bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Simulation of Laminar Film Boiling Heat Transfer From Vertically Suspended Smooth Surfaces in Cryogenic Fluids Subjected to Constant Wall Heat Flux
Authors: Akyuzlu K. M. , Malipeddi S.
Published: July 2023

This study is aimed at solving the one-field conservation of mass, momentum, and energy equations for laminar film boiling from vertically suspended smooth surfaces in cryogenic fluids subjected to constant wall heat flux boundary condition. Solutions to the problem of laminar film boiling under constant wall temperature boundary condition have been obtained in the past using analytical and iterative techniques. Here, the governing equations are solved under constant heat flux boundary condition using an analytical method supplemented with curve fitting techniques. The procedure is iterative because it assumes the vapor film thickness to start the calculations and then uses the energy equation at the interface to check the accuracy of this assumption. A computer program was developed to integrate this iterative procedure with a scheme that repeats the calculations at different discrete locations along the heated surface to estimate the laminar film thickness and to generate the velocity and the temperature profiles within the film boundary. The numerical results are compared to the experimental results for a stainless steel plate vertically suspended in liquid nitrogen where the plate is heated by constant current. The numerical predictions are matched with the experimental results by using a calibration parameter that relates various properties of the liquid and the vapor.
Measurement of Temperature, Concentration, and Velocity in Laminar Flow Using a Single Wire Probe
Authors: Nakabeppu Osamu , Kinoshita Atsuo , Hijikata Kunio
Published: July 2023

The measurement of three physical quantities: temperature, concentration and velocity in laminar flow using a single metal wire probe with an applied AC voltage was studied. The measurement setup is simple; it contains a thin metal wire, a bridge circuit and a lock-in amplifier. Furthermore its operation is very straight forward, thus it is a useful technique for heat and mass transfer research and monitoring of industrial processes. For the temperaure and velocity measurement the same principle used in the RTD and hot wire anemometer method is applied in AC mode. Whereas the 3w method was used for concentration measurement in forced convection. Measurement condition and performance is discussed for each measurement. Using a measurement example for flow composed of two liquids in a rectangle channel, it is shown that profiles of three physical quantities are measured like what is expected by this method, however the velocity and concentration measurement are delicate and improvement of accuracy is necessary.
Applications of Two-State M-Integral to a Triple Junction Vertex Under Thermal Loading
Authors: Im Seyoung , Jeon Insu
Published: July 2023

The two-state M-integral, which is derived from the M-integral and is applicable for two elastic states, is applied for computing an intensity of a singular near-tip field around the vertex of a triple junction of three different materials under thermal loading, often encountered in electronic packaging. Numerically we verify that a simple auxiliary field associated with every eigenfunction for the composite wedge under consideration exists in the form of the conjugate solution in the sense of the M-integral. The auxiliary field is then employed for superposition with the elastic field under consideration, and the associated two-state M-integral is computed via the domain integral technique. This enables us to extract the intensity for a leading singular eigenfunction. The proposed computational scheme enjoys the efficiency and simplicity in that the near-field information for a singular elastic boundary layer is extracted from the domain integral representation without resort to singular finite elements for the wedge vertex.
On Analysis of Discrete Systems With Variable Structure
Authors: Gavrilov Dmitri , Vinogradov Oleg
Published: July 2023

In many applications a discrete system undergoes structural (or connectivity) changes when subjected to loads or deformations. Each time the connectivity between the discrete elements changes a new system of equations must be generated and solved. In the paper a new method based on the numerically generated inverse matrix for the entire system allows the updating of the latter after each change in connectivity instead of generation and recalculation of the new system of equations. The method is symmetrical with respect to addition and elimination of links. The presented algorithm is based on recursive relationships between the inverse matrices for two systems differing by one element. The method is demonstrated for plane granular clusters, i.e. systems of particles bound together and having zero internal degrees of freedom, which is equivalent to any overconstrained system comprising the two-node finite elements. The problems of numerical efficiency and accuracy of the method are discussed and demonstrated on numerical examples.
Failure Mechanisms of a Ceramic-Metal Interface Under the Application of High Temperature Loading
Authors: Zarzour Joseph F. , Onesto Eugene J.
Published: July 2023

Controlled experiments with a thermal spray coating of aluminum oxide (alumina) on high purity nickel metal base were carried out to examine the mechanisms of cracking and delamination. Control of these phenomena will enhance the life of thermally sprayed components subjected to thermal shock. These experiments along with computer models will advance the fundamental understanding of this ceramic-metal interface. A plasma spray torch was used to prepare the test specimens, and a high power radiative furnace was used to apply a thermal shock load to the specimens during testing. Geometric effects studied include thickness ratio, thickness to diameter ratio, absolute coating thickness, and the effect of a peak temperature.

Experimental results show that using the same critical thermal cycle, specimens with 1mm thick coating failed by cracking, specimens with coating thickness below 1mm did not show any type of failures, and specimens with coating thickness higher than 1mm failed by spallation inside the coating layer.

A finite element model incorporating the rate-dependent inelastic behavior of nickel at high temperature was developed to provide a realistic estimate of the residual stresses that develop during the thermal cycle. From transient heating to room temperature cooling, residual stress gradient from compressive to tensile was observed in the coating layer. With decreased coating thickness, this phenomenon was less pronounced.
An Optimization Technique Using the Finite Element Method and Orthogonal Arrays
Authors: Young Stuart H. , Kwon Young W.
Published: July 2023

The objective of this research was to develop an optimization technique that can be used interactively by design engineers to approach an optimal design with minimal computational effort. The technique can be applied to both continuous and discrete values of design variables. A large number of design variables can be also considered.

In order to meet the objective, an optimization procedure was developed by coupling the finite element analysis (FEA) to the orthogonal array experimentation technique, because FEA is a common analysis tool for design engineers. From the results of the FEA and an orthogonal array, an average Jacobian matrix was constructed that showed the average overall sensitivity of the design variables. These sensitivities were then used to optimize the design parameters. The process could then be repeated at the discretion of the engineer until he was satisfied with the design. In general, the designer can predict and control the number of FEA calculations before an optimization process so that he can plan a budget and time for an optimal design.

Some examples of structural optimization with truss structures with continuous and discrete values of design variables were studied using the technique developed in this paper. Their optimal solutions were found with small numbers of iterations.
Bifurcation and Postbuckling Response of Asymmetric Laminated Columns
Authors: Vinogradov Aleksandra M. , Derrick William R. , Keck Andrew G.
Published: July 2023

The paper concerns the buckling and postbuckling response of laminated composite columns with arbitrary material lay-ups. The objective of the study is to examine the joint effects of bending-stretching couplings and initial imperfections on the nonlinear buckling behavior of irregular asymmetric laminates. In the paper, the analysis is focused on the nonlinear buckling problem of eccentrically loaded composite columns composed of n isotropic elastic layers. The response of such columns is examined over a range of structural parameters leading to several conclusions regarding the typical buckling characteristics and optimization of asymmetric laminates.
Stiffness Enhancement of Metallic Beam-Like Components
Authors: Rivin Eugene I. , Pankach Panchal
Published: July 2023

Stiffness is an important design criterion. Since bending deformations of structural components are much larger than tension/compression deformations under comparable loads, enhancement of bending stiffness of beam-like components is an important problem. Conventional techniques for stiffness enhancement (beefing up, optimization, use of high Young’s modulus materials) frequently do not achieve the desired results. The paper describes a novel approach to bending stiffness enhancement based on the inverse buckling effect. The beam is composed of the structural external member having an axial hole which is plugged and filled with a fusible metal alloy expanding during solidification thus stretching the external member and enhancing its stiffness. Experimental study resulting in 40% increase in bending stiffness is described.
Simulated Metallic Structures for Use in Radar Measurements
Authors: Barclay Jeffrey J.
Published: July 2023

The Naval Undersea Warfare Center, Division Newport has been active in quantifying radar signatures of periscopes, communication masts, and sensors, as well as different materials. Development of computational prediction codes, along with radar measurements of various targets, have provided the primary analysis tools in signature management. Because of the nature of these radar measurements, techniques were developed to simulate metallic structures. With these techniques, manufacturing time and cost were greatly reduced along with large reductions in structure weight. These techniques primarily used electrically conducting tape and paint as coatings to simulate a metallic, electrically conducting surface. Simulation validation, with computational code, was achieved with the production and measurement of several simulated metallic structures. By achieving this validation, reasonable geometrical design changes could be developed and studied with computational predictions. The most recent experiment involved using a simulated metallic surface to provide an entire environment for the targets under test. Again by using these metallic coated structures to create a multipath environment, expense and manufacturing time were reduced. This simulated environment will, it is hoped, provide a very controllable and repeatable measurement tool for incoherent scattering and fully polarimetric studies of a multipath environment.
Computational and Laboratory Analysis of Thermal Free-Form Fabrication of Metal Prototypes
Authors: Doumanidis Charalabos , Fourligkas Nikolaos
Published: July 2023

The advent of rapid prototyping methods for functional layered metal products has created the need for thermal off-line analysis and optimization of the process conditions, as well as for real-time control of the material structure and properties through the temperature field. For this purpose, this work introduces a scanned thermal processing technique, in which the heat source rapidly sweeps the surface of each deposited layer to ensure a flexible heat input distribution. For this method, the article establishes two dynamic thermal modeling tools: a finite-difference numerical simulation of the temperature field in layered objects, and an experimental linearized formulation with time-varying parameters identifiable in-process by thermal measurements. The models are applied and validated in elementary LOM thermal operations on a plasma-arc processing station with infrared thermal sensing and computer control, and their use for design of a closed-loop thermal regulator is discussed, together with the metal structure and properties of scanned parts.
Fracture Mechanics Approaches to the Prediction of Fatigue Life of a Beta Titanium Alloy (Ti-15V-3Cr-3Al-3Sn)
Authors: Rabeeh Bakr M. , Soboyejo Alfred. B. , Rokhlin Stanislav I. , Soboyejo Wolé
Published: July 2023

This paper highlight the results of recent efforts to develop mechanistically based, fracture mechanics models, for the prediction of the total fatigue life in Ti-15V-3Cr-3Al-3Sn (Ti-15-3). Acoustic emission techniques and visual observation (light and scanning electron microscopy) methods are used to monitor fatigue initiation and propagation phenomena in Ti-15-3. Mechanistically-based fracture mechanics idealizations of initiation and propagation stages are then formulated for the prediction of fatigue life. Using the measured initial crack length as the key variable in fatigue life prediction equations, the bounds in the predicted initiation and propagation lives are estimated using fracture mechanics techniques. The paper highlights the advantages of simplified fracture mechanics methods in the prediction of fatigue life.
Mechanical Properties of Polycrystalline Lamellar TiAl-Intermetallics
Authors: Schlögl S. M. , Werner E. A. , Fischer F. D.
Published: July 2023

TiAl-intermetallics with a fully lamellar microstructure seem to be potential candidates for industrial applications. In this paper a micromechanical study is presented focussing on the room temperature plastic flow behavior of polycrystalline lamellar intermetallics under uniaxial loading conditions. In this course plastic flow of single lamellar grains is analyzed by a crystal plasticity approach which takes into account crystallographic slip and deformation twinning. The dependence of the flow behavior on the angle between the lamellae and the loading direction reveals the highly anisotropic nature of the crystals. Then plastic flow in various lamellar polycrystals is modelled. The highest ductility (low work hardenability and high elongation to fracture) is predicted for microstructures containing grains of low strength arranged in continuous grain clusters.
A Petrov-Galerkin Method for the Direct Simulation of Fully Enclosed Flows
Authors: Suslov Sergey A. , Paolucci Samuel
Published: July 2023

A new Petrov-Galerkin method for computations of fully enclosed flows is developed. It makes use of divergence-free basis functions which also satisfy the boundary conditions for the velocity field. This allows the elimination of the unknown pressure, and subsequently decreases the computational cost substantially when the problem is formulated in primitive variables. The computational procedure reduces to the solution of a system of nonlinear first order ordinary differential equations for the spectral expansion coefficients, or, in the steady case, to the solution of a system of nonlinear algebraic equations. The paper illustrates the effectiveness of the method by solving the problem of the two-dimensional thermoconvective flow in a rectangular cavity at high Rayleigh numbers. The results compare favorably with ones obtained using finite-difference and pseudo-spectral schemes in terms of accuracy, and memory and computational time requirements. The generalization of the method to three dimensions is straightforward and preserves all the advantageous features found in two-dimensional computations.
Thermoacoustic Wave Propagation Modeling Using a Dynamically Adaptive Wavelet Collocation Method
Authors: Vasilyev Oleg V. , Paolucci Samuel
Published: July 2023

Thermoacoustic wave propagation in a two-dimensional rectangular cavity is studied numerically. The thermoacoustic waves are generated by raising the temperature locally at the walls. The waves, which decay at large time due to thermal and viscous diffusion, propagate and reflect from the walls creating complicated two-dimensional patterns. The accuracy of numerical simulation is ensured by using a highly accurate, dynamically adaptive, multilevel wavelet collocation method, which allows local refinements to adapt to local changes in solution scales. Subsequently, high resolution computations are performed only in regions of large gradients. The computational cost of the method is independent of the dimensionality of the problem and is O(N), where N is the total number of collocation points.
A Parameter Study of the Two-Phase Ground Water Transport in the Soil Surrounding a Growing Hemispherical In Situ Vitrification Melt
Authors: Schreiber W. C. , Lowery P. S. , Roberts J. S.
Published: July 2023

Numerical simulation is used to test the effect of several parameters on the water balance and pressure field surrounding a growing hemispherical In Situ Vitrification (ISV) melt. In the current project, a hemispherical annulus of unsaturated soil contained between a growing melt and an impervious wall is modeled. Water vapor vents to atmospheric conditions. The soil is considered a porous media; consequently, fluid velocity can be modeled by Darcy’s equation. The capillary pressure and relative permeability are modeled using the equations derived by van Genuchten. The computer model employs a grid which adapts to the transient boundary of the growing melt. The parameters considered include: initial liquid saturation, soil permeability, and melt growth rate. The combined effect of capillary pressure and permeability is also studied. The variation of these parameters in a Hanford soil are studied for their effect on pressure history at the melt interface and total liquid mass history. Transport of heat and mass in the soil is illustrated graphically in terms of the saturation and pressure fields as well as mass flux of liquid and vapor water.
Analysis of Heat Transfer and Contaminant Transport in Fume Hoods
Authors: Pathanjali Chockalingam , Rahman Muhammad M.
Published: July 2023

The paper presents the analysis of three-dimensional flow patterns and the associated heat and mass transfer mechanisms in a fume hood enclosure. The flow enters the hood through the front window opening (positive x-direction) and leaves the cupboard through an opening on the top of the hood (positive z-direction). The flow was assumed to be fully turbulent. The flow pattern for different sash openings were studied. The flow pattern around an object located at the bottom of the hood was studied for different locations of the object. It was found that air entering the hood proceeds directly to the back wall, impinges it and turns upward toward the top wall and exits through the outlet. The flow finds its way around any object forming a recirculating region at its trailing surface. With an increase in the sash opening, the velocity becomes higher and the fluid traces the path to the outlet more quickly. The volume occupied by recirculating flow decreases with increase in sash opening. Both temperature and concentration were found to be maximum near the source and gradually decreased as the heated air or gaseous contaminant entrained with incoming air. The local concentration decreased with increase in sash opening area. The results will be very useful to design experiments with optimum sash opening providing adequate disposal of contaminants with minimum use of conditioned air inside the room.
Flow Analysis in a Supercritical Water Oxidation Reactor
Authors: Oh Chang H. , Kochan Robert J. , Beller John M.
Published: July 2023

Supercritical water oxidation (SCWO), also known as hydrothermal oxidation (HTO), involves the oxidation of hazardous waste at conditions of elevated temperature and pressure (e.g. 500°C-600°C and 234.4 bar) in the presence of approximately 90% of water and a 10% to 20% excess amount of oxidant over the stoichiometric requirement. Under these conditions, organic compounds are completely miscible with supercritical water, oxygen and nitrogen, and are rapidly oxidized to carbon dioxide and water.

The essential part of the process is the reactor. Many reactor designs such as tubular, vertical vessel, and transpiring wall type have been proposed, patented, and tested at both bench and pilot scales. These designs and performances need to be scaled up to a waste throughput 10–100 times that currently being tested. Scaling of this magnitude will be done by creating a numerical thermal-hydraulic model of the smaller reactor for which test data is available, validating the model against the available data, and then using the validated model to investigate the larger reactor performance.

This paper presents a flow analysis of the MODAR bench scale reactor (vertical vessel type). These results will help us design the reactor in an efficient manner because the flow mixing coupled with chemical kinetics eventually affects the process destruction efficiency.
Data Acquisition Testing in Supercritical Water Oxidation Using Machine Cutting Oils and Metals
Authors: Garcia Karen M.
Published: July 2023

The Department of Energy (DOE) Office of Technology in cooperation with the Navy and SERDP provided funding for an extensive series of testing of a Supercritcal Water Oxidation (SCWO) system. The goal of the testing was to create performance data on the process when dealing with highly chlorinated wastes containing heavy metals, and radionuclides. The testing was performed in a MODAR vessel oxidizer. Performance was measured by the ability of the process to achieve greater than 99.99% destruction of the organic content, to partition the metals and radionuclide surrogates for mass balance, and survive the highly corrosive species in the effluent. The test data has shown that these goals were accomplished. 30 gal/day of highly chlorinated machine cutting oil was treated for 130 hrs. There were no significant corrosion or solids handling problems. This machine cutting oil, TRIM®SOL was chosen by DOE for its complex nature and has proven to be one of the more refractory organic feeds encountered by MODAR. The propylene glycol ether and propylene glycol constituents of TRIM®SOL may account for its resistance to oxidation. It is formulated with surfactants, anti-oxidants, viscosity modifiers, anti-friction agents, and stabilizers. The destruction efficiency achieved was 99.97%. To simplify the interpretation of the analytical chemistry, demineralized water was used for all aqueous input streams with all streams being once-through flow. The quench stream was a relatively large flow and made up the majority of the volume of the SCWO process effluent flow. Calculation of waste destruction efficiencies is skewed by the use of high quench water flow in combination with the analytical detection limits for analysis of waste residuals. The resultant destruction efficiencies calculated with high quench water flows are therefore, skewed to a lower value than could be demonstrated if SCWO process effluent water had been reused. These tests results provide clear indications that the SCWO system is well developed and robust enough to handle the most extreme conditions.

The Navy provided 8 waste streams collected from their shore facilities operation. These paints varied in solids content with wastes such as paint chips, and adhesives. The ninth test run was with all 8 series of wastes combined. The MODAR system successfully treated all of these waste streams providing performance data on the ability of SCWO to treat difficult sludges.
Radiation Simulation of a Microgravity Diffusion Flame
Authors: Ezekoye O. A. , Zhang Z.
Published: July 2023

This study numerically investigates the effects of radiation from both the soot and gas phase species on the soot kinetics in a quasi-steady state microgravity spherical acetylene-air diffusion flame by coupling the soot and gas phase chemistry with radiative heat transfer processes. The gas phase reaction is modeled by two step chemical kinetics. The soot reaction mechanism includes nucleation, surface growth, oxidation and coagulation steps. The radiation from both soot and the gas phase are calculated by employing a spherical harmonics (P-1 approximation) model. The local Planck mean absorption coefficients of the computed species are specified in the computations.

Unlike normal gravity acetylene-air steady state jet diffusion flames in which the radiation from soot dominates gas radiation effects, it is found that for a microgravity diffusion flame, except at very early times, the radiation from the gas products dominates soot radiation. In the microgravity flame configuration, it is noted that the radiation heat loss fraction (defined as the ratio of the radiation heat loss rate to the chemical heat release rate) increases up to 80% shortly after ignition.
Measurements and Modeling of Soot Formation and Radiation in Microgravity Jet Diffusion Flames
Authors: Ku Jerry C. , Tong Li , Greenberg Paul S.
Published: July 2023

This is a computational and experimental study for soot formation and radiative heat transfer in jet diffusion flames under normal gravity (1-g) and microgravity (0-g) conditions. Instantaneous soot volume fraction maps are measured using a full-field imaging absorption technique developed by the authors. A compact, self-contained drop rig is used for microgravity experiments in the 2.2-second drop tower facility at NASA Lewis Research Center. On modeling, we have coupled flame structure and soot formation models with detailed radiation transfer calculations. Favre-averaged boundary layer equations with a k-e-g turbulence model are used to predict the flow field, and a conserved scalar approach with an assumed β-pdf are used to predict gaseous species mole fraction. Scalar transport equations are used to describe soot volume fraction and number density distributions, with formation and oxidation terms modeled by one-step rate equations and thermophoretic effects included. An energy equation is included to couple flame structure and radiation analyses through iterations, neglecting turbulence-radiation interactions. The YIX solution for a finite cylindrical enclosure is used for radiative heat transfer calculations. The spectral absorption coefficient for soot aggregates is calculated from the Rayleigh solution using complex refractive index data from a Drude-Lorentz model. The exponential-wide-band model is used to calculate the spectral absorption coefficient for H2O and CO2. It is shown that, when compared to results from true spectral integration, the Rosseland mean absorption coefficient can provide reasonably accurate predictions for the type of flames studied. The soot formation model proposed by Moss, Syed, and Stewart seems to produce better fits to experimental data and more physically sound than the simpler model by Khan et al. Predicted soot volume fraction and temperature results agree well with published data for a normal gravity co-flow laminar flames and turbulent jet flames. Predicted soot volume fraction results also agree with our data for 1-g and 0-g laminar jet flames as well as 1-g turbulent jet flames.
Computation of Combusting Flows Using Unstructured Solution-Adaptive Meshes
Authors: Mathur S. , Murthy J. Y. , Missaghi M. , Faltsi-Saravelou O. S.
Published: July 2023

This paper presents a finite-volume scheme for multi-dimensional reacting fluid flows. Unstructured solution-adaptive meshes are used, with a cell-centered formulation. The SIMPLE algorithm is used for pressure-velocity coupling. Schemes for hanging-node and conformal adaption are presented. For combustion modeling, the eddy-breakup, and assumed-shape probability density function (PDF) models are implemented in the unstructured-mesh context. The methodology is applied to two benchmark problems; reasonable agreement with experimental measurements is found.
Combustion Characteristics of High-Energy/High-Density Hydrocarbon Compounds
Authors: Segal Corin , Friedauer Maxx J. , Udaykumar Holavanahalli S. , Shyy Wei
Published: July 2023

The combustion characteristics of PCU Alkene Dimers (C22H24) are evaluated as solid fuels in high speed flows, at conditions typical for ramjet operation (i.e., Mach 0.25, stagnation temperature and pressure of 300 K and 150 kPa, respectively). Samples of the dimer are binded into a solid layer with a styrene-polybutadiene copolymer (8% w/w) on the test chamber wall and convectively ignited by a gaseous flame in air. The goals of this research are of both practical and fundamental relevance: (i) determine the ability of the high energy fuel to increase practical devices’ performance, (ii) quantify and improve the combustion characteristics of the alkene dimers (i.e., ignition, flame stability, particulate formation), (iii) investigate the dynamics of the solid-gas interface combustion.

To date, ignition times and rates of heat release were measured and the theoretical modelling was initiated. Preliminary results indicate that, in the present configuration, the dimer ignition times fall within the range reported in literature for other solid fuels. Large differences exist among different sets of data due primarily to nonsimilar geometrical configuration of the test. The dimer exhibits substantial rates of heat release in comparison with other solid fuels.
Modification of Premixed Flame Shapes by Thermal Boundary Conditions
Authors: Hackert C. L. , Ellzey J. L. , Ezekoye O. A.
Published: July 2023

The effect of varying the heat transfer boundary conditions of a flame confined in a channel are examined. Two dimensional computations are performed for propagating laminar flames in a parallel plate channel using single-step chemistry. The channel walls may have adiabatic or constant temperature boundary conditions. It is shown that the flame shape follows from an ignition point which varies according to the thermal boundary condition. The effect of surface radiation heat transfer is also examined and is shown to produce a preheated thermal boundary layer that significantly affects the flame propagation characteristics.
Optimizing Reinforced Polyurethane as a Combined Structural and Damping Component
Authors: Ratcliffe Colin P. , Crane Roger M. , Santiago Armando L.
Published: July 2023

In many engineering applications, mechanical vibration can cause structural failure or other problems. While traditional composite systems are typically more heavily damped than metal structures, there may still be insufficient energy dissipation for vibration control. When more control is required, additional mechanical damping treatments may be applied, commonly in the form of viscoelastic free or constrained layers.

Reinforced polyurethane has been shown to be both a structural system, and one that dissipates significant amounts of vibration energy. This material system has been shown to significantly enhance the damping loss factor of cylindrical and flat plate structures. For these structures, mechanical strength and flexibility were the primary design requirements. The level of damping for each structure was quantified, but the material systems were not optimized for energy dissipation.

The high level of damping in these reinforced polyurethane systems was attributed to a combination of the flexibility, i.e. high strains, of the material, coupled with energy dissipation within the matrix. As the system deforms, the matrix is subject to time-varying shear, and energy is dissipated in the matrix. This mechanism can be likened to micro-mechanical constrained layer damping.

This paper presents an experimental technique for the determination of the damping of thin fiber reinforced damping layers. A conventional composite beam with varying thicknesses of reinforced polyurethane was modally tested. The results of the modal analysis were then processed to yield the damping of the free layer. The experimentally determined levels of damping were significantly higher than conventional free layer treatments, especially at low frequencies.
Fiber-Reinforced Structural Dynamics Modification (FRSDM)
Authors: Ahmadian Reza , Mantena P. Raju
Published: July 2023

Structural Dynamics Modification (SDM) is a method by which the local parameters such as stiffness, damping and mass are either added to or removed from the original system to meet the design requirements. This technique has been in practical use in the design and modification of systems constructed with conventional materials. The SDM method is generally restricted to geometrical changes in the original system which may not be applicable to some engineering applications. In this research Pultruded Fiber-Reinforced Composites (PFRC) and their associated mechanical properties are utilized in constituting the Fiber-Reinforced Structural Dynamics Modification (FRSDM) method. The modal behavior of structures, which is governed by the dynamic characteristics of the constituent components, can be modified according to design requirements through hybridization of PFRC. This method not only introduces more flexible design capabilities but also remedies the existing SDM’s geometrical limitations. Hybridized pultruded composite materials were applied for the modification and/or optimization of the dynamic response of frames and space structures. Candidate materials used in this investigation included pultruded glass/epoxy, graphite/epoxy and various lay-up combinations of hybrid glass-graphite/epoxy composite beams. Conventional materials were also tested and modeled for comparison purposes.

Experimental and finite element modal analysis were employed for the identification and validation of modal properties of the primary and modified frame structures. Commercial experimental and numerical modal analysis software package programs were used for the modeling, analysis, and post-processing of modal structures which were dynamically modified for design flexibility by coupling various combinations of pultruded glass/epoxy and graphite/epoxy flat beams. Both the experimental modal analysis (EMA) and finite element analysis (FEA) predictions were found to be in relatively fair agreement. The results of this research indicate the advantages of FRC in structural modifications, demonstrating their applicability and design flexibility.
Theoretical Investigation of Impact Responses for Nondestructive Evaluation of Composites
Authors: Haque A. , Raju P. K.
Published: July 2023

The contact impact response has been investigated as a nondestructive testing (NDT) parameter for identifying localized defects and damage in composite laminates, and the corresponding NDT method is known as the Acoustic Impact Technique (AIT). Theoretical formulation of the influence of defects on the contact impact response is the central focus of the present work. This impact method of nondestructive testing primarily involves applying a low velocity mechanical impact to the test specimen and evaluating the resulting localized acoustic response. The response from a force transducer that is attached to the impacter provides information about the presence of flaws and damage within the structure. The present work established a model of the contact impact response of AIT on the basis of nonlinear Hertz integral equation with the introduction of a local damping parameter. The results showed comparatively higher contact force and lower pulse width in linear analysis as compared to those obtained in nonlinear analysis. The magnitude of the contact force and pulse width are considered to be the primary NDT parameters for the AIT. It is evident that the formulation of nonlinear analysis with damping reduces discrepancy between the experimental and the theoretical findings of the Acoustic Impact Technique.
Tensile and Compression Performance: NDE Relationships of Glass/Epoxy Composites Fabricated Through Rapid Fabric Wetting Resin Infusion Process
Authors: Vaidya U. K. , Haque A. , Fotedar K. , Gajiwala H. , Mahfuz H. , Jeelani S.
Published: July 2023

In the current study, a vacuum assisted, rapid fabric wetting, resin infusion process was utilized to fabricate a triaxial weave composites using non-crimp E-glass fabric and a low viscosity EPON 862/R9550 resin. Full wetting of a five layer 12″ × 12″ triaxial fabric lay-up was achieved using two injection schemes, named as “center injection” and “3-sided injection”. Static tensile and compression failure characteristics of the composites were studied in conjunction with acoustic emission (AE) monitoring and ultrasonic nondestructive evaluation (NDE) tests. Tensile and compression failure modes were also studied using optical and scanning electron microscopy (OM and SEM). The results indicated that the tensile, compressive and mterlaminar shear properties were sensitive to the manner in which resin was infused during the processing.
Development of a Modal Solution Library for the Transverse Vibration of a Thick Beam
Authors: Ayorinde Emmanuel O. , Zheng Zhiyang
Published: July 2023

The authors apply a method of obtaining the modal solutions for the free lateral vibrations of a thick rectangular orthotropic plate where through-the-thickness shear and rotary inertia are important. The approach (Ayorinde, 1995) utilizes optimized modes and is based on the application of the Rayleigh method to the Timoshenko beam. The plate solution was synthesized from those of beams in the two transverse directions. With as few as three optimized modes this method is of comparable accuracy with other methods employing 36 (six per direction) modes. and thus presents a significant advantage. Nevertheless, obtaining the thick beam frequencies involves the numerical solution of complicated hyperbolic equations, which takes much more computer time than for a thin beam. There are many important procedures that require the results of this “forward” problem. Examples are the material identification and damage characterization of thick plates. Since such procedures could utilize literally thousands of trial solutions of the forward problem, methods of significantly expediting the forward solution are of great importance. In this work an intensive investigation has been made of tile parameter space of elastic constants and geometries for thick plates for the behavior of the fundamental (2.2) mode, which is usually the most important structural mode, obtaining definitive guidance that the feasible approach is the setting up of a solution library for a thick beam rather than for a plate directly. The thick beam solution library is actually developed and an interpolation algorithm set up. The library is utilized for the forward plate problem. Results with and without the library are compared, and they confirm the accuracy and significant time-economy of the beam solution library approach.
Flow of a Power-Law Fluid in a Distorted Annulus
Authors: Letelier Mario F.
Published: July 2023

The velocity field is analytically determined for the case of power-law fluid axial flow in non-circular annuli, in which the inner wall is essentially circular, and the outer wall may exhibit a wide variety of shapes. The flow is assumed driven by the axial motion of the inner wall.

A perturbation scheme is developed for power-law indices close the unity. The analysis is pursued for two specific shapes of the cross-section outer wall. By assigning appropriate values to the shape parameters, the two annulus shapes herein presented show three, and four, respectively, curved sides that generate, correspondingly, three, and four corners.

Plots of isovels and velocity profiles are shown for several values of the significant parameters. Relationships between pipe geometry, fluid constants and flow velocity are discussed.
Laminar Axisymmetric Recirculating Flow of a Nonlinear Viscoplastic Fluid
Authors: Hammad Khaled J. , Otugen M. Volkan , Vradis George C. , Arik Engin B.
Published: July 2023

The laminar flow of a nonlinear viscoplastic fluid through an annular sudden expansion was investigated experimentally. In addition to a yield-stress shear-thinning fluid, the flow of a Newtonian fluid through the same expansion was also studied to form a baseline for comparison. Velocity vectors were measured on the vertical center plane using digital particle image velocimetry (PIV). From these measurements, two-dimensional contours of axial and radial velocity as well as the stream function were calculated covering the separated, reattached and redeveloping flow regions. The Reynolds number range was Re = 1.8 to 31, based on the upstream pipe diameter and bulk velocity, and the corresponding yield number range for the non-Newtonian fluids was Y = 0.28 to 1.22. The results obtained for a power-law index of n = 0.68 indicate the existence of two distinct flow regimes as the Reynolds number increases and the yield number decreases. For a combination of low Reynolds numbers and high yield numbers, a non-moving fluid zone is observed immediately downstream of the step and no separated flow zone exists. For the higher Reynolds number and the lower yield number flow, a separated flow zone does exists downstream of the expansion step, which is followed by flow reattachment characterized by a three-dimensional zone of stagnant fluid.
The Evolution of Planar and Axisymmetric Yield / Power-Law Jets
Authors: Jafri Ijaz H. , Vradis George C.
Published: July 2023

The evolution of a steady, incompressible, non-isothermal submerged jet of a non-Newtonian yield/power-law fluid jet is studied using a numerical solution of the governing boundary layer equations. Emphasis is placed in studying the effects of the governing non-dimensional flow parameters i.e. the yield number, power-law index, and Prandtl number. Both yield-pseudoplastic and yield-dilatant fluids are studied for planar and axisymmetric geometries. Decay histories of the jet’s center-line velocity and temperature as well as the spread of the half-width of the jets are obtained. These results show that the jet evolution, as described by the decay of the centerline velocity and evolution of the jet’s half-width, becomes independent of the power-law index at higher yield numbers. The jet expansion boundary is concave to the jet-axis for all values of the power-law index for fluids that exhibit a yield stress. Moreover, the results depict the near independence of the decay of the centerline temperature from the power-law index. Also, it is established that for fluids exhibiting yield, mixing is much more rapid as compared to that of yield-stress free fluids.
Analysis of Slurry Flow Into a Slot
Authors: Clark Peter E. , Zhu Qinsheng
Published: July 2023

Since the paper by Cleary and Fonesca in 1992, there have been several attempts to determine if convection is an important factor in prop-pant placement. Papers by Clark and Courington, Clark and Zhu, and Barree and Conway have provided important clues, but the primary question remains unanswered. To address these questions, we have returned to the question of scaling in models. As mentioned in JPT paper (March 1995) by Clark and Zhu, scaling in a slot-flow model is difficult because each of the possible scaling factors (Reynolds number, velocity, shear rate and pressure drop) have a different dependence on width. Because of this, our initial model was scaled on shear rate and therefore flowing viscosity. Further examination of the problem lead us to believe that the ratio of the forces available to push the fluid in the horizontal and vertical directions is extremely important in determining whether or not convection is observed. This paper will discuss the development of two dimensionless groups that can be used to predict convection and the experimental evidence that validate these dimensionless group.
The Motion and Interaction of Solid Particles in Viscoelastic Liquids
Authors: Feng J. , Joseph D. D. , Huang P. Y.
Published: July 2023

In this paper we present numerical and experimental results on the motion and interaction of solid particles in polymeric fluids. The two-dimensional numerical work investigates the viscoelastic effects on the sedimentation of a particle in the presence of solid walls or another particle. The Navier-Stokes equations coupled with an Oldroyd-B model are solved using a finite element method, and the particles are moved according to their equations of motion. In a vertical channel, a particle settling close to one side wall experiences a repulsion from the wall; a particle settling farther away from the wall is attracted to it. Two particles settling in tandem attract and form a doublet if their initial separation is not too large. Two particles settling side by side approach each other and the doublet also rotate till the line of centers is aligned with the direction of fall. The experimental part studies the behavior of single particles and suspensions in polymer solutions in a torsional flow. Four issues are investigated: the radial migration of a spherical particle, the rotation and migration of a cylindrical rod, the particle-particle interaction and microstructures in a suspension of spheres and the microstructures in a suspension of rods. A spherical particle migrates outward at a constant velocity unless the polymer solution is very dilute. A rod has two modes of motion depending on its shape, initial orientation, the local shear rate and the magnitude of normal stresses in the fluid. When a suspension is sheared, spheres form chains along the flow direction. These chains may connect and form circular rings, which migrate outward at a velocity much higher than that for a single sphere. Rods interact with each other and aggregate in much the same way, but to a less extent than spheres. Particle interaction and aggregation can be explained by two fundamental mechanisms discovered in the numerical simulations of sedimentation.
Effect of Process Parameters on the Rheological Properties of O/W Emulsions
Authors: Gallegos C. , Sánchez M. C. , Guerrero A. , Franco J. M.
Published: July 2023

An overview of the effects that different processing conditions have on the rheology and droplet size distribution of o/w emulsions containing different macromolecular and low molecular weight emulsifiers is presented. The processing variables studied were emulsification time, agitation speed, temperature of emulsification, previous thermal treatment of the continuous phase and type of device used. Generally, an increase in the energy input during emulsification yields lower values of the mean droplet size, but does not always improve the viscoelastic properties of the emulsion. Thus, the bulk rheology of the emulsions may also be influenced by the phase behavior of the surfactant-water system, or by changes in the structural conformation of proteins. These influences are easily changed by modifying the temperature of emulsification or by a pre-emulsification thermal treatment of the continuous phase, which affect the microstructure of the emulsion and, subsequently, its linear viscoelastic behavior.
Microstretch Fluid Description of Fluidized Beds
Authors: Delassade Xavier A.
Published: July 2023

The specific purpose of this work is to consider the effect of particle inertia and other consequences of non-negligible spatial gradients of velocities and concentration, voidage, on vertically propagating concentration waves of small amplitude. The form of the momentum equations for one-dimensional unsteady mean motion of solid particles in a gas-fluidized bed is established. The fluidized bed is considered as a mixture of a microstretch fluid representing the particulate phase, and a classical Newtonian fluid. The constitutive relations expressing the contribution of the interaction forces in terms of phase velocities and the micro-inertia of the particles are given.

Voidage disturbances are briefly studied via nonlinear wave analysis. A fifth order Burgers-Korteweg-de Vries equation is derived. Accordingly, the linear stage of instability of a fluidized bed is replaced by a nonlinear stage in which voidage disturbances are represented by slowly amplifying soliton or radiating soliton pulses.