bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Properties of Polycrystalline Lamellar TiAl-Intermetallics
Authors: Schlögl S. M. , Werner E. A. , Fischer F. D. 
Published: July 2023

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.