bluuebunny/crossref_metadata_2025 huggingface dataset:
COVID‐19 vaccine acceptance: A comparative longitudinal analysis of the association between risk perception, confidence, and the acceptance of a COVID‐19 vaccine
Authors: Martinelli Mauro , Veltri Giuseppe A.
Published: July 2023

Following the outbreak of COVID‐19, scientists rushed to develop vaccines to protect individuals and ferry the world out of the pandemic. Unfortunately, vaccine hesitancy is a major threat to the success of vaccination campaigns. Research on previous pandemics highlighted the centrality of perceived risk and confidence as core determinants of vaccine acceptance. Research on COVID‐19 is less conclusive, and frequently it relies on one‐country, cross‐sectional data, thus making it hard to generalize results across contexts and observe these relationships over time. To bridge these gaps, in this article, we analyzed the association between perceived risk, confidence, and vaccine acceptance cross‐sectionally at individual and country levels. Then, we longitudinally explored whether a within‐country variation in perceived risk and confidence was correlated with a variation in vaccine acceptance. We used data from a large‐scale survey of individuals in 23 countries and 19 time‐points between June 2020 and March 2021 and comparative longitudinal multilevel models to estimate the associations at different levels of analysis simultaneously. Results show the existence of cross‐sectional relationships at the individual and country levels but no significant associations within countries over time. This article contributes to our understanding of the roles of risk perception and confidence in COVID‐19 vaccines’ acceptance by underlining that these relationships might differ at diverse levels of analysis. To foster vaccine uptake, it might be important to address individual concerns and persisting contextual characteristics, but increasing levels of perceived risk and confidence might not be a sufficient strategy to increase vaccine acceptance rates.
Improving Feature Extraction Through Closely-Coupled Integration of Fixture Analysis
Authors: Castano Fernando , Gaines Daniel M. , Hayes Caroline C.
Published: July 2023

This paper presents a view of feature extraction as a process that involves consideration of manufacturing tools, processes and the fixtures to be used. This view is implemented in MEDIATOR. Some feature extractors use almost entirely geometric considerations [29], others use process and tool information which is often implicitly encoded in the data structures to help guide the feature extraction process. Our view of feature extraction is similar to the second approach in that process and tool information is also used. However, we take this approach one step further and also use fixture information to determine features. The reason behind this is that a feature is considered relevant because there is a method for producing it in the task domain. The set of possible tools, tool motions and fixtures that can be used is generated during feature extraction in MEDIATOR and selection of specific fixture and details are done later in process planning. Advantages of this method include the ability to use task information to strongly constrain the search for valid features, increased likelihood that features recognized will be manufacturable and directly usable by the process planner, and ease of modifying the feature extractor.
An Analogical Problem Solving Approach to Planning for Disassembly
Authors: Zeid Ibrahim , Gupta Surendra M. , Bardasz Theodore
Published: July 2023

Disassembly has been emerging as an important potential response to recent environmental and recycling regulations as well as resource conservation needs. One can identify two distinct approaches to tackle the disassembly problem, viz., design for disassembly (DFD) and planning for disassembly (PFD). This paper focuses on the PFD approach. The evolution of a disassembly plan may require some heuristics and domain specific knowledge. In addition, disassembly planners may have a particular style to solve disassembly problems. Due to these facts and the nature of the PFD itself (open ended and iterative), the paper proposes the use of Analogical Problem Solving (APS) as an approach to assist planners to solve PFD problems. APS is based on the sensible notion that problem solving can be assisted by the reuse of solutions to similar problems encountered in the past. The framework of applying APS to PFD, the merits of this approach, and the issues relating to its use for PFD are discussed.
Stability and Forced Response of Beam-Like Structures Having Negative Viscous Damping and Displacement-Dependent Dry Friction Damping
Authors: Whiteman Wayne E. , Ferri Aldo A.
Published: July 2023

The flexural vibration of a beam-like structure damped with a displacement-dependent Coulomb friction force is examined. Due to the geometry of the dry friction damping element, the friction force grows linearly with the beam’s transverse displacement. Recent studies have shown that the damping of systems with displacement-dependent dry friction forces resembles linear structural damping. Taking advantage of this fact, the energy loss per cycle can be made to grow like the square of the vibratory displacement amplitude rather than linearly with amplitude as in the case of frictionally damped systems with constant normal forces. Furthermore, dry friction is well suited to hostile environments such as the high temperatures and high rotation speeds associated with gas turbines. These observations suggest that displacement-dependent dry friction may be an effective means of flutter suppression in turbine and fan blade applications. Destabilizing aerodynamic forces are represented in this study as negative viscous damping. This simple aerodynamic model is often used to capture the basic features of flutter in aeroelastic systems. Both single and multiple-mode analyses are conducted. Results show that energy losses from the displacement-dependent dry friction damper are large enough to overcome the destabilizing negative viscous damping under certain conditions. This result further suggests that it may be possible to design the geometry and location of frictional interfaces in turbine blade systems so that damping may be enhanced and flutter better controlled.
Experimental Evaluation of a Semi-Active Friction Damper
Authors: Dupont Pierre E. , Kasturi Prakash S. , Stokes Ann W.
Published: July 2023

Semi-active control of friction dampers has been proposed to improve the energy dissipation characteristics of passive friction dampers and to broaden the areas of application in which they can successfully be used. In this paper, we implement a control law which maximizes energy dissipation in an instantaneous sense by modulating normal force at the friction interface. This control law is valid for friction models with and without velocity dynamics. Using experimental results, we demonstrate under what operating conditions friction dynamics are vital to the control problem and, for these conditions, demonstrate the efficacy of the proposed controller. Furthermore, we show that for systems forced at a single frequency, the control law also increases the damper’s slip amplitude. The proposed controller is shown to increase energy dissipated per cycle by up to 200 percent in comparison to the case of constant normal force.
The Effects of Tangential Contact Stiffness on a Harmonically Forced Friction Oscillator
Authors: Liang J. W. , Feeny B. F.
Published: July 2023

This paper addresses the effects of a compliant contact on the dynamical friction behaviors in mechanical systems. Contact compliance is due to the elastic deformation at the contact point or the surrounding structure. This paper is divided into two parts. The first part focuses on oscillations with continuous macroscopic sliding. An idealized model consisting of a mass sliding harmonically on a massless compliant contact produces the hysteresis feature seen in friction-velocity plots. Transition features, depending on the contact stiffness, friction level, and frequency/amplitude of oscillation, are predicted and quantified. Experiments have been conducted to verify the model. The model and associated analysis provide a means for interpreting experimental transition behaviors.

The second part of the paper addresses the sticking dynamics associated with a macroscopic stick-slip process. During a stick, the mass undergoes a microscopic oscillation at the contact. This can involve a microscale stick-slip process. We refer to the entire process as a double stick-slip event. Numerical and experimental studies are compared.
Variation of Clamping Force in a Single-Bolt Assembly Subjected to Axial Vibration
Authors: Hess Daniel P. , Basava Srinivas , Rasquinha Ingrid A.
Published: July 2023

Recent experiments and analyses have revealed that threaded fasteners subjected to axial vibration can experience either loosening or tightening. In this paper, the authors examine the variation of clamping force in a single-bolt assembly model due to axial vibration. Specifically, the effect of vibration level and initial pre-load on clamping force is studied. It is found that the clamping force can remain steady, decrease, or increase when the assembly is subjected to axial vibration. However, changes in clamping force are generally transient and a steady value is reached over time.
Spatial Impact of a Flexible Link Using a Nonlinear Contact Force
Authors: Marghitu Dan B. , Boghiu Dan
Published: July 2023

An experimental analysis was conducted to study the rebound velocities of a freely dropped bar on a large external surface. The low velocity collision occured in the presence of a frictional impact. A 3D motion analysis system was used to capture the kinematic data. Tests were performed for central and oblique collisions. A spatial theoretical model is presented for the impact with friction of a flexible body. This model consists of a system of nonlinear differential equations which considers the multiple collisions as well as frictional effects at the contacting end, and allows one to predict the rigid and elastic body motion after the impact. The model uses a dry coefficient of friction, a nonlinear contact force, and the sound radiation from the impact. Analytical and experimental results were compared to establish the accuracy of the model.
Complex Frequencies and Modes of Externally Damped Shafts Under Different Boundary Conditions
Authors: Zu Jean W. , Melanson John M.
Published: July 2023

Vibration analysis of externally damped spinning Timoshenko beams with general boundary conditions is performed analytically. Exact solutions for complex natural frequencies and normal modes for the six classical boundary conditions are derived for the first time. In the numerical simulations, the trend between the complex frequencies and the damping coefficient is investigated, and complex mode shapes are presented in three-dimensional space.
A Study on the Competing Effects of the Dielectrophoretic Force and Buoyancy on Nucleate Boiling Heat Transfer Rates and an Analogy With Variable Gravity Boiling Results
Authors: Snyder Trevor J. , Chung Jacob N. , Schneider John B.
Published: July 2023

The purpose of this paper is to form a more general understanding of the effect an electric field has on boiling heat transfer by considering non-boiling electroconvection and boiling bubble dynamics separately. In an attempt to decouple these two heat transfer mechanisms, an electric field was utilized which produced a uniform dielectrophoretic force (DEP force) across a horizontal platinum wire. Boiling curves were produced with FC-72 as the working fluid for variable DEP and buoyancy forces by varying the electric field geometry (with a constant potential of 23 kV), by varying the orientation of the electric field with respect to gravity, and by performing experiments in a drop tower with very small buoyancy forces. In order to elucidate the relative contributions of the individual forces and correlate the data, an effective gravity g′(b,e) was defined which represents the ratio of the total DEP and buoyancy body forces on the vapor bubbles to the constant terrestrial-gravity buoyancy force.

It was concluded that the effect of the DEP force on the bubbles is analogous to reducing or increasing the gravity locally or inducing vapor flow across the heater surface similar to forced-convection. In semis of the relationship between the bubble dynamics and the heat transfer, it was concluded that nucleate boiling heat transfer will be enhanced if the effective gravity acts to hold the vapor bubbles near the heater surface, while at the same time permitting access of the liquid to the surface in order to prevent dryout. However, a large electroconvective effect can dominate and possibly reverse this trend. For the critical heat flux (CHF) it was discovered that for 1 < g′(b,e) < 3 a quarter power dependence is a reasonable engineering approximation for the increase in CHF with effective gravity.

Based on these results and support from the literature, we concluded that the overall heat transfer coefficient for boiling in the presence of an electric field can be considered as the summation of a heat transfer coefficient due to bubble dynamics and a heat transfer coefficient due to electroconvection. Furthermore, the heat transfer coefficient due to the bubble dynamics can be modeled with current theory based on variable gravity results and/or forced convection.
Convection in an Infinite Cylinder in the Presence of a Horizontal Magnetic Field
Authors: Mazuruk Konstantin , Ramachandran Narayanan
Published: July 2023

The use of a magnetic field to suppress convection in low gravity materials processing is an area of active research. This study aims to investigate some of the basic features of an imposed transverse magnetic field on convective motion in electrically conducting melts. The geometry considered is an infinite vertical column of liquid metal with an axial temperature gradient and an imposed transverse magnetic field. The incipience and azimuthal orientation of convective rolls is investigated. The governing transport equations arc nondimensionalized, linearized and the eigen value problem is solved to determine the most physically significant states. The analysis shows that the initial degeneracy (with no magnetic field) is removed by the presence of a magnetic field and the primary convection roll aligns itself so that its plane is perpendicular to the applied magnetic field. A cross over to another mode is also found when the strength of the magnetic field is increased. Velocity distributions are presented corresponding to the lowest modes and the system behavior within limits of non-linearity is discussed.
Development of an Efficient Solution Method for Solving the Radiative Transfer Equation
Authors: Ouyang Xing , Minardi Antonio , Kassab Alain
Published: July 2023

The radiative heat transfer equation in a participating medium is a Fredholm integral equation of the second kind whose kernels are formally singular at the position where the incident radiation is to be determined. A general method is developed to remove this singularity by capitalizing on the mutual interactions between the source function and the exponential integral appearing in the kernel. The method is based on an interpolation of the unknown source functions, and the analytical integration of the resulting product in the integrand (source function expansion multiplied by the known exponential integral). As such, the method is considered semi-analytical. The method is superior to traditional solution techniques which employ quadratures approximating both the unknown and known functions appearing in the integrand, and which consequently, have numerical difficulties in addressing singularities. The general approach is presented in detail for one-dimensional problems, and extensions to two-dimensional enclosures are also given. One and two-dimensional numerical examples are considered, comparing our predictions to benchmark work. The method is shown to be computationally efficient and highly accurate. In comparison with traditional quadrature based techniques, our method readily handles the singularity of the exponential integral of first order at zero, converges rapidly under grid refinement, and provides superior prediction for radiative heat transfer. The technique is shown to be valid for a wide range of values of the scattering albedo and optical thickness. The proposed technique could be applied to a wide range of conservation problems which lend themselves to an integral formulation.
Wavelets in the Solution of Nongray Radiative Heat Transfer Equation
Authors: Bayazitoglu Yildiz , Wang Bryan Y.
Published: July 2023

The wavelet basis functions are introduced into the radiative transfer equation in the frequency domain. The intensity of radiation is expanded in terms of Daubechies’ wrapped around wavelet functions. It is shown that the wavelet basis approach to modeling nongrayness can be incorporated into any solution method for the equation of transfer. In this paper the resulting system of equations is solved for the one-dimensional radiative equilibrium problem using the P-N approximation.
Radiation Heat Transfer Modeling in Electrorheological Fluids: Treatment as an Absorbing Medium
Authors: Hargrove Jeffrey B. , Lloyd John R. , Radcliffe Clark J.
Published: July 2023

Radiation heat transfer control utilizing the unique properties of electrorheological (ER) fluids has recently been the subject of considerable interest as an innovative new area of research. While much work has been done to demonstrate the concept and show the potential for radiation transmittance control, little has been done to specifically identify the fundamental radiation transport mechanism involved. This paper identifies particle absorption as the dominant mode for attenuation of radiant energy from the range of 500 nm to 800 nm incident upon an ER fluid made of micron sized zeolite particles. Furthermore, appropriate models are developed based on absorption theory to predict radiation heat transfer through a composite window featuring a layer of ER fluid. The levels of extinction predicted by these models are compared to data obtained by experimental measurement, with excellent agreement shown.
Radiative Heat Transfer Inside a Cylindrical Enclosure With Nonparticipating Media Using a Deterministic Statistical Method
Authors: Sivathanu Yudaya R. , Gore Jay P.
Published: July 2023

The radiative heat transfer inside a cylindrical enclosure is modeled using a discrete probability function method. The discrete probability function method involves solution of the equation of radiative heat transfer using Lagrangian simulations of representative photon trajectories on a discrete spatial grid. The DPF method is applied to radiation exchange in a cylindrical tube which has a hot source at one end and a detector at the other end. The cylindrical wall absorbs and reflects (both diffusely and specularly) the radiation incident on it. The calculations are used to simulate the effect of collimating tubes used in intrusive multi-wavelength emission spectroscopy. Results highlight the effect of surface properties on the apparent source temperature determined by the detector. The calculation procedure has application to the measurements of spectral absorption and reflection coefficient of the cylindrical surface using an inverse method.
Nonaxisymmetric Radiative Transfer in Cylindrical Enclosures
Authors: Moder Jeffrey P. , Chai John C. , Parthasarathy Girija , Lee HaeOk S. , Patankar Suhas V.
Published: July 2023

A finite-volume method for radiative transfer in cylindrical enclosures is presented. Angular redistribution terms in the equation of transfer are avoided by defining radiation directions in terms of angular coordinates measured with respect to Cartesian base vectors; this definition of radiation directions can result in control angles which overlap control-volume faces, depending on the type of spatial and angular grids used in the azimuthal direction. A simple treatment for such control-angle overlaps is presented which is also applicable to nonorthogonal curvilinear spatial-coordinates. A comparison of the present procedure with other similar methods is given. Solutions are presented for axisymmetric transfer through a cylinder and nonaxisymmetric transfer through two- and three-dimensional annular sectors. Results show that the procedure produces reasonable solutions for transparent and participating media in axisymmetric and nonaxisymmetric cylindrical enclosures.
Periodic Techniques for Low Temperature Radiative Property Measurements
Authors: Matteï S. , Especel D.
Published: July 2023

Ordinary steady-state methods lend themselves poorly to low temperature total emissivity and reflectivity measurements because extensive reflected power is superimposed on emissive power. A means of separating emitted and reflected fluxes from each other through periodic radiometry is proposed. This technique consists in modulating either emitted or reflected flux by using either a modulated temperature sample or a modulated temperature source. In both cases, the radiative flux leaving the sample is the sum of two fluxes — a modulated one and a non-modulated one. The former can be isolated from the latter using a Fourier analysis. For a given apparatus, an estimation of the statistical uncertainties can be performed from the temperature amplitude (sample or source), the optical path, the electrical characteristics of the detection system, and the measuring time. On the other hand, the accuracy of a particular result (emissivity or reflectivity) can be obtained by measuring the amount of noise in the FFT spectra. Both calculations are explained in detail, and numerical examples for low temperature measurements are given as well. Several emissivity and reflectivity measurement apparatus are described, their performances are discussed, and examples of experimental results are given.
Measurement of Time Varying Temperature Fields Using Visible Imaging CCD Cameras
Authors: Keanini Russell G. , Allgood Christopher L.
Published: July 2023

A method for measuring time-varying surface temperature distributions using high frame rate visible imaging CCD cameras is described. The technique is based on an ad hoc model relating measured radiance to local surface temperature. This approach is based on the fairly non-restrictive assumptions that atmospheric scattering and absorption, and secondary emission and reflection are negligible. In order to assess performance, both concurrent and non-concurrent calibration and measurement, performed under dynamic thermal conditions, are examined. It is found that measurement accuracy is comparable to the theoretical accuracy predicted for infrared-based systems. In addition, performance tests indicate that in our experimental system, real-time calibration can be achieved while real-time whole-field temperature measurements require relatively course spatial resolution. The principal advantages of the proposed method are its simplicity and low cost. In addition, since independent temperature measurements are used for calibration, emissivity remains unspecified, so that a potentially significant source of error is eliminated.
The Effect of Imprecision in Sensor Location on Optimal Sensor Locations
Authors: Emery Ashley F. , Fadale Tushar D.
Published: July 2023

Optimal sensor locations and the information content obtained when estimating parameters using the inverse method are significantly affected by uncertainties in sensor position and in the presumably known parameters. This paper describes the effect of these uncertainties. It is shown that the effect of sensor location uncertainties can be reduced by placing temperature sensors in locations of minimum heat flux. In transient experiments, the uncertainties in the boundary conditions have greatest effect at points of high heat flux and cause the optimal sensor locations to move from the boundary with the highest convective heat transfer coefficient to the boundary with the lowest in an abrupt manner.
A Numerical Study of the Effect of Interwall Spacing on Turbulent Flow in a Corrugated Duct
Authors: Ergin S. , Ota M. , Yamaguchi H. , Sakamoto M.
Published: July 2023

The effect of varying interwall spacing on periodic fully developed turbulent How in a corrugated duct is studied numerically. The k-ε model is adopted for turbulent closure, and computations are performed for the ratio of the corrugation height to the interwall spacing ranging from 0.45 to 2.0, and for the corrugation angles of 30° and 45°. The Reynolds number ranges from 500 to 7000 while the Prandtl number is 0.7. The numerical procedure and implementation of the k-ε model is validated by comparing numerical results with the experimental data directly. The results are also compared with the numerical values obtained by using a two-layer low-Reynolds number turbulence model. At a given Reynolds number, an increase in the interwall spacing increases the size of the separated region. On the other hand the friction factor first increases with the decreasing interwall spacing, reaches its maximum value, and then decreases.
On Two-Fluid Model of Turbulent Combustion Phenomena
Authors: Ilegbusi Olusegun J.
Published: July 2023

Flow characteristics of turbulent combustion in premixed ducted flames are investigated with a two-fluid model. The fluids are defined as the cold premixed, unburned mixture and the hot burned gas mixture. The model involves solution of separate transport equations for zone-averaged variables of each fluid with allowance for interface transfer of mass, momentum and energy. Combustion is assumed to be controlled by the turbulence transport and a simple Arhenius type of chemical reaction model has been employed. The fragment size which affects interfluid transfer terms and the transport properties is deduced from a transport equation that accounts for growth by entrainment and diminution by shear distortion. The growth and diminution constants of the length-scale equation are parametrically established. Predictions generally agree well with the experimental data. Effects of inlet flow rate and aspect ratio are also investigated.
Heat Transfer in Internal Turbulent Flows Using the PDF Method
Authors: Mazumder Sandip , Modest Michael F.
Published: July 2023

One of the strengths of the velocity-composition joint probability density function (PDF) method lies in its ability to predict scalar fields for reactive turbulent flows. The application of PDF methods to internal flows necessitates appropriate description of near-wall effects, namely, molecular transport, production of turbulence by inhomogeneities, and dissipation of the scalar fluctuations by viscosity. A Lagrangian transport equation has been derived for transport of energy, whereby convection is treated exactly. The temperature fluctuations are modeled by a modified version of a deterministic model, which was originally developed for homogeneous turbulence. The thermal wall-functions were used to incorporate these modifications. The resultant modeled Lagrangian energy transport equation is solved simultaneously with the hydrodynamic equations, for the test case of a thermally developing two-dimensional channel flow (parallel plate geometry). The model has been tested for both constant temperature and constant heat flux boundary conditions. Results obtained have been compared to k-ϵ and algebraic Reynolds stress model (ARSM) finite-volume calculations. Apart from the differences due to turbulence models, it was observed that the finite-volume calculations suffered numerical diffusion, which was completely eliminated in the Lagrangian PDF approach.
A Comparative Study on a Non-Linear Turbulent Heat Transfer Model for Separating and Reattaching Flows
Authors: Jia Shaobo , Chung Benjamin T. F.
Published: July 2023

Based on a previously proposed non-linear turbulence model, a turbulent heat transfer model is formulated in the present study using the concept of Generalized Gradient Diffusion (GGD) hypothesis. Under this hypothesis, an anisotropic thermal diffusivity can be obtained through the proposed non-linear turbulent model which is applied to the turbulent flow and heat transfer in a sudden expansion pipe with a constant heat flux through the pipe wall. The numerical results are compared with the available experimental data for both turbulent and thermal quantities, with an emphasis on the non-linear heat transfer predictions. The improved results are obtained for the bulk temperature distribution showing that the present non-linear heat transfer model is capable of predicting the anisotropic turbulent heat transfer for the pipe expansion flow. Some limits of the proposed model are also identified and discussed.
A Non-Boussinesq Model of Mixing in a 2-D Closed Cavity
Authors: Ilegbusi Olusegun J. , Mat Mahmut D.
Published: July 2023

Mixing of fluids inside a cavity under isothermal and non-isothermal conditions is studied with a two-fluid model. This model involves the solution of separate transport equations for zone-averaged variables of each fluid with allowance for interface transport of momentum and energy. The effects of solutal Grashof number, thermal Grashof number, buoyancy ratio and Prandtl number on the flow field, interface behavior and temporal evolution are considered. The calculations are performed over the parameter range: 1 ≤ Grs ≤ 3.7 × 105, 0 ≤ GrT ≤ 7.4 × 106, 0 ≤ N ≤ ∝ and 1 ≤ Pr ≤ 1000. The material interface is represented by the contour of volume fraction separating the fluids. Solutal buoyancy predominates over thermal buoyancy for comparable Grashof numbers. The system exhibits asymmetric behavior at low buoyancy ratio and low Prandtl number.
Melting Characteristics of a Vertical Ice Layer Immersed in Immiscible Liquid
Authors: Yamada M. , Fukusako S. , Sayed M. Eman-Bellah
Published: July 2023

Melting of a vertical ice layer immersed in immiscible liquid has been investigated experimentally to determine the interaction of melt flow based on ice melting and free convection induced by buoyancy in the liquid. Oil, which was contained in a rectangular vessel, was utilized as a testing liquid. During the melting process the solid-liquid interface behavior as well as the ambient liquid flow patterns were extensively observed. Three distinct flow regimes were identified for the ambient liquid temperatures of 7.6 to 30.0°C covered. Photographs of flow regimes are presented, and dependence of the flow structure on the melting morphology is discussed. The local/average heat transfer coefficient at the melting interface and the melt fraction were determined as a function of the ambient liquid temperature as well as melting time.
Genetic Algorithm Tracking Technique for Particle Image Velocimetry and Comparison With Other Tracking Models
Authors: Yoon Churl , Hassan Yassin A. , Ortiz-Villafuerte Javier , Schmidl William D.
Published: July 2023

Particle Image Velocimetry (PIV) is a non-intrusive measurement technique, which can be used to study the structure of various fluid flows. PIV is a very efficient measurement technique since it can obtain both qualitative and quantitative spatial information about the flow field being studied. This information can be further processed into information such as vorticity and pathlines. Other flow measurement techniques (Laser Doppler Velocimetry, Hot Wire Anemometry, etc..) only provide quantitative information at a single point.

A study on the performance of the Sub-Grid Genetic Tracking Algorithm for use in Particle Image Velocimetry was performed. A comparison with other tracking routines as the Cross Correlation, Spring Model and Neural Network tracking techniques was conducted. All four algorithms were used to track the synthetic data, and the results are compared with those obtained from a Large Eddy Simulation computational fluid dynamics program. The simulated vectors were compared with the results from the four tracking techniques, to determine the yield and reliability of each tracking algorithm.
Modeling of Two-Phase Flow Instabilites During Startup Transients Utilizing RAMONA-4B Methodology
Authors: Paniagua J. C. , Rohatgi U. S. , Prasad V.
Published: July 2023

RAM0NA-4B code is currently under development for simulating thermal hydraulic instabilities that can occur in Boiling Water Reactors (BWRs) and the Simplified Boiling Water Reactor (SBWR). As one of the missions of RAMONA-4B is to simulate SBWR startup transients, where geysering or condensation-induced instability may be encountered, the code needs to be assessed for this application. This paper outlines the results of the assessments of the current version of RAMONA-4B and the modifications necessary for simulating the geysering or condensation-induced instability. The test selected for assessment are the geysering tests performed by Prof. Aritomi (1993).
Scaling of High Heat Flux Flow Boiling Flow Systems
Authors: Castrogiovanni Anthony , Sforza Pasquale M.
Published: July 2023

The scaling of high heat flux boiling flow systems is examined using a computational technique newly developed by the present authors. The current work is an extension of our previously reported two-dimensional scaling technique to include flow development along the axis of a cooling channel. The new approach involves the solution of the energy equation for a pipe flow subjected to a step change in wall heat flux assuming a fully developed turbulent velocity profile at the point of initial heating. A boiling-induced turbulent eddy diffusivity term is used with an adaptive genetic algorithm closure scheme to predict both the transition to, and development of, the partial nucleate boiling regime based on a postulated minimization of the local wall temperature. Examination of the constitutive equations in non-dimensional form in conjunction with the use of previously established fluid-property scaling tools, leads to the development of a scaling procedure. Reasonable similarity between a high heat flux boiling flow system utilizing water, and a lower heat flux boiling flow system using R-12 is demonstrated. A numerical experiment is carried out to illustrate the scaling technique.
Conjugate Thermal and Hydrodynamic Analyses of Saturated Film Boiling From a Horizontal Surface
Authors: Banerjee D. , Son G. , Dhir V. K.
Published: July 2023

Film boiling is characterized by the existence of a continuous vapor layer between a heated solid surface and a liquid layer. The evolution of the vapor-liquid interface during film boiling on a horizontal surface is determined by Rayleigh-Taylor instability. To predict the heat transfer rates in film boiling, many studies have been reported in literature. Early attempts to model this phenomenon had used semi-empirical correlations. Recent work on simulation of the evolution of vapor-liquid interface without assuming any empirical vapor-liquid interface shape and by assuming the solid surface temperature to be constant has shown that the convective heat transfer coefficients, associated with the interface, vary both spatially and temporally. Consequently, the assumption of constant solid surface temperature in film boiling is not strictly valid.

In this work, saturated film boiling on a horizontal surface is simulated numerically. Finite difference method is used to simultaneously solve the equations governing conservation of mass, momentum and energy in the vapor and liquid layers. The equations for the two fluid phases are coupled through matching of normal and tangential stresses and continuity of mass and energy at the liquid vapor interface. Second order projection method is used along with numerical grid generation to construct a grid system which is aligned with the vapor-liquid interface. The heat conduction equation is solved separately in the solid, to obtain the wall temperature.

The results show that for most surfaces little coupling takes place between thermal response of the solid substrate and hydrodynamics of evolution of the interface. However, for thin plate heaters of relatively low thermal conductivity materials, the thermal response of the solid can significantly affect the hydrodynamics of the interface and in turn the local heat transfer.
Void Fraction Fluctuations in Two-Phase Flow at 1-G and μ-G
Authors: Elkow Kenneth J. , Rezkallah Kamiel S.
Published: July 2023

Void fraction measurements for adiabatic, two-phase vertical upward, water-air flow in a 9.53 mm ID tube were obtained using a helical wound capacitance sensor. Comparisons were made between 1-g and μ-g void fraction values by matching the flow rates obtained at μ-g conditions. A Probability Density Function was used to analyze the void fraction signals. It was found that a wider fluctuation in void fraction values occurred for slug flow at 1-g as compared to μ-g. For higher flow rates such as with annular flow, inertia forces become dominant. For these flows it was found that the void fraction fluctuations were similar at 1-g and μ-g conditions.
A Study of Intermittent Flow in Downward Inclined Pipes
Authors: Yang Jiede , Sarica Cem , Chen Xuanzheng , Brill James P.
Published: July 2023

The downward simultaneous flow of gas and liquid is often encountered in hilly terrain pipelines and steam injection wells. Most of the available methods for predicting the behavior of gas-liquid flow in pipes have been developed for horizontal and upward inclined pipes. In this study, co-current steady state slug flow in downward inclined pipes is investigated, experimentally and theoretically. A series of slug flow experiments are conducted with an air-kerosene system in a 2-in. diameter, 75-ft long pipe installed on an inclinable structure. Liquid holdup and pressure drop measurements are obtained for downward inclination angles from 0° to −90° at different flow conditions. Correlations for slug flow characteristics are obtained based on the experimental data. A mechanistic model based on a unit cell approach has been proposed for the prediction of the detailed slug structure, and subsequently the pressure gradient.

Fully developed slug flow could not be observed from −50° to −90°. A correlation was obtained for slug liquid holdup, and an analytical model and a correlation were developed for slug translational velocity. The lognormal distribution was found to best fit all the experimental slug length data. Equations for mean and design slug length were derived from the lognormal distribution function for inclination angles ranging from 0° to −30°. A slug frequency correlation was also developed.

The model can be used to predict intermittent flow behavior in downward inclined pipes. The correlations for slug liquid holdup, slug translational velocity, and slug length and frequency are closure relationships applicable to any model. Slug frequency information is also imperative for erosion and corrosion rate predictions.
Experimental Study on PORV Stuck-Open Accident in INER Integral System Test Facility
Authors: Liu T. J. , Lee C. H. , Hong W. T. , Chan Y. K. , Chang C. Y.
Published: July 2023

Four scaled small break loss-of-coolant accident (LOCA) tests simulating the pressurizer power-operated relief valve (PORV) stuck-open accidents and the recovery actions in a pressurized water reactor (PWR) were performed at the INER Integral System Test (IIST) facility. The objectives of this study are to verify the effectiveness of emergency operating procedure and emergency core cooling system on reactor safety. The break sizes were volumetrically scaled down based on one and all three fully-opened PORVs which is equivalent to 0.46% and 1.37% cold leg flow area. The experimental results indicate that in case of high pressure injection (HPI) system failure, the rapid depressurization of the steam generators is proved to be an effective way in the depressurization of the reactor coolant system and the core cooling. If the high pressure safety injection operates normally, the core cooling can be adequately provided without operating the secondary bleeding during PORV stuck-open transient.
Experimental Study of Flow Instability and CHF in a Natural Circulation System With Subcooled Boiling
Authors: Yang Rui C. , Shi De Q. , Lu Zhong Q. , Zheng Rong C. , Wang Yong
Published: July 2023

Experimental study has been performed to investigate flow instability and critical heat flux (CHF) in a natural circulation system with subcooled boiling. In the experiments three kinds of heated sections were used. Freon-12 was used as the working medium. The experiments show that which one of the two phenomena, flow instability and CHF condition, may first occur in the system depends on not only the heat input power to the heated section and the parameters of the working medium, but also the construction of the heated section. The occurrence of the flow instability mainly depends on the total heat input power to the heated section and the CHF condition is mainly caused by the local heat flux of the heated section. In the experiments two kinds of flow instability, flow instability with high frequency and flow instability with low frequency, were found. But they all belong to density wave instability. The influence of the parameters of the working medium on the onset of the flow instability and CHF condition in the system were investigated. The stability boundaries were determined through the experiments. By means of dimensional analysis of integral equations, a common correlation describing the threshold condition of onset of the flow instability was obtained.
Experimental Study of Phase Separation in Dividing Two Phase Flow
Authors: Yong Qian , Zhilin Yang , Jijun Xu
Published: July 2023

Experimental study of phase separation of air-water two phase bubbly, slug flow in the horizontal T-junction is carried out, the influences of the inlet mass quality XI, mass extraction rate G3/G1, and fraction of extracted liquid QL3/QL1 on phase separation characteristics are analyzed. For the first time, we have found and defined “Pulsating run effect” by the visual experiments, which show that under certain conditions, the down stream flow of the T-junction has strangely affected the phase redistribution of junction, and firstly point out that the downstream geometric condition is very important to the study of phase separation phenomenon of two-phase flow in T-junction.
Multi-Mode Methanol Flow Boiling Under Atmospheric and Subatmospheric Pressures
Authors: Lin W. W. , Liao Y. C. , Lee D. J.
Published: July 2023

This is a continuation work of Lin and Lee (1996 National Heat Transfer Conference, Houston) while reporting the experimental results of multi-mode methanol How boiling under atmospheric and subatmospheric pressures. An axial (discrete) heat flux distribution with neutral stability at which nucleate and film boiling can coexist steadily is identified under various system pressures and crossflow rates. Below this heat flux distribution, nucleate boiling mode is more stable. Above this distribution, film boiling becomes the more stable mode. An equal-area criterion based on the difference between bottom heat flux and surface boiling heat flux, and the wall superheat temperature relationship is employed for interpreting the experimental data. Effects of system pressure, mass flowrate, liquid subcooling and bottom heat flux on the relative stability of nucleate and film boiling modes are discussed.
Flow Patterns and Their Transitions of Vertically Downward Two-Phase Flow With High Viscosity Liquid
Authors: Wang Shu-Zhong , Lin Zong-Hu , Liang Zhi-Peng
Published: July 2023

The flow patterns and their transitions of air-oil two-phase flows in a vertically downward pipe were investigated experimentally and theoretically. The pipe diameter was 29mm, and the oil and air superficial velocity were up to 4m/s and 20m/s respectively. The flow pattern identifications were carried out by means of the combination of visual observations and analysis for corresponding pressure drop pulsation signals. The investigations express that the flow patterns and their transitions of oil and gas two-phase flow somewhat differed from those of low viscous liquid and gas two-phase flows. On the basis of this study and other previous investigations, one available approach is presented to predict the flow patterns and their transitions in vertically downward two-phase flow with high-viscosity liquid.
Drying of a Moist Porous Medium by Bulk Flow of Gas
Authors: Chen Y.-T. , Boehm R. F.
Published: July 2023

A model has been developed to describe the heat and mass transfer that occurs in the drying of a porous medium due to the bulk flow of a gas. This model is formulated in one dimension and describes the convective and evaporative phenomena that occur in an initially residually-saturated medium. Comparisons are made between the model and an experiment that resembles the modeled geometry. Temperature-versus-time and exiting-humidity-versus-time plots are given in the paper for two different thermal boundary conditions. Generally good agreement is shown between the model and experimental results. However, it is concluded that the rate of mass transfer manifest in the experiment may be greater than that represented in the model. Another artifact of the results is that there are some changes in slope in the experimental curve showing the exiting relative humidity that are not seen in the calculations. It is concluded that these may be due to non-uniform packing of the bed.
A General Governing Equation for Flow of Fluids in Porous Media
Authors: Moaveni Saeed
Published: July 2023

A general differential equation governing the motion of a fluid through porous media is formulated by applying the momentum balance to a formal control volume. The porous medium in the control volume is modeled as an assemblage bundle of hypothetical conduits through which fluid is transported across the medium. The momentum equation employed, will account for the rate of momentum influx and efflux by virtue of the bulk fluid motion in and out of control volume. This formulation will also take into consideration a net shear force acting on the surface of the control volume. The pressure forces acting on the fluid surfaces of the volume element and the resultant viscous force of the fluid acting on the interior wetted surfaces of hypothetical conduits are also included in the model. Furthermore, it is shown that equation of motion reduces to the familiar Darcy’s Law for slow flow rates; for higher velocities, it transforms into Forchheimer relationship. For non-uniform velocity fields, the governing equation yields additional cross-stream-inertia term and a drag term which do not appear in other formulations. In the absence of inertia effects, the derived equation of motion reduces to Brinkman’s findings. In addition, the individual coefficients of the expressions in the momentum equation are explicitly derived in terms of fluid properties, size characteristics of a given medium and some unknown coefficients. A procedure for extracting the unknown coefficients will also be discussed.