bluuebunny/crossref_metadata_2025 huggingface dataset:
A Constitutive Framework for the Inelastic Mechanical Behavior of Arteries
Authors: Holzapfel Gerhard A. , Gasser Thomas Ch.
Published: November 2021

A reliable constitutive model of arterial walls is an essential prerequisite to (i) understand the functions of diseased and non-diseased arteries, to (ii) optimize the design of arterial prostheses, and to (iii) improve diagnostics and therapeutical procedures that are based on mechanical treatments, such as percutaneous transluminal angioplasty (PTA) [1] or bypass surgery. PTA is the most frequent therapeutical intervention worldwide [2] to reduce the severity of atherosclerotic stenoses. It is of great and steadily growing medical, economical and scientific interest [3].
Effect of Thrombus in AAA on Pressure and Dilation Experienced by the Aneurysm Wall
Authors: Thubrikar Mano J. , Robicsek Francis , Labrosse Michel , Chervenkoff Vassil , Fowler Brett L.
Published: November 2021

Various factors are considered to play a role in the risk of abdominal aortic aneurysm (AAA) rupture. For instance, a maximum diameter of 7 cm is commonly used as an indication for surgery. There is a need for understanding what makes an aneurysm most likely to rupture. Our focus here is on the role of the intraluminal thrombus and how it affects the pressure and dilation experienced by the aneurysm wall. Since in most of the surgical procedures, the whole aneurysms are almost never removed, the data on the whole aneurysms with thrombus has not been available. The results presented here, therefore, are very important even though they come from a small number of whole aneurysms explored thoroughly. Two types of studies were performed: 1) in vitro and in vivo pressure measurements through the thrombus in three complete AAA, and 2) in vitro dilation measurements during pressurization of two whole aneurysms before and after the thrombus was removed.
Network Analysis of Cerebrospinal Fluid Dynamics
Authors: Zheng Lili , Egnor Michael , Banninger Keith
Published: November 2021

Hydrocephalus is a group of life threatening disorders of cerebrospinal fluid flow in and around the brain. It is characterized, in most cases, by accumulation of cerebrospinal fluid in the ventricles of the brain and a progressive increase in pressure in the cranium. The etiology has traditionally been ascribed to an imbalance between the formation and absorption of the cerebrospinal fluid (CSF). Based on this understanding, the treatment is to insert a shunt surgically in order to drain the accumulating fluid in the heart or abdomen. This treatment is invasive and has a high failure rate.
Estimate of Migration Force for Stent
Authors: Jou L.-D.
Published: November 2021

The stent has been a very effective device for treating vascular disease, such as in the coronary and carotid arteries. Due to the increasingly complex configuration of struts in the stent, it is instructive to investigate the relation between the strut configuration and the force that will result in stent deformation after stent placement. Although it is possible to obtain the same information through experiments or finite element analysis, a simple analytic relation may shed more light on the problem and also indicate new directions when it comes to redesign of existing stents. In our previous study (1), we investigated the drag force on a three dimensional strut structure, and the drag force appeared to be a function of strut configuration. The possible outcome of these drag forces is the focus of our current study.
A Lumped Parameter Model for Cerebral Blood Flow Regulation
Authors: Olufsen Mette S. , Lipsitz Lewis A. , Nadim Ali
Published: November 2021

Dynamic changes in cerebral blood flow and the associated vascular responses accompanying posture change that enable the brain to maintain perfusion during hypotensive stress are not fully understood. The aim of this work is to use a lumped parameter model of cerebral blood flow to analyze changes in key parameters (systemic and cerebrovascular resistances) during posture change from sitting to standing. Such a model sheds light on vascular adaptation to hypotensive stress, and could ultimately help determine the changes in cerebral autoregulation that occur in aging, hypertension, and other clinical conditions.
Effect of Endovascular Diagnostic Catheters on Human Coronary Artery Lesion Flow Coefficients
Authors: Banerjee Rupak K. , Back Lloyd H. , Back Martin R. , Cho Young I.
Published: November 2021

Lesion flow coefficients ( c ~ ) were determined from computational hemodynamics for the 32 patient group of Wilson et al. (1988) during coronary angioplasty in conjunction with quantitative angiography and measurements of the coronary flow reserve (CFR). The effect of the catheter insertion across lesions reduce blood flow during measurements, and also decrease ( c ~ ) due to larger viscous effects. The flow computations may be useful in interpretation of catheter measurements in the clinical setting for lesions of similar size, particularly for flow limiting hyperemic conditions.
CFD Analysis of the Bifurcation Based on a Precision Modeling System
Authors: Kimura Y. , Yamaguchi T.
Published: November 2021

The purpose of this study was to investigate the relationship between blood flow and atherosclerosis using Computational Fluid Dynamics. Atherosclerosis is suspected to be related to blood flow, since it develops at specific points on vessel walls. Among these specific locations, bifurcations of blood vessels are especially prone to atherosclerosis, particularly the lateral walls of the common iliac arteries1. This distribution of lesions is believed to depend on fluid dynamics phenomena, particularly the wall shear stress. Due to the complex geometry of a real artery, the fine flow structure in an arterial bifurcation may be too complex to study using in vivo or in vitro experiments. Therefore, CFD is one of the most powerful ways to investigate flow in an arterial bifurcation. However, the relevant CFD model must be constructed to obtain a reliable computational analysis. In general, a bifurcation has a complex 3-D configuration, particularly at its sharp edge. Any minute deformation or relative displacement of the bifurcation is thought to have a significant effect on blood flow. In this study, a histology technique, in which the embedded vessels are sliced into thickness of the order of 1 micrometer, was used to model the arterial bifurcation. A computer was used to capture 2-D images of the face of the specimen block after each slice was removed. Then, serial images were used to reconstruct the 3-D blood vessel configuration with a precision appropriate for CFD analysis.
Effects of Hydrostatic Loading Amplitude and Frequency on Rabbit Disc Nucleus Cells
Authors: Kasra Mehran , Goel Vijay , Martin James , Wang Shea-Tien , Choi Woosung , Buckwalter Joseph
Published: November 2021

Long-term occupational exposure to whole-body vibration increases the risk of disc degeneration and the consequent back pain [1]. The pathogenesis of vibration induced disorders is still not completely clear and there is no effective treatment. Although the potential effects of vibrational stress on extracellular matrix (ECM) assembly and degradation are particularly relevant to the clinical findings of the vibration induced disorders, the effects of vibrational loads on disc cells are largely unknown. It has been shown that hydrostatic pressure directly affects the synthesis of collagen and proteoglycan by the intervertebral disc cells [2–5]. However, these studies investigated only the extent of the effect of quasi-static hydrostatic loads. During daily occupational activities intervertebral disc is exposed to dynamic oscillatory hydrostatic loads, characterized by wide frequency spectrum and variable amplitude. In this case, a physiologic level of amplitude and frequency of hydrostatic pressure may be essential for maintaining the matrix of the disc, while an abnormal amplitude and frequency of hydrostatic pressure may accelerate disc degeneration. The ranges of good and bad loading frequencies and amplitudes still need to be discovered. The objective of this study was to find which of loading frequency and loading amplitude has more influence in affecting disc cell response to vibration. To address this issue we developed a mechanically-active culture system capable of delivering a wide range of loading frequency and amplitude of hydrostatic pressure to cultures of nucleus pulposus cells. We used nucleus cells, which are exposed mainly to hydrostatic loading in vivo.
A Novel Device for Direct Permeation Measurements of Hydrogels and Soft Hydrated Tissues
Authors: Andarawis Nelly A. , Seyhan Sara L. , Mauck Robert L. , Soltz Michael A. , Ateshian Gerard A. , Hung Clark T.
Published: November 2021

The goal of this study was to develop a system to reliably measure the intrinsic hydraulic permeability of hydrogels and soft hydrated tissues. Such a device can be used to assess the development of functional properties in tissue engineered constructs [1]. The design parameters for such a device include ease of assembly and the ability to measure hydraulic permeability over a range of specimen deformations. To meet these criteria, a device was designed that could quantify the hydraulic permeability of a sample under different levels of deformation, allowing characterization of strain-dependent effects. The device was tested on both agarose and articular cartilage specimens, yielding permeability values consistent with published data [2]. The intrinsic hydraulic permeability of a tissue is an important parameter that governs fluid exudation during deformational loading. The ability of articular cartilage, which exhibits non-linear strain dependent hydraulic permeability [3], to generate and sustain interstitial fluid pressurization is essential to its functional properties (e.g., load bearing and lubrication). This novel device allows for direct and reliable measurement of these physical properties.
Feasibility of Using an Active Actuator for Two-Dimensional Vibration Abatement in a Turning Process
Authors: Yan W. Y. , Al-Jumaily A. M.
Published: November 2021

A simulation model that considers the radial and tangential vibrations and their abatement using active actuators in a turning process is developed. The model is simulated using Simulink in Matlab environment to assess the possibility of using an active actuator to reduce vibrations in two directions. Comparison is made between the two orthogonal actuators scenario and the one inclined actuator scenario. The results indicate that vibrations reduction using an active inclined actuator is comparable to that of two orthogonal ones.
A Multi-Mode Approach for the Nonlinear Vibrations of Circular Cylindrical Shells
Authors: Pellicano Francesco , Amabili Marco , Païdoussis Michael P.
Published: November 2021

The nonlinear vibrations of simply supported, circular cylindrical shells, having geometric nonlinearities is analyzed. Donnell’s nonlinear shallow-shell theory is used, and the partial differential equations are spatially discretized by means of the Galerkin procedure, using a large number of degrees of freedom. A symbolic manipulation code is developed for the discretization, allowing an unlimited number of modes. In the displacement expansion particular care is given to the comparison functions in order to reduce as much as possible the dimension of the dynamical system, without losing accuracy. Both driven and companion modes are included, allowing for traveling-wave response of the shell. The fundamental role of the axisymmetric modes, which are included in the expansion, is confirmed and a convergence analysis is performed. The effect of the geometric shell characteristics, radius, length and thickness, on the nonlinear behavior is analyzed.
Estimation of Chaotic Parameter Regimes via Generalized Competitive Modes Approach
Authors: Yao Weiguang , Yu Pei , Essex Chris
Published: November 2021

A procedure is proposed to estimate the parameter regimes of chaos in nonlinear systems by implementing a mathematical version of mode competition. The idea is that for a system to be chaotic there must exist at least two generalized competitive modes in the system. The Lorenz system and a thin plate in flow-induced vibrations system are analyzed to find chaotic regimes by this procedure.
On a Chaos Control for the Logistic Map
Authors: Wang Xiaohua , Jing Zhongliang , Luo Albert C. J.
Published: November 2021

A method for chaos control based on the feedback control principle is presented. The chaotic behavior of logistic map for μ = 4 is discussed as a simple problem. Comparison of control performance between two different control methods is given. The simulation results show that the presented control method for chaos gives a better performance than the inverse system method.
Direct Perturbation Analysis on Transmission Lines With Detuning Pendulums
Authors: Pan Kelin , Yu Pei
Published: November 2021

A general model of cable dynamics is used to analyze the vibration of transmission lines equipped with the control device – detuning pendulums. The model considers complex loading, including nonlinear aerodynamic force and concentrated load. An early developed perturbation method, called direct perturbation method (DPM), is applied to study cable motion. This approach does not need to transform the original partial differential equation to an ordinary differential equation, and the solution procedure is systematic. Steady-state solutions and stability conditions are briefly discussed.
Asymmetrically Respiratory System Simulation for Identifying Airway Occlusion
Authors: Al-Jumaily A. M. , Al-Fakhri Y.
Published: November 2021

A theoretical model is developed to investigate the dynamic characteristic of a healthy and an occluded asymmetric respiratory system. The model takes the elastance and inertance of the airway walls into consideration. Frequency spectra of the input impedance determined at the throat are generated and examined for two regimes of airway terminations and for occlusion at each generation from the end terminal (alveolar sacs) up to the proximal end of the trachea. In the asymmetric arrangement the impact of merging dissimilar flows due to different airways geometry from the adjacent regions is considered. Further, the effect of the nature of the terminal impedance (ie. rigid termination or compliant termination) on the acoustic response is also investigated.
Air Velocity Regulation in a Wind Tunnel
Authors: Ebrahimi M. , Whalley R.
Published: November 2021

A wind tunnel model, relating fan motor speed and ventilator opening to the air velocity in the tunnel casing and working section, is presented. Regulation, using the naturally occurring outputs such that accurate adjustments in the air velocity at the working section, with prescribed transient, gusting conditions is required. Confined steady state interaction together with minimum control effort expenditure is essential. A simple feedback configuration with passive network compensation is proposed, satisfying these performance requirements thereby.
Electro-Hydraulic Camless Valvetrain System Modeling
Authors: Asgari J. , Hrovat D.
Published: November 2021

This report describes a development of Matrixx model of prototype Electro-hydraulic Camless Valvetrain (ECV). The model was developed using bond graph techniques and was partially validated with respect to limited available experimental data for a single-cylinder laboratory implementation. The report also discusses system sensitivity and other issues which characterize this in practice highly challenging concept.
Natural Convection Heat Transfer and Flow Pattern in an Inclined Arc-Shape Enclosure
Authors: Chen Chin-Lung , Cheng Chin-Hsiang
Published: November 2021

Numerical and experimental investigations have been conducted to study the flow and heat transfer characteristics for the buoyancy-induced flow inside an inclined arc-shape enclosure. Mathematical model in form of a stream function-vorticity formulation representing the laws of conservation in mass, momentum, and energy is expressed in a curvilinear coordinate frame and solved by a finite-volume discretization method. Heat transfer and flow pattern are predicted at various Grashof numbers and inclination angles. Meanwhile, an experimental system is developed and a flow-visualization technique using smoke is employed to observe the flow pattern. Results show that when the Grashof number is higher than 105, the increase in natural convection heat transfer becomes appreciable. The vortex strength and pattern are found to be greatly dependent on the inclination angle. The range of the Grashof number considered in this study is up to 107 and the inclination angle is varied from 0 to π.
Pressure Effects on the Buoyancy-Induced Convective Heat Transfer for Non-Boussinesq Fluid in a Rectangular Enclosure
Authors: Hung Kuo-Shu , Cheng Chin-Hsiang
Published: November 2021

Numerical predictions of pressure effects on natural convective heat transfer characteristics for a non-Boussinesq fluid in a rectangular enclosure are presented. The solution method is developed based on a compressible flow model and is employed to simultaneously determine the absolute pressure, density, temperature, and velocity distributions in the enclosure. Discretization equations are derived from the integral mass, momentum, and energy equations on a staggered grid. The fluid pressure in the enclosure is varied from 20 to 300 kPa such that the flow behavior in a vacuum or pressurized system can be observed. Physical situations investigated also include cases in a wide range of wall temperature difference associated with various length scales, corresponding to an equivalent modified Rayleigh number ranging from 104 to 106. The validity of the incompressible flow model coupled with the Boussinesq approximation for the fluid density, which is commonly used in the existing studies of the buoyant flows, is discussed.
A Numerical Study of Natural Convective Flow in a Narrow Open Top Enclosure With a Linearly Varying Side-Wall Temperature Attached to a Large Square Enclosure
Authors: Oosthuizen Patrick H. , Scott David
Published: November 2021

Natural convective flew in a large square enclosure with a narrow rectangular enclosure mounted symmetrically on the upper surface of this main enclosure has been considered. The horizontal bottom and vertical side-walls of the main enclosure are assumed to be at a uniform high temperature and the vertical side-walls of the narrow top enclosure are assumed have a temperature that varies linearly with height above the main enclosure. The top horizontal wall of the upper enclosure is assumed to be adiabatic The situation consider is an approximate model of that which arises when measurements have to be made in a large enclosure containing a hot fluid and in which the measuring instrument is mounted in a small enclosure which is open at one end to the main tank and which has the instrument mounted at the opposite closed end. In order to ensure that the instrument is not exposed to a temperature that is above its operational limit, the walls of this small enclosure are cooled. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces, this being treated by means of the Boussinesq type approximation. The governing equations have been written in dimensionless form and the resultant dimensionless equations have been solved using a finite-element method. Results have been obtained for a Prandtl number of 0.7. The effects of Rayleigh number and dimensionless height and width of the top enclosure on the maximum temperature of the top adiabatic surface have been investigated. The results show that provided the aspect ratio of the upper enclosure is kept large, overheating of the upper adiabatic surface of the top enclosure is not likely to occur.
A New Type Two-Layer Turbulence Model for Natural Convection Applied to a Diffrentially Heated Channel
Authors: Hammami T. , Bennacer R. , Mohamad A. A.
Published: November 2021

The near wall region poses numerical difficulties and current modellings are either expensive or lack universality. Using the recent DNS done on natural convection flow in an infinite channel differentially heated for (104 < Ra < 106) a scaling analysis is developed and a one-equation near-wall turbulence model is deduced. The model coupled with a Low Reynolds Number Model (LRN) in the outer region was applied to calculate natural flow for different Ra numbers. It yields good performance, computation time reduction and much better heat transfer prediction compared to the diffusive Jones Launder LRN model.
Resolution Requirements for DNS of Turbulent Heat Transfer Near the Heated Wall at Prandtl Number 5.4
Authors: Bergant Robert , Tiselj Iztok , Hetsroni Gad
Published: November 2021

Theoretically, the grid spacing for Direct Numerical Simulations of heat transfer at Prandtl numbers higher than one should be inversely proportional to the square root of Prandtl number (Tennekes, H., Lumley, J.L [1]). The grid refinement study of Na and Hanratty (2000) [2] at Pr = 10 showed that finer grid is not required in streamwise and spanwise directions, but is necessary in the wall-normal direction.

In the present work three different DNS studies were performed with different resolutions at Pr = 5.4 and friction Reynolds number Re = 171.

The first DNS was performed using the resolution, which is known to be sufficient for the velocity field simulation, the second simulation was performed with the refined grid in the wall-normal direction and the third DNS was using finer grid in all three directions.

Results have shown that there are no significant differences in the first-order statistics and spectra for all three cases.
Boiling Curve Measurement of Water Containing Dissolved Carbon Dioxide Around a Heated Wire
Authors: Heydari Ali , Carey V. P.
Published: November 2021

Proper thermal treatment of metals in metal processing plants is important both in terms of quality and economy of the final product. Addition of a highly soluble gas such as carbon dioxide to water has been shown to create an excellent quenching medium for metal objects in metal working processes. It causes slower rate of cooling due to the insulating effect of carbon dioxide on the surface of immersed metal objects which as a result hinders residual stress build up and warpage commonly observed in quenching metal objects in cold water. Additionally, absence of carbon dioxide-filled bubbles on the surface of quenching metal object causes cold water-like cooling of the surface, producing rapid cooling of the objects. In this study, boiling heat transfer characteristics of an electrically heated wire immersed in water mixed with different concentrations of carbon dioxide at various atmospheric and sub-atmospheric pressures are obtained and compared. The results indicate that the boiling behavior and heat transfer characteristics of carbon dioxide-water solution make it a favorable substitute to cold and hot water traditionally used as the heat transfer fluid in metal processing plants.
Effect of Fouling on Nucleate Pool Boiling and Critical Heat Flux
Authors: Fukada Yusuke , Haze Ikuya , Horiki Sachiyo , Osakabe Masahiro
Published: November 2021

Pool boiling experiment with a platinum wire was performed in earth and micro gravity. Bare surface and fouling surface with scale of calcium carbonate was used. The wettability on the scale surface was higher than that on the bare surface. The critical heat flux (CHF) was measured and movies of the bubbling were taken with a high-speed video camera. The more vigorous bubbling was observed on the scale surface compared to that on the bare surface at the same heat flux. The scale surface became thermal resistance and the boiling curve on the scale surface eventually shifted to the right side of that on the bare surface. However, the critical heat flux on the scale surface was higher than that on the bare surface. On the scale surface, the departure diameter of bubbles is relatively smaller than that on the bare surface. The smaller diameter of bubbles detaching from the scale surface is considered to be due to the high wettability. As the result, the coalescent of bubbles near the surface was prevented and the CHF was delayed and increased on the scale surface compared to that on the bare surface.
A Finite-Volume Based Time-Splitting Scheme for Computation of Electrodeposition
Authors: Xia Chunmei , Murthy Jayathi Y.
Published: November 2021

The final step in the LIGA process for manufacturing metallic microstructures is the electroplating of the metal part. The electroplating process can be described by homogeneous dissociation reactions in the electrolyte bath and finite rate surface reactions on the electrode. In this paper we develop a finite volume method for computing electrodeposition in the LIGA process. We employ a time splitting algorithm for coupling the bulk and surface reactions. As an alternative, the species concentration field is solved over the whole domain using a direct method. The two methods are compared to establish the validity and efficiency of the time-splitting algorithm.
Thermal Non-Equilibrium Effects at the Stagnation Wall in the Unsteady Micro-Flow
Authors: Park Jae Hyun , Baek Seung Wook
Published: November 2021

In the present study, the non-equilibrium effects at the stagnation wall in one-dimensional unsteady micro-flow responding to the external sinusoidal oscillation are investigated. The fluctuating behavior of the rarefied medium is simulated by employing the unsteady DSMC method for various conditions with the acoustic Reynolds number and the Knudsen number. The heat fluxes calculated from Maxwell-Smoluchowski’s relation and its higher order modifications are compared with the direct DSMC result. Consequently, it is found that there exists the non-equilibrium effect at the stagnation wall especially when the number of reflected molecules from the diffuse wall was small.
Pool Boiling of High-Frequency Conductors
Authors: Wright S. E. , Konecni S. , Ammerman C. N. , Sims J. R.
Published: November 2021

This study presents development of a unique, powerful method for cooling high-frequency, AC conductors that can benefit end users of transformer windings, electrical machine windings, and magnet coils. This method of heat removal involves boiling a dielectric, fluorinert refrigerant that is in direct contact with litz wire conductors. A pool boiling test vessel is constructed, which provides for temperature control of the pool of fluorinert liquid. The test vessel is fitted with viewing ports so that the experiments are observed and studied with the aid of high-speed photography. Tests are performed on a variety of litz wire conductors. The boiling heat transfer coefficient is dependent on the conductor surface roughness. The size of the features on the conductor surface depends on the single-strand wire gage from which the conductor is constructed. All tests are performed with the conductors mounted horizontally. These tests are performed using a DC power supply. The results of these experiments will aid in the design of future cooling systems.
Air-Water Transient Heat Transfer in a Stirred Tank
Authors: Dubovsky V. , Ziskind G. , Letan R.
Published: November 2021

The work is concerned with a stirred tank in which water is cooled batchwise by a continuous stream of bubbling air. The work is experimental, and the phenomena are simulated by an analytical model.

The experiments include direct contact of air bubbles with the stirred water, heat transfer to the ambient air through the interface, and heat transfer through the walls to cooling water in a jacket by natural or forced convection, or to ambient air by natural convection.

Heat-transfer coefficients are calculated in all the cases studied, starting with free convection and proceeding systematically to a complex interaction of mechanical stirring and agitation caused by dispersed air bubbles. Special attention is given to such phenomena as enhanced heat transfer through the liquid-air interface as a result of mixing and bubbly flow.

Theoretical considerations lead to a mathematical model that takes into account the heat-transfer mechanisms studied. The model simulations compare well with the experimental measurements.
Unsteady Analysis of Particle-Laden Gas Flows When Hit by a Moving Shock Wave
Authors: Park Jun Sung , Baek Seung Wook
Published: November 2021

A successful prediction of the thermo-fluid mechanical characteristics of gas and particles is very crucial and imperative for the successful design and operation of rocket nozzles and energy conversion systems. This paper describes an interaction phenomenon when a moving shock wave hits a two-phase medium of gas and particles. A particle-laden gas is considered to be located along a ramp so that numerical integration is accomplished from the tip of ramp for a finite period. For the numerical solution, a fully conservative unsteady implicit 2nd order time-accurate sub-iteration method and a 2nd order Total Variation Diminishing (TVD) scheme are used with the finite volume method (FVM) for gas phase. For particle phase, the Monotonic Upstream Schemes for Conservation Laws (MUSCL) as well as the solution of the Riemann problem for the particle motion equations is used. Transient development of thermo-fluid mechanical characteristics is calculated and discussed by changing the particle mass density and particle specific heat. Major results reveal that when the particle mass density is smaller, there is a stronger interaction between two phases so that the velocity and temperature differences between two phases more rapidly decrease. When the particle specific heat is varied, only a thermal effect (temperature difference between gas and particles) is observed while the other effects (variations of particle concentration and velocity fields) are minor.
Critical Heat Flux During Reflood Transients in Small Hydraulic Diameter Geometries
Authors: Holowach M. J. , Hochreiter L. E. , Cheung F.-B. , Aumiller D. L.
Published: November 2021

Critical Heat Flux (CHF) at a low flow condition in a small hydraulic diameter duct is an important phenomenon for a MTR/ATR (Materials Test Reactor/Advanced Test Reactor) design under a number of accident conditions including reflood transients. Current CHF models in the literature, such as the Mishima/Nishihara and Oh/Englert CHF models, are based on macroscopic system parameters and not local thermal hydraulic conditions. These macroscopic parameter-based models cannot be readily used for analysis in transient best-estimate thermal hydraulic codes. This investigation focuses on developing a low flow rate CHF correlation, based on local conditions, that is amenable to implementation into a best-estimate transient thermal hydraulic code for a small hydraulic diameter channel. The model development proceeds with a means of correlating CHF data to local conditions parameters and then applying a correction factor to the resulting correlation, that permits accurate predictions over a range of pressures. An evaluation of the proposed local conditions-based CHF model is conducted by predicting independent sets of CHF experimental results over a range of flow rate, pressure, and sub cooling conditions. Conclusions on the viability of the proposed CHF model and suggestions for future efforts in improving the reflood heat transfer CHF models for small hydraulic diameter ducts are provided with an evaluation of the model results.
Two-Phase Flow in Microchannels
Authors: Hetsroni G. , Mosyak A. , Segal Z.
Published: November 2021

Experimental investigation of a heat sink for electronics cooling is performed. The objective is to keep the operating temperature at a relatively low level of about 323–333K, while reducing the undesired temperature variation in both the streamwise and transverse directions. The experimental study is based on systematic temperature, flow and pressure measurements, infrared radiometry and high-speed digital video imaging.

The heat sink has parallel triangular microchannels with a base of 250μm. According to the objectives of the present study, Vertrel XF is chosen as the working fluid. Experiments on flow boiling of Vertrel XF in the microchannel heat sink are performed to study the effect of mass velocity and vapor quality on the heat transfer, as well as to compare the two-phase results to a single-phase water flow.
Void Fraction Physics Resulting From Chaos Control of Upward Gas-Liquid Slug Flow
Authors: MacMeccan Robert M. , Langford Heather M. , Beasley Donald E.
Published: November 2021

The present investigation examines open-loop control of chaotic upward gas-liquid slug flow. Though highly structured, slug flow is deterministically chaotic in nature. Recent analytical and experimental investigations indicate that perturbation of a system parameter has the potential to reduce or increase chaos in a system. Slug flow provides an interesting medium for the investigation into control of chaotic systems due to its high degree of structure and complex physics. The response of slug flow under control in turn lends insight into its complex dynamics. The results of the present study validate open-loop control, showing that periodic perturbation of the air inlet conditions at a specific frequency destabilizes dominant system dynamics, pushing the system to less stable orbits with different flow physics.
Bubble Nucleation on Micro Line Heaters
Authors: Lee Jung-Yeop , Park Hong-Chul , Kwak Ho-Young , Jeon Jin-Seok
Published: November 2021

Nucleation temperatures on the micro line heaters were measured precisely by obtaining the I-R (current-resistance) characteristic curves of the heaters. The bubble nucleation temperatures on the heater with 3 μm width are higher than the superheat limit, while the temperature on the heater with broader width of 5 μm are considerably less than the superheat limit. The nucleation temperatures were also estimated by using the molecular cluster model of bubble nucleation with effect of contact angle. The bubble nucleation process was observed by microscope / 35 mm camera unit with a flash light of μs duration.
Behavior of Single Bubble Growth With Constant Wall Temperatures Controlled by a Microscale Heater Array
Authors: Lee Hanchoon , Son Younggeun , Oh Byung Do , Bae Sungwon , Kim Moohwan
Published: November 2021

Experiments of nucleate pool boiling of R11/R113 mixtures were performed. The heat flux was measured with sufficient temporal and spatial resolution to show characteristics of the nucleate boiling with constant wall temperatures controlled by a novel microscale heater array. Instantaneous images of single bubbles were captured using a high-speed CCD camera, synchronized with the data acquisition from the microscale heater array. The heater was 0.27 × 0.27mm2, which is similar to the size of a typical bubble in nucleate boiling. The heating power was designed to automatically maintain a constant wall temperature. The experiments were performed with wall superheat using pure substances and mixtures with different mass ratios of R11 and R113. For pure substances, the bubble growth rate was much lower with the constant wall temperature than that with the constant wall heat flux. A high rate of bubble growth initially was observed for pure substances. The volume growth rate decreased for large bubbles when the wall temperature was constant, but increased continuously for a constant wall heat flux. The rate of bubble growth in mixtures is highly dependent on the mass fraction of their components. The peak value of the heat flux for mixtures is reduced because of concentration gradients at the bubble interface. A numerical simulation was also performed; qualitative agreement was noted between the numerical and experimental results.
New Phenomena of Mass Transfer in Gas/Liquid Flows
Authors: Bork O. , Schlueter M. , Scheid S. , Raebiger N.
Published: November 2021

Due to a lack of knowledge of mass transfer in multiphase flows, investigation into mass transfer is in great demand in order to obtain a better understanding of local phenomena. This paper describes the experimental investigation into mass transfer, in particular the influence of flow conditions around bubbles, contact time between phases, bubble size and viscosity of the liquid. Single bubbles are injected into a bubble column (diameter dR = 100 mm). The laser-induced fluorescence measuring technique (LIF) is used to visualize the concentration field around a freely rising bubble. A special experimental set-up has been developed which permits a three-dimensional (3d) reconstruction of the local concentration field around bubbles. Oxygen concentration fields of ellipsoid gas bubbles with equivalent diameters between 4mm and 8mm in aqueous solutions are shown and local mass flows are presented.
Mechanistic Model for Dynamic Forces in Micro-Drilling
Authors: Gong Yongping , Ehmann Kornel F.
Published: November 2021

By considering the effects of drill grinding errors and drill deflections, dynamic cutting chip thickness models were developed which in combination with workpiece surface inclination effects allowed the formulation of expressions for the dynamic cutting chip cross-sectional area. By using the dynamic chip thickness and dynamic cutting chip area to replace their static counterparts, static drilling force models were extended to facilitate the prediction of dynamic cutting forces in micro-drilling processes. The geometric characteristics of micro-drills were considered in these mechanistic force models. Separate thrust, torque and radial force models for the major cutting edges, secondary cutting edge and for the indentation zone were developed. The effects of drill installation errors on the radial cutting forces acting on the chisel edge and the major cutting edges were also included.
Analytical Convolution Model of Cutting Forces in 3-D Ball End Milling
Authors: Chiou Richard Y. , Zhao Bing
Published: November 2021

This paper presents an analytical convolution model of dynamic cutting forces in ball end milling of 3-D plane surfaces. The model takes into account the instantaneous slope on a sculptured surface to establish the chip geometry in cutting force calculation algorithm. A three-dimensional model of cutting forces in ball end milling is presented in terms of material properties, cutting parameters, machining configuration, and tool/work geometry. Based on the relationship of the local cutting force, chip load and engaged boundary, the total cutting force model is established via the angle domain convolution integration of the local forces in the feed, cross feed, axial direction, and inclination angle. The convolution integral leads to a periodic function of cutting forces in the angle domain and an explicit expression of the dynamic cutting force components in the frequency domain. Following the theoretical analysis, experimental study is discussed to illustrate the implementation procedure for force identification, and frequency domain data are presented to verify the analytical results.
An Investigation of the Predicting Capabilities of a Variable Flow Stress Machining Theory
Authors: Mathew P.
Published: November 2021

The Oxley Machining Theory, which has been developed over the last 40 years, is presented in this paper. The capability of the model is described with its initial two-dimensional machining approach followed by the extension to the generalised model for three-dimensional machining. The theoretical results from the model are compared with the experimental results to determine the model capability. A brief description of the work associated with the effect of strain hardening at the interface is presented and comparative results are shown. A further extension of the model to intermittent cutting process of reaming is also presented and a comparison with the experimental results indicates the model developed is quite capable of predicting cutting forces for reaming. In explaining the results obtain, the assumptions made are explained and the inputs required. The limitations of the modelling approach are presented. It is pointed out that the Oxley model is a versatile model as long as proper description of the material flow stress properties is presented.
Modeling of Necking/Shear Failure of Aluminum Sheet Metals With Consideration of Void Nucleation and Growth
Authors: Chien W. Y. , Pan J. , Tang S. C.
Published: November 2021

Failure of two aluminum sheets, AA5754 and AA6111, under stretching conditions is analyzed using a combined plane stress and plane strain approach. The sheet material is modeled by an elastic-viscoplastic constitutive relation that accounts for material plastic anisotropy, material rate sensitivity, and the softening due to the nucleation, growth, and coalescence of microvoids. Failure processes of sheet metals are modeled under plane strain tension. Also, failure strains are determined under bending conditions when the necking mode is suppressed. The results are consistent with experimental observations where the failure strain of the aluminum sheets increases significantly under bending conditions. The results indicate that when a considerable amount of necking is observed under stretching conditions, failure strains under bending conditions are higher.
Pressure Generated During Pulse Electrochemical Machining
Authors: Kozak J. , Rajurkar K. P.
Published: November 2021

Pulse electrochemical machining (PECM) provides an economical and effective method for machining high strength, heat-resistant materials into complex shapes such as turbine blades of titanium alloys. The dimensional accuracy of PECM can be improved if a small interelectrode gap is maintained. This paper presents an interelectrode gap model for estimating pulse pressure generated after pulse current switched on, and the subsequent dynamic loading on the electrodes during PECM. A specially built PECM cell and a high-speed data acquisition system are used to measurement of wave pressure for verification of estimated values.
Industry-University Educational Partnerships for the New Millennium: Experiences and Lessons Learned
Authors: Wiens Gloria J. , Grider David C. , Beale David G. , Magleby Spencer P. , Todd Robert H. , Pugh Len , Stanfill R. Keith , Coulter John P. , Gillette Frank C. , Franco James S. , Mattson Christopher A. , Clerc Jean-Philippe , Riger Hannah
Published: November 2021

Selected as one of the 2001 ASME / IMECE industrial highlight sessions, this panel focuses on the paradigm shift from the traditional capstone design course structure towards new design experiences formulated through industry-university educational partnerships. Such partnerships feature collaboration of multidisciplinary student, faculty and industrial teams for product and process realization. The two-session symposium addresses the following topics:

• Integrated product and process design

• Modern design methodologies integration

• Frameworks for university and industrial partnerships

• Recruitment, student profiles, graduation and placement

• Effective evaluation of student, team and project

• Grading and motivation techniques

• Program assessments and outcomes

• Implementation, institutionalization, and sustainability strategies

The ten-person panel brings together a group of faculty, program administrators, students and industrial sponsors from three different undergraduate engineering programs incorporating the new industry-university educational partnerships. The panel discussion highlights the attributes, pros/cons, obstacles/challenges, lessons learned, intellectual property issues, project failure drivers, role of industrial liaisons, recruitment, the effect on faculty and student participants, and program outcomes. The university programs represented are Brigham Young University, University of Florida, and Lehigh University.

The symposium organizers extend many thanks to the panelists and session chairs for providing the program content and energized discussions required for making this panel and symposium a success. Last but not least, R. Keith Stanfill’s continual behind-the-scenes leadership and assistance in bringing together the key elements of the program is greatly appreciated.
Issues and Directions of MEMS Research for the Electronics Industry
Authors: Pak Y. Eugene
Published: November 2021

The 20th Century has witnessed breathtaking developments in the miniaturization and the large-scale integration of microelectronic devices that have had an enormous impact on human affairs. The same miniaturization paradigm can be applied to mechanical devices using MEMS technology leading to ultra small micromachines that cannot otherwise be fabricated using conventional machining and assembly techniques. The MEMS technology is expected to have a great impact in the 21st century by enabling many complex electromechanical systems to be fabricated and integrated. In this paper, applications of MEMS to many areas relating to information and biotechnology are discussed. These topics are presented in the context of ongoing research at the Samsung Advanced Institute of Technology (SAIT). SAIT is the central research laboratory for the Samsung Corporation whose charter is to develop breakthrough technologies to be th leader in the 21st century.
Characterization of a Piezoelectric Membrane for MEMS Power
Authors: Bruce K. , Richards R. , Bahr D. , Richards C.
Published: November 2021

Work toward the development of a thin-film piezoelectric membrane generator is presented. The membrane generator is the central component of a new MEMS power generation system, the P3 micro power system. The P3 micro power system is based on a two-dimensional, modular architecture, in which the individual generic modules or unit cells each have all the functions of an engine integrated. Each unit cell is an external combustion engine, in which thermal power is converted to mechanical power through the use of a novel thermodynamic cycle that approaches the ideal vapor Carnot cycle. Mechanical power is converted into electrical power through the use of a thin-film piezoelectric membrane generator. This paper introduces the concept of the thin-film piezoelectric membrane generator, and describes its design and fabrication. Results of a study to characterize the performance of the piezoelectric membrane generator under expected operating conditions are presented. Current prototypes of the membrane generator are shown to be capable of producing a peak power of 0.1 milliWatts at a voltage of 0.5 Volts.
Multiplexed Detection of Nanoscale Microcantilever Deflections for High-Throughput Biomolecular Analysis
Authors: Dames Chris , Wu Guanghua , Lin Henry , Majumdar Aran
Published: November 2021

We present the first steps towards a device for the parallel detection of multiple biomolecules through the binding-induced deflection of microcantilevers. In this study the thermal bimorph effect is used to model the changes in surface stress that are caused by molecular binding. A bank of five cantilevers (each 600 μm long, 645 nm thick) is actuated thermally over a range of 3 μm of tip deflection. The cantilevers are illuminated with a laser and the resulting pattern of reflected spots is used to validate a new CCD-based detection method that tracks the deflections of multiple cantilevers simultaneously. A stress-balancing fabrication technique was also implemented to reduce the initial deflection by an nearly order of magnitude.