bluuebunny/crossref_metadata_2025 huggingface dataset:
Horizontal Two Phase Flow Regime Identification: Comparison of Pressure Signature, Electrical Capacitance Tomography (ECT) and High Speed Visualization
Authors: Kreitzer Paul J. , Hanchak Michael , Byrd Larry
Published: October 2013

Understanding the behavior of transient two phase refrigerant flow is an important aspect of implementing vapor compression systems in future aerospace applications. Pressure drop and heat transfer coefficient are important parameters that guide the design process, and are influenced by flow regime. Published two phase flow models rely heavily on a priori knowledge of the current two phase flow conditions including flow regime. Additional complications arise when applying published correlations to a range of systems because each correlation is based on a specific set of experimental conditions, including working fluid, flow orientation, channel size, and channel shape. Non-intrusive measurement techniques provide important advantages while measuring the behavior of two phase flow systems.

A two phase flow experimental test rig has been developed at the Air Force Research Laboratory, providing a closed loop refrigeration system capable of producing flow regimes from bubbly through annular flow. Two phase flow is produced by pumping subcooled R134a through a heat exchanger with 40 minichannels into an adiabatic transparent fused quartz observation channel with a hydraulic diameter of 7 mm. Refrigerant mass flux is varied from 100–400 kg/m2s with a heat flux from 0–15.5 W/cm2. Temperatures ranged from 18–25 °C and pressures between 550–750 kPa. The data from high speed pressure transducers were analyzed using standard signal processing techniques to identify the different flow regimes. Initial results indicate that different flow regimes can be identified from their pressure signature. In addition, real-time void fraction measurements were taken using Electrical Capacitance Tomography (ECT). This paper describes the process behind ECT systems used to measure two phase flow conditions. Comparisons with high speed video assess the accuracy of ECT measurements in identifying various two phase flow conditions. Results indicate variations between ECT and high speed images, however, enough information is provided to create flow pattern maps and regime identification for different superficial vapor and liquid velocities.
Design of a Heat Sink in an Undergraduate Heat Transfer Course
Authors: Smith Andrew N. , Volino Ralph J. , Flack Karen A.
Published: October 2013

Thermal design was incorporated into an undergraduate heat transfer course through a multistage design project. The students were tasked with designing water channels to be cut in an aluminum block using a wire electrical discharge machining (EDM) process. The students begin the process by analyzing the internal channels as a one dimensional array of fins using traditional analysis and correlations and Engineering Equation Solver (EES) to perform the calculations. Working in groups of two, the students conduct several parametric studies and develop a preliminary design using an array of fins method. The requirements for the design included outcomes that had to be met, along with weighting factors for key aspects of the design such as thermal performance, pressure drop, fabrication cost and volumetric flow rate. Next, the students analyze their preliminary design using SolidWorks flow simulation and compare their results to the one dimensional array of fins analysis. The groups then begin the process of refining their design using SolidWorks flow simulation to predict key parameters. Finally, the students select their best design which is fabricated using a wire EDM machine. The heat sinks are tested using a single experimental apparatus and the best design is determined based on the original requirements. The project is first introduced when the students are covering resistor networks and the analysis of an array of fins. The computational aspect of the project begins after the students have covered steady state conduction using finite difference methods. Using the computational results the students plot the heat transfer coefficient on the surface of the channel, which complements the lectures on internal developing flows.
Development of a Seismic Isolation System for Commercial Storage Racks
Authors: Johnson David H. , Michael Robert J. , Pollino Michael C. , Redovan Joseph D. , Moser Eric E. , Macdonald Blake A.
Published: October 2013

This paper provides an overview of an analysis performed on a new base isolation system developed for seismic isolation of steel pallet storage racks. Pallet storage racks are often found in warehousing for material storage and are designed to store materials on pallets in horizontal rows with multiple levels which are accessed by forklift trucks. The new isolation system provides seismic isolation in the cross-aisle direction by incorporating heavily damped elastomeric bearings (referred to here as seismic mounts) and low-friction bearing plates. The objective of the base isolation system is to reduce horizontal accelerations of the rack to eliminate product shedding and structural damage during a major earthquake without interfering with normal, day-to-day material handling operations. The paper presents a summary of numerical results (transient structural, finite element analysis simulation) comparing storage rack response against actual tests performed on a triaxial shake table in the Structural Engineering and Earthquake Simulation Laboratory (SEESL) at the University at Buffalo (see Filiatrault[1] et al. 2008 for comprehensive test details). The simulation model was then used to determine a set of optimal seismic isolation parameters that satisfy the practical range of rack shelf loads and configurations that can be expected in typical warehouse and store installations.
Influence of Projectile Momentum and Kinetic Energy on Bacterial Distribution in an Extremity Surrogate “Wound Track”
Authors: Krebsbach Meaghen A. , Muci-Küchler Karim H. , Hinz Brandon J.
Published: October 2013

This paper presents an experimental study that examines the relationship between the initial momentum and the initial kinetic energy of a projectile and the distribution of bacterial contamination along a “wound track” created in an extremity surrogate representative of the superior (upper) portion of the lower leg (i.e., the calf region) of an average adult human male. Initial surface contamination was represented using circular filter paper moistened with a solution containing 5 × 106 colony forming units per milliliter (CFU/ml) of Escherichia coli strain K-12 that was previously transformed to express green fluorescent protein (GFP) and be resistant to ampicillin. The contaminated filter paper and extremity surrogate were perforated with 11.43-mm (0.45-in) caliber round nose lead projectiles shot from commercially available air rifles. To match the initial momentum and/or kinetic energy between experiments, 11.0 g (170 grain) and 14.9 g (230 grain) projectiles were shot at velocities ranging from 145 m/s to 195 m/s. The “wound track” was extracted from the extremity surrogate and sliced into small, evenly spaced segments and the permanent cavity was removed from each segment using a biopsy punch, liquefied, and grown on selective agar containing ampicillin. Examination of the bacterial colony count and area covered by bacteria colonies per segment allowed comparison of differences between trends in the bacteria distribution along the “wound track”. The results obtained showed that, for the cases considered, the bacterial distribution trends were similar for the experimental groups with like initial kinetic energies.
Torsional Vibration Active Control of a Diesel Engine Based on Adjustment of the Fuel Injection Vector
Authors: Huang Ying , Yang Yongguang , Zhang Fujun , Zhao Zhenfeng
Published: October 2013

The torsional vibration of a crankshaft greatly affects engine performance, and the control and suppression of such vibration have thus always been a focus of engine research. The introduction of an electronic fuel-injection system for the diesel engine has made it possible to control individual cylinders, thus providing a new way to actively control the torsional vibration of a diesel engine. A V8 diesel engine model for co-simulation between crankshaft dynamics and engine performance was established with GT-SUIT software, and the model was verified by experiment data. The active control of crankshaft torsional vibration of a diesel engine by adjusting the fuel injection vector was simulated. First, the amplitude–frequency and phase–frequency characteristics of the excitation torque under different fuel-injection-vector conditions were analyzed. On the basis of the frequency characteristics, different active vibration-suppression schemes were studied, and the crankshaft vibration suppression effects were compared. The simulation results show that adjusting the fuel injection vector is an effective approach for controlling the torsional vibration of an engine crankshaft.
Research on Model of Noise Prediction of High-Speed Train by SEA Method
Authors: Yang Lifang , He Xiaowei , Meng Fanyu
Published: October 2013

China’s rapid development of high-speed train has been in the research spotlight over the years; this paper presents a method to predict the transmission of aerodynamic noise and rail noise inside train compartments for high-speed trains operating at speeds larger than 200 km/h. The numerical tool could be used in parameter studies for noise control. In order to develop the noise prediction model of high speed train, the noise source of high-speed train is analyzed. Based on the noise analysis, the SEA model is built. Due to the small noise difference in one train car, the SEA model is divided into head cab, head passenger cab and middle car three parts. Combined with the finite and boundary element method, the input power and SEA parameters are researched and calculated. In the end of the paper, the results of SEA noise predicting model are compared with theoretical calculation results in order to verify the engineering use.
Comparative Analysis of Fuel Cell and Photovoltaic Panels as Electrical Sources for RO Desalination Domestic Scale Systems
Authors: Abdel-Rehim Ahmed A. , Abdel-Mesih Bahy S. A. , Alostaz Jamal E.
Published: October 2013

Fuel cells and photovoltaic cells are two promising technologies for green sustainable societies. Both are technologies that are capable of producing electricity but with different techniques. A solar cell converts light directly into electricity by the photovoltaic effect. On the other hand, a fuel cell converts the chemical energy from the reaction between oxygen and a fuel into electricity and water. The fuel used is hydrogen which can be produced using solar energy. Both devices have different working principles, operation requirements, and efficiencies. However, they share the end goal of producing electricity from a non-fossil clean energy source. The main objective of this work is to investigate whether fuel cells or solar cells are more feasible for domestic use by considering the available technologies and information. The comparison is based on the electricity produced by the two technologies provided the same input of energy from the sun. The research focuses on the electrical output, their efficiencies, and the cost of purchasing, operation, and thus the cost of energy produced from the whole system. A desalination domestic scale system based on Reverse Osmosis (RO) technique was proposed as an application to consume this energy.
Modeling of a Hybrid-Hydraulic Electric Vehicle
Authors: Hamzehlouia Sina , Izadian Afshin , Anwar Sohel
Published: October 2013

This paper introduces modeling of a gearless hydraulic transmission system that provides an infinite speed ratio like continuous variable transmission (CVT). The transmission system is modeled in various operating conditions such as all-electric and gasoline configurations. The results demonstrate the high performance operation of the transmission system.
Impact of Heat Transfer on Centrifugal Compressors of Micro Turbines
Authors: Verstraete Dries , Hewakuruppu Yasitha
Published: October 2013

Micro turbines are small, high-speed gas turbine engines. When designed for a power output of 5 to 15 kW, micro turbines could provide the power for a household or a small set of units, serve as a range extender for hybrid electrical vehicles, or an auxiliary power unit to meet anti-idling requirements for heavy-duty diesel truck engines. The smaller the gas turbine, the harder it however is to achieve a competitive efficiency. At the considered power level, manufacturing limitations become significant and heat transfer and fluid leaks start to dominate. Significant development in material science has enabled higher temperatures to be sustained, so that reasonable efficiencies could be obtained. Achieving these efficiencies however depends critically on limiting the effect of inter component heat transfer. In this paper the impact of heat losses on the performance of small centrifugal compressors are investigated. The paper presents the adaptation of a 1D design and performance analysis code to accommodate heat transfer effects. The modifications made to the code to account for heat transfer will be discussed and a validation of the adapted code will be given. After that the performance of several non-adiabatic compressor impellers will be discussed in detail. Design modifications will be presented that reduce the impact of heat transfer for the investigated compressors. The impact on heat transfer on the compressor maps will also be detailed.
A Compact Cantilever Model That Includes Fillets
Authors: Chigullapalli Aarti , Clark Jason V.
Published: October 2013

In this paper we present analytical expressions for determining the stiffness of cantilevers with fillets and tappers. We consider the unavoidable fillet due to the feature size limitation of lithography that rounds acute vertices, and the intentional tapper that is often used for reducing stress concentrations or can be used to reduce the effect of fillets. Previous compact models have not included the stiffness contributions from fillets. However, although fillets are small, they can measurably affect the performance of MEMS by affecting deflection or resonance frequency by their second most significant digit. We extend the well-known analytical beam model to include fillets. To our knowledge, this is the first analytical model of a filleted cantilever. In addition to the typical model parameters of beams, our model also includes process variation overcut and fillet radius of curvature, which are key parameters for MEMS designers. Our analytical solution is within 0.01% of finite element analysis.
Static Pull-In Analysis of Micro-Cantilevers in Wet Etching Fabrication Process
Authors: Darvishian Ali , Moeenfard Hamid , Ahmadian Mohammad Taghi
Published: October 2013

Parallel micro actuators are mostly fabricated using the wet etching process within which the presence of capillary force and the resulting pull-in instabilities can severely affect the success of the fabrication process. In the case the capillary force is large enough then the beam like structure of the micro actuators is collapsed. The current paper investigates; static behavior of micro-cantilevers under effect of capillary force. It is observed that with increasing the instability number defined in the paper, the deflection of the micro-cantilevers is increased. This study shows in the wet etching fabrication process, if the distance between the beam and substrate is small enough, the beam would collapse and adhere to the underneath substrate. Results of this paper can be used for successful fabrication of micro-beams and failure prevention of micro-cantilevers in wet etching process.
Influence of Fringing Field Effect on the Pull-In of Size Dependent Micro-Beams
Authors: Darvishian Ali , Moeenfard Hamid , Ahmadian Mohammad Taghi
Published: October 2013

This study investigates influence of fringing field effect on the voltage dependent behavior of electrostatically actuated micro-beams. For this purpose, the size dependent beam model is used. Strain gradient formulation is utilized to consider size effects. The effect of fringing field effect on the beam’s behavior is investigated and it is shown that lack of considering the fringing field effect in the formulation of the problem may lead to considerable error in predicting the size dependent micro-beams behavior under the effect of electrostatic actuation. The results of this research can be used for safe and stable design of electrostatically actuated micro-beams.
Characterization of Static Behavior of Electrostatically Actuated Micro Tweezers Using Modified Couple Stress Theory
Authors: Darvishian Ali , Moeenfard Hamid , Ghaderi Nasser , Ahmadian Mohammad Taghi
Published: October 2013

In this paper, static behavior and pull-in of micro tweezers is studied. The micro tweezer is modelled as two cantilever beams. Static behavior of the micro tweezer under the effect of electrostatic actuation is modelled using the Euler-Bernoulli beam theory. In order to capture size effects on the behavior of micro tweezers, modified couple stress theory is utilized. It is shown when the voltage between two electrodes increased from some specific value, micro beams adhere to each other and it is observed that the pull-in voltage predicted by the modified couple stress theory considerably differs with that of the classical theory of elasticity. Results of this paper can be used for accurate design, synthesis and optimization of micro tweezers.
Coupled Direct Numerical Simulation and Experimental Approach to Develop Framework for Nano Fluids
Authors: Sloan Gregory , Feng Zhi-Gang , Bhaganagar Kiran , Banerjee Debyjoti
Published: October 2013

Nanofluids are considered to be attractive as heat transfer fluids (HTF) and thermal energy storage (TES) for concentrated solar power (CSP) applications. Solvents doped with relatively low concentrations of nanoparticles (with diameters up to 100 nm) are termed as nanofluids. Numerical models for exploring the forces experienced by the nanoparticles are needed in order to ascertain the transport processes responsible for the anomalous material properties of the nanofluids that are observed in experimental measurements.

In this study a multiscale approach to modeling the forces acting on these particles was performed and the dynamics of transient nanoparticle agglomeration have been explored. The validity of the multiscale approach is demonstrated by examining a pair of nanoparticles in a fluid. The force interactions due to the presence of the electric double layer (EDL) were identified as a significant factor in determining the propensity for agglomerative of the nanoparticles. Simulations were performed to demonstrate the clustering and agglomeration of an ensemble of nanoparticles. The simulation results provide an estimate for the time scale for the agglomeration and the resultant structure of the agglomerated ensemble of nanoparticles. Subsequently simulations were performed using this numerical model corresponding to the available experimental data in the literature. The predictions from the numerical simulations show that the change in zeta potential (determined in part by the pH of the solvent phase) is a crucial parameter that affects the level of agglomeration of the nanoparticles. Finally, the numerical scheme is extended for performing true 3-D simulation. This approach is more sophisticated than the contemporary schemes that are reported in the literature that project 3-D forces on to a 2-D plane.
Nonlinear Analysis of Pull-In Voltage for a Fully Clamped Microplate With Movable Base
Authors: Karimzade Ali , Moeenfard Hamid , Ahmadian Mohammad Taghi
Published: October 2013

Micro-electro-mechanical systems (MEMS) such as sensors and actuators are rapidly gaining popularity in a variety of industrial applications. Usually these systems are constructed by a cantilever beam or plate along with a fixed substrate. The movable beam or plate deflects due to applied voltage between the plates. Pull-in voltage and contact time are the most important characteristic of these systems. Allowing the substrate to be movable in vertical direction pull-in voltage in comparison with the fixed substrate is expected to be much smaller. In this paper the pull-in voltage and the point at which pull-in takes place for a fully clamped microplate is evaluated. The nonlinear differential equation of microplate utilizing minimum total potential energy principle is obtained. The governing equations are solved using Extended Kantorovich method and first order Galerkin approximation technique. Results revealed that in movable based MEMS pull-in voltage decreases considerably in comparison with fixed substrate while center point deflection increases when the beam is under compression inplane loads.
Nonlinear Analysis of Pull-In Phenomenon and Maximum Deflection of MEMS With Movable Base Under Capillary and Van Der Waals Forces
Authors: Karimzade Ali , Ahmadian Mohammad Taghi , Asemani Hamidreza
Published: October 2013

In the analysis of micro structures, due to proximity of the elements Van der Waals forces plays an important role on the dynamics of the structure. In the modeling process a similar approach should be considered for the capillary effect caused by the moisture in the environment. Microplates and microbeams are used widely in the design and manufacturing of sensors and actuators. These structures are usually made of a cantilever beam or plate along with a fixed substrate. The cantilever beam usually deflects due to applied voltage. By increasing the voltage the pull-in phenomenon takes place. It is believed that the short contact time is one the important characteristic of any micro switches. In this paper allowing the substrate to be movable in the vertical direction and considering the combined effect of capillary and Van der Waals (VdW) effects maximum deflection and pull-in phenomena in terms of applied voltage is evaluated. The minimum potential energy is utilized to find the nonlinear differential equations of movable based micro-electro-mechanical systems (MEMS). Results show that pull-in voltage decreases drastically for fully clamped micro plates considering capillary and VdW effect.
Effect of Breakout Angle on Tripod Injection Hole Geometries on Flat Plate Film Cooling
Authors: LeBlanc Christopher , Ramesh Sridharan , Ekkad Srinath , Alvin Mary Anne
Published: October 2013

In this study, effect of breakout angle of side holes from the main hole in a tripod hole design on film cooling performance is evaluated on a flat plate surface with steady-state IR (infrared thermography) technique. The designs are compared a cylindrical hole design inclined at 30° from the surface with pitch-to-diameter ratio of 3.0 and a shaped hole design, which is identical to the cylindrical hole design with the addition of adding a 10° flare and laydown to the exit on the mainstream surface. The two tripod hole designs are one where the two side holes, also of the same diameter, branch from the root at a 15° angle while maintaining the same 30° inclination as the cylindrical and shaped designs witha pitch-to-diameter ratio between the main holes for this design is 6.0. The other tripod hole design is a modified tripod hole design that increases the branch angle to 30°, which has the added effect of increasing the pitch-to-diameter ratio between the main holes to 7.5. Two secondary fluids — air and carbon-dioxide — were used to study the effects of coolant-to-mainstream density ratio (DR = 0.95 and 1.45) on film cooling effectiveness. Several blowing ratios in the range 0.5–4.0 were investigated independently at the two density ratios. Results show that the tripod hole design provides similar film cooling effectiveness as the shaped hole case with overall reduced coolant usage. Increasing the breakout angle from 15° to 30° reduces overall cooling effectiveness but increases jet-to-jet interactions.
RANS Investigation of the Transitional Flow Over Stepped NLF(1)-0416
Authors: Sammak Shervin , Mojgani Rambod , Boroomand Masoud
Published: October 2013

The Computational Fluid Dynamic simulation of RANS equations over NLF(1)-0416, utilized by backward facing step, is investigated for enhancement of aerodynamic characteristics. This article concentrates on the effects of step location transition point and reattachment of separated flow by backward facing step on pressure distribution and skin friction coefficient and subsequently on lift and drag. Reynolds number (based on the free stream velocity and airfoil chord) is 2.0 million. The finite volume method has been employed to numerically solve the steady state compressible Reynolds Averaged Navier-Stokes (RANS) equations with second order Roe’s scheme. Steps at different chordwise locations are chosen on both suction and pressure sides of the airfoil in order to determine their effects on skin friction, lift, lift to drag ratio and near stall behavior. In specific cases decreasing in drag is achieved due to step point on the chord followed by transition inception. The results show that all stepped studied airfoil cases experienced higher drag in comparison with base airfoil. Lift to drag ratio enhancement is seen in step on pressure side while the step extended to leading edge, this effect increases. Based on the results, delaying stall in some cases with step on suction surface is concluded.
Computational Analysis of a Compressor Rotor With Enhanced Airfoil
Authors: Sammak Shervin , Boroomand Masoud
Published: October 2013

In this article, a compressor rotor blade is numerically modeled and solved by a CFD code. A stepped blade with higher aerodynamic characteristics is used to investigate unstable zone and improve operational limit and compressor stall. To validate numerical data original test case compared with experimental measurements. In this study, several locations of step on suction side of blades are tried, finally the results are compared with the case with no step on blades. It is shown that, by moving the step towards the leading edge, surge is delayed due to the reattachment of flow after the step. Efficiency is also decreased but lower than previous case.
Layered Hepatocytes and Endothelial Cells on a Transwell Membrane: Toward Engineering the Liver Sinusoid
Authors: Kang Young Bok (Abraham) , Cirillo Joseph , Rawat Siddhartha , Bouchard Michael , Noh Hongseok (Moses)
Published: October 2013

This paper presents a novel liver model platform that mimics the liver sinusoid, a functional unit of the liver where most liver activities occur. A key component of the current liver model is a layered co-culture of primary rat hepatocytes (PRH) and primary rat liver sinusoidal endothelial cells (LSEC) or a bovine aortic endothelial cells (BAEC) as an alternative. Poly-dimethylsiloxane (PDMS) microchannels were fabricated and attached to transwell membranes that contain submicroscale pores. Cells were cultured either on one side or on both sides of the transwell membrane, and in both cases cells formed confluent layers. A thin matrigel coating or micro porous membrane was applied between the two cell layers in order to mimic the Space of Disse. We used three different methods to check cell viability: recombinant adenovirus expressing green fluorescent protein, mito-tracker red to stain live mitochondria, and an expression plasmid expressing red fluorescent protein (RFP). It was shown that PRH retained normal morphology and remained viable for about 3 days with BAEC in the PDMS microchannel, about 57 days with BAEC on the transwell, and about 39 days with primary LSEC on the transwell. Preliminary observation suggests that there is formation of structures between hepatocytes that appear similar to bile canaliculi when PRH are co-cultured with endothelial cells. The layered co-culture system seems to be a promising method to generate accurate liver models.
Computational Study of Edge Cooling for Open-Cathode Polymer Electrolyte Fuel Cell Stacks
Authors: Sasmito Agus Pulung , Shamim Tariq , Birgersson Erik , Mujumdar Arun Sadashiv
Published: October 2013

In open-cathode polymer electrolyte fuel cell (PEFC) stacks, a significant temperature rise can exist due to insufficient cooling, especially at higher current densities. To improve stack thermal management whilst reducing the cost for cooling, we propose a forced air-convection open-cathode fuel cell stack with edge cooling (fins). The impact of the edge cooling is studied via mathematical model of the three-dimensional two-phase flow and associated conservation equations of mass, momentum, species, energy and charge. The model includes stack, ambient, fan and fins used for cooling. The model results predict better thermal management and stack performance for the proposed design as compared to the conventional open-cathode stack design, which shows potential for practical application. Several key design parameters — fin material and fin geometry — are also investigated with regards to the stack performance and thermal management.
Interface Turbulence Treatments in RANS Models of Stratified Gas/Liquid Flows
Authors: Thompson Chris P. , Sawko Robert
Published: October 2013

Computational fluid dynamic analyses for industrial purposes often rely on Reynolds averaged models for resolving turbulent flows. These models were developed primarily for single phase fluids and their extension to multiphase flows requires additional modifications and careful considerations. Modelling the effect of gas-liquid interface on turbulence in adjacent fluids has been a subject of many investigations but the results of these studies have not yet made its way into RANS models. This paper presents a model that incorporates recent DNS studies as well as some analytical considerations. Although an improvement in the flow rate prediction was obtained the improvement was sensitive to mesh refinement. Possibilities of further research is outlined.
Modeling Flows in Porous Media Using Immersed Boundary Based Lattice Boltzman Method
Authors: Feng Zhi-Gang , Andersson Maria
Published: October 2013

Flows in porous media of fixed arrays of spheres have been studied numerically in the present work. The flow velocity and pressure fields are solved by the lattice Boltzmann method; the no-slip boundary condition at the solid-fluid interface is enforced by the immersed boundary method with the direct forcing scheme. This numerical method, which we call Proteus and initially was developed for simulations of particles in motion, has been extended to study flow over fixed arrays of spheres. The method is validated by comparing the simulated drag coefficient on a single sphere to the one obtained using an empirical drag law. The present method is then applied to obtain the dimensionless drag force on a sphere in both ordered face-centered cubic arrays of spheres and random arrays of spheres. Our results at low solid volume fraction for ordered arrays of spheres show good agreement with the theoretical solution of Hasimoto (1959). A correlation on the drag coefficient at solid fraction ranging from 0 to 0.66 has been derived based on our simulation results. This will help improve the modeling of particulate flows. The case of flow over random arrays of spheres at the solid fraction of 0.345 and flow Reynolds numbers up to 57 has also been studied. Our results agree well with the Ergun’s empirical correlation.
Determination of Two-Phase Flow Void Fraction of R600a in a Horizontal Smooth Tube
Authors: Ağra Özden , Demir Hakan , Atayılmaz Ş. Özgür , Yurtseven Ahmet , Dalkılıç A. Selim , Wongwises Somchai
Published: October 2013

In this paper, the void fraction of alternative refrigerant R600a flowing inside horizontal tube is determined by means of an experimental technique, well known correlations in the literature and a generalized neural network analysis. The horizontal tube is made from smooth glass tubing of 4 mm inner diameter. The test runs are done at average saturated condensing temperatures between 30 and 40 °C while the average qualities and the mass fluxes are between 0.45–0.91 and 68.5–138.1 kg m-2s-1 respectively. The flow regime determination inside the tube is performed by means of sight glasses placed at the inlet and outlet sections of the test section, used for in-tube condensation tests, virtually. An image processing technique, performed by means of a high speed camera, is used to determine the void fractions of stratified and annular condensing flow of R600a experimentally. The void fractions are determined using relevant measured data together with 11 different void fraction models and correlations reported in the open literature analytically. Artificial neural network (ANN) analysis is developed to determine the void fractions numerically. For this aim, mass flow rate, average vapor quality, saturation temperature, liquid and vapor densities, liquid and vapor dynamic viscosities and surface tension are selected as the input parameters, while the void fraction is selected as the output.

Three-layer network is used for predicting the void fraction. The number of the neurons in the hidden layer was determined by a trial and error process evaluating the performance of the network and standard sensitivity analysis. The measured void fraction values are found to be in good agreement with those from ANN analysis and correlations in the literature. It is also seen that the trained network are more predictive on the determination of void fraction than most of the investigated correlations.
NVH Performance of Lightweight Glazing Materials in Vehicle Design
Authors: Gur Yuksel , Wykoff Rick , Nietering Kenneth E. , Wagner David A.
Published: October 2013

Fuel economy and NVH (noise, vibration, and harshness) performance of vehicles are important parameters in a customer’s vehicle purchase decision. Lightweight vehicle designs are necessary to help with fuel economy improvements. In this research work, the weight saving potential and NVH performance of different lightweight glazing materials are investigated to help the lightweight design effort. The lightweight glazing materials included in this study are “Material A”, “Material B”, “Material C” with regular lamination, and “Material C” with acoustic lamination. The results of this research work indicate that the lightweight glazing materials have 30% to 40% weight saving potentials without NVH penalty. These materials have much higher damping properties than conventional tempered glass so they can compensate for the mass reduction influence on vehicle NVH. The tire patch noise reduction, vehicle transparency, and wind noise results of “Vehicle A” tested with different lightweight backlight designs indicate that there is almost no acoustic response difference between the tempered glass and other lightweight alternative backlight designs. Damping loss factor measurements indicate that “Material C” with acoustic PVB (polyvinyl-butyral) has the highest damping loss factor value of 37%. The “Material C” backlight with acoustic PVB is the best among all the lightweight alternatives and brings 29% weight reduction without any NVH degradation. Statistical Energy Analysis (SEA) results also indicate that it is possible to eliminate the NVH degradation by using glazing material having high material damping properties or using laminated panels having damping loss values in the range of 6% to 20%. In this paper, we only address the weight reduction and NVH performance of light weight glazing materials but not the costs or any potential assembly procedure changes.
Temperature Distribution and Fluid Flow Modeling of Electron Beam Melting® (EBM)
Authors: Jamshidinia M. , Kong F. , Kovacevic R.
Published: October 2013

A three-dimensional (3D) numerical model is developed by using control volume method to analyze the effects of the electron beam scanning speed on the temperature distribution and fluid flow of the liquid phase in the electron beam melting® (EBM) of Ti-6Al-4V powder. The numerical calculations are performed by Fluent codes, in which thermal analyses with and without considering fluid flow in the molten pool are compared. A series of experiments are performed with an Electron Beam Melting® machine to verify the numerical accuracy. Compared to thermal analysis without considering convection in the molten pool, a closer numerical prediction of geometrical size of molten pool to the experimental data can be achieved by using thermal and fluid flow modeling. The difference between the melt pool geometry in the two models is due to the consideration of the effects of the outward flow in the fluid flow model caused by surface tension.
Fully-Developed Thermal Transport in Microchannels With Streamwise Grooved Superhydrophobic Walls at Constant Heat Flux
Authors: Maynes D. , Vanderhoff J. , Rosengarten G.
Published: October 2013

This paper presents an analytical investigation of constant property, steady, fully-developed, laminar thermal transport in a parallel-plate channel comprised of metal superhydrophobic walls. The superhydrophobic walls considered here exhibit micro-ribs and cavities aligned in the streamwise direction. The cavities are assumed to be non-wetting and contain air, such that the Cassie-Baxter state is the interfacial state considered. The scenario considered is that of constant heat flux through the rib surfaces with negligible thermal transport through the air cavity interface. Closed form solutions for the local Nusselt number and local wall temperature are presented and are in the form of infinite series expansions. The analysis show the relative size of the cavity regions compared to the total rib and cavity width (cavity fraction) exercises significant influence on the aggregate thermal transport behavior. Further, the relative size of the rib and cavity module width compared to the channel hydraulic diameter (relative module width) also influences the Nusselt number. The spatially varying Nusselt number and wall temperature are presented as a function of the cavity fraction and the relative module width over the ranges 0–0.99 and 0.01–1.0, respectively. From these results the rib/cavity module averaged Nusselt number was determined as a function of the governing parameters. The results reveal that increases in either the cavity fraction or relative module width lead to decreases in the average Nusselt number and results are presented over a wide range of conditions from which the average Nusselt number can be determined for heat transfer analysis. Further, analogous to the hydrodynamic slip length, a temperature jump length describing the apparent temperature jump at the wall is determined in terms of the cavity fraction. Remarkably, it is nearly identical to the hydrodynamic slip length for the scenario considered here and allows straightforward determination of the average Nusselt number for any cavity fraction and relative rib/cavity module width.
Bond Strength Models for Adhesively Bonded Flip-Chip Interconnects
Authors: Sinha K. , Dasgupta A. , Caers J.
Published: October 2013

This paper investigates the role of gold-to-gold interfacial metallurgical bonding on the bond strength of adhesively bonded flip-chip interconnects in microelectronic assemblies. [44] dealt with experimental investigation of the effect of bonding parameters on Au-Au interfacial bond strength. One of the major conclusions in [44] was that interfacial creep deformation closely correlated with the measured evolution of bond strength over time. This study presents a viscoplastic finite element analysis to capture the physical creep mechanisms that drive the development of this strength, so that the effect of the system architecture and bonding parameters can be effectively quantified. Based on the studies in literature [42, 43], the strength is assumed to depend on the area of the contact “a-spots,” which are defined here as the area over which the interfaces come into intimate, atomistically flat contact.

The most important inputs to the finite element model consist of (i) interfacial geometry (with special emphasis on the surface roughness topology); (ii) viscoplastic mechanical properties of gold; and (iii) bonding parameters (force, temperature and time). The viscoplastic constitutive properties for gold are obtained partly from experiments conducted in this study and partly from the existing literature. The model inputs are parametrically varied in a systematic way within the design space, to obtain the variability expected in the bond strength. The simulation results are captured in a response surface model that can predict bond strength for a given set of fabrication conditions. The response surface model thus serves as a prediction tool critical for optimizing the interconnect strength and the durability of adhesively bonded flip chip assemblies.
Time-Efficient Method for Test-Based Optimization of Technical Systems Using Physical Models
Authors: Albers Albert , Schwarz Alexander , Behrendt Matthias , Hettel Rolf
Published: October 2013

Technical systems must be continuously improved so that they can remain competitive on the market. Also, the time-to-market is an important factor for the success of a product. To achieve this goal, new methods and processes are needed. Especially the testing and calibration are important phases in the development process.

This paper introduces a method, which helps to reduce the time effort while increasing the quality of the calibration process. The basic idea is to use measured test data to parameterize a physical (or mostly physical) model structure to create adequate models for the optimization. The main advantage of the method is the reduction of test effort because the number of variations of the design parameter is one, or extremely decreased (depending on the system). Another advantage is that the uncertainty and the limit of the model can be quantified more accurately compared to common approaches based on non-physical model structures. These normally use artificial neuronal networks (ANN) or polynomial approaches for the test-based optimization.

This contribution illustrates the method by using the example of the calibration process of a double clutch gearbox (DCT) regarding energy efficiency and drivability on a roller test bench. First step is the test planning and test execution. In this step the method calculates the optimal execution order of the measuring points. In this example 81% timesaving can be achieved compared to the equivalent on the test track. The second step is the automated generation of the simulation model. In this step the unknown parameters of the model structure are calculated. The contribution shows different approaches for the identification of non-linear systems. In the last step the model is used to perform the optimization of the design parameters.
Anthropogenic Heat Release Into the Environment
Authors: Wong Kaufui V. , Dai Yading , Paul Brian
Published: October 2013

This work is intended to systematically study an inventory of the anthropogenic heat produced. This research strives to present a better estimate of the energy generated by humans and human activities, and compare this estimate to the significant energy quantity with respect to climate change.

Because the Top of Atmosphere (TOA) net energy flux was found to be 0.85±0.15 W/m2 the planet is out of energy balance, as studied by the group from NASA in 2005. The Earth is estimated to gain 431 TW from this energy imbalance. This number is the significant heat quantity to consider when studying global climate change, and not the 78,300 TW, the absorbed part of the primary solar radiation reaching the Earth’s surface, as commonly cited and used at present in the literature.

Based on energy supplied to the boilers (in the Rankine cycle) of at least 13 TW, body energy dissipated by 7 billion people and their domestic animals, the value of the total world anthropogenic heat production rate is 15.26 TW or 3.5% of the energy gain by the Earth. Based on world energy consumption and the energy dissipated by 7 billion people and their domestic animals, the value of the total world anthropogenic heat production rate is 19.7 TW or about 5% of the energy gain by the Earth. These numbers are significantly different from 13 TW. More importantly, the figures are 3.5 to 5% of the net energy gained by the Earth, and hence significant. The quantity is not 0.017% of the absorbed part of the main solar radiation reaching the Earth’s surface and negligible.
Simulation of Discreet Damage Evolution in Laminated Composite Compact Tension Specimens
Authors: Breitzman T. D. , Mollenhauer D. H. , Iarve E. V. , Safriet S.
Published: October 2013

Damage progression in laminated Overheight Compact Tension specimens was modeled using discrete representations of individual cracks and delaminations. Matrix cracking and delamination initiation, propagation, and interaction, without any prior knowledge and/or meshing of matrix cracking surfaces, is accomplished by combining stress and fracture mechanics-based constitutive modeling within a mesh independent crack-modeling framework. Simulation results including only matrix damage for specimens with [452/902/−452/02]s and [04/904]2s stacking sequences were compared with load-displacement curves and 3D X-ray micro computed tomography results from tested specimens. Excellent correlation was shown between the simulated and experimental load-displacement curves including statistical variations and proper representation of both the curve non-linearity and peak load. Similarly, remarkable correlation between simulated and experimental damage extent was shown. Additionally, a [45/90/−45/0]2s specimen exhibiting significant fiber fracture was modeled and results compared with experiment. Fiber fracture was simulated using a continuum damage mechanics approach in addition to the discrete cracking and delamination damage representations of matrix damage. The simulated load displacement curve and damage extent compared favorably with experimental results.
Electrostatically Actuated Compliant Microvalve
Authors: Dankovic Tatjana , Feinerman Alan
Published: October 2013

We present an electrostatically operated normally opened microvalve for gas flow control. The valve is made of thermoplastic materials and uses a new fabrication method. The voltage required to close the 0.9 mm wide microvalve was ∼350 V for fluid (air) pressure ∼1kPa.

A new technique [1] has been developed to fabricate valves, micromixer [2, 3] and other microfluidic structures, by patterned welding of compliant thermoplastic films using Universal Laser System CO2 laser. The normally opened valve is electrostatically actuated by applying the voltage on its metalized thermoplastic surfaces. There is no movable membrane or cantilever which closes the fluid path as reported in many other electrostatic microvalves. The walls of the channel collapse toward each other when sufficient voltage is applied, thus effectively closing the fluid path. The material used is 1.4 μm thick Mylar™ sheets (DuPont) coated on one side with ∼10nm of gold.