bluuebunny/crossref_metadata_2025 huggingface dataset:
Coupled Fluid Structure Interaction (FSI) Modeling of Parallel Plate Assemblies
Authors: Kennedy John C. , Solbrekken Gary L.
Published: August 2012

As part of the Global Threat Reduction Initiative (GTRI) Reactor Conversion program, the fuel assembly at the University of Missouri Research Reactor (MURR) is undergoing a significant redesign. The proposed fuel structure is based on low-enriched uranium foils. The proposed aluminum-clad LEU foil fuel plates for the MURR core are significantly thinner than the currently used fuel plates. Further, the monolithic structure of the proposed fuel is fundamentally different than the current design based on powder metallurgy. Consequently, coolant flow reduction due to flow induced deformation of the proposed fuel plates is of concern. The goal of the current analysis is to estimate the amount of flow induced deformation of the proposed LEU-based fuel plates when subjected to coolant flow imbalance due to fuel plate assembly tolerances. Previous methods for assessing fuel plate deflection have relied heavily on analytic and experimental techniques. With the continued advancement of computational codes, new options are now available to assess structural stability. The current approach is to explicitly couple a commercial CFD code with a commercial FEM code. This paper will describe the convergence and stability criteria that were developed to obtain an accurate deflection solution. Time step management and pressure ramping strategies were effectively used as relaxation parameters to improve the computational stability. Additionally, mesh quality criterion were developed and are enforced during a simulation. Benchmarking of the numeric results to analytic calculations is also presented.
Modeling Guidelines for Large Telecom Rack CFD Models
Authors: Elyyan Mohammad A. , Shankaran Gokul V.
Published: August 2012

Large electronics systems such as telecom racks and VME bus systems contain arrays of several cards where fan trays consisting of multiple fans are employed to provide forced convective cooling. Typically, flow distributors such as slotted plates are used to distribute the flow evenly through the cards. Thus, a typical telecom rack system contains a large number of parts, with a wide range of length scales. Thus, modeling such large electronic systems with all components can be challenging in terms of solution time and computational resources. In this paper, we presented two techniques to create compact board models that capture the overall physical behavior of detailed boards: 1) the Lumped Block (LB) method, which is a geometry based simplification technique, 2) the Calibrated Porous Medium (CPM) method, which is based on wind tunnel calibrations. Although different in concept, both schemes showed similar behavior when compared to the detailed card, where the maximum difference from pressure drop across the board was less than 10% and less than 30% for the thermal resistance. Moreover, both schemes resulted in mesh reduction that is greater than 83%. Despite the relatively large deviation in the thermal part, both techniques provide good choices for system level analysis where general information about the flow structure and thermal behavior of the system is required.
Biocompatible Nanocomposite for Lab-on-a-Chip Application
Authors: Islam Nazmul , Askari Davood , Trad Tarek
Published: August 2012

Lab-on-a-chip (LOC) devices integrate multiple laboratory functions and processes to a miniaturized chip format. Many LOC devices are used in a wide range of biomedical and other analytical applications including rapid pathogen detection, clinical diagnosis, electrophoresis, flow cytometry, and protein and DNA analysis. LOC devices can be fabricated from many types of material including various polymers, glass/silicon, or combinations of these materials. A broad variety of fabrication technologies are used for LOC device fabrication. LOC systems have several common features including microfluidics (e.g. channels, micro-pumps, mixers and valves) and sensing capabilities. This paper describes a technique for the fabrication of a micro-pump that can be used in implantable biocompatible devices. This paper will also discuss the synthesis and properties of biocompatible iron oxide nanoparticles (NPs) for AC electrokinetic micro-pumping. Iron oxide NP will be incorporated with PDMS (polydimithylsiloxane) to obtain biocompatible nanocomposite. The use of photoluminescence, hydrophobic, and reflective optical response of these materials for in-vitro and in-vivo sensing and micro-pumping will be highlighted.
Implementation of Genetic Algorithms Into Development of Mechatronic Multi-Edge’s Grinder Design
Authors: Flizikowski Jo´zef , Macko Marek , Czerniak Jacek , Mrozinski Adam
Published: August 2012

Authors of the study propose the method aiming at determination of design properties of a multi-edge grinder. This method is based on a genetic algorithm and its purpose is to optimise the geometric shape of the cutting edges. The input data include population of individuals. Each individual is represented by a set of cutting disks. Whereas the fitness function was assumed as a combination of several postulates of the mechanical design foundations. Those postulates include mechanical, design and energy metrics. Each individual constitutes a complete solution of the disk set whereas the population represents the entire class of solutions. The fitness function of an individual is calculated as the fitness average of each disk supplemented by information describing the relationship between both disks and discs. The method for calculating function values was selected to ensure its maximisation in the process of evolution. Despite promising results of the genetic algorithms operation, one can consider improvement of the method efficiency. The authors used morphological operations in order to better adjust the method to the task. Results of the simulations were verified in laboratory conditions with positive effects.
Steady and Dynamic Rheological Properties of Dense Slurries of Chlorella vulgaris
Authors: Breckel Alex , Ozkan Altan , Berberoglu Halil
Published: August 2012

This experimental study reports the steady and dynamic rheological properties of dense slurries of the green algae Chlorella vulgaris. Biofuel production from algae growth is a promising technology that has the potential to serve as a significant component of the world’s revised energy mix. Along with providing a renewable fuel source, algae production acts as a CO2 sink, potentially reducing net CO2 emissions. Design and operation of algae biofuel production facilities require accurate knowledge of the flow characteristics of algae slurries and estimation of the pumping and harvesting energy requirements. Reliable rheological data is needed to optimize production processes to lower costs and increase yields. This study reports steady state viscosity measurements conducted using the ARES TA rotational rheometer using the common algae strain Chlorella vulgaris over the packing factor range from 0.1 to 0.8. Viscoelastic data was gathered using oscillatory tests conducted on the rotational rheometer with a double wall coquette fixture geometry. Dynamic frequency sweep tests were used to recover the storage shear modulus (G′), and the loss shear modulus (G″), which correspond to the elastic and viscous properties of the fluid, respectively. Apparent viscosity of the cell suspensions increased with increasing packing factors. Packing factors lower than 0.3 exhibited Newtonian characteristics, whereas at larger packing factors the behavior was shear-thinning. The algae suspensions exhibited both viscous and elastic behavior when subjected to oscillatory flow, behaving as a dilute solution. Finally, the frequency of the gel point increased with increasing packing factor.
The Integration of Process Heat Applications to High Temperature Gas Reactors
Authors: McKellar Michael G.
Published: August 2012

A high temperature gas reactor, HTGR, can produce industrial process steam, high-temperature heat-transfer gases, and/or electricity. In conventional industrial processes, these products are generated by the combustion of fossil fuels such as coal and natural gas, resulting in significant emissions of greenhouse gases such as carbon dioxide. Heat or electricity produced in an HTGR could be used to supply process heat or electricity to conventional processes without generating any greenhouse gases. Process heat from a reactor needs to be transported by a gas to the industrial process. Two such gases were considered in this study: helium and steam. For this analysis, it was assumed that steam was delivered at 17 MPa and 540°C and helium was delivered at 7 MPa and at a variety of temperatures. The temperature of the gas returning from the industrial process and going to the HTGR must be within certain temperature ranges to maintain the correct reactor inlet temperature for a particular reactor outlet temperature. The returning gas may be below the reactor inlet temperature, ROT, but not above. The optimal return temperature produces the maximum process heat gas flow rate. For steam, the delivered pressure sets an optimal reactor outlet temperature based on the condensation temperature of the steam. ROTs greater than 769.7°C produce no additional advantage for the production of steam.
Bio-Testing of Poly-L-Lactic Acid/Hydroxyapatite Porous Bone Scaffolds
Authors: Zhang Qingwei , Zhang Wei , Augustin Jephte , Yao Donggang , Wootton David M. , Kleinbart Fredric A. , Johanson Norman A. , Wasko Kimberly A. , Lelkes Peter I. , Zhou Jack G.
Published: August 2012

Tissue engineering is a rapidly growing interdisciplinary field which offers a promising new technology to create artificial constructs for regeneration of tissues. One important aspect of bone tissue engineering is to build scaffolds with interconnected 3-D porous structure in order to mimic natural bone architecture. In this work, co-continuous micro-porous scaffolds made of Poly-L-lactic acid (PLLA) with 50% porosity and PLLA/hydroxyapatite (HA) with 40% porosity were prepared by injection molding of an immiscible polymer blend with polystyrene as sacrificial material. The sacrificial material was then removed by solvent leaching with cyclohexane. The porous PLLA/HA matrix supported murine osteoblast (7F2) cell growth for up to 9 days, suggesting that that the introduction and replacement of sacrificial material had no negative effects on cell proliferation. In vitro studies also indicate an increase in mineralization by osteoblasts cultured on the porous structure, as compared to cells cultured on solid scaffold. One month subcutaneous degradation tests showed a mild foreign body reaction and complete fibrous encapsulation. Following surgical implantation of the scaffolds into circular defects in canine tibia, we observed after 12 weeks new bone tissue grew into the porous structures. Taken together our data suggest that interconnected porous structures with good cytocompatibility and increased mineralization in vitro paired with enhanced osteoinductive properties in vivo suggest a great potential of the porous PLLA/HA for inducing and sustaining bone tissue repair.
Experimental Investigation of Natural Convection Heat Transfer of an Ionic Liquid in a Rectangular Enclosure Heated From Below
Authors: Paul Titan C. , Morshed A. K. M. M. , Fox Elise B. , Visser Ann , Bridges Nicholas , Khan Jamil A.
Published: August 2012

This paper presents an experimental study of natural convection heat transfer for an Ionic Liquid. The experiments were performed for 1-butyl-2, 3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide, ([C4mmim][NTf2]) at a Rayleigh number range of 1.13×107 to 7.7×107. In addition to determining the convective heat transfer coefficients, this study also included experimental determination of thermophysical properties of [C4mmim][NTf2] such as, density, viscosity, heat capacity, and thermal conductivity. The results show that the density of [C4mmim][NTf2] varies from 1.437–1.396 g/cm3 within the temperature range of 10–50°C, the thermal conductivity varies from 0.125–0.12 W/m.K between a temperature of 10 to 70°C, the heat capacity varies from 1.015 J/g.K–1.760 J/g.K within temperature range of 25–340°C and the viscosity varies from 243cP–18cP within temperature range 10–75°C. The results for density, thermal conductivity, heat capacity, and viscosity were in close agreement with the values in the literature. Measured dimensionless Nusselt number was observed to be higher for the ionic liquid than that of DI water. This is expected as Nusselt number is the ratio of heat transfer by convection to conduction and the ionic liquid has lower thermal conductivity (approximately 20% of DI water) than DI water.
An Exploration of Transport Within Micro and Nano Droplet Clusters During Dropwise Condensation of Water on Nanostructured Surfaces
Authors: Mendoza Hector , Beaini Sara , Carey Van P.
Published: August 2012

Experimental studies of dropwise condensation have generally indicated that higher heat transfer coefficients correspond to smaller mean sizes for droplets growing through condensation on the surface. Recent investigations of dropwise condensation on nanostructured surfaces suggest that optimizing the design of such surfaces can push mean droplet sizes down to smaller values and significantly enhance heat transfer. This paper summarizes a theoretical exploration of the limits of heat transfer enhancement that can be achieved by pushing mean droplet size to progressively smaller sizes. A model analysis is developed that predicts transport near clusters of water droplets undergoing dropwise condensation. The model accounts for interfacial tension effects on thermodynamic equilibrium and noncontinuum transport effects, which become increasingly important as droplet size becomes progressively smaller. In this investigation, the variation of condensing heat transfer coefficient for droplet clusters of different size was explored for droplet diameters ranging from hundreds of microns to tens of nanometers. The model predictions indicate that the larger droplet transport trend of increasing heat transfer coefficient with decreasing mean droplet size breaks down as droplet size becomes smaller. The model further predicts that as drop size becomes smaller, a peak heat transfer coefficient is reached, beyond which the coefficient drops as the size continues to diminish. This maximum heat transfer coefficient results from the increasing importance of surface tension effects and non-continuum effects as droplet size becomes smaller. The impact of these predictions on the interpretation of dropwise condensation heat transfer data, and the implications for design of nanostructured surfaces to enhance dropwise condensation are discussed in detail.
An Experimental Study of Acid Exposed Fibre Reinforced Plastic Gratings
Authors: Alam Firoz , Jazar Reza N.
Published: August 2012

Fibre Reinforced Plastics (FRPs) generally have greater advantages over conventional materials for their structural properties. However, the service life can significantly be shortened if the fibre reinforced plastics are exposed to adverse environmental conditions especially acid vapour, humidity and high temperature. In many chemical industrial plants in Australia and elsewhere fibre reinforced plastic gratings are used as structural components of stairs and passages where they are subjected to varying degrees of fluosilicic acid, a byproduct of the industrial manufacturing process. As currently no experimental data on the effects of fluosilicic acid on FRPs is available in the public domain, it is difficult to predict the service life of FRPs with some certainty. In order to understand the structural strength of fluosilicic acid exposed FRPs, an experimental study was undertaken. A series of specimens from various locations of a chemical plan in Australia were acquired and studied. Some new specimens (not exposed to acid, humidity and high temperature) were also studied to provide a benchmark for the comparison. The results indicated that the long time exposure to harsh environment and acid vapour can significantly deteriorate the flexural strength and service life of FRPs.
Position Control of a Magnetically Levitated Robot Based on Magnetic Flux Measurement
Authors: Mehrtash Moein , Tsuda Naoaki , Nobori Tatsuya , Khamesee Mir Behrad
Published: August 2012

Magnetic actuation has opened a new horizon in biological/biomedical applications. A novel magnetic actuation platform has been developed at Maglev Microrobotics Laboratory, University of Waterloo. In the previous work, laser sensors were used for positioning the levitated microrobot. This technique can be used only in transparent environment. In this paper, for applications in an enclosed environment, which may not be transparent, a novel position estimation method was proposed. The proposed method uses hall sensors, mounted on the disk pole-piece. The hall sensors’ optimal installation position has been investigated, and a function which relates hall sensors’ output and the position of robot was derived. Based on this function, position control of horizontal axis using hall sensors in place of laser sensor can be achieved. Usability of two dimensional controls in horizontal axis without laser sensors will be experimentally validated as future work of this research.
Heat Transfer Across Metal-Dielectric Interfaces During Ultrafast-Laser Heating
Authors: Guo Liang , Hodson Stephen L. , Fisher Timothy S. , Xu Xianfan
Published: August 2012

Heat transfer across a metal-dielectric interface involves coupled transport of electrons and phonons in metal and phonons in dielectric, which can be accomplished by coupling between phonons in metal and dielectric or direct coupling between electrons in metal and phonons in dielectric. Direct electron-phonon coupling across the metal-dielectric interface is neglected in some studies [1, 2] but considered in some others [3–5]. We investigate heat transfer across metal-dielectric interfaces during ultrafast-laser heating by employing transient thermo-reflectance (TTR) measurements on Au-Si samples. With ultrafast-laser heating that creates strong thermal non-equilibrium between electrons and phonons in metal, it is possible to isolate the effect of direct electron-phonon coupling across the interface. Simulation results based on the two-temperature model (TTM) are compared with the measurement results. The comparison shows a strong direct coupling between electrons in metal and phonons in dielectric.
Material Properties of Carbon-Infiltrated Carbon Nanotube-Templated Structures for Microfabrication of Compliant Mechanisms
Authors: Fazio Walter C. , Lund Jason M. , Wood Taylor S. , Jensen Brian D. , Davis Robert C. , Vanfleet Richard R.
Published: August 2012

Carbon nanotubes can be grown vertically from a substrate to form dense forests hundreds of microns tall. The space between the nanotubes can then be filled with carbon using chemical vapor deposition to create solid structures. These infiltrated structures can be detached from the substrate and operated as single-piece MEMS. To facilitate the design of compliant microdevices using this process, we explored the influence of two fabrication parameters—iron layer thickness and infiltration time—on the material’s mechanical properties, using the fracture strain to judge suitability for compliance. We prepared samples of a simple meso-scale cantilever beam pattern at various levels of these parameters, applied vertical loads to the tips of the beams, and recorded the forces and deflections at brittle failure. These data were then used in conjunction with a nonlinear FEA model of the beams to determine Young’s modulus and fracture stress for each experimental setting. From these data the fracture strains were obtained. The highest fracture strain observed was 2.48%, which is approximately 3.5 times that of polycrystalline silicon. This was obtained using an iron layer thickness of 10 nm and an infiltration time of 30 minutes. We used a test device—a compliant gripper mechanism for holding mammalian egg cells—to demonstrate the use of this material in compliant MEMS design.
Teaching Microcontroller Programming Graphically
Authors: Rogers John R. , Avdashchenko Konstantin
Published: August 2012

The ability to develop algorithms for microcontroller-based systems has traditionally required a computer science background. Many undergraduate mechanical engineering programs lack the time in the curriculum to devote to the necessary coursework. This paper presents a graphical method of developing algorithms. The method enables engineering students with weak computer science backgrounds to rapidly iterate microcontroller programs. The proposed method uses Simulink and chip-specific Simulink blocksets to access microcontroller inputs, outputs, internal timers, and other chip functions. Before- and after- observations from the implementation of the method in a mechatronics course are presented. The proposed method is compared to the traditional C language method of developing an algorithm. It is shown that it is easier to convey the algorithm in the Simulink implementation than it is to convey the C-language implementation of the same algorithm. It is quicker to develop algorithms using the Simulink-based method. The method is relevant in constrained undergraduate engineering programs, particularly mechanical engineering, where there is little instruction in computer programming. The method is scalable to industrial applications outside academia although it is not yet widely used there.
Thermoelastic Response of Thin-Walled Cylindrical Shell Under the Effect of Moving Point Load and Heat Source
Authors: Keskinen Erno , Karvinen Timo , Dospel Vladimir , Cotsaftis Michel
Published: August 2012

Cylinder grinding has been the subject of an intensive research, because delay-type resonances, commonly known as chatter-vibrations, have been reason for serious surface quality problems in industry [1]. As a result of this activity it has been developed a simulation platform, on which the complete grinding process including delay-resonances can be driven [2]. This platform consists of models for the grinder, for the cylindrical work piece and for the stone-cylinder grinding contact. The elastic cylinder model is based on analytical eigenfunctions in bending vibrations, which basis has been used to present the rotordynamic equations of cylinder in modal coordinates. Stone-cylinder interaction mechanism has been derived by combining the rules of mass and momentum transfer in the material removal process. The contribution of this paper is to update the platform to include the thermal effects of the work body undergoing shell deformations. Following the method to use the eigenfunctions of a thin-walled circular cylindrical shell to describe the rotordynamic motion of the work body, a promising method could be to use in a similar way the eigenfunctions of a thermally isolated cylinder to solve the temperature distribution of the cylinder. The temperature distribution and terms related to the non-homogeneous boundary conditions will then be the input to the thermoelastic problem. It can be shown that the eigenfunction basis consists of trigonometric functions in axial and circumferential directions while the radial eigenfunctions are Bessel functions. The stone-cylinder interface has to be updated also to include thermal effects. A portion of the mechanical power is transferred to the work piece. The rest goes to the stone, to the material, which is removed and to the cutting coolant. On the other hand, thermal deformations modify the grinding forces, which are loading the work piece. The solution of the coupled thermal and thermoelastic problem will be done in terms of modal coordinates corresponding to the eigenfunction basis. This leads to numerical time integration of two groups of differential equations, the solution of which can be used to perform the temperature distributions and the corresponding thermal deformations.
Simulation of the Turbulent Dispersion of 10 Micron Particles in a Generic Half-Cabin Model
Authors: Ebrahimi Khosrow , Zheng Zhongquan C. , Hosni Mohammad H.
Published: August 2012

Study of particle dispersion in ventilated indoor environments is a very useful and effective way to understand the mechanism for disease transmission in an enclosed environment. In this investigation, a computational approach is adopted in order to gain more knowledge about the transport of particulate materials in a simplified half cabin model of a Boeing 767. The simulations are performed using a commercial Computational Fluid Dynamics (CFD) software and are validated through comparing the predictions with the corresponding experimental measurements. The Lagrange-Euler approach is invoked in the simulations. In this approach, while the air is considered as the continuous first phase, the particles are treated as the discrete second phase. By solving the particles equation of motion, the trajectory of particles is computed. The discrete phase equation of motion is coupled with the continuous phase governing equations through the calculation of drag and buoyancy forces acting on particles. The continuous phase flow is turbulent and Reynolds Averaged Navier Stokes (RANS) is employed in the calculation of velocity field. A complete study on grid dependence of RANS simulation is performed through a controllable local mesh refinement scheme. The grid dependence study shows that using unstructured grid with tetrahedral and hybrid elements in the refinement region are more efficient than using structured grid with hexahedral elements. The effect of turbulence on particle dispersion is taken into account by using a stochastic tracking method (random walk model). Through the comparison of computational predictions with corresponding experimental measurements the capability of Discrete Phase Model (DPM) in predicting the behavior of particles is studied.
CFD Analysis of the Vortex Dynamics Generated by a Synthetic Jet Impinging on a Heated Surface
Authors: Silva Luis , Ortega Alfonso
Published: August 2012

A canonical geometry has been used to investigate the flow and heat transfer of a purely oscillatory jet that is not influenced by the manner in which it is produced. Such a jet has been popularly termed a synthetic jet in the literature, and recently has been investigated for thermal management of electronics by causing the jet to impinge onto the heated surface. Because of its oscillatory nature, the impinging jet thus formed is dominated by vortices that are advected towards the surface. This surface-vortex interaction is key to understanding the fundamental mechanisms of convective heat transfer by the impinging synthetic jet and hence is the subject of the current investigation. The unsteady two-dimensional Navier-Stokes equations and the convection-diffusion equation were solved using a fully unsteady, two-dimensional finite volume approach in order to capture the complex time dependent flow field. Various vortex identification methods were investigated for proper identification of the train of vortices emanating from the jet and their evolution and eventual dissipation. Intuitive definitions of vortices such as spiraling streamlines, pressure minima and isovorticity surfaces suffer from inaccuracies. In the present work, the vortex-identification criteria employed was the Q-criterion (Hunt et al. 1988), which defines vortices as connected fluid regions with positive second invariant of the velocity gradient tensor. By tracking vortices, it was found that a primary vortex advecting parallel to the target surface gives rise to a secondary vortex with opposite net vorticity. It was found that the secondary vortex is largely responsible for enhancement of the heat transfer within the wall jet region. In addition it was found that in some situations vortex coalescence or pairing occurs, leading to degradation in the heat transfer enhancement due to the reduction in the frequency of vortices interacting with the surface.
Cornering Analysis of Vehicles Using Multibody Dynamics
Authors: Prescott William
Published: August 2012

Dynamics software usage in the analysis of vehicles is becoming more prevalent in industrial settings. Multibody tools allow the user to put together a digital or virtual model of the vehicle before any physical prototype is built. The tools have now reached a level of sophistication that allows the same tests to be performed on the digital model as on the physical model. In the analysis of a vehicle a virtual model allows the user to analyze the vehicle’s performance in ride and comfort scenarios as well as in durability scenarios. Multibody tools also allow the user to perform design of experiments or trade-off studies in these scenarios by varying different parameters of the vehicle. However, to be of optimal usage in a design of experiments approach the solution times of the complex models must be short allowing larger parameter studies to be done quickly. In the analysis of many vehicles and in particular race cars only the vehicle’s limits in a turn or corner are needed. Limiting the vehicle analysis to cornering allows the multibody code to use steady-state analysis instead of a full dynamic simulation. Typically, multibody codes construct differential-algebraic equations (DAE) to form the equations of motion and then must use complex numerical analysis techniques to solve the DAEs. By making the assumption that the vehicle is in a corner the DAEs can be reduced to a set of algebraic equations, which can then be solved very efficiently by a statics solver. A statics solver by definition requires the velocities and accelerations to be zero, but in the cornering analysis of a vehicle this assumption can not be made. This paper will document the extensions necessary to convert the Virtual.Lab multibody statics solver into a steady-state solver it will then apply this steady-state solver to the cornering analysis of a full vehicle model.
Characterization of Gold Nanowire Through Beam Deflection Using Atomic Force Microscopy
Authors: Phamduy Paul , McLaughlin Adam , Gao Fan , Kim Byungki , Gu Zhiyong
Published: August 2012

The objective of this report is to calculate the Young’s modulus of gold cantilevers on the nanoscale using a force-deflection test performed on an Atomic Force Microscope (AFM). These results are then compared to the Young’s modulus of gold on the macroscale. As shown from the results, the beam deflection tests confirm that the elastic modulus values obtained by this method are on the same order of magnitude as its macroscale counterpart.
Design of a Low Cost, Partial Flow Dilution Tunnel With Tapered Element Oscillating Microbalance Particulate Measurement
Authors: Christensen Victor , Cordon Dan , Beyerlein Steve , Steciak Judi , Budwig Ralph
Published: August 2012

Accurate, repeatable measurement of tailpipe emissions is an important factor in the development of internal combustion engines and testing of alternative fuels. A dilution tunnel simulates the action of exhaust mixing with atmospheric gases and prevents condensation prior to gas and particulate measurements. In this work, a micro dilution tunnel was designed for the University of Idaho Small Engine Laboratory (SEL), and experiments were conducted to establish the controllability and accuracy of the tunnel. The tunnel design implements partial flow, Constant Volume Sampling (CVS) using an ejector diluter. Real-time measurement of CO2, CO, O2, NOx, hydrocarbons, and particulate emissions are collected using the combination of a NDIR/electrochemical 5-gas analyzer and a Tapered Element Oscillating Microbalance (TEOM). Data from these instruments and the flow conditioning equipment are collected and logged by a National Instruments data acquisition system. For the desired 11:1 dilution ratio, the system should be operated at 700°F suction temperature and 35 psia motive pressure. This results in an uncertainty of 3% at the 80% confidence level. A procedure has been developed for obtaining and verifying dilution ratios between 11:1 and 15:1. The characterization and use of an ejector diluter have made it possible to create an inexpensive dilution tunnel that will be useful in studying effects of freezing chemical reactions, and analyzing emissions of diesel and two-stroke engines that typically produce elevated levels of hydrocarbons and particulates beyond the saturation range of many emissions analyzers.
Opto-Mechanical Methodology for Feature Detection of Contours
Authors: Shetty Devdas , Campana Claudio , Dinan Robert , Gurimitkala Anil , Nazaryan Nikolay , Moslehpour Saeid
Published: August 2012

Precise measurement of curvature is of critical importance in the aerospace industry. This paper presents a methodology for non-contact measurement of radius of curvature on the finished surface of manufactured parts. Unique optical methods including a Line Laser and a backlight are explored. In each case, a light source illuminates the features to be measured and several sets of high-contrast images are produced. For that purpose a low power (2mW) Helium-Neon (HeNe) laser source has been used. The images are processed using specific software and data points are mapped along the region of interest. A mathematical relationship is used to extrapolate the radius of curvature from the measured data.
Contact Pressure of a Non-Pneumatic Tire With Three-Dimensional Cellular Spokes
Authors: Kim Kwangwon , Kim Seunghye , Ju Jaehyung , Kim Doo-Man
Published: August 2012

Contact pressure distribution has been an important issue on the tire design due to its significant effect on passengers’ comfort, vehicle handling, wear, and noise. Motivated by our previous finite element results on contact pressure reduction with a non-pneumatic tire (NPT) of two-dimensional (2D) lattice spokes, we explore structural performance of a NPT tire with three-dimensional (3D) lattice spokes. In this study, static contact pressure of a NPT with 3D lattice spokes is investigated as a function of vertical load and is compared with that of a pneumatic tire. Finite element based numerical simulation of the contact pressure of a NPT is conducted with ABAQUS for varying vertical forces and 3D lattice spoke geometries.
Aerodynamic Analysis in Lean Blade Effects in Centrifugal Compressor
Authors: Xu Cheng , Amano R. S. , Alkhalidi A.
Published: August 2012

Turbomachinery industries are interested in using optimization procedures that enable to enhance compressor efficiency and wide operating ranges. Most of the design processes are focus on either in aerodynamics or structure. However, the compressor design is an integration between the aerodynamics and structure. This paper presents the recent developments of the aerodynamic integral design system. A design process including the meanline design, throughflow optimization and three-dimensional viscous analysis was used in the centrifugal compressor design. The aerodynamic design design needs to optimize at same time. Normally the most of performance of the favorite features are not friendly to the structure reliability of the compressor wheel. The optimization between aerodynamic performance and structure reliability is critical to provide the maximal potential of the compressor design. The main purpose of current paper is to discuss the importance of the aerodynamic optimization through lean effects. It can be seen from the discussion that the integration of aerodynamics is very important.
Development of Visualization Methods of Air Flow Into Perforating Projectile Wounds
Authors: Krebsbach Meaghen A. , Muci-Ku¨chler Karim H. , Hinz Brandon J.
Published: August 2012

In ballistic wounds the tissue along the path of the projectile experiences transient displacements resulting in what is known as the temporary wound cavity. The motion of the tissue caused by the formation of the temporary cavity gives rise to a low pressure pull that sucks air and airborne debris into the wound. The latter could be a significant mechanism for bacterial and particulate contamination of projectile wounds that should be explored in detail since it can lead to infection or delayed wound healing. In order to better understand the flow of air into the temporary cavity and how it relates to particulate entry into the wound, a methodology to visualize the air flow into perforating projectile wounds was proposed and explored using an extremity surrogate. The proposed approach was only intended for qualitative observations and comparisons and was implemented in a very rudimentary fashion to determine its usefulness. The experimental setup used and visualization results corresponding to the air flow at the entry and exit regions of perforating projectile wounds using 0.45-in and 0.22-in caliber round nose lead projectiles and a PERMA-gel lower extremity surrogate are presented.
Effect of Initial Surface Concentration on Bacterial Distribution in a Surrogate Ballistic Wound
Authors: Krebsbach Meaghen A. , Muci-Ku¨chler Karim H.
Published: August 2012

In ballistic injuries, contamination can be carried from the environment, clothing, and skin surface into the wound track. Bacteria and contaminated debris can be introduced into the wound by several means, including physical transport by the projectile or by the suction caused by the formation and collapse of the temporary wound cavity. In this paper, the relationship between initial bacterial concentration on the surface and resultant bacterial distribution along the wound channel is examined using a leg surrogate. Escherichia coli strain K-12 was used to represent skin surface contamination. In order to reduce the possibility of contamination by outside bacteria and assist in colony visualization, the E. coli first underwent a transformation protocol to express Green Fluorescent Protein and to be resistant to the antibiotic ampicillin. Different concentrations of bacteria were pipetted onto circular filter paper and placed onto the surface of a ballistic gelatin leg surrogate, and an 11.43-mm (0.45-in) caliber projectile was shot through the contaminated area into the gel. The “wound track” was sliced into small, evenly spaced samples and the permanent cavity was removed using a biopsy punch, liquefied, and grown on selective lysogeny broth media containing ampicillin. Examination of a normalized bacterial colony count and normalized area covered per segment allowed comparison of variations in the initial concentration, and confirmed that within a range the normalized contamination distribution trend along the “wound track” remained similar. This verification allowed additional confidence in results obtained using this bacteria distribution methodology by eliminating concerns over small variations in initial bacterial concentration.
Experimental Study of Wetting Anisotropy and Condensate Drainage Enhancement on Microgrooved Aluminum Surface
Authors: Rahman M. A. , Jacobi A. M.
Published: August 2012

Minimization of condensate (frost melt water) retention on a surface operating under frosting/defrosting condition is of tremendous importance in a wide range of air conditioning and refrigeration applications. In the present study, the wetting characteristics, condensation and frosting pattern and the drainage of frost melt water from aluminum surfaces with parallel microgrooves have been examined and compared to the flat baseline surfaces. These surfaces are fabricated by topographical modification only, via standard photolithographic process. The microgrooved samples exhibit wetting anisotropy and static contact angles are as high as 149 and 112° when viewed from parallel and perpendicular directions to the grooves, respectively. Frost is grown on the samples inside a thermally controlled chamber at 3 different plate temperatures of −8°C, −13°C and −18°C, air temperature of 20±2°C and for 3 relative humidity conditions (50%, 70% and 90%). The duration of the frosting cycle is 45 minutes and tests are continued up to 5 frosting cycles, each time defrosting for a certain length of time at the end of frosting period. Significantly different size, shape and distribution of condensed and frozen water droplets on the grooved surfaces are observed from that on the flat baselines. The microgrooved samples are found to manifest better water drainage behavior and drained up to 50% more melt water compared to the flat baseline surfaces. While the amount of water retention on the baseline surfaces increases in the subsequent refrost cycles and is highest in the 5th frost cycle, the microgrooved surfaces show consistently improved water drainage in all cycles.
An Isotropic Auxetic Structural Network With Limited Shear Stiffness
Authors: Spadoni Alessandro
Published: August 2012

The chiral lattice is a unique structural network not symmetric to its mirror image, and with a negative Poisson’s ratio. Previous investigations have considered this structural network for the design of superior structural components with sandwich construction, but these were limited by the in-plane Poisson’s ratio predicted to be exactly −1. This paper presents estimates of the mechanical properties of the chiral lattice obtained from a multi-cell finite-element model. It is shown that the chiral lattice has a shear stiffness bound by that of the triangular lattice and it is very compliant to direct stresses. The minimum in-plane poisson’s ratio is estimated to be ≈ −0.94.
CFD Calculations of Natural Circulation in a High Temperature Gas Reactor Following Pressurized Circulator Shutdown
Authors: Tung Yu-Hsin , Johnson Richard W.
Published: August 2012

It is anticipated that in the event of the failure of the gas circulator in a prismatic gas-cooled very high temperature gas reactor (VHTR), there will develop natural convection currents in the core with the helium coolant. It is of interest to know the amount of energy transported by the helium plumes impinging on material surfaces in the upper plenum. Additionally, in the event of a rupture in an intermediate heat exchanger which contains water, it will be of great interest to understand the potential for free convection as it will convect water vapor, which will have detrimental effects on the core graphite. It is well known that heating a gas causes it to rise because the buoyant forces overcome gravitational forces. In the reactor, there will be hot walls that can provide heating to the helium, though the temperature of the coolant channel walls will be a function of the core depth, which makes the presence of free convection dependent on the particular conditions. In addition to the uncertainty of whether there will be sufficient buoyant forces to drive free convection, there is uncertainty as to what paths the helium will take in forming natural circulation loops. Computational fluid dynamic (CFD) calculations are reported herein that demonstrate the potential for the occurrence of natural circulation considering the core itself along with upper and lower plena and including flow paths in the gaps between the graphite blocks that allow bypass flow to occur. It is shown that multiple paths are possible for circulating flow.
An Experimental Study of Natural Convection in a Rectangular Enclosure Using PIV Measurement Techniques
Authors: Akyuzlu K. M. , Farkas J.
Published: August 2012

An experimental study is conducted to determine the circulation patterns inside a rectangular enclosure due to natural convection using a Particle Image Velocimeter (PIV). Experiments were conducted using two different fluids (air and water) and for rectangular enclosures with aspect ratios 0.5 and 1.0. Natural convection in enclosures has been experimentally studied in the past. Many of these studies cited in the literature use some kind of an optical method like interferograms, shadowgraphs, streak photographs, or multi-exposure photographs to visualize the flow patterns in the enclosure. The present study employs a commercial two-dimensional PIV to capture, instantaneously, the circulation patterns inside the test section. The test cavity in the present setup is of rectangular shape, which is 5 inches (127 mm) wide, where the height of the enclosure can be changed to obtain aspect ratios of 0.5 and 1.0. The depth of the rectangular enclosure measures 12 inches (305 mm) to minimize the effect of walls normal to the two dimensional flow patterns that are expected in this type of arrangement. The walls of the cavity are made of Aluminum plates. These plates are kept at constant but different temperatures during the experiments. In the present study, hollow glass sphere particles with 10 microns in diameter were used as seeding for water experiments and fine particles/flakes of ash generated from burned incense were used as seeding in the air experiments. For each working fluid, the experiments were repeated for different aspect ratios and for different wall temperature differences which corresponded to Rayleigh numbers in the range of 106 and 107. Velocity fields were captured at steady state for each experiment using the two-dimensional PIV system. Numerical studies were also carried out using a commercial CFD software. Comparisons of the numerical and experimental results indicate a good match in terms of circulation patterns and velocity magnitudes in the core of the buoyancy driven flow. Discrepancies in measured and predicted values of velocities are more pronounced near to the boundaries of the enclosure. Separate measurements with finer interrogation areas and different PIV setting were required to improve the accuracy of the measurements near the corners (top and bottom) of the enclosure. The results of these measurements are also presented.
Inter-Laminar Mechanical Properties Improvements in Carbon Nanotubes Reinforced Laminated Nanocomposites
Authors: Askari Davood , Ghasemi-Nejhad Mehrdad N.
Published: August 2012

Owing to their superior mechanical properties, carbon nanotubes (CNTs) can be used as an additional reinforcement to improve the mechanical properties of laminated composite materials. To incorporate the excellent properties of CNTs into the existing traditional composite technology, vertically aligned high density arrays of CNTs were grown perpendicular to the surface of 2-D woven cloths and tows of various fibrous materials. The nano-forest like structures of fabrics is used to fabricate 3-D reinforced nanocomposites. Due to the presence of aligned CNTs in through-the-thickness direction, it is expected that the inter-laminar and through-the-thickness properties of the composite laminate will be improved considerably. To demonstrate the effectiveness of our approach, various composite single lap-joint specimens were fabricated for inter-laminar shear strength testing. Carbon woven cloths with and without CNTs nano-forests were inserted in between the single lap-joints using epoxy adhesive to measure the interlaminar shear strength improvements due to the presence of through-the-thickness aligned CNTs nano-forests. It is observed that single lap-joints with carbon cloth insertion layers having CNTs nano-forest can carry up to 12% higher shear stress and 16% higher strain-to-failure. The failures of samples with nano-forests were completely cohesive while the sample with carbon woven cloth insertion failed adhesively. This concludes that the adhesion of adjacent carbon fabric layers can be considerably improved due to the growth of vertically aligned CNTs nano-forest in through-the-thickness direction.