bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction Between Wire and Ingot in Wiresaw Slicing
Authors: Yang Fuqian , Li J. C. M. , Kao Imin
Published: December 2021

The deformation of the wire in the wiresaw slicing process was studied by considering directly the mechanical interaction between the wire and the ingot. The wire tension on the upstream is larger than on the downstream due to the friction force between the wire and the ingot. The tension difference across the cutting zone increases with friction and the span of the contact zone. The pressure in the contact zone increases from the entrance to the exit if the wire bending stiffness is ignored. The finite element results show that the wire bending stiffness plays an important role in the wire deformation. Higher wire bending stiffness (larger wire size) generates higher force acting onto the ingot for the same amount of wire deformation, which will leads to higher material removal rate and kerf loss. While larger wire span will reduce the force acting onto the ingot for a given ingot displacement in the direction perpendicular to the wire.
Process Characterization and the Effect of Process Defects on Flip Chip Reliability
Authors: Lewis Brian J. , Sasso Hilary
Published: December 2021

Processing fine pitch flip chip devices continues to pose problems for packaging and manufacturing engineers. Optimizing process parameters such that defects are limited and long-term reliability of the assembly is increased can be a very tedious task. Parameters that effect the robustness of the process include the flux type and placement parameters. Ultimately, these process parameters can effect the long-term reliability of the flip chip assembly by either inhibiting or inducing process defects. Therefore, care is taken to develop a process that is robust enough to supply high yields and long term reliability, but still remains compatible with a standard surface mount technology process. This is where process optimization becomes most critical and difficult. What is the optimum height of the flux thin film used for a dip process? What force is required to insure that the solder bumps make contact with the pads? What are the limiting boundaries in which high yields and high reliabilities are achieved, while maintaining a streamlined, proven process?

The following study evaluates a set of process parameters and their impact on process defects and reliability. The study evaluates process parameters including, flux type, flux application parameters, placement force and placement accuracy to determine their impact. Solder voiding, inadequate solder wetting, and crack propagation and delamination in the underfill layer are defects examined in the study. Assemblies will be subjected to liquid-to-liquid thermal shock testing (−55° C to 125°C) to determine failure modes due to the aforementioned defects. The results will show how changes in process parameters effect yield and reliability.
Major Parameters Affecting Nonlinear Finite Element Simulations of Vehicle Crashes
Authors: Omar Tarek A. , Kan Cing Dao , Bedewi Nabih E. , Eskandarian Azim
Published: December 2021

The three explicit nonlinear Finite Element (FE) codes, LS-DYNA, PAM-CRASH, and RADIOSS are widely used by the automotive companies and government for vehicle and roadside hardware crash simulations. As simulation results from these commercial codes gain wider acceptance for crashworthiness evaluations, the codes also are becoming more sophisticated, including advanced features and options for the user than ever before. While these advanced modeling and simulation features are beneficial to users, they also raise a question regarding the trade off between the FE accuracy and the associated computational time and cost required.

The main objective of this paper is to investigate the effects of the major modeling and simulation features of the commercial FE codes and its direct impact on the simulation accuracy and computational efficiency when solving crash problems. The four major parameters considered in this study are element size/mesh density, shell element formulations, hourglass control form, and integration time step strategy. An intensive parametric study is conducted through FE simulations for quasi-static crush of a simple box beam. The nonlinear, dynamic, explicit FE code, LS-DYNA has been used to perform the parametric study. The accuracy of the FE simulations are measured by comparing the simulation results with experimental test results conducted, in the literature, for the same box beam.

Based on the results of the parametric study, final recommendations and guidelines for choosing the major simulation parameters are offered, to compromise between the FE simulation accuracy and the associated computational time and cost.
The Development of an Aluminum Failure Model for Crashworthiness Design
Authors: Yeh J. R. , Summe T. L. , Seksaria D. C.
Published: December 2021

Providing vehicle occupant protection with advanced structural design for crash energy management is an important consideration in vehicle development. In most cases energy absorption by structural deformation requires a material that is able to accommodate high strain levels in order to prevent or limit material separation which could lead to an undesirable collapse mode and poor energy absorption. Therefore, the development of crashworthy alloys and design concepts is critical to the application of new, lightweight materials in automotive structures. To this end, analytical methods and computer simulations are widely used in the automotive industry to provide a better understanding of the crash mechanisms and to improve the overall development process.

This paper describes the development of a material failure model for efficient design of aluminum alloys, thin-wall components and structures in the consideration of crash energy management. The results of the verification studies are illustrated to demonstrate the accuracy of the failure model for various test conditions. These studies include simulations of coupons and components made from aluminum castings and extrusions under free bend, three-point bend, axial crush and lateral crush tests. The simulations successfully predicted the locations of the major cracks observed in the tested specimens and the energy absorption capability of the specimens.

The major benefits of this tool include (1) Improved alloy development and selection, (2) Reduced number of tests and (3) Decreased design time and cost. These benefits lead to a more optimized design for cost, weight and crash energy management, therefore, facilitating the implementation of aluminum components and structures into automotive applications.
Development of a MADYMO3D Model of the SID-IIs Dummy
Authors: Weerappuli D. Para V. , Chai Li , Barbat Saeed , Wan Deborah , Prasad Priya
Published: December 2021

This paper describes the development of a mathematical model of the new small-sized side impact dummy, SID-IIs. The model, utilizing both lumped-mass and finite element methods of analysis, was developed using the commercially-available software MADYMO3D. As the SID-IIs dummy is based on a 12–13 year-old adolescent/5th percentile female, the head, neck, pelvis, and lower extremities were taken from MADYMO3D lumped-mass models of the Hybrid-III 5th percentile female dummy. The shoulder rib, the three thoracic ribs, the two abdominal ribs, and the foam insert in the dummy jacket were modeled using the finite element method. The ribs were characterized using elastic and visco-elastic material models. The foam insert and the jacket were modeled using foam and elastic material models, respectively. The visco-elastic and foam material constants were determined using data from dynamic tests and an optimization scheme based on the “Box” iteration method.

Preliminary validations of the model were carried out at both sub-assembly and fully-assembled dummy levels. At the sub-assembly level, test results of blunt impacts on the isolated thorax were compared with model results. At the fully-assembled dummy level, data from verification pendulum tests and rigid-wall sled tests were compared with model results.

Generally, for all validation simulations, the model predictions of rib displacements and accelerations showed good agreement with corresponding test results during the loading phase. During unloading, however, there were discrepancies between test data and model results. Additionally, for the rigid wall tests, head acceleration, neck moment, and pelvic acceleration compared well with test data. Overall, the predicted responses provide a reasonable level of confidence in the fidelity of the model.
Modeling the f and j Characteristics for Transverse Flow Through an Offset Strip Fin at Low Reynolds Number
Authors: Muzychka Y. S. , Yovanovich M. M.
Published: December 2021

Analytic models for predicting the thermal-hydraulic characteristics for transverse flow through an offset strip fin array are developed. These models are developed by combining the creeping or low flow asymptotic behaviour with laminar and turbulent boundary layer wake models. Expressions for each of these characteristic regions are developed using fundamental solutions of fluid dynamics and heat transfer. The proposed models are compared with new experimental data for ten offset strip fin configurations. Model predictions are within ± 20 percent for 92 percent of friction factor data and 71 percent for Colburn j factor data.
Numerical Assessment of Hot-Wire Data Deviations in the Vicinity of Walls
Authors: Lange C. F. , Breuer M. , Durst F. , Shi J. M.
Published: December 2021

A detailed numerical assessment of the data deviations and the corresponding corrections needed by hot-wire anemometry (HWA) measurements in wall vicinity was performed. The aim of this study was to determine effective correction functions to HWA data for different wall materials. Two extreme cases were first investigated: a perfectly heat conducting and an adiabatic wall. In the case of the perfectly conducting wall the computed results agreed well with available experimental data for highly conducting materials. However, the numerical results for the case of an adiabatic wall contradicted previous experimental observations based on low-conducting wall materials. A close evaluation of the numerical results led to a better understanding of the physical problem and motivated the simulation of realistic wall materials, such as aluminum and glass.
Heat Transfer From a Moving Surface due to Impinging Jets
Authors: Chattopadhyay H. , Biswas G. , Mitra N. K.
Published: December 2021

Turbulent flow field and heat transfer from an array of impinging slot jets on a moving surface have been numerically investigated by large-eddy simulation (LES) with a dynamic subgrid stress model in the Reynolds number range of 500 to 3000. The surface velocity directed perpendicular to the jet plane is varied up to two times the jet velocity at the nozzle exit. Nusselt number distributions for varying surface velocity are presented. It has been observed that while increasing velocity of the impingement plate reduces heat transfer, distribution of Nusselt number over the impingement surface becomes more and more uniform.
Effect of Fouling on Nucleate Pool Boiling in Microgravity and Earth Gravity
Authors: Motoya Daiju , Haze Ikuya , Osakabe Masahiro
Published: December 2021

Nucleate pool boiling of water on clean and fouling surfaces was conducted in microgravity and earth gravity. The microgravity experiments were conducted in 8 s JAMIC drop shaft in Hokkaido of Japan. Platinum wires of 0.2 mm in diameter with or without fouling scale were used to provide uniform heat flux and measurement of the mean temperature of wires. The generated bubble volume was measured with high-speed video or CCD images.

The more vigorous bubbling was observed on the fouling wire compared to that on the clean wire at a same heat flux both in earth gravity and microgravity. The enhancement of the bubbling was associated with the fact that the hydrophilic porous structure in the fouling scale provided the sufficient number of active sites for bubbling nucleation. The wettability of the surface with the fouling scale was much higher than that of the clean bare surface. The bubble departure diameter on the fouling wire was smaller due to the high wettability than that on the clean wire. The latent heat transportation ratio to the total heat flux was calculated with the generated bubble volume measured with high-speed video or CCD images. The ratio was approximately the same at the clean and fouling wires in spite of the apparent difference in bubbling behavior, but it was significantly affected with the gravity level. The ratio increased with an increase of the heat flux in the earth gravity but it remained at the smaller value in the microgravity. The nucleate heat transfer coefficient on the bare surface did not depend on the gravity levels although the bubbling behavior strongly affected with the gravity level.

As the wire radius is small compared to the capillary length scale in microgravity, a growing and coalescing bubble sometimes completely covered the clean wire, evaporating all liquid in contact with the surface and inducing a transition to film boiling. However, on the fouling wire, many small bubbles were generated and sprang from the surface in various directions in microgravity. The spring out action of bubbles suppressed the transition to the film boiling on the fouling wire in the present experimental range.
Forced-Convective Condensation of Pure Steam and Ammonia-Steam Vapor Mixtures in a Shell-Tube Condenser
Authors: Sharma Ratnesh K. , Hassani Vahab , Mahajan Roop L.
Published: December 2021

In this paper, we present our experimental findings for the forced-convective condensation of pure steam and ammonia-steam vapor mixture in a horizontal annulus in a counter-current shell-tube condenser. Experiments with ammonia-steam mixtures were conducted for ∼ 90% ammonia concentration (by wt.) for vapor inlet mass fluxes ranging from 2 to 5 kg/m2s. The local heat transfer coefficient varied considerably along the condenser and this variation was strongly linked to the condensate flow patterns in the annulus. Based on a condensate drainage model, the flow in the annulus was mapped on to flow maps for horizontal in-tube condensing flows. The delineated flow regimes were utilized to explain augmentation or deterioration of local heat transfer in the condenser. The average heat transfer coefficients are presented as a function of the condensate and vapor Reynolds number for both steam and ammonia-steam mixture. The results for pure steam are higher than those predicted by annular flow correlation developed in the past. For ammonia-steam mixtures, the average heat transfer coefficients are about 16% of those for pure steam due to the vapor layer resistance at the interface.
A Computational Model to Predict Pressure Drop and Droplet Removal Efficiency of Chevron Mist Eliminator
Authors: Rhodes Curtis A. , Khan Jamil A. , Wechsler Harry , Mansson Norman
Published: December 2021

Chevron mist eliminators are widely used in industry to remove liquid droplets from gas streams. A major application of these devices is in the flue gas desulfurization (FGD) of coal burning power plants. Before the exhaust gas is released to the atmosphere, liquid droplets entrained in the gas must be removed. A chevron mist eliminator relies on droplet inertia to cause the droplets to impinge on a surface where they are collected and drained away. The droplet removal efficiency is the critical design parameter of the mist eliminator. Pressure drop and flow capacity is also of major importance.

The droplet removal efficiency, pressure drop, and flow capacity have been investigated experimentally by several investigators. The experimental results were obtained using an air-water system of gas and fluid droplets.

This paper presents the results of a study using computational fluid dynamics to model the two-phase flow through the mist eliminator. Droplet removal efficiency and pressure drop were determined and compared with the experimental results. Three-stage chevron mist eliminator with 45° angle to flow was modeled.

Comparison of the model results with previous experimental results indicated that the model is reasonably accurate. The model predicts pressure drop and the diameter at which 95% of droplets are removed with reasonably good accuracy. However, calculated droplet removal efficiencies of droplets with diameters less than 20μm did not agree well with experiments. The main advantage of the proposed model is that it can be used to predict droplet removal efficiencies for gas streams whose properties differ appreciably from that of an air-water system. Actual gas streams properties are input to the computational model. Therefore, the present model provides an effective and useful design tool.
Experimental Studies of Hydrodynamics and Heat Transfer in Channels With High-Porous Cellular Materials in Single-Phase Forced Convection and Flow Boiling of Working Fluids
Authors: Gortyshov Yury F. , Popov Igor A. , Gulitsky Konstantin E.
Published: December 2021

In this paper we consider experimental studies of hydraulic resistance, surface heat transfer, internal heat exchange and critical heat fluxes for the flow of single-phase and boiling working fluids in channels with high-porous inserts.

Experiments were carried out with more than 40 samples of high-porous cellular materials with the porosity 0.8...0.98 and mean pore diameter 0.62...4 mm and with more than 10 samples of regular porous inserts and porosity ε = 0.512...0.86 and mean pore diameter 1.5...3.5 mm. These samples were made of porcelain, invar, nichrome, bronze and copper.
Hysteresis in Flow in Porous Media With Phase Transitions
Authors: Bedrikovetsky Pavel , Marchesin Dan , Ballin Paulo Roberto
Published: December 2021

Two-phase flow with hysteresis in porous media is described by the Buckley-Leverett model with three types of fractional flow functions: imbibition, drainage and scanning. The mathematical theory for the Riemann problem and for non-self-similar initial-boundary problem is developed. The structure of the solutions is presented and the physical interpretation of the phenomena is discussed.

We obtain the analytical solution for the injection of water slug with gas drive into oil reservoirs. The solutions show that the effect of hysteresis is to decrease gas flux (in the case where the drainage relative permeability lies below the imbibition relative permeability). This effect increases oil recovery for Water-Alternate-Gas injection in oil reservoirs.
Heat Transfer in Flow Freezing Over the Isothermal Cylinders
Authors: Sadeghipour Sadegh M. , Shotorban Babak B.
Published: December 2021

Heat transfer in the transient flow freezing on the external surfaces of circular cylinders in a bundle with in-line arrangement is studied, numerically. Low Reynolds numbers are considered, therefore, flow is assumed to be symmetric.

Local and average Nusselt numbers are calculated, at different time steps. The steady state average Nusselt numbers are compared with the reported experimental results. Their agreement is reasonable.
Melting Rate of a Solid With Periodic Melt Removal
Authors: Nemchinsky Valerian
Published: December 2021

The melting rate of a solid, subjected to a heat flux at its surface, changes with time. When a fresh unmelted surface is first exposed to a heat source, the melting isotherm moves quickly inside the solid. Then its motion slows down: this decrease in melting rate is obviously because of increasing thermal resistance of the growing liquid layer that separates solid-liquid interface from the heat source. If the liquid layer is not removed, the melting rate approaches zero. The resultant melting rate depends on the manner in which the melt is removed. In a number of cases of practical interest, the melt is removed not continuously but periodically, in the form of drops. For example, during arc welding with a consumable electrode, these drops are accumulated at the tip of the electrode. When the drop becomes big enough, it is detached from the electrode under action of gravity or electromagnetic force the melt is removed not continuously but periodically, in the form of drops. A simple approximate method is suggested to calculate the melting rate of a solid in the case when melt is removed periodically in form of drops. The method allows one to consider separately the heat transfer in the solid and in the liquid and, thus, to include different heat processes in both phases. Good agreement was demonstrated for exact and approximate solutions for a wide range of parameters.
On Physical Mechanisms of Mushy Zone Formation in Solidification of Pure Semitransparent Materials
Authors: Wang G.-X. , Yao Chengcai , Chung B. T. F.
Published: December 2021

Two different models, the isothermal mushy zone model and the non-equilibrium planar interface model, are employed to solve the solidification problem of a one-dimensional semitransparent slab subject to radiative and convective cooling at the surface. The mushy zone model is based on the assumption of local equilibrium and predicts the formation of a mushy zone as soon as the temperature of the slab surface reaches the equilibrium melting temperature. The non-equilibrium planar interface model, on the other hand, assumes a stable planar solid/liquid interface during solidification. It allows the existence of melt undercooling at the interface and in the bulk melt. The stability of the planar interface is then examined approximately using the linear stability criterion derived for an opaque material. It is found that a planar interface would be stable even if a large undercooling is generated in the bulk melt in front of the interface. If the rate of external heat transfer is small, however, the planar interface will break down and develop into thermal cells or dendrites. In addition, a transition from a mushy zone to a planar interface is also observed. Based on these results, the thermodynamics and kinetics of crystalline nucleation and growth are examined to illustrate the physical mechanisms of mushy zone formation during solidification of a semi transparent material. It is suggested that the isothermal mushy model and the planar interface model are valid only under corresponding processing conditions, and more research is needed to provide a complete description of the process.
Pool Boiling Heat Transfer in Aqueous Surfactant Solutions
Authors: Wasekar Vivek M. , Manglik Raj M.
Published: December 2021

Saturated, nucleate pool boiling of aqueous surfactant solutions on a horizontal, cylindrical heater has been experimentally investigated. Sodium dodecyl or lauryl sulfate (SDS or SLS), an anionic surfactant is employed. Boiling performance, relative to that for pure water, is found to be enhanced significantly by the presence of SDS, with an early onset of nucleate boiling. An optimum level of enhancement is observed in solutions at or near critical micelle concentration of the surfactant; the enhancement decreases considerably in higher concentration solutions. The dynamic surface tension measurements indicate a considerable influence of temperature on the overall adsorption isotherm. The diffusion kinetics of surfactant molecules and micelles is, therefore, expected to be quite different at boiling temperature than at room temperature. This greatly modifies the boiling mechanism, that is generally characterized by the formation of smaller-size bubbles with increased departure frequencies, and a decreased tendency to coalesce which causes considerable foaming.
Sub-Continuum Simulations of Heat Conduction in Silicon-on-Insulator Transistors
Authors: Sverdrup Per G. , Ju Y. Sungtaek , Goodson Kenneth E.
Published: December 2021

The temperature rise in compact silicon devices is predicted at present by solving the heat diffusion equation based on Fourier’s law. The validity of this approach needs to be carefully examined for semiconductor devices in which the region of strongest electronphonon coupling is narrower than the phonon mean free path, Λ, and for devices in which Λ is comparable to or exceeds the dimensions of the device. Previous research estimated the effective phonon mean free path in silicon near room temperature to be near 300 nm, which is already comparable with the minimum feature size of current generation transistors. This work numerically integrates the phonon Boltzmann transport equation (BTE) within a two-dimensional Silicon-on-Insulator (SOI) transistor. The BTE is coupled with the classical heat diffusion equation, which is solved in the silicon dioxide layer beneath a transistor with a channel length of 400 nm. The sub-continuum simulations yield a peak temperature rise that is 159 percent larger than predictions using only the classical heat diffusion equation. This work will facilitate the development of simpler calculation strategies, which are appropriate for commercial device simulators.
Design and Analysis of a Meso-Scale Refrigerator
Authors: Ashraf N. S. , Carter H. C. , Casey K. , Chow L. C. , Corban S. , Drost M. K. , Gumm A. J. , Hao Z. , Hasan A. Q. , Kapat J. S. , Kramer L. , Newton M. , Sundaram K. B. , Vaidya J. , Wong C. C. , Yerkes K.
Published: December 2021

The preliminary design and analysis of a meso-scale refrigerator is presented here. The device is to be designed out of layers of silicon wafers bonded together and is to be fabricated through the techniques of microelectronics. The intended application of the device is an integrated heat removal system for electronics or photonic chips or modules. The paper presents a functional decomposition of the entire system, thermodynamic feasibility analysis, alternative configurations for two of the functions: actuation and compression, and parametric analysis for two alternative candidates for compressor actuation.

A set of reasonable design requirements is first formulated. Overall function of the devices is decomposed into nine major sub-functions. Comparison of different alternatives for compression and actuation suggests that electrostatic actuation integrated with centrifugal compression is a viable option. Two different ways to implement electrostatic actuation are considered in details: variable capacitance motor and electrostatic induction motor. A set of design relations and criteria needed to obtain the optimal design of each motor is presented along with a discussion on relative effects of the main design parameters.
Laser-Induced Fluorescence Measurements in Venturi-Cascaded Propane Gas Jet Flames
Authors: Qubbaj Ala R. , Gollahalli S. R.
Published: December 2021

“Venturi-cascading” technique is a means to control pollutant emissions of diffusion flames by modifying air infusion and fuel-air mixing rates through changing the flow dynamics in the combustion zone with a set of venturis surrounding the flame. A propane jet diffusion flame at a burner-exit Reynolds number of 5100 was examined with a set of venturis of specific sizes and spacing arrangement. The venturi-cascading technique resulted in a decrease of 33% in NO emission index along with a 24% decrease in soot emission from the flame, compared to the baseline condition (same flame without venturis). In order to understand the mechanism behind these results, Laser Induced Fluorescence (LIF) spectroscopy was employed to study the concentration field of the radicals (OH, CH and CN) in the baseline and venturi-cascaded flames.

The LIF measurements, in the near-burner region of the venturi-cascaded flame, indicated an average decrease of 18%, 24% and 12% in the concentrations of OH, CH and CN radical, respectively, from their baseline values. However, in the mid-flame region, a 40% average increase in OH, from its baseline value, was observed. In this region, CH or CN radicals were not detected. The OH radical, in the downstream locations, was mostly affected by soot rather than by temperature. In addition, prompt-NO mechanism appeared to play a significant role besides the conventional thermal-NO mechanism.
Measurements of Fire Whirls From a Single Flame in a Vertical Square Channel With Symmetrical Corner Gaps
Authors: Satoh Kohyu , Yang K. T.
Published: December 2021

One of the most destructive forces in large urban fires is the occurrence of fire whirls. Despite the relatively recent experimental and numerical simulation studies on the global behaviors of small-scale whirling fires, much of the whirling fire phenomena still remain unknown. The purpose of this experimental study is to examine closely the detailed structures of the velocity and temperature fields in a stable whirling flame generated in a vertical square channel with symmetrical corner gaps by both physical measurements using conventional means and by quantitative observations using both a high-speed motion camera and a thermographic infrared camera. The results showed a rather complex non-uniform velocity and temperature field in the lower half of the whirling flame and could provide an important basis to validate the fire field models for the study of real large-scale fire whirls.
Nuclear Safety Analysis for Cassini Accidental Earth Reentries
Authors: Baker Richard L. , Nelson Duane A.
Published: December 2021

An engineering analysis model for predicting the response and potential breakup of Cassini spacecraft nuclear fuel modules during accidental Earth reentries is described. Physical aspects considered include aerodynamics, aerothermodynamics, thermostructural loads and ablation response. The extreme velocity, 19 km/sec, of an inadvertent reentry during the Earth gravity-assist flyby requires the development of a new model to predict the dominant radiative heating rates. Uncertainty estimates are established for each of the major factors in the model. Sensitivity analyses are also carried out to determine the effect of off-nominal environments on the predicted outcome. This allows output from the calculations to be expressed as a probability density function for atmospheric fuel release. It is concluded that 18 to 36 percent of the nuclear fuel contained in the spacecraft will be released as respirable material if reentry occurs.
Incorporating Risk Concepts Into Performance-Based Building and Fire Regulation Development
Authors: Meacham Brian J.
Published: December 2021

As the United States transitions to performance-based building and fire regulations, it will become increasingly important to incorporate risk concepts into the regulations. However, there is a general lack of acceptance of the concepts of risk and risk analysis by the building and fire communities. There are many reasons for this, including a lack of consensus on risk characterization and quantification, inadequate expressions of acceptable risk limits, a lack of risk analysis tools and methods tailored to building and fire safety, and a lack of guidance for addressing uncertainty. As a means to begin addressing these issues, a research project is underway with the aim of outlining a process for identifying, characterizing, and incorporating risk concepts and analysis methods into building and fire regulation development. This paper presents outcomes of the research project that are being evaluated and incorporated into the development of the International Code Council’s Performance Building Code.
Drag Reduction of Surfactant Solutions for an Enclosed Rotating Disk
Authors: Ogata Satoshi , Watanabe Keizo
Published: December 2021

Recently, many studies on surfactant solutions have been conducted for drag reduction in a circular pipe flow. However, currently there are very few studies on rotating disks in the solutions. In this study, drag reduction for an enclosed rotating disk in surfactant solutions was clarified experimentally. Experiments were carried out to measure the torque acting on one side of a rotating disk, using a torque measurement device located at the top of the rotating shaft. Test surfactant solutions were Ethoquad O/12 at concentrations of 50, 100 and 200ppm. The temperatures of solutions were 18°C and 28°C. The clearances between the disk and the stator were 10mm and 20mm. It was shown that the Reynolds number at the transition point increased with increasing concentration and temperature of these solutions. The maximum drag reduction ratio was about 41% in 200ppm Ethoquad O/12 solution at 28°C.
Experimental Procedures of Characterizing the Viscoelastic Properties of Certain Materials
Authors: Murty V. Dakshina
Published: December 2021

Experimental procedures for characterizing the material properties of viscoelastic materials are proposed. The procedures described are based on extrusion process and squeeze flow process. The fundamental features within each of these procedures are discussed in detail. If the material is assumed to be either a generalized Newtonian fluid or Bingham plastic, the relevant parameters are the viscosity and yield stress. The results of the experiments on these two properties are shown along with the effects of temperature on the yield stress are discussed.
Optimization of Adhesively Bonded Single Lap Joints by Adherend Notching
Authors: Sancaktar Erol , Simmons Sean R.
Published: December 2021

The effect of adherend notching on the joint strength/failure and joint deformation behavior of single lap joints was investigated. First, a parametric study was conducted using Finite Element Analysis (FEA). The results of the parametric study were used to select the most promising lap geometries for further study. Next, more detailed FEA were conducted on the selected lap geometries. This data was compared with the experimental tensile test results to assess the applicability of different failure criteria.
On Crack Growth in Composite Cylindrical Shells
Authors: Rasheed Hayder A. , Tassoulas John L.
Published: December 2021

Interfacial defects, in the form of cracks or layer separation, may occur in composite cylindrical shells during the manufacturing process, transportation or service life. Such defects are expected to affect the integrity of laminated composite structural elements and may reduce their capacity to resist the applied loads. In this article, the growth of pre-existing cracks in moderately thick composite cylinders is studied for the case of externally applied fluid pressure. The cracks considered separate thick layers, which are unlikely to buckle locally prior to the final collapse of the structural component. The potential of growth is assessed by computing the energy release rate. It is found that any initial out-of roundness imperfection introduces a shear force at the crack tip by causing the cross section to ovalize slightly. The energy release rate is found to vary exponentially with the applied pressure, when geometric nonlinearities are considered. The analysis is applied to a carbon/glass-fiber hybrid composite tube and the parameters influencing growth are examined. Crack length, through the thickness location, circumferential location relative to the ovalization orientation and the amount of imperfection are found to control the nature of growth. Unstable as well as stable crack growth and arrest cases are observed for various combinations of these parameters.
A Study on the Constitutive Law for Porous Solids With Pressure-Sensitive Matrices and on the Material Behavior of Rubber-Toughened Epoxies
Authors: Jeong Hyun-Yong
Published: December 2021

A macroscopic yield criterion for porous solids with pressure-sensitive matrices modeled by Coulomb’s yield criterion was obtained by generalizing Gurson’s yield criterion with consideration of the hydrostatic yield stresses for a spherical thick-walled shell and by fitting the finite element results of a voided cube. The macroscopic yield criterion is valid for negative mean normal stresses as well as for positive mean normal stresses. From the yield criterion, a plastic potential function for the porous solids was derived either for plastic normality flow or for plastic non-normality flow of pressure-sensitive matrices. In addition, elastic relations, an evolution rule for the plastic behavior of the matrices, a consistency equation and a void volume evolution equation were presented to complete a set of constitutive relations. The set of constitutive relations was implemented into a finite element code ABAQUS to analyze the material behavior of rubber-toughened epoxies. The cavitation and the deformation behavior were analyzed around a crack tip under three-point bending and around notch tips under four-point bending. In the numerical analyses, the cavitation of rubber particles was considered via a stress-controlled void nucleation model. The numerical results indicate that a reasonable cavitation zone can be obtained with void nucleation being controlled by the macroscopic mean normal stress, and a plastic zone is smaller around a notch tip under compression than under tension. These numerical results agree well with corresponding experimental results on the cavitation and plastic zones.
Computations of Three-Dimensional Viscous Flow Through Turbine Blade Passage
Authors: Xiao Yumin , Amano R. S.
Published: December 2021

An implicit 3-D solver for computations of viscous flow has been developed and the computations of the flow through a blade passage are presented. The validation cases include subsonic and transonic viscous flows in C3X cascade. Results for these turbine cascade flows are presented and compared with the experimental data. Computed pressure distributions on blade surfaces show good agreement with the published experimental data. From these computations it was found that the proposed method possesses good convergence characteristics and can be extended to unsteady flow calculations. Three-dimensional calculations show that the flow pattern in the trailing edge is quite complicated. There appear a couple of sinks near the trailing edge caused by the endwall vortices. The change of the flow pattern was clearly observed at several vertical planes away from the endwall. It was also demonstrated that the secondary flow mechanism in a transonic cascade exhibit different patterns from those in a subsonic case.
New Apparatus and Blower Centrifugal Fan Design Features to Improve its Performance
Authors: Botros Monier B. , Hanna Dorothy F. , Boulos Jasmine E. , Lai Ming-Chia
Published: December 2021

Different design philosophies of a blower centrifugal fan blades and hub are evaluated by airflow performance, computational fluid dynamic analysis (CFD) and experimental Laser Doppler Velocimetry (LDV). A design criterion of fan blade, vanes, channels is developed to eliminate or minimize air separation from the blades suction side. The effect of the fan hub design on the air radial velocity profile is discussed.

A new apparatus is developed to control the air flow field at the blower inlet ring. It directs the air to flow in radial directions at the entrance of the fan blade passages, channels.

The blower systems with the new features operates at high mechanical efficiency over a broad range of airflow rate in different blower scroll sizes. Its peak static efficiency reaches 62% and total mechanical efficiency 68%, which is 5 to 10% above efficiencies of previous designs. As a result, power consumption is reduced by 7–15% through the operating range.
Computerized Model of Transition in Circular Pipe Flows: Part 2 — Calculation of the Minimum Critical Reynolds Number
Authors: Kanda Hidesada
Published: December 2021

From the conclusions of the previous paper, Part 1, it is clear that the transition occurs in the entrance region and the critical Reynolds number takes the minimum value of about 2000 for the case of a straight pipe. In the entrance region, the velocity profile changes from a uniform distribution at the pipe inlet to a parabolic one at the entrance length. Kanda and Oshima (1998b) found that in the entrance region, the radial component of the curl of vorticity multiplied by (2/Re), which we call the normal wall strength, works as an acceleration force together with the continuity equation, and that the normal wall strength decreases inversely as the Reynolds number increases. Hence, the onset of the transition should depend on whether or not the acceleration power provided by the normal wall strength exceeds a required value. In this study the author calculated the acceleration power via finite difference calculations, and thus obtained the minimum critical Reynolds number of 2040 when using J0 = 101 grid points, and 2630 when using J0 = 51.
Simulation of Transient Cavitating Water-Hammer Pipe Flow
Authors: Qin Jian-Rong , Yu S. T. John , Lai Ming-Chia
Published: December 2021

Direct calculations of the transient cavitating water-hammer pipe flows using the Space-Time Conservation Element and Solution Element method, or the CE/SE method for short, is reported. The principles of the CE/SE method is treating space and time as one entity, and the calculation of flow properties is based on the local and global space-time flux conservation. As a contrast to the modern upwind schemes, no Riemann solver is used, thus the logic of the present scheme for cavitating flows is much simpler. Two numerical examples are reported in this paper: (1) a hydraulic shock problem, and (2) a cavitating pipe flow. For the hydraulic shock problem, we demonstrate the capability of the CE/SE method for capturing contact discontinuities in cavitating fluids. For the pipe flows, a two-phase homogeneous equilibrium cavitation model is employed. In both cases, numerical results compared favorably with the experimental data and analytical solution.
Space Weather Simulation on Networks of Workstations
Authors: Freitas Christopher J. , Crowley Geoffrey
Published: December 2021

Space weather refers to the complex phenomena that develop in the near-earth region of space and the upper layers of earth’s atmosphere. Presented in this paper are the elements required to develop a parallel computer algorithm for the real-time simulation of this highly dynamic region of space. The architecture developed for this parallel algorithm is based on Networks of Workstations connected by highspeed data links, and executed using the Parallel Virtual Machine library. This paper reviews the progress completed in developing a real-time analysis system for prediction of upper-atmospheric conditions.
A Parallel Adaptive Fast Multipole Method for High Performance Vortex Method Based Simulations
Authors: Collins James P. , Dimas Athanassios A. , Bernard Peter S.
Published: December 2021

A fast vortex method for the simulation of turbulent flows based on a parallel implementation of the Fast Multipole Method (FMM) is presented. The vortex method includes a hybrid vortex filament/sheet representation of the flow field, a vortex filament creation model that imitates the physical vortex self-replication process, and a hairpin removal and reconnection mechanism to limit the number and scale of vortical structures to those that are dynamically essential. The FMM, which is used to reduce the operation count in computing the velocity field, is the main focus of this paper. Two related FMM methods, referred to as the uniform and the adaptive FMM, are described. Both methods are parallelized using the Message Passing Interface (MPI) library, and timings for single and multiple processor calculations are given. Results are presented from a simulation of the flow past a prolate spheroid in a uniform stream at 30° angle of attack.
Design and Operation of a Droplet Deposition System for Freeform Fabrication of Metal Parts
Authors: Tseng Ampere A. , Lee Munhee , Zhao Bosen
Published: December 2021

Based on a linear stability theory for liquid jets, the design of a droplet generator system is presented for freeform fabrication. The linear stability theory of forming droplets is first reviewed and its suitability to the present droplet deposition system is then discussed. The analytical formulae for predicting droplet size and break-up length at optimal conditions are developed. Based on the present formulation, a droplet generator is designed and built to make wax and tin alloy droplets. Experiments have been conducted at a wide range of jet velocities, frequencies, and droplet sizes. Good agreements are found between the analytical predictions based on the linear theory and experimental results. It has also been found that using the present design and procedure recommended, the droplet sizes can be controlled having a size deviation of less than 3 % and the variation of the deposited layer can be managed within 3% of its width deposited.
Prediction of Phase Segregation During Mold Filling of Semi-Solid Slurries
Authors: Mat Mahmut D. , Ilegbusi Olusegun J.
Published: December 2021

Phase segregation during the mold filling of semisolid slurry (Sn-15%Pb) is numerically investigated under non-isothermal conditions. The effects of operating parameters on the phase segregation including inlet velocity, initial solid fraction, heat transfer rate, mold geometry are considered. The semi-solid slurry is considered a non-Newtonian fluid below a critical solid fraction (fcr) and a viscoplastic medium saturated with liquid phase above the critical solid fraction. A group of particles are introduced at the mold inlet and phase segregation is studied by following the trajectories of these particles. The sharp property change at the slurry air interface is resolved with Van Leer numerical method. It is found that phase segregation is significantly affected by processing parameter. The segregation decreases with high inlet velocity, low heat transfer rate from the mold wall and cylindrical mold geometry.
Incorporating a Motion Analysis App in Middle School Badminton Unit
Authors: Yu Hyeonho , van der Mars Hans , Hastie Peter A. , Kulinna Pamela H.
Published: December 2021

Purpose: Mobile applications (apps) may help students develop their motor skills by using instant, augmented feedback. This study incorporated an app technology that may support students’ skill and game play development during a badminton unit. Methods: Two eighth-grade classes participated in the study (the teacher only used the app in Class A; students used the app in Class B). The Poole forehand overhead clear shot skill test, game performance assessment instrument, and opportunity to respond observation tool were used to measure students’ skill and game improvement in the study. Students in both intervention classes improved in the clear shot skill, game performance assessment instrument scores, and opportunity to respond rates throughout the badminton unit. Further research on the use of such app technologies should focus on how the apps can be innovative to foster student learning in game play within a variety of contexts in physical education settings.
Teaching for Immigrant Girls’ Inclusion: Social Justice Physical Education Teachers’ Involvement With School Stakeholders
Authors: Nieva Boza Carolina , Lleixà Arribas Teresa
Published: December 2021

Purpose: This study seeks to analyze the involvement of the various stakeholders related to the educational context, namely school management team, teaching staff, families, and students, to foster the social inclusion of immigrant girls through their participation in physical activities. Methods: Data consisted of interviews and focus group sessions involving 19 physical education (PE) teachers from state primary schools in Catalonia, Spain. Results: The involvement of the stakeholders can foster greater inclusion of such immigrant girls through initiatives, such as: extracurricular physical activities specifically designed for them; the creation of specific spaces for their physical activities; a greater number of PE class hours for immigrant newcomer pupils; supportive feedback for these girls from PE teachers; and greater consideration of these girls’ interests and preference in PE programming. Conclusion: These findings suggest that the greater the degree of involvement and cohesion among the various parties, the higher the likelihood of successful social inclusion.