The experiment was designed to represent steam injection into highly fractured basalt. For grid spacing equal to the block size heat transfer from the fractures to the blocks was severely under predicted, resulting in an over prediction of the condensation front velocity. A method was developed to accurately simulate the propagation of a steam condensation front through a fractured porous media using grid spacing equal to the block dimension. The method accounts for non-equilibrium conduction within a grid node, allowing the grid spacing to be increased well beyond the local equilibrium restriction. Simulation results compare well with the experimental results, validating the non-equilibrium model, and also indicating that M2NOTs can be effectively used to model the steam enhanced extraction process in fractured porous media.
Optimum Design of Chills in the Sand Casting Process
Authors: Manzari M. T. , Gethin D. T. , Lewis R. W. 
Published: November 2021

Abstract
A re-meshing free algorithm is presented for optimizing the size and shape of chills in a sand casting process. The heat conduction in each chill is assumed to be one-dimensional normal to its contact surface. The chill is removed from the casting layout and replaced with heat fluxes applied on the associated mould and casting interfaces. The change in size and shape of the chill is modeled by moving the borders of the interface contact regions. A change in thickness of the chill is also included using a parameter which controls the magnitude of the interface heat fluxes and implies the thermal capacity of the chill. The model is linked to an optimization tool to search for the optimum set of dimensions of the chill that produces a prescribed directional cooling in the casting. A test case is solved to demonstrate the capability of the proposed algorithm in optimizing chill design in complex geometries.
New Finite Element Modeling Strategy for Large-Scale Industrial Problems in Structural Acoustics
Authors: Dey Saikat , Couchman Luise S. 
Published: November 2021

Abstract
A simple scheme to model and mesh stiffened shell-like structures is presented. Combined with a high-order finite/infinite element based infrastructure, it enables the solution of complex structural acoustics problems at high wave numbers. Numerical examples are presented to show the applicability of the method at high wave-numbers.
Modeling the Space-Time Correlations in the Wake Region of a Turbulent Boundary Layer
Authors: Gavin Joseph R. , Lauchle Gerald C. 
Published: November 2021

Abstract
An empirical turbulence model has been developed for boundary layer flows. The goal is to simulate the statistical behavior of turbulent velocity fluctuations in both space and time using the two-point correlation field.
The new model is based on physical concepts from earlier measurements and flow visualizations. In particular, it is useful to think of packets of turbulent fluid that are angled to towards the wall and convect with a velocity similar to the local mean. However, the actual behaviors which exist are complicated and sometimes quite subtle (but physically important). For instance, measurements show that the correlation field is only strongly peaked at zero time delay. This is interpreted in wavenumber space as a rapid decorrelation of the small scale eddies, and is modeled in a way that captures the transition.
The new turbulence model has been calibrated using recent measurements and is now available for general studies. Efforts are underway to refine the model, improve its theoretical basis, and confirm its application to high Reynolds number flows.
Acousto-Optic Sensors for Real-Time, Wide-Area Inspection of Advanced Materials and Components
Authors: Sincebaugh Patrick J. , Sandhu Jaswinder S. , Wang Honghui , Popek Witold J. 
Published: November 2021

Abstract
The objective of this paper is to provide details on the development of a novel acousto-optic sensor that can be utilized to nondestructively evaluate materials and components in near real-time. The acousto-optic sensor, which is the basis for Acoustography, provides wide-area, near real-time ultrasonic attenuation maps that can be analyzed to detect anomalies such as cracks, delaminations, and porosity. Details on applying Acoustography to inspect complex shaped parts will be provided. Future work in the area of Acoustography will also be presented.
Chlorination in Combustion Systems
Authors: Tsang Wing , Babushok Valeri 
Published: November 2021

Abstract
This paper is concerned with the formation of polychorinated organics in the gas phase in combustion systems. The results are derived from simulation studies with inputs from the fundamental kinetics of single step thermal gas phase reactions. Attention is focussed on the case where initial chlorine loading is low. It is shown that in a well mixed system high degrees of chlorination are difficult to attain due to the decrease in thermal stability with chlorination. A hypothesis for their formation as a consequence of chlorine formation during lean combustion followed by chlorination of organics as a result of the mixing and quenching of the products from rich combustion is tested. Under such conditions the competition between oxidation and chlorination of intermediates governs the final product distribution. The stability of propargyl radicals (C3H3) to oxidation makes chlorination of its products a preferred mode and results have been obtained where more highly chlorinated compounds are found in the products. Since this radical is a known precursor to benzene formation, this provides a direct route for the formation of polychlorinated benzenes. The scenario presented here extends regions for possible gas phase chlorination into the exhaust system of combustors.
CFD Modeling of NOx Reduction Technologies in Utility Boilers
Authors: Cremer Marc A. , Adams Bradley R. , Wang David H. , Heap Michael P. 
Published: November 2021

Abstract
This paper discusses the development and application of CFD modeling tools that have been utilized to assess and design NOx reduction systems that are currently being evaluated by the electric utility industry. Stringent limits on NOx emissions have been imposed by the Clean Air Act Amendments, and a number of NOx reduction technologies are available to help meet these limits including selective noncatalytic reduction (SNCR) and reburning, as well as various combinations of these. This paper discusses the development and implementation of global and reduced chemical mechanisms for NOx formation/destruction into a comprehensive CFD code so that these various options for NOx control can be evaluated. Also, some examples showing the application of these tools to full-scale utility boilers utilizing low-NOx burners, air staging, and SNCR are presented.
Simulations of Transonic Diffuser-Volute System Using Hybrid Unstructured CFD
Authors: Hosangadi A. , Ahuja V. , Lee Y. T. 
Published: November 2021

Abstract
Simulations for a vaneless diffuser-volute configuration at transonic flow conditions are presented using a multi-element unstructured CFD code CRUNCH. The unstructured framework permits the generation of a contiguous grid without internal boundaries between the diffuser-volute interface, and also provides good local resolution around the cut-water region. The increased numerical stability resulting from these factors coupled with the parallel solution framework yields an efficient solution procedure. Numerical results indicate good comparison with experimental data for the baseline geometry where the measured performance was below the design prediction.
A Numerical Investigation on the Volute/Diffuser Interaction due to the Axial Distortion at Impeller Exit
Authors: Gu Fahua , Engeda Abraham , Cave Mike , Di Liberti Jean-Luc 
Published: November 2021

Abstract
A numerical simulation is performed on a single stage centrifugal compressor using the commercially available CFD software, CFX-TASCflow. The steady flow is obtained by circumferentially averaging the exit fluxes of the impeller. Three runs are made at design condition and off-design conditions. The predicted performance is in agreement with experimental data. The flow details inside the stationary components are investigated, resulting in a flow model describing the volute/diffuser interaction at design and off-design conditions. The recirculation and twin vortex structure are found to explain the volute loss increase at lower and higher mass flows, respectively.
Mesoscale Analysis of Porous Shape Memory Alloys
Authors: DeGiorgi Virginia G. , Qidwai Muhammad A. 
Published: November 2021

Abstract
Shape memory alloys are frequently used in smart materials and structures as the active component. Their ability to provide high force and large displacements has been used to the advantage in many applications. The majority of applications to date utilize solid shape memory alloy materials in quasi-static loading conditions. Recent work has proposed the use of porous SMAs as an energy absorbing material under dynamic loading conditions. The use of porous SMAs under dynamic loading will require advancements in the understanding of SMA behavior both in the dense or solid form and in the porous form. The current work examines the quasi-static behavior of porous SMA as a first step. The material behavior is modeled on a mesoscale level allowing for the examination of pore size and shape variation effects. Bulk material response is estimated and compared with micromechanical periodic unit cell predictions.
Wind-Tunnel Determination of Aeroelastic Response of Piezoelectric and Aileron Controlled 3-D Wing
Authors: Suleman Afzal , Crawford Curran A. , Costa António P. 
Published: November 2021

Abstract
This paper presents the results of wind tunnel testing performed on a true three dimensional adaptive wing structure. The focus of this study was to test the aeroelastic response and control of a wing built with conventional stressed skins. The aeroelastic performance of the wing using traditional aerodynamic surface control methods is compared to the results obtained using piezoelectric actuators on the skins of the wing. Results are presented for the system identification, free stream vibration and buffeting tests performed in the wind tunnel. The design of the adaptive wing and control interface is discussed in addition to the experimental setup.
Study of Microstructure in 0.9PMNTa-0.1PT Ceramics
Authors: Wang Jin T. , Tang Feng 
Published: November 2021

Abstract
Ta-Doping effect on the microstructure of lead magnesium niobate-lead titanate crystalline solutions 0.9PbMg1/3(Nb(1−x)Tax)2/3O3-0.1PbTiO3(PMN-PT) have been firstly investigated in this paper. Scanning Electron Micrographs (SEM) were taken from fractured surfaces of the samples with different additives of x = 0.0, 0.1, 0.2, 0.3 and 1.0 by Hitachi F-2460N microscope operating at an accelerating voltage of 25kV. The chemical content analysis for the synthesized samples performed on JEOL Super Prob733 Energy Perspective Spectrum. The x-ray diffraction was carried out with a Siemens D5000 Dual Diffraction Meter. It is clearly evident that doping Ta in PMNTa-PT can affect the grain size and density of the compounds. Smaller grain size (3.1μm) is formed in the specimens with the additives of x = 0.1, 0.2 and 0.3 in comparison with those of the specimens without doping (6.6μm) or over doping (6.4μm). The porosity at grain intersections increase with increasing of additive tantalum for niobium site in 0.9PMNTa-0.1PT. Larger grain size (6.4μm), greater non-uniformity and more inter-granular voids are found in the compound, if tantalum completely substitutes niobium (x = 1). No non-reacted starting regents were observed in any of the compositions mentioned above.
Damage Detection Using Piezoelectrics Modal Analysis and PSD Technique
Authors: Liberatore Sauro , Carman Gregory P. 
Published: November 2021

Abstract
A damage detection method has been implemented on a simply supported beam structure. The method is developed with both a theoretical model and experimental results. The simply supported beam contains one piezoelectric actuator and one piezoelectric sensor. The theoretical model was obtained from an energy formulation and a Rayleigh-Ritz approach. Matrices were composed in a State Space model to reproduce the input-output system between actuator and sensor. The damage was modeled with material properties variations. The experimental set up consisted of an aluminum beam with damage introduced by adding different weights in various locations. The dynamic changes produced were investigated and compared with theoretical prediction with reasonable agreement obtained. In order to quantify the size of damage, Power Spectral Density approach was used. To locate damage, frequency changes were used.