bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinearities due to Joint Friction and Clearance in a Structural Dynamic Test Fixture
Authors: Tinker Michael L.
Published: July 2023

Modal survey testing of the Space Station Common Module Prototype in a test fixture designed to simulate Shuttle Orbiter constraints revealed a number of sources of nonlinearities in the measured frequency response functions. First, the test fixture original design, which utilized spherical bearing joints and an airbag suspension system for offloading the test article weight, is described in detail in order to provide a basis for understanding the test data. Several experimental and analytical lowest-frequency mode shapes are compared, and differences are pointed out. One of the basic modes predicted by the finite element model was not observed at all in the experimental data. Then the measured acceleration/force frequency response functions are examined for different shaker force amplitudes and air pressure levels in the airbag offload system. It is shown that the character of the response functions, and the mode shapes and frequencies of the Common Module, varied depending on the test parameters. Static stiffness and stick-slip measurements for the fixture-to-test-article interfaces were made to provide insight into the behavior of the bearing mechanisms.

Careful examination of the experimental mode shapes, frequency responses, static stiffness curves, and bearing stick-slip data led to a determination that the spherical joint interfaces between the Common Module test article and the test fixture were not functioning as designed. Friction in some interface joints prevented relative motion between the test article and fixture that was essential for simulating Shuttle Orbiter constraints of the Common Module in its flight configuration. In other instances, clearances between the spherical bearings and the surfaces of the test article interface structures caused highly nonlinear response as a function of load at the interface. The severity of the unintended joint friction and clearances and the resulting nonlinearities made necessary a redesign of the modal test fixture in the interface regions before the flight constraints of the test article could be adequately simulated.
Interaction Dynamics Between a Flexible Rotor and an Auxiliary Clearance Bearing
Authors: Lawen James L. , Flowers George T.
Published: July 2023

This study investigates the application of synchronous interaction dynamics methodology to the design of auxiliary bearing systems. The technique is applied to a flexible rotor system and comparisons are made between the behavior predicted by this analysis method and the observed simulation response characteristics. Of particular interest is the influence of coupled shaft/bearing vibration modes on rotordynamical behavior. Experimental studies are also performed to validate the simulation results and provide insight into the expected behavior of such a system.
The Origin of the Dynamic Growth of Vapor Bubbles Associated With Vapor Explosions
Authors: Lee Ho Sung , Merte Herman
Published: July 2023

An explosive type of vapor bubble growth was observed during pool boiling experiments in microgravity using R-113, where heater surface superheats as high as 70 °C were attained at nucleation. This corresponds to approximately 65% of the computed superheat limit of the fluid, compared to the approximate 30% observed at earth gravity for the same system. Photographs and measurements of the vapor bubble growth provide evidence for rates of growth not accountable by conventional models. The photographs reveal that the liquid-vapor interface of the explosive bubbles become wrinkled and corrugated, leading to the conclusion that some type of instability mechanism is acting.

The classical hydrodynamic instability theories of Landau and Rayleigh-Taylor, used in conjunction with a model of the early growth of spherical vapor bubbles developed by the authors, predict that the early growth should be stable. These theories do not consider the effects of heat transfer at the interface, which is believed responsible for the observed instability of the evaporating surface. This was confirmed by the mechanisms proposed by Prosperetti and Plesset which, although including the effects of heat transfer, required that the unperturbed liquid temperature distribution be known at the moment of onset of the instability. This is generally unknown, so that no comparisons with experiments were possible up to this point. The present pool boiling experiments conducted in microgravity, some of which result in the explosive vapor bubble growth referred to, permit the precise determination of the unperturbed liquid temperature distribution using a model of the early vapor bubble growth along with the measurement of heater surface temperature at nucleation. The limited results to date provide good agreement with the mechanisms proposed by Prosperetti and Plesset.
Linear Stability Analysis of Thermocapillary Convection in a Liquid Bridge With Encapsulation by Inverse Iteration Algorithm
Authors: Li Minwei , Sun Zequan , Zeng Danling
Published: July 2023

Linear stability theory was applied in the present paper to analyze the stability of the basic state solution of thermocapillary convection in a liquid bridge with liquid encapsulation. Discretizing the linearized disturbance equations by using finite-difference approximation, stability analysis is evolved to a complex generalized eigenvalue problem with a complicated band structure of matrix. The influence of dimensionless parameters on the stability of the system is revealed through solving the complex generalized eigenvalue problem by inverse iteration. The results provide a theoretical and numerical foundation for crystal growth by float-zone method and for other engineering applications.
Thermal Contact Conductance of Sintered Copper Coatings on Ferro-Alloy
Authors: Marotta E. , Fletcher L. S. , Aikawa T. , Maki K. , Aoki Y.
Published: July 2023

This experimental investigation presents heretofore unpublished thermal contact conductance data of sintered powder copper disks which were hot-pressed onto a sintered powder Ferro-alloy proposed for automotive valve-seat applications. The sintered copper disk acts as an enhancement coating to decrease the surface imperfections and increase the rate of heat transfer across the valve seat/engine block interface. The experimental interface temperature was varied between 100 to 200 °C (212 to 392°F) while the interface pressure was varied between 2.5 to 25 MPa (363 to 3625 psi). These experimental parameters approximate some of the conditions (such as interface pressure) that exist at a valve seat/engine block interface of an internal combustion engine. The thermal contact conductance values for an uncoated Ferro-alloy/cast aluminum alloy interface, and for 0.2, 0.5, 1.0, and 2.0 mm sintered copper coatings were obtained over the range of interface temperatures and pressures.
Thermal Contact Conductance of a Paper/Elastomer Interface
Authors: Mohr J. W. , Seyed-Yagoobi J. , Wirtz J. W. , Price D. C.
Published: July 2023

A better understanding of the parameters associated with the heating of paper during copying and printing processes would permit more accurate design and control of the process. One parameter affecting the heat transfer from an elastomer covered roller to the paper sheet is the thermal contact conductance at the interface between the paper sheet and the roller. The main objective of this work was to measure the thermal contact conductance of an elastomer/paper sheet interface. Two types of elastomers (A and B) were considered.

The thermal contact conductance values for elastomer A varied from 217 W/m2K to 258 W/m2K within the applied pressure range of 34.5 kPa to 344.7 kPa. This pressure range is representative of the pressures encountered in typical printing and copying processes. The corresponding thermal contact conductance values for elastomer B were 803 W/m2K and 2,072 W/m2K. The thermal contact conductance values for elastomer B were significantly higher than those for elastomer B due to a combined effect of the higher thermal conductivity and more uniform surface flatness characteristics of elastomer B compared to elastomer A.
A Transient Experimental Method for the Indirect Measurement of Thermal Contact Conductance
Authors: Hook Randy C. , Clements Randy A. , Crane Roger A.
Published: July 2023

A study has been completed to illustrate the use of an experimental apparatus for the implicit measurement of transient thermal contact conductance between dissimilar metals The two metals selected for a trial evaluation are 304 stainless steel and 6061-T6 aluminum. An inverse heat transfer method is used, which employs the analytic solution for a one dimensional heat flow between dissimilar metals to calculate the contact conductance by sequential function estimation. Relevant programs for the collection and reduction of data have been developed and are available. Sample test results are presented.
Heat Flux Determination at the AWJ Cutting Zone Using IR Thermography and Inverse Heat Conduction Problem
Authors: Mohan Ram S. , Kovacevic Radovan , Beardsley Heather E.
Published: July 2023

In abrasive waterjet (AWJ) cutting, the cutting tool is a thin stream of high velocity abrasive waterjet slurry which can be considered as a moving line heat source that increases the temperature of the narrow zone along the cut kerf wall. A suitably defined inverse heat conduction problem which uses the experimentally determined temperature histories at various points in the workpiece, is adopted to determine the heat flux at the cutting zone. Temperature distribution in the workpiece and the cutting nozzle during AWJ cutting is monitored using infrared thermography. A suitable strategy for on-line monitoring of the radial and axial wear of the AWJ nozzle based on the nozzle temperature distribution is also proposed.
Thermal Stress Limits of Plates Subjected to Extremely High Heat Flux
Authors: Lienhard John H. , Napolitano Dominic S.
Published: July 2023

For heat fluxes in the range of 20 MW/m2 to 400 MW/m2, solid surfaces usually experience large thermal stresses and degradation of mechanical properties. The resulting mechanical failure of such surfaces is a primary limitation to the design of thermal systems at extremely high heat flux. This paper is an investigation of the general mechanical behavior of plates operated at extremal fluxes. Two prototypical configurations are considered. Several candidate materials are examined, accounting for the temperature dependence of thermal and mechanical properties. The elastic performance of plates at high flux is investigated and conditions for yielding are identified for various materials, mechanical restraints, and heat source distributions. Plastic behavior, which is characteristic of higher flux levels, is also examined. New material figures of merit are developed, taking account of the temperature dependence of thermal, elastic, and/or plastic properties.
Combined Heat and Mass Transfer by Natural Convection in a Saturated Thermally Stratified Porous Medium
Authors: Angirasa D. , Peterson G. P. , Pop I.
Published: July 2023

A numerical study is presented for the combined heat and mass transfer by natural convection adjacent to a vertical surface embedded in a stably thermally stratified, fluid-saturated, low porosity medium. A wide range of thermal stratification levels is considered in flows with both aiding and opposing buoyant forces. The thermal stratification was shown to have a profound influence on the heat and mass transfer rates, and the direction of flow and transport. The underlying physical phenomena are explained while providing the Nusselt and Sherwood number data.
An Experimental and Numerical Study of Natural Convection From a Horizontal Cylinder With Longitudinal Baffles
Authors: Facas George N. , Zhang Yan , Brown Harry L. , Ruff Gary A.
Published: July 2023

Laminar natural convection over an isothermal horizontal cylinder with multiple longitudinal baffles has been experimentally and numerically studied. The effect of multiple longitudinal baffles on the heat transfer, in terms of the Nusselt number, has been established over the range 2 × 104 ≤ Ra ≤ 8 × 104. The numerical results are in excellent agreement with the experimental data. For the cases considered in this study, both the experimental and numerical results show that the heat lost from a horizontal cylinder can be reduced by 30% when six baffles are used. The energy savings are about 10% when two baffles are used.
Measurements of Turbulent Natural Convection Flow Over a Vertical Backward-Facing Step
Authors: Abu-Mulaweh H. I. , Armaly B. F. , Chen T. S.
Published: July 2023

Measurements of turbulent natural convection boundary-layer air flow over a two dimensional, vertical backward-facing step are reported. The upstream and downstream walls of the step were heated to a constant and uniform temperature, while the step is kept adiabatic. The experiment was carried out for a step height of 22 mm and a temperature difference ΔT = 30°C between the heated walls and the ambient air. Laser-Doppler velocimeter and cold wire anemometer were used, respectively, to measure simultaneously the mean turbulent velocity and temperature distributions and their turbulent fluctuations. Measurements of the mean velocities and temperature distributions along with the distributions for turbulent intensities, turbulent heat fluxes, and Reynold stress are presented at various axial locations upstream and downstream of the step. These detailed measurements can serve as benchmark data for testing the accuracy of turbulence models in predicting numerically the flow and heat transfer characteristics in this geometry and flow conditions.
Air Cooling of a Vented Enclosure by Combined Conduction, Natural Convection and Radiation
Authors: Yu Enchao , Joshi Yogendra K.
Published: July 2023

A three-dimensional investigation of combined conduction, natural convection and radiation in vented enclosures is carried out. A discrete flush type heat source mounted on a vertical substrate is used to simulate an electronic component. A uniform volumetric generation rate is assumed within the heat source. Combined natural convection in the air, conduction in the heat source, the substrate and the enclosure walls, and surface radiation are solved for Rayleigh numbers at 2.6 × 106 and 2.0 × 107. Radiation is incorporated based on the radiosity/irradiation approach. The resulting flow and temperature patterns are discussed, focusing on radiation and three-dimensional effects. The relative contributions of natural convection and radiation are investigated for different emissivities of internal surface of the substrate. Heat transfer rates from the substrate and other internal walls are presented to illustrate conjugate heat transfer due to combined modes. The numerical solutions are found in reasonably good agreement with the experimental data.
Experimental Studies of Interfacial Area in a Horizontal Slug Flow
Authors: Riznic Jovica R. , Lewis Steven P. , Kojasoy Gunol
Published: July 2023

The internal flow structure of horizontal slug flow has been experimentally investigated by measuring the local interfacial area concentration, void fraction and interfacial velocity distribution. The four-sensor electroresistivity probe was used to detect the instantaneous interface velocities and interfacial area. Experimental studies were performed on the plug/slug flow regimes with an air-water system. Data were acquired at the axial location of L/D = 253 from the mixing chamber. Four different liquid flow rates in combination with five different gas injection rates were studied. The superficial liquid velocity was varied between 0.55 and 2.20 m/s and gas velocity between 0.27 and 2.20 m/s. With these experimental conditions, the total void fraction, including contributions from small and large slug bubbles, ranged from 10 to 70%. The void fraction measurements were checked against the raw signal data, high speed video recordings, and measurements obtained by the hot film anemometer probe. The agreement between the data was very good, confirming that the four-sensor probe measurements can be performed with a high degree of confidence. In the region of transition between plug and slug flow regime, with an increase in the gas flow rate, the number and contribution of the small follow-up bubbles increased. The increase in the liquid flow rate produced similar effects. The slug bubble frequency also increased with an increase in the gas velocity and also slugs are longer at higher gas flow rates.

Total interfacial area concentration profile includes the contribution from both slugs and small follow-up bubbles. Experimental data showed higher interfacial area concentration in the lower part of a slug bubble, with a larger curvature of interface. This is expected, since along the steeper curvature a ratio of local surface area to volume is increasing. Radial profiles of interfacial area concentration for slug bubbles show almost a flat profile in the upper part of slug bubble. The larger values of the total interfacial area concentration indicates that the contribution from the small bubbles is increasing. Experiments showed that in the plug/slug flow regime, contribution from the increasing number of small bubbles to the interfacial area concentration is substantial in upper part of the horizontal channel.
Water-Droplet Cooling Process in a Steam-Turbine Bypass Flow
Authors: Amano R. S. , Draxler G. R. , Golembiewski J. M.
Published: July 2023

This paper presents a study of the numerical simulations of a steam flow and heat transfer behavior when subjected to a cooling water spray in the pipe downstream from a high-pressure turbine bypass valve. The structure of a cooling water spray injected into a steam flow was studied for the purpose of developing a physical model to investigate the dissipation and evaporation processes of the cooling water droplets in a high temperature, high turbulent steam flow passage. Heat transfer rates were calculated for a better understanding of the temperature variations in the entire system. A dispersed two-phase model was incorporated for the particle tracking of the droplets injected into the steam flow and the water evaporation process was observed. Further, this study was continued by installing a perforated plate in the pipe section downstream from the water cooling injections. The results of the calculations are quite reasonable, and show a physically sound state.
Local, Instantaneous Heat Transfer in Pulse-Stabilized Fluidization
Authors: Pence Deborah V. , Beasley Donald E.
Published: July 2023

The Pulsed Atmospheric Fluidized Bed Combustor (PAFBC), a hybrid combustor concept that couples a pulsed combustor with an atmospheric bubbling fluidized bed, has technical advantages in energy efficiency and emissions. The present study examines the effect of an opposing oscillatory flow on the local, instantaneous heat transfer in a laboratory scale bubbling gas-fluidized bed. This opposing secondary flow consisted of a steady mean component and an oscillating component thereby modeling the flow in the tailpipe of a pulsed combustor.

Spectral and contact time analyses of local, instantaneous heat flux measurements from a heated, submerged horizontal cylinder clearly indicate that the bed hydrodynamics were significantly altered by the opposing secondary flow. These heat flux measurements were accomplished by employing an isothermal platinum film heat flux gage. For the present investigation, data were acquired for a monodisperse distribution of particles with a mean diameter of 345 μm and total fluidization ratios ranging from 1.1 through 2.7.

Heat transfer observed under conditions of secondary flows with a superimposed waveform exhibit characteristics of globally dominated, as opposed to locally dominated, hydrodynamics. For low primary and secondary flow rates and a forcing frequency of 5 Hz, a substantial enhancement in heat transfer was observed. Increases in the bubble phase and emulsion phase heat transfer coefficients were identified as the primary contributors to the observed increases in time-averaged local heat transfer coefficients.
Combined Concentration and Temperature-Induced Marangoni Convection in a Binary Mixture
Authors: Suzuki Yuji , Noguchi Suguru , Longtin Jon P. , Hijikata Kunio
Published: July 2023

In binary and multi-component mixtures, surface-tension-driven flow, i.e., Marangoni convection, can arise from both concentration and temperature gradients at the liquid surface. Depending on the liquids, concentration effects can complement or oppose temperature effects, which is important for many areas of engineering interest, e.g., mixing, solidification, evaporation, and drying. This work experimentally investigates combined temperature and concentration-induced Marangoni convection for an ethanol-water binary mixture in an enclosed cell with heated and cooled walls. Velocity profiles are obtained using a photochromic dye technique, and concentration variation at the liquid surface is measured using an interferometric technique. The results indicate that concentration effects dominate at 50/50 and 80/20 ethanol-water volume percent mixtures, resulting in a large surface velocity in the opposite direction to the bulk flow. Concentration effects can be arrested by exposing the free liquid surface to non-condensable gas at atmospheric pressure.
Critical Heat Flux During Subcooled Flow Boiling in Narrow Rectangular Channels
Authors: Nakajima Ryo , Ramanujapu Naresh K. , Dhir Vijay K.
Published: July 2023

The critical heat flux during subcooled flow boiling in narrow one-side heated rectangular channels was investigated experimentally using fluorinert liquid PF-5060 as a coolant. Three channel widths were examined, that is 1.3mm, 2.0mm, and 3.0mm. The heating surface was 10mm wide and 200mm long and only vertical upflow was experimented. Experiments were conducted at nearly atmospheric pressure under the following conditions: subcooled coolant mass velocity 2000–5000 kg/m2s; inlet temperature 24–47 °C; exit pressure 1.0–1.4 bar; equilibrium quality at channel exit −0.58 to −0.28.

Critical heat flux under the above experimental conditions was found to increase with increase in mass velocity, with decrease in the channel width, and with increase in the inlet subcooling. Visual observations showed that bubbles were small and had diameter less than 100μm. A comparison of the data with correlations reported in the literature showed that the correlations generally tended to overpredict the data. The correlations also do not show a proper trend with respect to the effect of channel width on critical heat flux. A new correlation based on dimensional analysis has been proposed. The correlation proposed can predict experimental data within 20% uncertainty.
Phase Distribution Measurements in Liquid-Liquid Pipeline Flows Using an Impedance Probe
Authors: Angeli Panagiota , Hewitt Geoffrey F.
Published: July 2023

A high frequency impedance probe was used for volume fraction distribution measurements and flow pattern identification in oil-water flow. The signal processing technique was based on a method by van der Welle (1985) that attributes to the beginning of the signal rise or fall the contact of the interface with the probe tip. The experiments were performed in two 1 inch nominal bore horizontal test sections made from stainless steel and acrylic resin. Measurements were made for mixture velocities from 1.3 m/s to 1.7 m/s and input oil volume fractions from 25% to 85%. Under these conditions different complex flow patterns exist, whose discrimination with visual observation is difficult. The results revealed that the mixing of the liquid phases is much greater in the rougher steel pipe than in the acrylic pipe under the same conditions and also helped to clearly identify the three layer, the stratified mixed and the fully mixed flow patterns.
On Some Approach for the Problem of Heat Transfer in Bubbly Liquids
Authors: Khabeev Nail S.
Published: July 2023

Transfer processes in a multiphase flows are determined by the distributions of microparameters near inhomogeneties. For an analysis not to be too complicated, one has to make use the models that could considerably simplify the microprocess equations. The simplest is two-temperature model, but the main problem is to determine the effective value of heat transfer coefficients that would be valid for a certain class of process. It seems natural that the effective heat transfer coefficients be selected from the condition that these should ensure the same heat dissipation as that of the exact solution for the problem of heat exchange between single bubble and liquid. In the present work the propagation of small perturbations in liquid with vapor bubbles has been studied on the basis of this approximate approach for the heat transfer problem in bubbly liquids. The results of calculations are in good agreement with the solutions, obtained by using much more complicated models.
Waves and Instabilities in Inclined Gas-Liquid Pipe Flow
Authors: Grolman Eric , Fortuin Jan M. H.
Published: July 2023

The Modified Apparent Rough Surface (MARS) model (Grolman et al., 1996) successfully predicts liquid holdup and pressure gradient for wavy gas-liquid pipe flow in slightly inclined pipes, up to the transition to slug (intermittent) flow. Additional equations are used to predict the transition from wavy-to-intermittent flow and for the velocity of waves on the gas-liquid interface.

In this paper, Linear (stability) Theory is compared with the MARS model, on the basis of measurements in horizontal and slightly inclined (0° ⩽ β ⩽ 6°) pipes. Viscous terms in the linear analysis require estimates of shear stresses. Using the MARS model for the interfacial and liquid-to-wall friction factors, stability can be predicted to within reasonable degree of accuracy. Credible wave velocities are also obtained, provided the interfacial waves are not assumed to be marginally stable.

Earlier semi-theoretical equations (MARS model) still provide better estimates of both stability and wave velocity and are much easier to handle than Linear Theory. However, the use of good friction factor equations, i.e. those capable of predicting liquid holdup and pressure gradient, has significantly improved the results obtained with Linear Theory. This opens the way to further studies into the mechanisms determining the velocity, growth and instability of waves in gas-liquid pipe flow.
A Universal Bubble-Growth Equation for Pure Liquids and Binary Solutions With a Non-Volatile Solute
Authors: Miyatake Osamu , Tanaka Itsuo , Lior Noam
Published: July 2023

A simple equation suitable for predicting the growth rate of a vapor bubble in uniformly-superheated pure liquids and in binary solutions with a non-volatile solute was developed. The equation also improves on the popular pure-liquid bubble growth expression of Mikić et al. (1970) in that it is valid throughout the bubble growth history, i. e. in the surface-tension-, inertia-, and heat-transfer-controlled regimes, it accounts for bubble growth acceleration effects, and uses correctly-related and variable fluid properties. It was found to agree very well with experimental data for pure water and for aqueous NaCl solutions As the bubble growth in superheated solutions with a non-volatile solute was found to be quite insensitive to diffusion and non-equilibrium effects in a broad range of common solution properties, this equation is likely to be universally valid for many liquids and solutions.
Analysis of Freezing in an Eccentric Annulus
Authors: Zhang Yuwen , Faghri Amir
Published: July 2023

Freezing in an eccentric annulus is investigated numerically by using a temperature transforming model. Since the effect of the heat conduction along the circular direction on the growth of the freezing layer is very small, an analytical solution by employing integral approximate method is proposed. The freezing rate obtained by the analytical solution agreed very well with that of the numerical solution, although the analytical solution is much simpler than the numerical solution. The effects of the eccentric annulus geometric structure on the freezing process is also investigated.
Finite Element Analysis of a Biaxially Loaded Woven Fabric Composite Laminate With a Central Hole
Authors: Kelkar Ajit D. , Chaphalkar Pramod , Sankar J.
Published: July 2023

Textile composites are structural materials reinforced by a network of fibers and are formed by processes such as braiding, weaving, or knitting. Woven fabric composites are two dimensional constructions where the warp and fill fiber tows are woven into each other to form a layer. The layers are impregnated, stacked in predetermined orientations and cured to obtain composite laminates. The composite laminates thus formed have good properties in mutually orthogonal directions as well as more balanced properties and better impact resistance than the unidirectional laminates.

Woven fabric laminated composites are likely to play a key role in modern design, principally owing to their attractive strength to weight and stiffness ratios. To compete effectively with other materials, these woven fabric laminates are often utilized in plate form with cutouts in them. Analytical models that predict the moduli, Poisson’s ratios from the weave architecture and the properties of the constituents are desirable. In this paper, a plain weave model is presented to develop the constitutive relationships (i.e., A, B and D matrices). The results from the plain weave model are used in conjunction with the classical laminate theory and linear finite element model of a woven fabric laminate to predict the stress concentration around a central hole. A graphite/epoxy material system was used. The woven fabric plies were assumed to be of constant thickness and were arranged symmetrically about the mid plane. In addition to woven fabric plies, regular unidirectional plies were also stacked at different angle orientation. The square plate with a hole was then subjected to biaxial in-plane loading. The stress concentration factors were determined by computing the ratio of stresses around the hole to those without hole at the same location.
Reliability of Welded Joints With Short Fatigue Cracks
Authors: Lanning David B. , Shen M.-H. Herman
Published: July 2023

This study investigates the reliability of a cracked welded T-joint typically found in offshore structures. In the initial stages of crack propagation, when the crack is very small, propagation rates have been found to vary from those determined using traditional linear elastic fracture mechanics, possibly resulting in significant differences in the predicted lifetime of a structure. This effect is shown in a reliability analysis that uses measurements of crack closure tests performed by other workers to predict the lifetime of a welded T-joint with a surface crack located at the toe of the weld. The reliability in terms of fatigue lifetime is calculated using Paris’ crack propagation equation based upon an effective stress intensity factor calculated with Newman and Raju’s formulation for a cracked flat plate and modified with a weld magnification factor. The obtained reliabilities are then compared to those found without short crack considerations.
Implications of Anisotropy and Structural Couplings on Dynamics and Instability of Spinning Thin-Walled Beams
Authors: Song Ohseop , Librescu Liviu
Published: July 2023

The problem of the mathematical modeling of anisotropic beams rotating with constant angular speed about the longitudinal body-axis fixed in the inertial space is addressed. The analysis is conducted in the context of thin-walled anisotropic composite beam theory which incorporates a number of non-classical effects. Among them there are the transverse shear, as well as primary and secondary warping effects. Special attention is paid to the influence played by anisotropy of constituent materials, boundary conditions and spinning speed on forward and backward precession frequencies and on instability speed. A number of applications involving both axisymmetric and doubly symmetric cross-section beams are presented and pertinent conclusions are outlined.
Investigation of Seismic Response for a Quarter Scale Reactor Containment Model
Authors: Jang Young-Sun
Published: July 2023

The effect of soil-structure interaction is an ongoing subject of experimental and numerical studies, since the seismic responses of structures play an important role in design of nuclear power plants. As a result, a quarter scale model of a pressurized-water reactor building was constructed by an international research consortium Hualien, Taiwan. This region of Taiwan is a seismically active area. In this study, the seismic responses due to an earthquake of magnitude 5.6 which occurred on January 20, 1994 have been used for comparison with numerical results. The sub-structure method and the hybrid method are adopted to analyze the structural responses, and we investigate the differences between numerical results of the two methods in detail.
ASME/US Bureau of Mines Investigative Program on Vitrification of Combustion ASH/Residue: Findings and Conclusions
Authors: Hollander Herbert I. , Decesare Roger S. , Hoecke David A. , Plumley Arthur L.
Published: July 2023

Vitrification of the residues from thermal processes into a dense, grainless, amorphous, glasslike material may provide an opportunity to permanently relieve our concerns regarding aquifer contamination and ... if the vitrified products are utilized, conserves those land areas which are suitable for disposal for those discards for which we have not as yet found a practical use.

This discussion briefly describes and illustrates the implementation of the $1.2 million ASME/U.S. Bureau of Mines (BuMines) investigative program. The discussion will cover the scope and methods followed, equipment systems employed, and areas of investigation, as well as findings and conclusions in determining the potential effectiveness of sequentially vitrifying significant quantities of ash/residue from (a) three different types of mass burning municipal solid waste energy recovery facilities, (b) a regional wastewater treatment plant sludge combustor, and (c) air quality control products from a large energy recovery facility that burned refuse-derived-fuel while utilizing a fraction of the electric energy recovered. The project also identified potential beneficial applications for the resulting products, the environmental implications and projected overall economics.
Investigation of Remediation of Soil Contaminated With Diesel Fuel Using Air Venting
Authors: Fotinich Artemiy , Joo Youngcheol , Dhir Vijay K.
Published: July 2023

Soil venting is an effective and widely used method to remediate hydrocarbonically contaminated soils. A non-isothermal model, proposed by Lingineni and Dhir (1992) to predict evaporation rates of organic contaminants in an unsaturated non-sorbing soil, was incorporated into a computer code capable of numerically analyzing multi-component diesel fuel. The program accounts for 14 major components of diesel fuel as well as for temperature variation due to evaporation of the contaminant, preheating of the venting air, and heat loss. Experiments to verify the model performance were conducted in a one-dimensional column. Temperature readings from thermocouples located in the test section were recorded during the experiment and the composition of hydrocarbons in the effluent air was also monitored. The effluent gas samples were extracted at the selected times and analyzed with the help of a gas chromatograph.

The experimental temperature readings and vapor composition in the extracted samples are in general agreement with the predictions from the computer program. The results show that the diesel components are removed according to their volatility with the higher volatility components being removed first. It is also found that preheating of the venting air can significantly increase the removal rates of the components.
Chaotic Fluctuations of Soot Particles in Turbulent Diffusion Flames: Experimental Data and Logistic Map Models
Authors: Mengüç M. P. , McDonough J. M. , Manickavasagam S. , Mukerji S. , Swabb S. , Ghosal S.
Published: July 2023

In this paper, we discuss an experimental and theoretical methodology to characterize soot volume fraction fluctuations in turbulent diffusion flames. The approach is based on the hypothesis that the fluctuations of properties in turbulent flames are deterministic in nature, rather than statistical. Experiments are conducted to measure the scattered light signals from fluctuating soot particles along the axis of an ethylene-air diffusion flame. Using these time series data, the corresponding power spectra and delay maps are determined. The results indicate a period doubling sequence, suggesting a route to chaos. The psds from experiments are modeled using a series of logistic maps. These logistic maps can be used in simulation of the fluctuations in these type of flames, without extensive computational effort or sacrifice of physical detail. Availability of accurate models of these kinds allows investigation of radiation-turbulence interactions at a more fundamental level than previously possible.
Enhancing Burner Diagnostics and Control With Chaos-Based Signal Analysis Techniques
Authors: Fuller Timothy A. , Flynn Thomas J. , Daw C. Stuart
Published: July 2023

Driven by economic pressures and government emissions regulations, the electric power industry is moving toward tighter control of boilers to improve plant efficiency and reduce emissions. Tighter control depends on better diagnostic tools that discriminate short-time-scale flame patterns and correlations between those flame patterns and overall performance. Our research indicates that improved discrimination of short-time-scale patterns in boilers can be achieved by combining traditional data analysis techniques and chaotic time series analysis. Suggested analysis tools and data acquisition procedures are described, along with example results for measurements from a low-NOx pulverized coal combustor.
Dynamic Stress Behavior in Catalytic Combustors
Authors: Boehman André L. , Simons Jeffrey W. , Niksa Stephen J. , McCarty Jon G.
Published: July 2023

Dynamic stress behavior during catalytic combustion of methane has been simulated under transient warm-up, cool-down and cyclic conditions. The numerical model combines a two-dimensional solution to the transport equations, solution of an energy balance on the monolith wall, and the NIKE3D structural analysis code to predict thermal stresses. The model also includes a detailed heterogeneous kinetics model for a proprietary palladium oxide (PdO) catalyst, but the model ignores gas phase reactions. Results illustrate that thermal stresses as high as 630 MPa can form during transient operating modes, which risks structural failure of the ceramic monolith. The maximum computed thermal stress concentrations occur near the inlet of the monolith. Peak transverse stresses (which act to form axial cracks) typically form near the inlet and centerline of the monolith structure, while peak axial stresses form near the edges of the flat plate that represents the monolith structure. Increasing the preheat temperature of the incoming fuel and air mixture lessens the peak thermal stress. To a first approximation, the magnitude of the peak transverse stress during any transient cycle considered with our model can be estimated from the maximum value of the gradient in the computed temperature profiles.
NOx Formation and Control in Radiatively/Conductively-Stabilized Pulverized Coal Combustors: A Numerical Analysis
Authors: Kim Changsik , Lior Noam
Published: July 2023

In an attempt to study ways for reducing NOx emissions from radiatively/conductively stabilized combustors (RCSC) for pulverized coal, a comprehensive conjugate heat&mass transfer and reaction kinetics model of that combustor was developed. As compared with a simple three-reaction model, the radiation intensity distribution obtained by a more comprehensive one shows a substantial decrease in the flame region. The effect of a 10% deviation in the diffusion coefficients on the results was found to be negligible, indicating that the use of binary coefficients instead of those for a multi-component system may be good enough in such combustion modeling. Flame location was found to have little effect (∼6%) and internal wall emittance an insignificant effect, on NO emissions. However, it was found that these emissions could be lowered significantly by lowering the flame temperature, accomplished by increasing the excess air ratio.
Dynamic Characterization of Smart Structures for Active Vibration Control Applications
Authors: Wilson D. G. , Searle I. , Ikegami R. , Starr G. P.
Published: July 2023

The purpose of this paper is to report on the stages required to develop smart structures for active vibration control for application to lightweight robots. The authors have designed, analyzed, fabricated, and tested several prototype smart structures. The structures were developed using graphite/epoxy material with embedded piezoceramic patches for both actuation and sensing. Finite element models were used to predict the dynamic characteristics of these composite beams. A series of tests were performed to confirm the static and dynamic characteristics of the smart structures for active vibration control applications.
Micromechanical Modeling of Material Damping in Coated Fiber Polymer Composites
Authors: Cartian Ioana , Gibson Ronald F.
Published: July 2023

The major objectives of this paper are to describe preliminary results from a systematic analytical study of the improvement of damping in polymer composites at the micromechanical level by the use of special fiber coatings. Since shear deformation is essential for viscoelastic damping in polymers, and large shear strains are generated near the fiber/matrix interface in composites, it is believed that the use of special viscoelastic polymer fiber coatings will be an effective way to improve damping in such composites. The analysis was carried out by developing finite element, theory of elasticity, and mechanics of materials models. A strain energy approach was implemented in both the finite element and theory of elasticity formulations to analyze the damping in the coated fiber composites. The models, based on a “representative volume element” or repeating element of a continuously reinforced fiber composite, are used to study damping and stiffness under longitudinal normal (LN), transverse normal (TN), transverse shear (TS) and longitudinal shear (LS) loading. Of particular interest are hybrid composites having a mixture of coated and uncoated fibers, since coating all the fibers would cause unacceptable reductions in other important properties like strength and stiffness. In order to analyze hybrid composites, two and three dimensional multi-cell finite element models have been developed. Parametric studies were done with particular emphasis on the effect of fiber coating thickness and coating volume fraction in order to improve the damping of the composite structure. Large shear strain deformations occur in the fiber coating material since the stiffness of the coating material is lower than that of the fiber or the matrix. This condition leads to improved damping in the coated fiber reinforced composite. A rapid increase in damping with increasing coating volume fraction was found for the cases of TN, TS, and LS loading. For the case of LN loading, damping does not change much with increasing coating volume fraction. Good agreement for the damping and stiffness results was obtained by using the finite element, elasticity, and mechanics of materials formulations.
Mathematical Model and Calculation Method of Thermodynamic Characteristics in the Flow of Chemically Reactive and Inert Rheologically Complex Media
Authors: Nazmeev Yuri G.
Published: July 2023

The paper presents a mathematical model and a method of calculation of diskrete values of thermodynamic characteristics in a flow of Theologically complex liquids. Our approach is based on the solution of a conjugate set of non-linear differetial equations in therms of partial derivatives of a second order. The mathematical model comprises: a set of equations of motion and continuity; a set of equations of heat and mass transfer a rheological equation of medium state; a macrokinetic model of chemical reaction; the residence time function and the molecular-mass distribution obtained with its help as well as a set of equations to calculate chemical and thermal exergy, enthalpy and entropy. The method can also be applied to calculate thermodynamical characteristic values for inert media. Both Newtonian and Theologically complex media, including non-linearly viscoelastic ones, may be subject to calculation. The method can be applied to a wide range of channel shapes and cross-sections. The versatility of the method has been confirmed by the calculation of several technological processes of polymer chemistry.
Quantitative Description of Vortical Region Length of Non-Newtonian Fluids Through an Abrupt Contraction
Authors: Liang J. Z. , Ling Z. Y. , Li R. K. Y. , Tjong S. C.
Published: July 2023

In the present paper, the flow of a viscoelastical fluid through a sudden contraction duct was discussed. Based on previous work, the authors proposed some equations for estimating the vortical region length (Lv). The values of the Lv during capillary extrusion of a rubber compound were calculated proximally. It was found that the ratio of Lv to reservoir diameter was about 0.14–0.32, which it was decreased with a rise of temperature or decreasing shear rates.
Couette Flows of Liquid Crystal Polymers
Authors: Wang Qi
Published: July 2023

Using the BMAB theory with the Doi closure approximation and a biaxial representation of the orientation tensor, we demonstrate that the steady states of liquid crystal polymeric Couette flows between two concentric, circular cylinders in relative rotation exhibit biaxial symmetries. Therefore, two order parameters and a triad of directors must be employed to model average molecular orientation in the flow. With two directors confined to the plane orthogonal to the axis of rotation, stable steady states may exhibit flow-aligning, log-rolling and mixed flow-aligning and log-rolling behavior depending on the initial orientation between the two cylinders. The orientational pattern and the degree of orientation is sensitive to the value of the polymer concentration, the anisotropic drag coefficient and the ratio of the radius of the two cylinders. Molecules achieve higher degree of orientation at the wall of the inner cylinder than at that of the outer cylinder in the flow-aligning regime, and vice versa in the log-rolling regime.
Calculation of Relaxation and Retardation Spectra Using the Tikhonov Regularization Method: Application to Emulsions
Authors: Madiedo J. M. , Muñoz J. , Gallegos C.
Published: July 2023

Flocculated oil-in-water emulsions exhibit very complicated relaxation spectra, showing different regions depending on oil and emulsifier concentrations, processing parameters, etc. In this work, the linear viscoelastic behavior of concentrated oil-in-water emulsions stabilized by two sucrose stearates with different hydrophilic-lipophilic balances has been studied. This characterization has been achieved by calculating the relaxation and retardation spectra of the emulsions, using regularization techniques. With this aim, oscillatory shear and creep compliance tests, in the linear viscoelasticity region, were carried out in a controlled-stress rheometer. Three different regions in the relaxation spectra of these systems have been identified: the transition region at low relaxation times; an intermediate plateau region; and a pseudo-terminal region at long relaxation times, characterized by a tendency to a crossover of G′ and G″ in the frequency sweep curves. The evolution of these regions depends mainly on the characteristics of the sucrose stearates used and has been related to their aqueous phase behavior.