bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Fretting Fatigue Crack Nucleation Experiments to Multiaxial Fatigue Theory Life Predictions
Authors: Szolwinski Matthew P. , Harish G. , Farris Thomas N. 
Published: March 2022

Abstract
Fretting is associated with microslip at the interface of contacts experiencing oscillatory loads. One consequence of fretting is the formation and subsequent growth of cracks at the edge of contact, a phenomenon known as fretting fatigue. Fretting fatigue is an important high cycle fatigue failure mechanism in aircraft structural lap joints and turbine blade/disk contacts. A well-characterized, integrated fretting test system has been developed in which both normal and cyclic tangential fretting loads are applied and monitored in conjunction with a bulk load on the specimen. The experimental data includes histories of the three applied forces and a detailed record of the evolution of interfacial friction coefficient, as driven by the surface microslip. The experimental system has been exercised to observe fretting crack nucleation and growth under a wide range of loading conditions in the context of a statistically-designed test matrix. An extensive multiaxial fatigue analysis based on the stress-strain cycle experienced by each point of the bodies subjected to the fretting loads reveals that the critical location for crack formation is the trailing edge of contact, consistent with observations made in the laboratory. The resulting stress-strain cycles are coupled with strain-life theory and literature values of uniaxial fatigue constants to predict fretting fatigue crack nucleation. The data collected for 2024-T351 aluminum alloy correlates very well with this prediction.
Probabilistic Mesomechanics for High Cycle Fatigue Life Prediction
Authors: Tryon Robert G. , Cruse Thomas A. 
Published: March 2022

Abstract
This paper presents an analytical modeling approach to characterize and understand high cycle fatigue life in gas turbine alloys. It is recognized that the design of structures subjected to fatigue cannot be based on average material behavior but that designs must consider −3σ or some other appropriate extreme value (tail of the distribution) loading and/or material properties. Thus, a life prediction capability useful in a design application must address the scatter inherent in material response to fatigue loading. Further, the life prediction capability should identify the key micromechanical variables that are critical in the tail of the scatter in the materials durability distribution. The proposed method addresses the scatter in fatigue by investigating the microstructural variables responsible for the scatter and developing analytical and semi-analytical models to quantitatively relate the variables to the response. The model is general and considers the entire range of damage accumulation sequences; from crack nucleation of the initially unflawed structure to final fast fracture.
Numerical Simulation of Instability of Interfaces Between Superposed Layers With Application to Phase Change Processes
Authors: Dhir V. K. , Son G. , Banerjee D. 
Published: March 2022

Abstract
The past efforts on the use of linear Taylor instability theory to predict heat transfer and minimum heat flux during film boiling on flat plates are briefly reviewed. This is followed by a review of recent work on numerical evaluation of non-linear growth of the interface between superposed layers of immiscible fluids. In these studies the numerical results were obtained for the temporal and the spatial variation of the heat transfer rate and the interface shape during saturated film boiling on a horizontal surface at low and near critical pressures, and during melting of a substrate supporting a pool of warmer liquid. New physical insights gained from the analysis are discussed.
Experiments on Liquid Surface Deformation Upon Impingement by a Gas Jet
Authors: Eletribi S. , Mukherjee D. K. , Prasad V. 
Published: March 2022

Abstract
The impingement of a gas jet on a liquid surface has several applications including electric arc furnace steel-making, top blown copper converting, welding and dust removal from the producer gas obtained from biomass gasification. An experimental model has been developed to study the effect of a circular air jet impinging upon a liquid surface. Experiments are conducted with variations in the type of liquid, jet velocity, and separation distance between the nozzle and the liquid surface. Upon jet impingement a cavity (depression) is created on the surface of the liquid. The width and height of this cavity have been determined using sophisticated image processing and edge detection software. The shape of the cavity is either parabolic or Gaussian depending on the conditions of the jet flow and the liquid bath. The shear of the impinging air jet causes recirculatory flow patterns within the liquid that are visualized using aluminum particles as tracers. The measurements show that the previously reported theoretical analysis cannot make accurate predictions of the width and height of the cavity unless surface tension and viscous effects of the liquid are properly accounted for.
Studies on Flow Pattern Transitions and Wavy Films in Gas-Liquid Two-Phase Flows in Microgravity
Authors: Jayawardena Subash S. , Balakotaiah Vemuri 
Published: March 2022

Abstract
Two phase flows are important in both normal and microgravity operations. Using our recently proposed dimensionless flow pattern maps for microgravity flows, we develop system specific flow pattern maps which can be used in designing such systems.
In the second part, we compare the characteristics of micro-gravity annular flows with normal gravity downward co-current annular flows. It is found that the proper length scale for normalization in microgravity is the length scale defined using the friction velocities based on the pressure gradients. Using the universal velocity profile, we present a correlation for the mean film thickness h+ and the standard deviation h+rms for microgravity annular flows. A comparison of the interfacial friction factors and wave celerities shows that a higher friction factor and a larger celerity are observed in microgravity flows.
Turbulent Boundary Layer of Vapor Phase on a Wavy Falling-Film Condensation of Steam-Air Mixture
Authors: Park Su-Ki , Kim Moohwan 
Published: March 2022

Abstract
The wave structure of condensate film and the characteristics of boundary layer flow in the vapor phase were investigated experimentally for condensation of steam-air mixture on a vertical surface. The instantaneous film thickness and the fluctuating temperature in the boundary layer were measured simultaneously. Also the heat transfer coefficient across the condensate film and the diffusion layer formed by air (noncondensable gas) was obtained at various film Reynolds numbers and vapor velocities. The influence of the wavy interface on the temperature field and the heat transfer depend strongly on film Reynolds number and vapor velocity. The condensation heat transfer coefficient increases more than several tens percents with the increase of film Reynolds number depending on the vapor velocity. The fluctuating temperature correlates strongly with the waviness of condensate film corresponding to film Reynolds number. The RMS (root-mean-square) of the temperature fluctuation increases considerably due to the waviness and shows a maximum value around the crest of large amplitude waves.
Heat Transfer Characteristics in Partial Boiling, Fully Developed Boiling, and Significant Void Flow Regions of Subcooled Flow Boiling
Authors: Kandlikar Satish G. 
Published: March 2022

Abstract
Subcooled flow boiling covers the region beginning from the location where the wall temperature exceeds the local liquid saturation temperature to the location where the thermodynamic quality reaches zero, corresponding to the saturated liquid state. Three locations in the subcooled flow have been identified by earlier investigators as the onset of nucleate boiling, the point of net vapor generation, and the location where x = 0 is attained from enthalpy balance equations. The heat transfer regions are identified as the single phase heat transfer prior to ONB, partial boiling (PB), and fully developed boiling (FDB). A new region is identified here as the significant void flow (SVF) region. Available models for predicting the heat transfer coefficient in different regions are evaluated and new models are presented based on our current understanding. The results are compared with some of the experimental data available in the literature.
A Study of Droplet Vaporization in a Longitudinal Acoustic Field Using Exciplex Vapor/Liquid Visualization
Authors: Ondas Michael S. , Santavicca Domenic A. 
Published: March 2022

Abstract
Droplet vaporization has been targeted as one of the primary mechanisms for initiating and sustaining combustion instability. Past research has studied droplet vaporization in the presence of an acoustic field to determine if the acoustic field has an influence on the vaporization rate. These studies looked for an increase or decrease in the time averaged vaporization rate due to the acoustic field by measuring droplet diameter as a function of time. This research focuses on the fuel vapor wake as a means to reveal the instantaneous perturbation in the droplet vaporization due to an imposed acoustic field. An exciplex vapor/liquid visualization technique is used to image the fuel vapor wake downstream of a vaporizing droplet at discreet phases of a longitudinal acoustic field. The results indicate that longitudinal acoustic waves can couple with the vaporization process and cause perturbations in the spatial distribution of the fuel vapor that occur at the same frequency of the imposed acoustic field.
Coalescence of Droplets of an Ink Jet
Authors: Watanabe Keizo , Che Feng , Mutoh Masayuki 
Published: March 2022

Abstract
Measurements of the velocity of ink jet droplets were made using a microscope in an experimental apparatus in which the nozzle is about 18 μ m in diameter. It was shown that the distance for the coalescence of droplets from the liquid jet increases with the increase of density of liquid.
The equation of motion for the droplet is analyzed numerically by assuming the air velocity around a droplet, and trajectories are obtained. The results of numerical simulation for the coalescence correspond to the experimental results well. It is pointed out that the droplet stream stability is affected by the surface tension of the jet.
Gas-Solid Suspension Flow in a Nozzle and the Overexpanded Free Jet
Authors: Ben-Dor G. , Elperin I. , Igra O. , Vasiliev E. 
Published: March 2022

Abstract
Two-phase gas-solid particles nonstationary axisymmetric flows through converging-diverging nozzles and the free overexpanded jets emerging from the nozzles are studied numerically. The solution of the flowfield is carried out until a steady flow is established. The Eulerian approach is used to describe the flowfield and both phases are treated in the homogeneous mixtures approximation. A monotone second order accurate in space and time W-modification of Godunov’s scheme is applied for the numerical solution of the governing equations. The evolution of the discontinuities is investigated as well as the effects of the particle size and the loading ratio on the flow pattern. The two-phase flowfield is compared with a similar pure gas flowfield in a two-dimensional nozzle and in the plume. Limiting cases of the two-phase flow, frozen and equilibrium, are considered. Intermediate regimes of the two-phase flow are compared with the frozen and the equilibrium flows.
Industrial Applications of Spray Technology
Authors: Chigier Norman 
Published: March 2022

Abstract
Spray Systems are used very extensively in a wide range of industrial applications. Injection of liquid fuel in gasoline and diesel automotive engines, gas turbine aircraft and land-based engines, rocket engines and a wide variety of industrial furnaces and boilers, require improved control of atomization and spray characteristics to improve performance and efficiency and to reduce emission of pollutants to satisfy EPA regulations. Spray painting of automobiles, aircraft, bridges and a large range of manufactured products results in the waste of large proportions of paint that does not hit the target and is carried away by offspray, which requires expensive treatment to prevent pollution. In manufacturing processes, molten metal sprays are used for direct manufacture, using near net shaping, high temperature arc spray coatings (thermal spraying) and for coatings. The need to achieve uniform thickness film layers with low porosity, requires control of drop size, velocity, temperature and number density in the spray. More than 80% of agricultural crops are sprayed with herbicides, fungicides and insecticides, using aircraft and tractors. Drop size needs to be maintained sufficiently large during evaporation to prevent drift by wind away from the target crop. Drops that are too large cause wastage and low target transfer efficiencies. Control is required of initial drop size distributions and subsequent changes of spray characteristics from nozzle to target crops. Many industrial chemical and food processes use spray drying where liquid slurries, colloids and solutions are injected into heated gas (air) environments. Control of atomization and spray characteristics is required in order to meet the end product specifications, of particle size, agglomeration, porosity and friability. In the field of medicine, inhalation therapy is used for treatment of respiratory diseases. New developments include inhalation of cyclosporin to prevent rejection after lung transplants, deep lung inhalation of insulin as a more effective and comfortable treatment for diabetics and inhalation of chemotherapy for prevention of lung cancer for heavy smokers. The generation of monosize particles in nebulizers targeted to particular locations in the respiratory tract and lung surfaces requires accurate control of particle size and velocity during inhalation. Control of all these spray processes is achieved by improved atomizer design and accurate measurement of spray characteristics by phase Doppler, diffraction and imaging laser diagnostic instruments.
Visualization and Measurement of Automotive Electrostatic Rotary-Bell Paint Spray Transfer Processes
Authors: Lai Ming-Chia , Im Kyoung-Su , Liu Yi , Skender Margie M. , Nivi Hossein 
Published: March 2022

Abstract
In order to improve the transfer efficiency and finish quality in automotive spray painting, a better understanding of the paint spray structure and transfer processes of the electrostatic rotary bell applicators is needed. This paper briefly reviews the current technological challenges and research issues, then describes the spray visualization, droplet size, and velocity measurement results of a water-borne paint spray system under various operating parameters. The optical techniques used are copper vapor laser light sheet visualizations and phase Doppler particle analyzer. Four main operating parameters are varied in this study: liquid flow rate (100 ml/min to 250 ml/min), shaping air flow rate (120 l/min to 180 l/min), bell rotational speed (20,000 rpm 50,000 rpm), and high voltage setting (60 kV to 90 kV, and 0 V for comparison). For simplicity, water is used as paint surrogate, and a flat metallic panel is used as the target surface. The results show that bell speed dominates the atomization, but high voltage and flow rate settings significantly modify the spray transport. The results of this study also provide detailed information on the paint spray structure and transfer processes, which can be used in future model development and validation.
Experimental Study on the Spray Cooling of a Heated Solid Surface
Authors: Cho Chris , Ponzel Rainer 
Published: March 2022

Abstract
Spray cooling of a heated solid surface using water spray was investigated. In this experiment, uniform heat flux condition was assumed, and the liquid flow rates and nozzle orifice diameter were selected as main variables. Two water spray temperatures were used for the tests. Saturated water spray was used to measure the wall superheat temperature. Subcooled water was used to measure the effect of water spray in the single-phase regime. Tests using the saturated water showed that the heat transfer rate was a function of Weber number and the superheat temperature. The surface temperature was related to the characteristic velocity and the droplet diameter. On the other hand, tests using the subcooled water spray showed little dependence on the liquid flow rate and the nozzle orifice diameter in the single-phase regime. A correlation was obtained in terms of Reynolds number and Prandtl number. Test results indicated that the spray cooling was more effective during the evaporation of the thin liquid film above the saturation temperature.
Tomographic Identification of Bubbles in Two-Phase Flows Using a Genetic Algorithm
Authors: Lyons Donald P. , Kihm Ken D. 
Published: March 2022

Abstract
Genetic algorithm (GA)-based tomographic reconstruction algorithm is examined to use for nonintrusive optical or acoustic imaging of bubbles in two-phase flows. Individual bubble boundaries are described by elliptical basis functions whose major and minor axes specify the bubble shape and sizes. Genetic algorithm, a robust combinatorial non-linear optimization based on fittest survival principle, allows a regressive determination of the bubble center locations, shape and sizes simultaneously by maximizing the fidelity of guessed images compared with measured images. Preliminary results indicate a strong potential of GA-based tomography for accurate reconstruction of two-phase flow images.
An Alternative Modeling Procedure for Describing Coupled Heat and Mass Transfer in Semi-Dry Porous Media Samples
Authors: Rieder William G. , Prunty Lyle D. 
Published: March 2022

Abstract
An alternative modeling approach is described for unsaturated porous-media samples, where both irreversible and equilibrium thermodynamic arguments are used to set up a simple coupled differential equation set. Predictions based on numerical evaluations of the foregoing set demonstrate the nonlinear temperature and fluid profiles that have been observed in experiments with unsaturated water-in-soil samples. Minimal literature and empirical input is required to quantify parameters. Comparisons with data from small scale experiments show good agreements. It is argued that such an approach could lead to acceptable simulation schemes for poorly-defined media containing several nonreacting fluids.
Thermal Dispersion in Thermally-Developing Region of a Porous Channel
Authors: Hsieh W. H. , Lu S. F. 
Published: March 2022

Abstract
The thermal dispersion and heat-transfer processes in the thermally-developing region of a sintered porous channel with asymmetric heating are analyzed by a two-equation model. The thermal dispersion conductivity is modeled as the product of an entrance-effect function, the dispersive length and the Peclet number. The empirical coefficients in the entrance-effect function are determined by matching the experimental data. The calculated distributions of wall temperature and local Nusselt number are in good agreement with experimental data. From the calculated results it is found that most of the energy at the heated wall is absorbed by the solid. The heat transfer between the solid and the fluid reaches a maximum and then drops in the transverse direction; in the axial direction it increases due to the enhanced local heat transfer coefficient caused by the flow acceleration.
A Parallel Programming Model for Industrial CFD Applications on Microprocessor Based Systems
Authors: Wang G. , Tafti D. K. 
Published: March 2022

Abstract
In this paper, we examine the performance of typical CFD kernels on five major microprocessor-based systems, and show that, for large problem sizes, performance is bounded by the speed of main memory. We further show that, for the solution of large sparse linear systems, preconditioning with a multilevel additive Schwarz method, not only enhances convergence, but also, improves performance by a factor of two to three. This is a direct result of better cache utilization. Further, we show the excellent parallel performance of this method. Finally, we apply the parallel solution technique developed to the unsteady Navier-Stokes equation in the study of transitional heat transfer in louvered fin heat exchangers.
Assessment of Chip-Scale Package Design Options
Authors: Teng Sue Y. , Guo Yifan , Sarihan Vijay 
Published: March 2022

Abstract
The trend in portable products continues towards shrinking size, faster speeds, increased functionality, and, above all, low cost. Chip-scale packages are able to meet these demands of reduced board space consumption, increased functional density, and low cost while still maintaining compatibility with the existing assembly infrastructure.
A chip-scale package development effort for low to moderate I/O count devices has been initiated within Motorola using a flip-chip interposer type of design. This CSP design has been coined the JACS-Pak (Just About Chip Size Package). This work outlines a comparative analysis of various interconnect design schemes being evaluated for future versions of the JACS-Pak. Experimentally validated finite element simulation is used to predict the thermal stresses and strains induced by the manufacturing and assembly processes and thermal cycling tests. Various package design parameters are evaluated in terms of their impact on the mechanical performance of the package, and design enhancements are recommended for enhanced mechanical integrity of the chip-scale package under consideration.
This work illustrates the application of simulation during the initial design stages of the JACS-Pak, demonstrating its importance in contributing to the overall direction and success of the program.
Assessment of an Axisymmetric Analytical Model of a Square Areal Array Assembly
Authors: Shakya S. , Heinrich S. M. , Liang J. , Lee P. S. 
Published: March 2022

Abstract
Three-dimensional (3-D) finite element analyses have been performed for square assemblies, each with a homogeneous component attached to a homogeneous substrate by an areal array of solder joints to test the assumption of replacing the square geometry of the component, substrate, and joint array by equivalent circular disks. Three different square assemblies, namely a Plastic Ball Grid Array (PBGA), a Ceramic Ball Grid Array (CBGA), and a Flip-Chip package have been considered for comparing the maximum shearing displacement, obtained from the 3-D numerical model, with the analytical estimate, which is based on an axisymmetric model. Comparison of the analytical and the finite element results indicates excellent agreement in estimating maximum shearing displacement, provided that the array stiffness is sufficiently smaller than the Young’s moduli of the component and substrate materials. These convincing comparison results indicate that the analytical approach may in some applications provide a useful alternative to the more expensive and time-consuming finite element method.