bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of Flow Pattern Transitions for Horizontal Two-Phase Flows
Authors: Hervieu Eric , Seleghim Paulo 
Published: January 2022

Abstract
This work concerns the development of a methodology the objective of which is to characterize and diagnose two-phase flow regime transitions. The approach is based on the fundamental assumption that a transition flow is less stationary than a flow with an established regime.
In a first time, the efforts focused on:
the design and construction of an experimental loop, allowing to reproduce the main horizontal two-phase flow patterns, in a stable and controlled way,
the design and construction of an electrical impedance probe, providing an imaged information of the spatial phase distribution in the pipe,
the systematic study of the joint time-frequency and time-scale analysis methods, which permitted to define an adequate parameter quantifying the unstationarity degree.
In a second time, in order to verify the fundamental assumption, a series of experiments were conducted, the objective of which was to demonstrate the correlation between unstationarity and regime transition. The unstationarity degree was quantified by calculating the Gabor’s transform time-frequency covariance of the impedance probe signals. Furthermore, the phenomenology of each transition was characterized by the joint moments and entropy.
The results clearly show that the regime transitions are correlated with local time-frequency covariance peaks, which demonstrates that these regime transitions are characterized by a loss of stationarity. Consequently, the time-frequency covariance constitutes an objective two-phase flow regime transition indicator.
Void Fraction Distribution Patterns of Steady Air-Water Two-Phase Flow in a Rod Bundle With a Spacer
Authors: Takenaka N. , Asano H. , Fujii T. , Yoshii K. , Matsubayashi M. 
Published: January 2022

Abstract
Void fraction distributions of a steady air-water two-phase flow in a 4 × 4 rod-bundle with circular ferrule type spacers were visualized by neutron radiography. A high flux thermal neutron radiography system at JRR-3M in Japan Atomic Energy Research Institute and a fast neutron radiography system at Yayoi reactor in the University of Tokyo were used. Thermal neutron radiography was suitable for high void fraction two-phase flow and fast neutron radiography was suitable for low void fraction two-phase flow. Visualization with high spatial resolution up to 0.1 mm was carried out by using a cooled Charge Coupled Device (CCD) camera. The Computed Tomography (CT) reconstruction was carried out to obtain three-dimensional (3-D) void fraction distributions by a filtered back projection method. Cross-sectional averaged one-dimensional (1-D) void fraction distributions were also calculated for many experimental conditions by image processing methods. The 1-D and 3-D void fraction distributions were clearly visualized by neutron radiography. The void fraction distribution patterns in the rod bundle were discussed.
Unsteady Behavior of the Adiabatic Two-Phase Flow in Parallel Vertical Channels
Authors: Jović Valerije D. , Jović Larisa A. , Afgan Naim H. 
Published: January 2022

Abstract
Unsteady behavior of two phase mixture is very complex phenomena which depending on the characteristic of the system and range of the working parameters, will appear in the form of the deformed or selfsustanable flow rate oscillations, pressure, temperature and other parameters. In this paper results of the experimental and analytical study devoted to the investigation of unsteady regimes in air-water adiabatic two phase flow in the system three parallel hydrodinamicaly not identical vertical channels are presented. The onset of oscillatory instability parallel channel two phase flow in time and complex domain is analysed. Using experimentally determined transfer function of the system the criterion’s for the determination of the linearity or nonlinearity was defined. Obtained results show that dynamic equilibrium of conservative forces in two phase system do not ensure stable flow in all its parts. For the regimes when friction forces in two phase part of the channel are dominant over the dissipation and inertial forces, appearance of the unstable pulsation of pressure drop in one, two or all three parallel channels under stable system characteristics is possible.
Auto-Regressive Modeling for Flow Pattern Characterisation
Authors: Legius Erik J. W. M. , Mudde Robert F. , Van Den Akker Harry E. A. 
Published: January 2022

Abstract
The two-phase flow of air/water has been investigated in two ‘complex’ geometries: a vertical pipe with contraction and a line/riser system with a bend. Pressure recordings and optical fiber measurements have been analysed using Auto-Regressive modeling. This type of modeling describes the data as a linear combination of previous data. It is discussed how the transition from one flow regime to an other is influenced by the flow obstructions. The Auto-Regressive modeling provides a quantitative measure of the similarity between two flow realisations. It is found that identification of flow regimes based on this measure coincides with visual observation. With the Auto-Regressive technique the width of the transition could also be quantified. Furthermore it is shown, that the upward bend stabilises the slug flow in the vertical part downstream of the bend: the transition towards churn flow is postponed.
Flow Regime Map for Two-Phase Cocurrent Downflow in a Porous Medium
Authors: Revankar Shripad T. 
Published: January 2022

Abstract
Several flow regimes exist in a gas-liquid cocurrent downflow in a packed bed (trickle bed). These are given descriptive names such as trickle, pulsing, spray and bubble. The hydrodynamic and transport properties of trickle bed are dependent on these flow regimes. The hydrodynamic modeling of gas-liquid cocurrent downflow through a packed bed based on pore scale is presented. The pore scale hydrodynamic is related to the macroscopic scale flow parameters. The two-phase flow at pore level channel is modeled similar to annular two-phase flow in tubes. Using the film instability due to shear by the gas at the pore level channel, the transition criterion for the trickle flow to pulse flow regime is obtained. The model predictions agree with the published data. A model for transition from partial wetting to complete wetting in trickling flow was presented. The model predictions are in agreement with previous models. The model indicates better wetting of the smaller size packing for the same liquid mass flux.
Symbol-Sequence Statistics for Monitoring Fluidization
Authors: Finney C. E. A. , Nguyen K. , Daw C. S. , Halow J. S. 
Published: January 2022

Abstract
We propose that data-symbolization methods derived from nonlinear dynamics and chaos theory can be useful for characterizing and monitoring patterns in fluidized-bed measurement signals. Data symbolization involves the discretization of a measurement signal into a limited set of values. In this discretized form, the measurements can be processed very efficiently to detect dynamic patterns that signify various types of physical phenomena, including bubbling, slugging, and transitions between fluidization states. Besides computational efficiency, symbolic methods are also robust when noise is present. Using various types of measurements from experimental beds, we illustrate specific examples of how symbolization can be applied to fluidization diagnostics. We also suggest directions for future research.
Attenuation of Sound Waves in Liquids With Gas Bubbles in the Presence of a Combustible Gas Component
Authors: Khabeev Nail S. , Zolovkin N. A. 
Published: January 2022

Abstract
The effect of the combustible gas component on the propagation and damping of perturbations in bubbly mixtures is analyzed. For describing the propagation of acoustic perturbations in a liquid with bubbles containing combustible gas component it is possible to employ a one-velocity, two-pressure model of the medium that takes into account the radial inertia of the liquid with change in the voulume of the medium. The liquid carrier phase is assumed to be compressible, and the changes in bubble volume are described within the framework of a spherically symmetric model using the equation of the radial pulsations of the bubble. For simplification we introduced effective viscosity for taking into account heat dissipation. It is shown considerable effect of admixtures, such as chemical energy release due to the presence of a combustible gas component, on the interphase heat exchange in gas-liquid media, as well as on the phase velocity and attenuation of sound in bubbly mixtures.
Hybrid Approach to Tomographic Reconstruction of Bubbles in Two-Phase Flows Using Genetic Algorithm
Authors: Rajesh A. , Ko H. S. , Kihm Ken D. 
Published: January 2022

Abstract
Main hurdles in the application of genetic algorithms to complex problems are two folds. One is the high computational cost due to their slow convergence rate. The other is to reduce the input parameters of a conventional genetic algorithm as in the case of tomographic reconstruction of bubbles. In our present work great strides have been made to alleviate both the problems by using a Hybrid model of Algebraic Reconstruction Technique (ART), Simplex Method and Genetic Algorithm (GA).
Transient Three-Dimensional Density Distribution Reconstructed From Limited Interferogram Images
Authors: Okamoto Koji , Tsuru Daigo 
Published: January 2022

Abstract
Measurement of three-dimensional density distributions in a transient unstable stratified flow is important for the safety analysis on the advanced type nuclear power plant. Three-dimensional density distribution can be reconstructed using computer tomography technique from interferogram images. However, in the experiment, only a few interferogram images could be taken. Conventional tomography techniques have low accuracy with the limited interferogram images, since the information of the projection is not enough for the reconstruction.
While, the transient interferogram images can be easily taken using the real-time holographic interferometer and/or Mach-Zehnder interferometer. That is, there are enough information for the temporal domain. In this study, a transient three-dimensional (4D) reconstruction technique was proposed. The four-dimensional density distribution was assumed to be expressed as the summation of Elementary Distribution Functions (EDFs). The EDFs were distributed not only in the spatial domain, but also in the temporal domain. The tomography was carried out as the optimization of the arrangement for EDFs, using the temporal projection information.
Three-Dimensional Tomography of Thermal Flows for Limited Angle of View
Authors: Likhachov Alexey V. , Pickalov Valery V. 
Published: January 2022

Abstract
The paper is devoted to the study of 3D-tomography problems of flows with the numerical simulations, when the data being measured in the narrow angle range. The algebraic algorithms and ones based on the Fourier transform properties seem to be more appropriate for the considered case. The following of them have been investigated: ART, MART, MENT, Gerchberg-Papoulis type algorithm (mGP3D), combined algorithms cART and cMART.
Application of Transient Heat Flux Sensors to Resolve Time-Dependent Convective Heat Transfer From Wall-Mounted Cubes
Authors: Meinders E. R. , Geuzebroek M. J. , Hanjalić K. , Ortega A. 
Published: January 2022

Abstract
The application of an active fast-responding heat flux sensor to time-dependent heat flux measurements was studied for two aero-dynamically interfering wall-mounted cubes. This sensor was in-house made and it consisted of a heated thin platinum film deposited on an insulating substrate of glass. The frequency response of the sensor was determined from a calibration with chopped laser beams and with responses to on forehand known periodic oscillations in the flow. The purpose of the study was to measure possible correlation between the vortex shedding, induced at the upstream cube in the tandem, and the convective heat flux from the side faces of the downstream cube. This implied that we were mainly interested in detecting possible characteristic frequencies carried by the time-dependent heat flux signal rather than determining the absolute value of the time-dependent convective heat flux. The results showed maxima in the power density spectra of the heat flux signal at frequencies which were in good agreement with the shedding frequencies found in the corresponding velocity spectra.
Evaluation of an Insert Heat Flux Gage in a Transonic Turbine Cascade
Authors: Peabody Hume L. , Diller Thomas E. 
Published: January 2022

Abstract
The effects of using an insert Heat Flux Microsensor (HFM) versus an HFM deposited directly on a turbine blade to measure heat flux in a transonic cascade are investigated. The HFM is a thin-film sensor, 6.35 mm (0.250 in.) in diameter (for an insert gage, including the housing) which measures heat flux and surface temperature. The effects of physical gage offset from the blade surface were measured with an insert HFM in the high acceleration region of the suction side of the blade. This region of high convex curvature and thin boundary layer on a 5 cm (0.197 in.) chord blade makes exact matching of the flat-faced insert sensor with the surface difficult. For comparison, an identical thin-film sensor was deposited directly onto an identical blade surface at the same location, providing a minimal surface disruption on the order of the surface roughness of the blade itself.
The average heat transfer coefficients were compared for intentional offsets of ± 0.25 mm (0.01 in.) with the baseline cases. Turbulence grids were also used to study how the offset affects the heat transfer coefficient with freestream turbulence added to the flow. At the gage location the estimated laminar boundary layer thickness was 0.10 mm (0.004 in.). Both positive and negative offsets produced a higher average heat transfer coefficient than the zero offset case. Using an insert HFM reduced the effects of freestream turbulence and resulted in a substantially higher average heat transfer coefficient relative to the directly deposited gage, even for the zero offset case. Consequently, to accurately measure heat transfer coefficients and the effects of freestream turbulence for transonic turbine blades, the disruption of the flow caused by a gage must be minimized.
Equivalency of Counter-Current Vessel Heat Transfer Formulations
Authors: Roemer Robert B. 
Published: January 2022

Abstract
Models of counter-current blood vessel heat transfer have used one of two, different, previously unreconciled formulations, based either on: 1) an average vessel wall temperature difference, or 2) a bulk mean blood temperature difference. This paper shows that these two formulations are only equivalent when the four, previously undefined, “convective heat transfer coefficients” that are used in the bulk mean temperature difference formulation (two each for the artery and vein) have very specific, problem dependent relationships to the standard convective heat transfer coefficients. These bulk mean temperature difference formulation “convective heat transfer coefficients” are shown to be either: 1) arbitrary, user defined values, or 2) specific functions of a) the tissue conduction resistances, b) the standard convective heat transfer coefficients, and c) the independently specified bulk mean arterial, bulk mean venous and tissue temperatures. Thus, they are not true convective heat transfer coefficients, and must change values dependent on the blood and tissue temperatures, a dependence which significantly limits their usefulness.
A Semi-Infinite Model of Diffusion-Limited Water Transport During Osmotic Cell Dehydration
Authors: Kasharin Alexander V. , Karlsson Jens O. M. 
Published: January 2022

Abstract
A model of diffusive mass transport in a semi-infinite binary liquid solution with a moving semipermeable membrane is developed, in order to analyze dehydration of cells during cryopreservation. An analytic solution is obtained for the water concentration near the membrane, and a characteristic time-scale for cell dehydration is identified.
Mass Transfer Performance Evaluations of an Intravenous Membrane Oxygenator
Authors: Guzmán Amador M. , Amon Cristina H. 
Published: January 2022

Abstract
The mass transfer performance of an Intravenous Membrane Oxygenator is investigated by computational simulations of the conservation of mass, momentum and species equations. The Intravenous Membrane Oxygenator (IMO), is a device developed experimentally to provide consistent and reproducible oxygen and carbon dioxide exchange. The IMO is composed by an elastic and non-permeable pulsating balloon positioned within the vena cava, and micro-porous-membrane fibers that transport oxygen and carbon dioxide, located longitudinally between the balloon and vena cava. During the operation regime, the blood flow motion is originated by a blood pressure gradient and a pulsating balloon motion. A three-dimensional physical-computational model consisting of equally-spaced fibers and a Newtonian and time-dependent incompressible flow is used for the simulations. The numerical simulation results for the stationary balloon configuration, obtained using the spectral element method, demonstrate that the flow remains parallel, laminar and with absence of secondary flows in the whole domain. Evaluations of the mass transfer characteristics and parameters, such as the oxygen concentration profile around the fiber and the Sherwood number, for increasing Reynolds numbers, indicate that the parabolic flow regime increase the oxygen transfer rate until an asymptotic limit in the oxygen transfer capability is reached. A further increase in the Reynolds number beyond this asymptotic limit does not increase the oxygen transfer rate.
Freezing of Aqueous Solutions of Glycosylated Bovine Beta-Casein
Authors: Hoke John L. , Georgiadis John G. , Jimenez-Flores Rafael 
Published: January 2022

Abstract
Genetic engineering of milk proteins allows control of their physicochemical properties in foods and dairy products during processing, storage, and consumption. Robust methods for the estimation of the quality and function of the proteins during downstream processing are sought. The focus of this study is a systematic microscopic investigation of the freezing of sub-microliter pendent droplets of buffer solution of glycosylated bovine beta-casein. The freezing and crystallization is observed with a scanning confocal microscope fitted with a stage cooled with vapor boiled off a liquid nitrogen dewar. Four liquid samples (with glycosylated bovine beta-casein concentrations of 35, 125, 500, and 1000 μg/ml) are compared against the control (10 mg/ml of wild type non-glycosylated bovine beta-casein). The freezing of similar size samples consisting of de-ionized water, ice-nucleating mixture (Pseudomonas syringae), and pure buffer solution is also examined for comparison. Higher concentrations of the engineered-beta casein result in increasing antifreeze action, corresponding to depression of the freezing point, and thermal stabilization of the supercooled liquid. This conclusion is supported by a non-parametric statistical analysis based on the Jonckheere test. A freezing point assay can thus be made to assess the quality of glyco-bovine beta-casein.
An Improved Diffusion Model for Radiative Transport in Turbid Media
Authors: Venugopalan V. , You J. S. , Tromberg B. J. 
Published: January 2022

Abstract
The diffusion approximation to the Boltzmann transport equation is commonly used to analyze data obtained from biomedical optical diagnostic techniques. Unfortunately, this approximation has significant limitations which constrains its applicability to highly scattering systems and over length scales much larger than the transport mean free path l*. Using an approach formulated independently by Prahl and Star [11, 13, 14], we present a form of the diffusion approximation which adds a delta function term to both the radiance and phase function expressions. This formulation is presented and solved for steady illumination in infinite media with a collimated source of finite size exhibiting spherical symmetry. The solution is compared to results given by standard diffusion theory and to measurements made in a strongly scattering and strongly absorbing turbid phantom with reduced single scattering albedos a’ of 0.997 and 0.248, respectively. The results show that this approach provides accurate predictions of optical dosimetry in both low and high scattering media and at positions proximal to collimated light sources.
Non-Invasive Evaluation of Biological Materials Using Pulsed Photothermal Tomography
Authors: Milner Thomas E. , Telenkov Sergey A. , Tanenbaum B. Samuel , Nelson J. Stuart , Goodman Dennis M. 
Published: January 2022

Abstract
Progress is reported on the development of pulsed photothermal tomography (PPT) for determination of the initial three-dimensional temperature increase in biological materials immediately following pulsed laser irradiation. PPT uses a fast infrared focal plane array (IR-FPA) to detect temperature rises in a substrate, induced by pulsed radiation. The temperature rise, due to the selective optical absorption of pulsed laser light, creates an increase in infrared emission that is measured by a fast IR-FPA. A tomographic reconstruction algorithm computes the initial space-dependent temperature increase in subsurface chromophores from a time sequence of recorded infrared emission images. We present tomographic reconstructed images of laser heated blood vessels in the in-vivo chick chorioallantoic membrane (CAM) model.
Defining the Quality of Indoor Air Supply Based on Dilution and Ventilation Concepts
Authors: Beyene Asfaw 
Published: January 2022

Abstract
Empty space could be ventilated continuously to keep some level of Indoor Air Quality (IAQ) in order to eliminate or minimize accumulation of pollutants, and to reduce odors in the air channels or in enclosed spaces. With the exception of some applications, such as hospital rooms where air is supplied to create a positive pressure, such an air amount that can be used for empty space ventilation can be taken as the minimum air supply that has to be provided at all times. Any additional air supply to the conditioned space is primarily for respiration purposes. This respiration amount has a minimum based on ;i per person oxygen need, and an additional amount to dilute whatever pollutants are present in the conditioned space, as defined by standards, codes, and regulatory aerosol concentration limits. This paper discusses and defines the minimum air supply, the respiration air need, and the dilution terms. It combines these terms into a basic air supply equation to serve IAQ criteria. The approach can be used as a practical guideline for the designer to calculate the total air supply needs to a conditioned space.