bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Showerhead Cooling on Turbine Vane Suction Side Film Cooling Effectiveness
Authors: Ethridge Marcia I. , Cutbirth J. Michael , Bogard David G. 
Published: November 2021

Abstract
The process of film cooling is known to severely disturb the boundary layer around a turbine airfoil. Since most film-cooled airfoils have more than one injection station, the flow field approaching a row of film cooling holes could be altered by the presence of an upstream cooling station. To investigate this possibility, an experimental investigation was conducted on the suction side of a scaled-up turbine vane. Adiabatic effectiveness measurements were made downstream of a single row of cooling holes both with and without the upstream showerhead holes operating. A range of suction side blowing ratios, 0.3 ≤ M ≤ 1.3, were investigated with large-scale mainstream turbulence intensities of Tu∞ = 0.5% and Tu∞ = 21%. The effects of the showerhead coolant were evaluated at an engine-typical showerhead blowing ratio of Msh = 1.6, with three of the six rows of cooling holes in the showerhead directed towards the suction side of the airfoil. Experiments were conducted with a coolant-to-mainstream density ratio of DR = 1.6. An infrared camera was used to obtain spatially-resolved surface temperature measurements, which were corrected for conduction effects and converted to adiabatic effectiveness. The results showed that showerhead coolant had a strong impact on suction side adiabatic effectiveness levels under low mainstream turbulence. Although effectiveness levels increased with the showerhead operating, the suction side coolant jets increased dispersion of the showerhead coolant. Under high mainstream turbulence conditions, there was very little interaction between the showerhead coolant and the suction side coolant jets. Adiabatic effectiveness levels were considerably lower than those for the low turbulence case, which was partially due to increased dispersion of the showerhead coolant upstream of the suction side holes. The superposition model over-predicted adiabatic effectiveness levels under low mainstream turbulence conditions, but was very effective in predicting the combined performance of the showerhead and the suction side cooling holes under high mainstream turbulence conditions.
Implementation Issues in Artificial Neural Network Based Thermal Analysis
Authors: Yang K. T. 
Published: November 2021

Abstract
It is now known the generally it can be demonstrated that artificial neural network (ANN), particularly the fully-connected feedforward configuration with backward propagation error-correction routine, can be a rather effective and accurate tool to correlate performance data of thermal devices such as heat exchangers (Sen and Yang, 2000; Kalogirou, 1999). Good examples are the recent demonstrations for the compact fin-tube heat exchangers (Diaz et al., 1999a; Yang et al., 2000; Pacheco-Vega et al., 1999) including those with complex geometries and also two-phase evaporators (Pacheco-Vega et al., 2000) as well as the dynamic modeling of such heat exchangers and their adaptive control (Diaz et al., 1999b; Diaz et al., 2000). Unfortunately, despite such successes, there are still implementation issues of the ANN analysis which lead to uncertainties in its applications and the achieved results. The present paper discusses such issues and the current practices in dealing with them. Those that will be discussed include the number of hidden layers, the number of nodes in each hidden layer, the range within which the input-output data are normalized, the initial assignment of weights and biases, the selection of training data sets, and the training rate. As will be shown, the specific choices are by no means trivial, and yet are rather important in achieving good ANN results in any given application. Since there are no general sound theoretical basis for such choices at the present time, past experience and numerical experimentation are often the best guides. However, many of these choices and issues relating to them involve optimization. As a result. Some of the existing optimization algorithms may prove to be useful and highly desirable in this regard. The current on-going research to provide some rational basis in these issues will also be discussed. Finally, it will also be mentioned that successfully implemented ANNs have many additional uses in practice. Examples include parameter sensitivity analysis, training, design of new experiments, and clustering of data sets.
Laser Processing of Silica Aerogels Using Ultrashort Pulses
Authors: Sun J. , Longtin J. P. , Norris P. M. 
Published: November 2021

Abstract
Silica aerogels are unique nanostructured materials that possess many distinctive qualities, including extremely low densities and thermal conductivities, very high surface-area-to-volume ratios, and large strength-to-weight ratios. Aerogels, however, are very brittle, and are not readily shaped using traditional machining operations. Ultrafast laser processing may provide an alternative for precision shaping and machining of these materials. This paper discusses investigations of ultrafast laser machining of aerogels for material removal and micromachining. The advantages of ultrafast laser processing include a minimal thermal penetration region and low processing temperatures, precision removal of material, and good-quality feature definition. In this work, an amplified femtosecond Ti:sapphire laser system is used to investigate the breakdown threshold, material removal rate, and specific issues associated with laser processing of aerogels, as well as recommendations for further investigations for these unique materials.
Thermal Transport During Seeding and Shouldering in the Czochralski Crystal Growth
Authors: Saha A. K. , Zhang H. , Prasad V. 
Published: November 2021

Abstract
Czochralski (Cz) growth during seeding and shouldering of silicon single crystal has been studied. During seeding, the diameter increases from a small value to the desired value of the fully-grown crystal. The convection in the melt, conduction in the crystal and radiation from the melt surface and crystal, surface tension at the free surface of the melt and crystal rotation have been considered to investigate the effect of seeding on thermal transport. The rotational Reynolds number, the radiation from the crystal and Marangoni number are varied to investigate their effect on the interface shape. A few selected cases have been studied using a cylindrical crystal to understand the effect of geometry on the heat transfer rate and subsequently on the interface shape. The governing equations are solved using the curvilinear finite volume discretization scheme and the grids are redistributed using the multizone adaptive grid generation after each iteration. The movement of free surface is taken care by employing suitable equations for energy and stress balance. Results show the dependency of both the radiation from the crystal and rotation of the crystal on the interface shape.
Electrohydrodynamic Induction Pumping of a Stratified Liquid/Vapor Medium in the Presence of Heat Transfer
Authors: Brand K. , Seyed-Yagoobi J. 
Published: November 2021

Abstract
The effect of heat transfer on the performance of the EHD induction pumping of a liquid/vapor stratified medium is theoretically investigated. The analytical domain considered is represented by a two-dimensional developing plane channel flow of a liquid separated from a vapor by a horizontal interface in a channel bound from below and above by two infinite rigid boundaries. The electrodes generating the electric traveling wave are placed at the bottom of the liquid film. The liquid temperature is assumed constant at the interface of liquid/vapor media while the liquid is cooled or heated at the lower boundary. The dimensionless numerical results are obtained for three different dimensionless wall heat fluxes representing no heat transfer, cooling, and heating at the lower boundary. The controlling parameters include: vapor height, liquid height, voltage, wavelength, and frequency. For the selected operating conditions, the performance of the pump increases with increasing wall heat flux.
Mass Transfer Process of Gaseous Carbon Dioxide Into Water Jet Through Orifice Mixing System
Authors: Zheng Y. H. , Amano R. S. 
Published: November 2021

Abstract
This paper summarizes the mass transfer modeling that can simulate the process of gaseous carbon dioxide dissolution into water in an orifice mixing system. In order to establish the operating characteristics of the orifice mixing system, ordinary tap water and pure carbon dioxide were used as the liquid-gas system. Using the model, computations were performed for an orifice mixing system to better understand the mass transfer process of gaseous carbon dioxide into water through both the elbow tube and the junction Venturi-tube. All computed results show different performance of the carbon dioxide dissolution rates for the given inlet water and carbon dioxide conditions of the four different designs of the junction type Venturi-tubes and an orifice mixing system. After examining the computed results it was found that the mass transfer efficiency of gaseous carbon dioxide into the water stream through the orifice mixing system was superior to that through the junction Venturi-tubes.
Simulation of Micro-Scale Jet Impingement Heat Transfer
Authors: Boeschoten Paul A. , Pence Deborah V. , Liburdy James A. 
Published: November 2021

Abstract
The heat transfer performance of a micro-scale, axisymmetric, confined jet impinging on a flat surface at high Mach numbers (0.2 to 0.6) and low Reynolds numbers (419 to 1310) was computationally studied. The flow is characterized by Knudsen numbers, based on the jet radius, large enough (0.0013) to warrant slip-flow boundary conditions at the impinging surface. The effects of Mach number, compressibility, and slip-flow on heat transfer results are presented, along with the local Nusselt number distributions, and velocity and temperature fields near the impingement surface. Results for uniform wall heat flux show that the wall temperature decreases with increasing Mach number, with a local minimum at r/D = 0.7. The slip velocity also increases with Mach number with peak values also near r/D = 0.7. The resulting Nusselt number increases with increasing Mach number, and a local maximum in the Nusselt number is observed at r/D = 0.6, not at the centerline. In general, compressibility improves heat transfer due to increased fluid density near the impinging surface. Also, inclusion of slip-velocity increases the rate of heat transfer. However, the accompanying temperature-jump condition at the wall is found to reduce the local heat transfer rate. The net effect of the slip-flow boundary conditions applied in this study was an overall reduction in heat transfer.
Numerical Analysis of Buoyancy-Induced Flow and Heat Transfer in an Enclosure With Vents
Authors: Calmidi V. V. , Sathe S. B. 
Published: November 2021

Abstract
This paper reports a numerical study of buoyancy-induced flow and heat transfer in an enclosure with vents. The geometry closely resembles a “set-top-box” application frequently encountered in electronics cooling applications. The heat generating module is modeled as a planar heat source placed on a conducting printed circuit board (PCB). Full 3D and simplified 2D conjugate heat transfer models accounting for conduction and radiation in the solids and conduction and convection in the fluid were used Experiments performed to validate the 3D model have shown excellent comparisons with numerical results. A parametric study involving vent size, power dissipation, number of high conductivity power planes in the PCB has been performed with both the 3D and the 2D models. Although the quantitative results obtained from both types of analyses are similar only under certain conditions, qualitatively, the 2D analysis can be used to obtain useful insights into the complex overall transport mechanisms.
Large Eddy Simulation of Naturally Induced Fire Whirls in a Vertical Square Channel With Corner Gaps
Authors: Farouk B. , McGrattan K. B. , Rehm R. G. 
Published: November 2021

Abstract
Naturally occurring fire whirls are rare but highly destructive phenomena. These are mostly generated by the interaction between a buoyant fire plume and its surroundings. The whirling motion generated can enhance the plume length and sustain burning. In this paper, we report the results of a numerical investigation of whirling fires generated in vertical square channels with symmetric corner gaps. The numerical investigations of swirling fire plumes are used to analyze how the corner gaps alters the plume dynamics and combustion. An approximate (low Mach number) form of the Navier-Stokes equations is solved to calculate the mixing and transport of combustion products. Large scale eddies are directly simulated and sub-grid scale motion is represented with a Smagorinsky model. The current approach is based on a fixed heat release rate, regardless of the strength of the whirl generated by the corner slots. The effect of corner slot widths and their configuration on the swirling motion are studied systematically for a given channel geometry and fixed fuel-loss rate.
Monte Carlo Simulation for Radiometric Temperature Measurement in Rapid Thermal Processing
Authors: Zhou Y. H. , Shen Y. J. , Zhang Z. M. , Tsai B. K. , DeWitt D. P. 
Published: November 2021

Abstract
This work employs a Monte Carlo method to study the radiative process in a rapid thermal processing (RTP) furnace. A “true” effective emissivity, accounting for the directional optical properties, is defined and predicted in order to determine the wafer temperature from the measured spectral radiance temperature using light-pipe radiation thermometry. The true effective emissivity is the same as the hemispherical effective emissivity for diffuse wafers, in which case the Monte Carlo model gives the same results as the net-radiation method. Deviations exist between the hemispherical effective emissivity and the true effective emissivity for specular wafers because the effective emissivity is directional dependent. This research will help reduce the uncertainty in the temperature measurement for RTP furnaces to meet the future requirements for integrated circuit manufacturing.
Large Eddy Simulation of Rotating Channel Flows With and Without Heat Transfer
Authors: Meng Ning , Pletcher Richard H. 
Published: November 2021

Abstract
Large eddy simulation of rotating channel flow with and without heat transfer is reported. The rotation axis is parallel to the spanwise direction of the parallel plate channel. An implicit finite-volume scheme was used to solve the preconditioned time-dependent filtered Navier-Stokes equations using a dynamic subgrid-scale model to account for the subgrid-scale effects. Comparisons are made with available results in the literature for isothermal rotating flows. The combined effects of rotation and heat transfer on the structure of turbulence channel flow is discussed.
Viscosity Effects on the Propagation of Acoustic Transients
Authors: Gaunaurd G. C. , Everstine G. C. 
Published: November 2021

Abstract
The propagation of an impulsive excitation applied at the origin of a lossy viscous medium is studied by operational techniques as the excitation advances through the medium. The solution of the governing partial differential equation (PDE) for such transient propagation problems has been elusive. Such solution is found and quantitatively examined here using a one-dimensional model in space and time. As expected, as the transient advances through space, its amplitude decreases, and its width broadens. Such is the damping effect of viscosity that one would anticipate from elementary considerations in related disciplines such as electrodynamics. Such is also the smoothing-out effect of dispersion. We also obtain an approximate solution of the present boundary-initial value problem based on the method of steepest descents. This approximation agrees with the first term of the complete analytic solution given here. The pertinent dispersion relation associated with the governing parabolic PDE is shown to impose a restrictive condition on the allowable values of the propagation speed and the kinematic viscosity coefficient, thus assuring that propagation with attenuation does take place. Various numerical results illustrate and quantitatively describe the propagation of the transient pulse in several nondimensional graphs.
Implementation of Local, High-Order Accurate Boundary Conditions for Time-Dependent Acoustic Scattering
Authors: Thompson Lonny L. , He Dantong , Huan Runnong 
Published: November 2021

Abstract
A sequence of high-order accurate radiation boundary conditions involving local differential operators of auxiliary functions on a circular boundary are implemented in a spectral finite element method with mixed time integration. The semi-discrete finite element equations are integrated explicitly in time while the auxiliary functions on the circular boundary are integrated using a semi-implicit time-integration method. An efficient algorithm results which avoids the need to update either the solutions for the field variable or the boundary functions at intermediate time steps. Using this mixed time integration approach, a very natural and efficient implementation of the high-order accurate, local boundary conditions is obtained without altering the local/sparse character of the finite element equations. Numerical studies of time-dependent scattering from an elliptic object demonstrate the rapid convergence and accuracy of the implementation.
Possibilities for a Silicon Model of the Cochlea
Authors: Steele Charles R. , Fitzgerald Alissa , Kenny Thomas , Lim Kian-Meng , Puria Sunil 
Published: November 2021

Abstract
The purpose of this study is to resolve questions regarding the fundamental physical behavior of the cochlea of the inner ear. We seek a convergence of measurement and computation on physical models that capture essential features. Since there are unique features in the performance of the cochlea, the physical models could lead to device development. A much longer-term goal is a device for the assistance of hearing impaired individuals. The cochlea can be modeled as a tube of fluid divided by a partition, a portion of which is elastic and called the basilar membrane (BM). In preliminary work, the cochlear partition is constructed on a silicon wafer using current capabilities for micro-machining. The silicon nitride partition is inserted into a chamber of Plexiglas which is filled with solute and has a “stapes” for acoustic input and a “round window”. The silicon BM has the correct length, but is wider and isotropic. The measurements, supported by calculations, show that the deviation from the actual structure has a detrimental effect on the sharpness of the spatial distribution of the response for a fixed input frequency. Possibilities for improved models and for an active non-linear model with distributed sensors and actuators are discussed.
Photoacoustic Leak Testing
Authors: Yönak Serdar H. , Dowling David R. 
Published: November 2021

Abstract
Leak testing is a critical manufacturing quality control process. Unintended leaks in pressurized or evacuated containers may be detrimental to consumers, manufacturers, and/or the environment. This paper describes a leak detection and localization technique based on photoacoustic sounds produced by scanning a carbon dioxide laser over leaks emitting a photoactive tracer gas, sulfur hexaflouride. Photoacoustic signals are recorded in a bandwidth from 3 up to 110 kHz by multiple microphones. From these recorded signals, the presence or absence of a leak may be deduced by comparison with background noise levels. When a leak is present, its location is determined from a simple model of the acoustic environment and matched field processing (MFP). Current results show that a gas leak of 1 cm3 per day can be detected and localized to within ±1 mm in a few seconds using four microphones placed 0.41 m from the leak location and an incoherent average of the MFP ambiguity surfaces at twelve signal frequencies.
The Features of Flow in a Parallel-Walled Radial Vaneless Diffuser
Authors: Abidogun K. B. , Ahmed S. A. 
Published: November 2021

Abstract
Detailed experimental investigation of flow features in a parallel-walled radial vaneless diffuser of a centrifugal blower was carried out. Maximum flow rate through the blower, at a constant impeller speed of 1500 rpm, was maintained throughout the experiment to ensure that no self-exited flow oscillation occurs in the diffuser. The symmetrical flowfield in the diffuser was measured along a radial path using an X-wire probe. The radial and tangential velocity distributions and their statistics, as well as flow angle distribution, are reported. The results presented in this paper agree well with earlier work on this subject. For instance, the flow angle at half the diffuser width, which is the position at which critical flow angle (measured from the radial direction) have been generally reported to be about 78°, did not exceed 65° from the diffuser inlet to its outlet along the measurement path. The result also showed that the flow exiting the impeller is skewed as revealed by the triple velocity product correlations. This data is a useful tool for vaneless diffuser calculation model developers as there are very limited data that paralleled the current one as expounded in the text of this paper.
Effect of Foam Core Density and Facesheet Thickness on the Low Velocity Impact Response of Foam Core Sandwich Composites
Authors: Motuku M. , Rodgers R. M. , Jeelani S. , Vaidya U. K. 
Published: November 2021

Abstract
The effect of foam core density and facesheet thickness on the low velocity impact response and damage evolution in homogeneous foam core sandwich composites was studied. The failure characteristics, initiation and evolution of damage as well as the effect of impact energy were investigated. A Dynatup 8210 Impact Test Machine was utilized to conduct the low-velocity impact tests. Characterization of the impact response was performed by comparing the impact load histories, impact plots and failure characteristics. Fractography analysis was conducted through the use of scanning electron microscopy (SEM) and optical microscopy. Three types of foam cores with different densities, namely Airlite B12.5, Rohacell IG-71R63 and Airex R63.5 foam cores, were used to study the effect of core density. Considering four groups of facesheets made of different layers of cross-ply carbon prepregs performed the effect of facesheet thickness.
For all the facesheet thicknesses (0.011-0.894-cm thick) and impact energy (11-40 J) range considered in this study, the maximum load (Pm), deflection-at-maximum load (δm) and time-to-maximum load (tm) exhibited strong influence or dependence on the type of foam core as opposed to the facesheet thickness. The energy-to-maximum load (Em), total energy absorbed (Et) and total energy-to-impact energy (Et/Eimp) ratio became less sensitive on the foam core density (or type) with increasing facesheet thickness. A transition point from foam core to facesheet controlled impact behavior as a function of impact energy level was observed. The impact parameters varied either linearly or parabolically with impact energy depending on the impact energy level, type of foam core and facesheet thickness. Excellent repeatability of impact data was generally obtained with increase in foam core density.