bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sensitivity of Natural Gas HCCI Combustion to Fuel and Operating Parameters Using Detailed Kinetic Modeling
Authors: Flowers Daniel , Aceves Salvador , Westbrook Charles K. , Smith J. Ray , Dibble Robert 
Published: December 2021

Abstract
This paper uses the HCT (Hydrodynamics, Chemistry and Transport) chemical kinetics code to analyze natural gas HCCI combustion in an engine. The HCT code has been modified to better represent the conditions existing inside an engine, including a wall heat transfer correlation. Combustion control and low power output per displacement remain as two of the biggest challenges to obtaining satisfactory performance out of an HCCI engine, and these are addressed in this paper.
The paper considers the effect of natural gas composition on HCCI combustion, and then explores three control strategies for HCCI engines: DME (dimethyl ether) addition, intake heating and hot EGR addition. The results show that HCCI combustion is sensitive to natural gas composition, and an active control may be required to compensate for possible changes in composition. The three control strategies being considered have a significant effect in changing the combustion parameters for the engine, and should be able to control HCCI combustion.
The Minimum Separation Work for Desalination Processes
Authors: Çerçi Yunus , Çengel Yunus A. , Wood Byard 
Published: December 2021

Abstract
A general relation is obtained for the minimum work input requirement for desalination processes using the second-law of thermodynamics. The relation developed can be used to determine the minimum work input for any salinity of the incoming water, and the recovery ratio. It is also shown that there is a lower and an upper limit for the minimum work, corresponding to recovery ratios of 0% and 100%, respectively. The minimum work input per unit mass of fresh water produced is determined for various salinities of incoming water, and the salinities of fresh water produced, and the results are tabulated and plotted. It is shown that the minimum work is a strong function of salinity, and increases with salinity and the recovery ratio. It is also shown that the minimum work input requirement remains fairly constant for recovery ratios of up to about 80%; the minimum work increases drastically at high recovery ratios; and an optimum value of recovery ratio exists to minimize the power consumption of actual desalination plants. But the value of this optimum recovery ratio decreases with increasing salinity of the incoming saline water. The results presented in this paper can be used as a basis to evaluate the performance of actual desalination plants.
Exergy as a Direct Measure of Environmental Impact
Authors: Sciubba Enrico 
Published: December 2021

Abstract
This paper describes an original approach to the evaluation of the influence of environmental pollution reduction measures on the energetic balance of conversion processes and systems. The quantifier taken to represent this influence is based on an extended representation of the exergy flow diagram of the process. The approach constitutes both a synthesis and a substantial extension of two different methods recently proposed by several independent Research Groups [6,8,15,30], with the purpose of providing Process Designers a general framework to include into their Design Procedures the engineering effects of effluents clean-up. The method presented here provides indeed such a coherent and consistent framework for evaluating environmental externalities, and at the same time constitutes a rational and theoretical basis which can be used to assess present and future pollution reduction technologies and policies. The paper begins with a brief summary of the existing state-of-the-art of environmental accounting techniques is given. It is then argued that some of the issues which are difficult to address with the present Thermoeconomic theory of value can be resolved in a straightforward manner by Extended Exergy Accounting (“EEA” in the following) methods. The importance of selecting the proper control volume (the portion of the biosphere affected by the system) and the correct time scale (the time span which the analysis must cover) are also discussed, and it is shown that their choice strongly affects the outcome of any environmental analysis. As an example of application, a standard cogeneration process is discussed in some detail, albeit at a rather general level.
Effective Yielding Characterization of Ductile Matrix Composites Containing Aligned Spheroidal Particles
Authors: Sun L. Z. , Ju J. W. 
Published: December 2021

Abstract
The effective yielding characterization of ductile matrix composites containing randomly located yet unidirectionally aligned elastic spheroidal reinforcements is investigated. The ensemble-volume averaging procedure is employed to micromechanically derive the effective yield function of composites based on the probabilistic spatial distribution of aligned spheroidal particles and the particle-matrix interaction. The proposed effective yield surfaces of composites are shown to be convex. The initial effective yield criterion of composites under axisymmetric loading is specifically discussed.
Ultrasonic Detection of Fatigue Cracks by Thermoelastic Modulation
Authors: Yan Zhongyu , Nagy Peter B. 
Published: December 2021

Abstract
Pulsed infrared laser irradiation was used to positively identify small fatigue cracks on the surface of fatigue damaged 2024 Al and Ti-6Al-4V specimens. The resulting transient thermoelastic deformation perceptibly changes the opening of partially closed surface cracks without affecting other scatterers, such as surface grooves, corrosion pits, coarse grains, etc., that might hide the fatigue crack from ultrasonic detection. We found that this method, which is very effective in 2024 aluminum alloy, must be modified in order to successfully adapt it to Ti-6Al-4V titanium alloy, where significant thermo-optical modulation occurs even from straight corners or open notches. This spurious modulation is caused by direct thermal modulation of the sound velocity in the intact material rather than thermal stresses via crack closure. It was found that the modified thermo-optical modulation method can increase the detectability of hidden fatigue cracks in 2024 Al and Ti-6Al-4V specimens by approximately one order of magnitude.
Mixed Mode Stress Singularities in Anisotropic Composites
Authors: Yin Wan-Lee 
Published: December 2021

Abstract
Multi-material wedges composed of fully anisotropic elastic sectors generally show intrinsic coupling of the anti-plane and in-plane modes of deformation. Each anisotropic sector has three complex conjugate pairs of material eigensolutions whose form of expression depends on five distinct types of anisotropic materials. Continuity of the displacements and the tractions across the sector interfaces and the traction-free conditions on two exterior boundary edges determine an infinite sequence of eigenvalues and eigensolutions of the multi-material wedge. These eigensolutions are linearly combined to match the traction-boundary data (generated by global finite element analysis of the structure) on a circular path encircling the singularity. The analysis method is applied to a bimaterial wedge near the free edge of a four-layer angle-ply laminate, and to a trimaterial wedge surrounding the tip of an embedded oblique crack in a three-layer composite. Under a uniform temperature load, the elasticity solution based on the eigenseries yields interfacial stresses that are significantly different from the asymptotic solution (given by the first term of the eigenseries), even as the distance from the singularity decreases to subatomic scales. Similar observations have been found previously for isotropic and orthotropic multi-material wedges. This raises serious questions with regard to characterizing the criticality of stress singularity exclusively in terms of the asymptotic solution and the associated stress intensity factors or generalized stress intensity factors.
Postbuckling and Growth Behavior of Face-Sheet Delaminations in Sandwich Composites
Authors: Kadomateas George A. 
Published: December 2021

Abstract
A bending load on a sandwich beam consisting of two fiber-reinforced sheets (skins) separated by a low stiffness core is equivalent to a compressive force on one face and a tensile force on the other. Should an interface crack between the layers of the composite face-sheet or between the core and the composite face-sheet exists on the compressively loaded face, local buckling and subsequently growth of this interface crack (delamination) may occur. This may also naturally occur under pure compression. In this study, the buckling, postbuckling and delamination growth behavior is studied through a procedure that is based on the large deflections of the delaminated layer. First, the solution is derived for the postbuckled states by using the elastica theory to model the large deflections of the thin delaminated layer and the sandwich beam theory (for unsymmetric sections) that includes transverse shear, to model the (relatively modest) deflections of the rest of the structure. This postbuckling solution is subsequently used to study the growth of the mixed mode interface crack through an energy release rate approach. The consequences of the elastic mismatch between core and face sheet are discussed and illustrative results are presented for several sandwich construction configurations.
Three Dimensional Effects in Composite Plates
Authors: Prabhu Santosh , Lambros John 
Published: December 2021

Abstract
In this study, a finite element investigation of the three dimensional nature of stress fields in the near tip region of a cracked orthotropic plate was conducted. Two and three dimensional finite element analyses were used to investigate the relative extent of regions of three dimensional to two dimensional (plane stress or plane strain) deformation in the cracked plate. The material properties used in the simulations corresponded to those of a graphite/epoxy composite. A three point bend loading geometry, with the fiber directions either parallel or perpendicular to the crack, was simulated. In analogy to isotropic materials, it was observed that a plane stress K-dominant region does not arise arbitrarily close to the crack tip because of the existence of a three dimensional zone. However, it was seen that the shape and the size of this three dimensional zone in the cracked composite plate is substantially different from that of an isotropic plate, and depends intimately on material properties. For a crack parallel to the fiber direction the three dimensional zone extends to 0.46h (h = specimen thickness) ahead of the crack tip but only to 0.27h at 30°. Fibers perpendicular to the crack produce a highly elongated three dimensional zone in the direction of the fibers (up to 0.78h). The zone is also sensitive to the variations in the Poisson’s ratio’s of the orthotropic solid.
Thermal Issues That Arise due to Manufacturing Processes: Evaluation and Measurement Techniques
Authors: Sammakia Bahgat , Sathe Sanjeev 
Published: December 2021

Abstract
This paper describes the methodology used to design and evaluate the strength and reliability of the thermal interface between the chip and heat sink (coverplate) in a TBGA first level package. TBGA is a new technology that is part of the new generation of organic ball grid array chip carriers that are quickly gaining popularity for packaging various microprocessors and memory in portables, desktops, mid-range and high-end mainframes. The package consists of a Kapton or Upilex dielectric layer with one signal plane and one ground plane on either side, as shown in Figure 1. The chip is attached to the package with the signal side ‘down’, that is, facing the card. This leaves the backside of the chip available for coverplate (flat copper heat sink) attach. This direct access to the chip allows for a very effective thermal path from the chip directly to the heat sink, resulting in outstanding thermal performance. It is therefore essential to ensure that the interface between the chip and the heat sink remains intact through the end of the assembly processes for the package, including second-level attach to the board and rework. The interface must also remain intact through the life of the product. It is also necessary to ensure that the interface survives all of the necessary qualification stresses including accelerated thermal cycling, thermal age and deep thermal cycling, to name a few. First the results of a numerical analysis are presented showing the impact of surface de-lamination upon the thermal performance of the package. The model used is a full three-dimensional conjugate model accounting for conduction and radiation effects in the package, as well as the natural convection flow in the surrounding air. The results confirm that delamination of the interface degrades the thermal performance of the package. The model and test results also indicate that, due to the robustness of the package, voids or incomplete coverage of the chip with the thermal adhesive results in a relatively small degradation of the thermal performance of the package, provided total de-lamination of the chip or coverplate does not occur. The methodology used in evaluating different design options, such as adhesive material and heat sink surface treatment, is then described in detail. The primary method used for evaluating interfacial strength is a modified fracture toughness test (MFTT). This is the best measure of resistance to crack propagation. In conjunction with the MFTT, a sonographic technique was used to evaluate the integrity of the interface as a function of stress. Finally, a laser moiré tool is employed to evaluate the strains in the package due to thermal stress. The moiré results are shown for an intact package as well as for a completely de-laminated package, showing the differences in the mechanical response of the package due to delamination.
Towards the Development of a Comprehensive HIC: Predicted Injury – Brain Material Dependency
Authors: Taleb L. , Brown M. J. , Sadeghi M. M. 
Published: December 2021

Abstract
This study proposes a systematic computer simulation technique, using strain as a criterion to assess the severity of brain damage under rotational loading, in particular diffuse axonal injury (DAI). A plane strain model representing realistically a section of the brain in the frontal plane (coronal section) is used in this investigation. The Brain-Skull interface has been modelled using a new representation, allowing the brain to move in a true bio-fidelic way, as well as taking into account the damping role of the Cerebrospinal Fluid (CSF), which acts as a buoy forming a protective cushion around the brain. Based on accident reconstruction data from the literature, the model is validated against the injury observed on the victims. Furthermore, this study proposes a parametric study of brain material properties to assess their effect on the brains’ dynamic response and suggests a new injury criterion for the DAI. It appears that the need to develop a comprehensive head injury criterion (CHIC) which takes into account head injuries caused by non-direct impact or by inertial loading becomes crucial.
Natural Convective Heat Transfer Through a Liquid Between a Heated Horizontal Surface and a Vertical Fin Attached to a Cooled Surface
Authors: Oosthuizen Patrick H. 
Published: December 2021

Abstract
Natural convective heat transfer from a heated horizontal surface directly exposed to a liquid into which vertical fins, attached to a cooled horizontal surface, project vertically downwards has been numerically studied. It has been assumed that the flow is steady, laminar and two-dimensional. The governing equations have been written in terms of dimensionless variables and have been solved using the finite element procedure. The solution has the following parameters: the Rayleigh number, the Prandtl number, the dimensionless half-width i.e. the ratio of the half-distance between the fins to the liquid depth, the dimensionless gap between the bottom of the fin and the lower surface, and the ratio of the thermal conductivity of the fin material to that of the liquid. Because of the application being considered, the Prandtl number has been taken as 5. Solutions have been obtained for Rayleigh numbers of between 10 and 1,000,000 for dimensionless half-widths of between 1 and 0.2 for thermal conductivity ratios of 20, 10 and 4 for a range of dimensionless fin gaps and widths.
Transitions and Bifurcations to Chaos in Combined Radiation and Natural Convection in a Two-Dimensional Participating Medium
Authors: Lan Chao-Ho , Ezekoye Ofodike A. , Howell John R. 
Published: December 2021

Abstract
Combined radiation and natural convection in a square cavity with emitting and absorbing participating medium is studied numerically. The equation of radiation transfer is analyzed by the P-1 approximation. The momentum and energy balance equations are calculated using spectral methods. The presence of a radiation source increases the bulk temperature of the fluid, and has a significant influence on the flow pattern and temperature distribution. In this work, the flow is initially stationary, and is simulated from transition to chaos by varying with Rayleigh numbers of 104, 105, 106, 107, and 108. The conduction-radiation parameter ranges from 100 to 0.1, and optical thickness ranges from 10 to 0.01. Comparisons are made with some existing results. The influence of the conduction-radiation parameter, Rayleigh numbers and optical thickness on flow instabilities and bifurcations is discussed.
The Effect of Streamwise Diffusion on Natural Convection From Isothermal, Vertical Parallel Plates
Authors: Li H. H. , Chung B. T. F. 
Published: December 2021

Abstract
More and more evidence has shown that, at low Rayleigh numbers, the natural convective heat transfer from vertical isothermal channel walls is higher than the widely accepted fully-developed asymptote. This paper attempts to analyze the reason for this discrepancy by numerically solving the full Navier-Stokes equations and comparing with the results obtained from the parabolic type of equations. Calculations are made for the air on a wide range of the Rayleigh number and the channel aspect ratio. It is found that the vertical diffusion contained in elliptic formulation becomes important at a low Rayleigh number and cannot be neglected. The fully-developed asymptote supported by the parabolic solution appears to underpredict the Nusselt number except for special conditions.
Features of Natural Convective Air Flows Inside Vertical Parallel-Plate Channels Subject to Step Heat Fluxes: Insulated Upstream and Heated Downstream
Authors: Campo Antonio , Manca Oronzio , Morrone Biagio 
Published: December 2021

Abstract
This paper addresses the impact of adding insulated extensions at the entrance of a parallel-plate channel in which the plates receive a uniform heat flux and a natural convection air flow is responsible for the cooling. The full elliptic conservation equations are solved numerically in a composite I-type computational domain. It was found that the wall temperatures increase when the channel extensions are appended at the inlet. The pertinent results are reported in terms of maximum wall temperatures, induced mass flow rates, as well as velocity, pressure and temperature profiles of the fluid.
Large Eddy Simulations of Jets in Crossflow: Large Scale Turbulence Effects
Authors: Tyagi Mayank , Acharya Sumanta 
Published: December 2021

Abstract
Large eddy simulations of jets in crossflow are performed to study the effect of energy containing scales present in the freestream on the penetration and spread of the coolant jet. Two specific freestream turbulence conditions are examined, one corresponding to 15% small scale Gaussian turbulence, and the other corresponding to a 15% freestream turbulence that satisfies the Von-Karman spectrum and has its peak energy specified in the small wave number range (large scales). The small-scale freestream turbulence can be viewed to be similar to grid generated turbulence. The large scale freestream turbulence spectrum has energy peak at a small wave number (corresponding to a specified length scale taken to be 4 hole diameters in this study) and has energy in the inertial subrange for large wave numbers. In the present study, the jets are issued through a row of square holes into the main crossflow. The jet to crossflow blowing ratio is 0.5 and the jet Reynolds number is approximately 4,700.
Greater jet penetration and jet-mainstream mixing, in both the vertical and lateral directions, are observed for large-scale turbulence. The energy contained in large scales is mostly preserved although the energy carrying scales themselves undergo subsequent breakdown process due to the effect of the jet. In the nearfield of the jet, the large scales play a major role in enhancing the turbulent stresses, and the near wall transport. In the presence of the large scales, the horseshoe vortex is energized, and there is greater crossflow entrainment into the wake region. These large scale effects lead to significantly greater wall friction.
Influence of Cross-Flow Induced Swirl and Impingement on Heat Transfer in an Internal Coolant Passage of a Turbine Airfoil
Authors: Ekkad Srinath V. , Pamula Gautam , Acharya Sumanta 
Published: December 2021

Abstract
Detailed heat transfer distributions are presented inside a two-pass coolant channel with crossflow-induced swirl and impingement. The crossflow is generated from one coolant passage to the adjoining coolant passage through a series of straight or angled holes along the dividing wall. The communicating holes provide for the flow turning from one passage to another typically achieved in a conventional design by a 180° U-bend. The holes direct the flow laterally from one passage to another, and depending on the injection angle, cause impingement and generate swirl. The heat transfer enhancement in the second pass is achieved by the combination of impingement and crossflow-induced swirl. Heat transfer distributions are presented on the sidewalls of the passages. Three different hole configurations are tested for three flow channel Reynolds numbers (Re = 10000–50000). The hole configurations were varied by angle of delivery and location on the divider wall. A transient liquid crystal technique is applied to measure the detailed heat transfer coefficient distributions inside the passages. Results for the three hole supply cases are compared with the results from the traditional 180° turn passage. Results show that the new feed system, from first pass to second pass using crossflow injection holes, produces significantly higher Nusselt numbers on the second pass walls. The enhancement is as high as 7–8 times greater than obtained in the second pass for a channel with a 180° turn. The additional pressure drop (rise in friction factor) caused by flow through the crossflow holes is compensated by the significant heat transfer enhancement obtained by the new configuration.