bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of Finite Volume Shell Conduction Model for Complex Geometries
Authors: Mathur S. R. , Lim C. K. , Nair R. 
Published: November 2021

Abstract
Thin, plate-like structures are often encountered in industrial heat transfer applications. Discretizing them as volumetric elements along with the rest of the domain results in a large number of elements and significantly increases the cost of computational analysis of such problems. It can also cause numerical errors and convergence difficulties because of the large aspect ratios and skewness of the mesh. On the other hand, treating the conduction in such regions separately is also unattractive because the inherent coupling of the two problems makes for very slow convergence. In this paper we present an alternative approach which treats such structures as planar elements while still maintaining full coupling between the temperature fields in the two regions. Consequently the solution for the entire domain can be obtained simultaneously without significant increase in problem complexity. The method is validated using canonical problems as well as solutions obtained by full discretization of the thin structures. Compared to the latter, the present approach is found to be significantly more efficient and robust.
Buoyancy Effect on Developing Turbulent Flow and Heat Transfer in a Helical Pipe With Finite Pitch
Authors: Zheng B. , Lin C. X. , Ebadian M. A. 
Published: November 2021

Abstract
Numerical modeling was performed to investigate the buoyancy effect on developing turbulent flow and the heat transfer characteristics of saturated water in a helical pipe with finite pitch. The renormalization group (RNG) κ–ε model was used to account for the turbulent flow and heat transfer in the helical pipe at a constant wall temperature with or without buoyancy force effect. A control volume method with second-order accuracy was used to numerically solve the three-dimensional full elliptic governing equations for this problem. The O-type nonuniform structured grid system was adopted to discretize the computation domain. The Boussinesq approximation was applied to deal with the buoyancy. This study explored the influence of buoyancy on the developing heat transfer along the helical pipe. Based on the results of this research, the velocity, temperature, and Nusselt number are presented graphically and analyzed.
Modelling of Convective Melt Flow and Interface Shape in Commercial Bridgman-Stockbarger Growth of CdZnTe
Authors: Rule Toby D. , Li Ben Q. , Lynn Kelvin G. 
Published: November 2021

Abstract
CdZnTe single crystals for radiation detector and IR substrate applications must be of high quality and controlled purity. The growth of such crystals from a melt is very difficult due to the low thermal conductivity and high latent heat of the material, and the ease with which dislocations, twins and precipitates are introduced during crystal growth. These defects may be related to solute transport phenomena and thermal stresses associated with the solidification process. As a result, production of high quality material requires excellent thermal control during the entire growth process. A comprehensive model is being developed to account for radiation and conduction within the furnace, thermal coupling between the furnace and growth crucible, and finally the thermal stress fields within the growing crystal which result from the thermal conditions imposed on the crucible.
As part of this effort, the present work examines the heat transfer and fluid flow within the crucible, using thermal boundary conditions obtained from experimental measurements. The 2-D axisymetric numerical model uses the deforming finite element method, with allowance made for melt convection, solidification with latent heat release and conjugate heat transfer between the solid material and the melt. Results are presented for several stages of growth, including a time-history of the solid-liquid interface (1365 K isotherm). The impact of melt convection, thermal end conditions and furnace temperature gradient on the growth interface is evaluated. Future work will extend the present model to include radiation exchange within the furnace, and a transient analysis for studying solute transport and thermal stress.
Dispersion Analysis of Stabilized Finite Element Methods for Acoustic Fluid-Structure Interaction
Authors: Thompson Lonny L. , Sankar Sridhar 
Published: November 2021

Abstract
The application of stabilized finite element methods to model the vibration of elastic plates coupled with an acoustic fluid medium is considered. New stabilized methods based on the Hellinger-Reissner variational principle with a generalized least-squares modification are developed which yield improvement in accuracy over the Galerkin and Galerkin Generalized Least Squares (GGLS) finite element methods for both in vacuo and acoustic fluid-loaded Reissner-Mindlin plates. Through judicious selection of design parameters this formulation provides a consistent framework for enhancing the accuracy of mixed Reissner-Mindlin plate elements. Combined with stabilization methods for the acoustic fluid, the method presents a new framework for accurate modeling of acoustic fluid-loaded structures. The technique of complex wave-number dispersion analysis is used to examine the accuracy of the discretized system in the representation of free-waves for fluid-loaded plates. The influence of different finite element approximations for the fluid-loaded plate system are examined and clarified. Improved methods are designed such that the finite element dispersion relations closely match each branch of the complex wavenumber loci for fluid-loaded plates. Comparisons of finite element dispersion relations demonstrate the superiority of the hybrid least-squares (HLS) plate elements combined with stabilized methods for the fluid over standard Galerkin methods with mixed interpolation and shear projection (MITC4) and GGLS methods.
Introduction to Acoustic Compressors
Authors: Lipkens Bart , Lalande Fred , Perkins David 
Published: November 2021

Abstract
The emergence of acoustic compressors has been made possible by the development of a new technology called Resonant MacroSonic Synthesis (RMS). RMS allows the creation of macrosonic standing waves in acoustic resonators. The shape of the resonator controls the nonlinear fluid dynamic processes by which energy is transferred to higher harmonics. Through this process resonators have been designed that allow high-amplitude shock-free waveforms. A variable reluctance driver is used to transfer energy into the resonator. The entire resonator is oscillated along its axis at the fundamental acoustic resonance frequency. This process is called entire resonator drive. The valve technology used in these compressors is similar to that of conventional reciprocating compressors. Acoustic compressors are inherently variable capacity and oil-free. Other unique characteristics are flexible orientation and low profile packaging option. Development focuses on vapor-compression applications. The application discussed here is spot-cooling.
Response to an Induced Flow/Pressure Transient During Well Fracturing
Authors: Loth John L. , Echavarria Erika , Stephenson Stan 
Published: November 2021

Abstract
Hydraulic fracturing of oil and gas wells is often needed to increase well production. The fluid pumping schedule is designed to control the fracture growth in length, width and height. This paper investigates the potential for using the fracture fluid acoustic properties to measure, on-line, the length of the fracture and or reduce the enormous pumping power required. This preliminary study shows that most induced flow or pressure transients are critically damped inside the fracture. Pulses with pressure rising or dropping faster man the time required for the wave to travel the length of the fracture, behave differently. Those pulses excite the natural frequency of the fracture, which is about 10 Hertz for a 100 ft. (30 m) long fracture. If the fracture natural frequency can be detected at the surface, it provides an on-line insight into the length of the fracture created.
Non-Linear Least-Squares Estimation of Material Properties and Structural Intensity in Non-Uniform Beams
Authors: Halliday Peter J. , Grosh Karl 
Published: November 2021

Abstract
Algorithms for determining material properties and power flow in vibrating structures are presented. The new techniques are achieved by synthesizing wave component identification methods developed previously (Halliday and Grosh, 2000) with new methods targeted towards material property and structural intensity estimation. The effectiveness of this nonlinear least-squares approach is investigated through laboratory and numerical experiments on a non-uniform structure, yielding guidelines for spatial sampling and the effects of noise.
Modelling of Rigid-Frame Porous Materials: A Simple Approach
Authors: Brennan M. J. , To W. M. 
Published: November 2021

Abstract
This paper is concerned with the modelling of rigid-frame porous materials. Currently there are very simple models which describe the acoustic behaviour of such materials, and there are also very complicated models. The aim of this paper is to present a model which occupies the “middle ground”, but is simple enough to be used by practising noise control engineers. Using concepts of acoustic mass, stiffness and damping, non-dimensional expressions for the acoustic wavenumber and the characteristic impedance of a rigid-frame porous material are derived. These expressions are used to give a “rule of thumb” for the optimum flow resistivity for a given thickness of material.
Low-Velocity Impact Response and Dynamic Characteristics of Glass-Resin Composites
Authors: Mantena P. Raju , Mann Richa , Nori Chandrasekhar 
Published: November 2021

Abstract
This paper describes a test methodology used for characterizing different glass-resin composite systems with respect to their low-velocity impact response, dynamic modulus and inherent damping properties. Impact tests were conducted on SMC plaque samples in an instrumented impact test machine. A Dynamic Mechanical Analyzer was used for testing small rectangular samples in the fixed frequency mode of operation. An impulse-frequency response vibration technique was used for obtaining the dynamic modulus and loss factor of cantilever beam specimens at ambient conditions. The dynamic modulus, glass transition and damping peak intensities obtained from the DMA and the vibration techniques are correlated with the impact test data. The potential application for screening glass-resin formulations with respect to their impact performance is discussed.
Characterization of Shot-Peened Surfaces by a Noncontacting Thermoelectric Method
Authors: Carreon Hector , Nagy Peter B. 
Published: November 2021

Abstract
Shot peening is widely used in the aerospace and other industries to increase the damage tolerance of metal parts via producing a thin surface layer of compressive residual stress that prevents crack initiation and retards crack growth during service. Nondestructive evaluation of the prevailing compressive residual stress in the shallow subsurface layer is complicated by the adverse effects of shot peening, such as surface roughness and cold work that manifests itself through increased dislocation density and localized texture. Recent research efforts have revealed that conventional ultrasonic and eddy current NDT methods are simply too sensitive to surface roughness to quantitatively assess the subtle variations in mechanical and electrical properties that are caused by shot peening. On the other hand, noncontacting thermoelectric techniques are very unique among all other methods used in nondestructive materials characterization in that they are solely sensitive to intrinsic material variations regardless of the size, shape, and surface quality of the specimen to be tested. Noncontacting thermoelectric methods, based on magnetic detection of local thermoelectric currents around inhomogeneities in metals when a temperature gradient is established throughout the specimen, are especially well suited for the characterization of shot peened surfaces. Experimental evidence suggests that this method can reliably detect and quantitatively assess otherwise hidden variations in material properties within the shallow surface layer of shot peened specimens. The thermoelectric method is sensitive to all three “material” effects of shot peening, namely residual stress, local texture, and increased dislocation density, but it is entirely insensitive to its “geometrical” by-product, i.e., the rough surface topography. Further development of the thermoelectric method is necessary to study the underlying physical phenomena before it can be successfully adapted to practical inspection problems, but the preliminary results presented in this paper are very promising.
Enhanced Methane-Air Mixing Using Shock and Expansion Waves
Authors: Brasoveanu Dan , Gupta Ashwani K. 
Published: November 2021

Abstract
A unified model of gaseous fuel-air mixing is applied here to study the effect of shock waves on enhanced methane-air mixing. The model uses the fuel mass fraction within infinitesimal fluid elements and the total derivative of this fraction with respect to time to measure the degree and rate of mixing, respectively. The model is strictly accurate only for low-pressure combustors because of the ideal gas law assumption incorporated in the model. The model is also limited to gaseous fuels that contain single chemical specie, or behave like single specie. The model can be applied to any operational conditions or combustor geometry.
Results show that mixing can be completed within the narrow region of the shock wave and therefore in a negligibly short time, if pressure, temperature and velocity distributions within this region are optimized. Furthermore, combining the effects of air preheat and shock waves can enhance both mixing with air penetration into fuel and fuel dispersion into the surrounding air. These results provide important guidelines for the design of supersonic combustors to achieve high efficiency and high intensity, while maintaining a low level of pollutants emission.
Inverse Design of Radial Compressor Components by Modern CFD
Authors: Van den Braembussche R. A. , Antolin J. , Thygesen R. 
Published: November 2021

Abstract
The use of a three-dimensional inverse method for the design of inlet guide vanes, a centrifugal impeller and return channel is demonstrated. The geometry of the different components are iteratively defined until a prescribed velocity distribution is obtained.
The procedure and design criteria for each component are described and the final result is presented. The advantages, disadvantages and problems related to the use of inverse methods are discussed.
The Influence of Inlet Flow Distortion on the Performance of a Centrifugal Compressor and the Development of Improved Inlet Using Numerical Simulations—Part I: Experimental Test Comparison for Compressor Stage Performance
Authors: Kim Yunbae , Engeda Abraham , Aungier Ron , Direnzi Greg 
Published: November 2021

Abstract
The performance of centrifugal compressors can be seriously affected by inlet flow distortion that is by non-uniform inlet flow. The distortion can be in static pressure or stagnation temperature, but the most common distortion is stagnation pressure. Such distortions often occur because of the unsatisfactory nature of the inlet configuration and the resulting inlet flow structure.
In this current work, Part I of two parts, experimental test has been carried out for the comparison of a centrifugal compressor stage efficiency with two different inlet configurations, one of which is straight with constant area and the other is a 90-degree curved pipe with nozzle shape as inlet models. The comparative result from the test showed significant stage efficiency difference between the two different inlet configurations. The result is analyzed and attempt is made to understand the flow structure caused by each type of configuration and the resulting effect on the performance of the stage.
Effects of Scalloped Centrifugal Impellers on Aerodynamic and Rotordynamic Performance Using CFD Techniques
Authors: Moore J. Jeffrey 
Published: November 2021

Abstract
Impeller scallops are intentional cuts in the hub and shroud surfaces at the exit of centrifugal impellers that are intended to prevent high cycle fatigue in these areas. The goal of this analysis is to determine what effect the scallops have on aerodynamic performance, rotordynamic stability, rotating stall criteria, axial thrust, and mechanical shaft power. Furthermore, this study improves the understanding of the interaction with the secondary passage and determines the effect on the flow field entering the diffuser. A 3D viscous CFD model is generated of a single blade passage that couples the primary flow passage with the secondary shroud passage. This approach captures the complex interaction that occurs at the impeller exit due to the presence of the scallops. The predictions show a small penalty in thermodynamic efficiency with the presence of the scallops compared to a baseline case. The results also show a moderate increase in shaft horsepower calculated by integrating static pressure and shear stress acting on the impeller and shroud surfaces. Circumferential swirl in the shroud passage shows only modest increases with the addition of the scallops. Therefore, rotordynamic performance is not significantly affected nor is axial thrust acting on the impeller. The predictions demonstrate the effect the scallops have on the flow field entering the diffuser including variations in flow angle at the impeller exit.
Centrifugal Compressor Design and Testing in Finnish High Speed Technology
Authors: Larjola J. , Backman J. , Esa H. , Pitkänen H. , Sallinen P. , Honkatukia J. 
Published: November 2021

Abstract
This paper reports on the design procedure to produce radial compressors for high speed applications. These compressors are directly connected to a high speed electric motor. Speed control is used instead of IGV and diffuser vane control, and this sets some additional requirements e.g. for the shape of the compressor performance map. It is required that at the design pressure ratio the compressor has a wide operating range in mass flow, when optimal speed control is used. It is also required that the high efficiency range of the compressor is as wide as possible. One-dimensional computation giving the basic geometry and performance map of the compressor is done with a non-commercial program. Then a geometry generation 3D program is used to define the whole compressor wheel geometry. The wheel geometry data is used in the flow and structure analyses. The compressor flow is calculated with a three-dimensional CFD-program, which has specially been modified for centrifugal compressor flow. Particularly in the optimization process of the volute, also time-dependent computation of the complete compressor using the sliding mesh technique is used. The performance of the final compressor geometry is measured in the University test facility and the test results are used to develop the design process. Up to this date, 15 different high speed compressors have been aerodynamically designed and tested in this design loop. The typical pressure ratio of the compressors ranges from 1.6 to 2.5.
Dynamic Mechanical Analysis of Nitinol Beams
Authors: Krishnan Sridhar , Yoon Sung-Ho , White Scott R. 
Published: November 2021

Abstract
The bending behavior of thin nitinol beams under dynamic loading conditions was experimentally characterized using a three-point bending fixture in a Dynamic Mechanical Analyzer (DMA). Differential Scanning Calorimetry (DSC) was also used to measure the transformation temperatures and assess the effects of annealing treatment on the material behavior. The alloy (54.4Ni/45.5Ti wt. %) was chosen so that the austenitic finish temperature was in the range of 50–100°C. Simple beam bending theory was used to calculate the dynamic moduli of the beam and the transformation temperatures were observed in the form of a hysteresis curve of storage modulus. Monotonic three-point bend loading tests were conducted for pure martensite and pure austenite to measure the critical stresses for martensitic (stress-induced) transformation.
Micromechanics of Porous Shape Memory Alloys
Authors: Lagoudas Dimitris C. , Entchev Pavlin B. , Qidwai Muhammad A. , DeGiorgi Virginia G. 
Published: November 2021

Abstract
This work focuses on establishing the properties — both static and dynamic — of porous SMA materials, and their energy absorption capabilities. To accomplish this, micromechanics-based analysis of the overall behavior of SMAs is carried out in the present work. The porous SMA is modeled as a composite with a solid SMA matrix, which is in turn described by a constitutive model available in the literature, and elastic inclusions, which in the limit represent the voids in the porous material. The static macroscopic constitutive behavior of the material is established using both the Mori-Tanaka averaging method and the unit cell finite element method. The dynamic macroscopic constitutive behavior is described using the results obtained by the Mori-Tanaka averaging method.
Compact Drive Electronics for Solid-State Actuators
Authors: Paine Jeffrey S. N. , Bennett David S. , Cuadros Carlos E. 
Published: November 2021

Abstract
As piezoelectric actuators are developed for high strokes and/or high force applications, the amount of piezoelectric material used in the actuator must also increase. Reducing the size of drive electronics becomes difficult using traditional linear power electronics packages when applications require as much as 40 μF of piezoelectric load. In order to efficiently drive piezoelectric actuator systems, bi-directional systems (drivers that recover the energy put into the piezoelectric capacitor) must be used. Since less than 10% of the power going into the piezoelectric actuator is real versus the large reactive load used to power the piezoelectric materials, bidirectional systems have a much higher efficiency. A comparison is made between traditional linear and PWM amplifier systems and tailored piezoelectric bi-directional driver systems. Bi-directional systems have power dissipation levels up to 1/8th those of traditional linear amplifier systems. In the course of the research both linear and PWM concepts were investigated. A rationale for comparing the overall efficiency of drive electronics systems is presented. Some innovative efficient concepts for piezoelectric system drivers are presented and discussed.
Double Adjustable Shock Absorbers Utilizing Electrorheological and Magnetorheological Fluids
Authors: Lindler Jason E. , Wereley Norman M. 
Published: November 2021

Abstract
Double adjustable shock absorbers allow for independent adjustment of the yield force and post-yield damping in the force versus velocity response. To emulate the performance of a conventional double adjustable shock absorber, an electrorheological (ER) and magnetorheological (MR) automotive shock absorber were designed and fabricated at the University of Maryland. For the ER shock absorber, an applied electric field between two tubular electrodes, located in the piston head, increases the force required for a given piston rod velocity. For the MR shock absorber, an applied magnetic field between the core and flux return increases the force required for a given piston rod velocity. For each shock absorber, two different shaped gaps meet the controllable performance requirements of a double adjustable shock absorber. A uniform gap allows for control of the yield force of the shock absorber, while a non-uniform gap allows for control of the post-yield damping. Force measurements from sinusoidal displacement cycles, recorded on a mechanical damper dynamometer, validate the performance of uniform and non-uniform gaps for adjustment of the yield force and post-yield damping, respectively.