bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Lateral Vibrations of a Vertically Moving String With a Harmonically Varying Length
Authors: Gaiko Nick V. , van Horssen Wim T.
Published: March 2016

In this paper, the free lateral vibrations of a vertically translating continuum modeled as a taut string with variable length are studied. The time-varying length of the cable is described by a harmonically varying function about a constant mean length. This model can be used to describe the lateral vibrations of an elevator cable with changing length. A Fourier series approach is used to predict resonant frequencies arising because of the length fluctuation. The amplitudes of vibrations are represented by the infinitely dimensional system of coupled ordinary differential equations. This system is studied by Galerkin’s truncation method for the lowest resonant frequency. The obtained results are in agreement with the energy analysis, but the truncation technique leads to inaccurate approximations on long timescales. Hence, an alternative analytical method is proposed promising an accurate approximation of the response on long timescales for the general resonant frequency.
Energetic Assessment of a Local District Heating Network With a Small-Scale Trigeneration Plant: Comparison of Different Performance Indices
Authors: Badami Marco , Portoraro Armando , Savarese Dario
Published: March 2016

Combined Heat and Power (CHP) is a technology that has been proven to be very effective in the industrial sector, when both thermal and electrical energy are required, as it allows a more rational use of the input primary energy. However, CHP technology is not limited to industrial uses, as it can also be effectively exploited in the civil sector, such as in District Heating (DH) applications. Moreover, in recent years the opportunity to develop hybrid systems, in which traditional and renewable energy sources are integrated, is gaining more and more consideration. For these reasons, the most recent European Standards propose a set of newly conceived indices whose aim is easily assessing the energetic performances of DH networks, but the effectiveness of these indices in the study of DH networks coupled with CHP and renewable energy systems has not yet been thoroughly investigated.

This paper presents a comparative study, based on these indices, of different electrical and thermal generation technologies, with the aim of assessing their effectiveness when hybrid systems are analyzed. A CHP-DH application, actually installed and in operation in Turin, Italy, has also been considered in the analysis, in order to have a comparison with a real case. The results of the study are presented and discussed in detail in the following sections.
Advanced Exergy-Based Analyses Applied to the Supercritical CO2 Power Cycles
Authors: Morosuk T. , Tsatsaronis G.
Published: March 2016

The idea of developing supercritical CO2 power cycles and applying them to industrial processes became increasingly popular in the last decade. Significant research has been done in this field, including the investigation of characteristics of equipment, and parametric optimization of power systems. There are only few publications on refrigeration using CO2, under hot climatic conditions. This paper deals with an application of an integrated conventional and advanced exergetic analysis to a supercritical CO2 power cycle operating in hot climatic conditions. The objective is to obtain detailed useful information about the optimization of the structure and the parameters of the system being considered. Conventional exergetic analyses have some limitations, which are significantly reduced by the so-called advanced analyses. In addition to conventional analyses, the latter evaluate, (a) the interactions among components of the overall system, and (b) the real potential for improving a system component. A conventional exergetic analysis emphasizes more the relative importance of the regenerative heat exchanger compared to the remaining four components (compressor, cooler, expander, and heat exchanger) than the advanced analysis does. The results obtained from the advanced exergetic analysis show that the system being analyzed can be improved by improving the components in isolation from the overall system, because the avoidable inefficiencies caused by the components interconnections are relatively low.
Relationship Between Tool Deterioration and Cutting Force During Milling of a Nickel-Based Superalloy Using Cemented Carbide Tool
Authors: Razak Nurul Hidayah , Chen Zhan W. , Pasang Timotius
Published: March 2016

Nickel-based superalloys have long been recognized as difficult-to-machine alloys. Chipping and breakage are understood as the dominant features of tool deterioration particularly in milling of these alloys. But how tool deterioration affects cutting force (Fc) has not been sufficiently established so that force model base deterioration detection methods can be practically developed. Thus, this study intends to better demonstrate the relationship between modes of tool deterioration and Fc. Milling experiments were conducted using 718Plus superalloy and uncoated cemented carbide tool and a commonly used set of milling parameters, with or without the use of coolant. During these experiments, Fc was recorded and in between milling passes the traditionally used flank wear value (VB) was precisely measured. We have observed that as milling progressed, along with the slow edge wear, edge chipping and fracturing intensified and Fc increased. However, before the final catastrophic failure, the rate of increase was relatively small in comparison to the scatters in Fc vs VBMax plot. Thus, a model based on Fc vs VBMax for detection of tool deterioration may not be suitable. We will explain the reasons for the scatters and relate the fracturing path to the effect of it to cutting edge contact area, thus to Fc.
Experimental Evaluation of Heat Transfer Rate in Automobile Cooling System by Using Nanofluids
Authors: Naik Ravin G. , Mohite Arvind S. , Dadi Juneyd F.
Published: March 2016

The demand for more powerful engines in smaller hood spaces has created a problem of insufficient rates of heat dissipation in automotive radiators. Insufficient heat dissipation can result in the overheating of the engine, which leads to the breakdown of lubricating oil, metal weakening of engine parts, and significant wear between engine parts. To minimize the stress on the engine as a result of heat generation, automotive radiators must be redesigned to be more compact while still maintaining high levels of heat transfer performance. Moreover, this can be done without significant modification to the existing internal radiator structure, this can be done by increasing (i) heat transfer area, (ii) temperature, and (iii) heat transfer co-efficient. However, technologies have already reached their limit for the cases heat transfer area and temperature. Recently many researchers found that dispersing nano-sized particles into the liquids result in higher heat transfer co-efficient of these newly developed fluids called nanofluids compared to the traditional liquids. This kind of fluids are now of great interest not only for modifying heat transfer performance of fluids, but also for improving other different characteristics such as mass transfer and rheological properties of fluids. A major goal of the nanofluids project is to reduce the size and weight of the vehicle cooling systems by greater than 10% despite the cooling demands of higher power engines. Nanofluids enable the potential to allow higher temperature coolants and higher heat rejection in the automotive engines. It is estimated that a higher temperature radiator could reduce the radiator size approximately 30%. In this paper we have considered two nanofluids comprising of aluminium oxide and copper oxide in water mixture has been studied experimentally to compare their performance in automobile radiator. The study shows that for a particle volume concentration of 0.1%, both nano fluids show improvements in their performance over the base fluid. Comparison has been made on the basis of three important parameters; equal mass flow rate, equal air flow rate and equal radiator inlet temperature of coolant. For both nanofluids exhibit increase in heat transfer rate compared to base fluid.
Energy Absorption/Dissipation Performances of Magnetic-Sensitive Rubber (MSR) With Hollow Iron Balls
Authors: Zhang Shengqiang , Sun Lingyu , Leng Dingxin , Huang Bincheng , Xu Jun , Wang Ligang
Published: March 2016

A kind of novel smart buffer material, magnetic-sensitive rubber (MSR) with embedded thin-walled iron balls, is provided, and the energy absorption and energy dissipation properties are investigated numerically. Two kinds of representative volume elements (RVEs) of MSR specimens with solid or hollow iron balls are studied, respectively. Under uniaxial compression alone or combined with magnetic field, the relation between effective stress and effective strain and that between strain energy desity and total compression deformation for these two specimens are established, respectively. With the increase of strain, it is demonstrated numerically that the MSRs with hollow iron balls have better energy absorption/dissipation capability than previous MSRs with solid balls. And the applied external magnetic-field increases this capability more. Under compression, the stress concentrations in elastomer matrix around the hollow balls decrease, that could increase the ultimate compression loads before the matrix failures. This is beneficial for us to design lightweight and efficient buffers according to different application cases.
Study of Wear of Planetary Concrete Mixer Blades Using a 3D Optical Scanner
Authors: Valigi Maria Cristina , Logozzo Silvia , Gasperini Ilaria
Published: March 2016

Performance optimization of a concrete mixer is fundamental in many industrial technologies. Wear is one of the main phenomena to be forecast and tested during the design and service of mechanical components. In all the concrete mixers types, blades suffer the wear more than other components.

Two different blade shapes have been tested in order to evaluate the wear rates and which of them has the best performance in terms of wear resistance. One of the two shapes has been designed in order to minimize wear rates and to allow longer durability, on the basis of a theoretical approach.

To guarantee the consistence of the comparison, the two different blades have been tested in a dedicated planetary concrete mixer, with the same operating conditions (time-period, same mixture and mixer).

The purpose of this paper is to show optical non-contact measurements of worn blades operating in a planetary concrete mixer in order to evaluate wear rates and to validate the efficiency of the new blade design.
Dynamic Analysis of a Microscale Cricket Filiform Hair Socket
Authors: Hossain A. , Mian A.
Published: March 2016

Filiform hairs of crickets are of great interest to engineers because of their highly sensitive response to low velocity air currents. In this study, the cercal sensory system of a common house cricket has been analyzed. The sensory system consists of two antennae like appendages called cerci that are situated at the rear of the cricket’s abdomen. Each cercus is covered with 500–750 flow sensitive hairs that are embedded in a complex viscoelastic socket that acts as a spring -dashpot system and guides the movement of the hair. When the hair deflects due to the drag force induced on its length by a moving air-current, the spiking activity of the neuron and the combined spiking activity of all hairs are extracted by the cercal sensory system. The hair has been experimentally studied by few researchers though its characteristics are not fully understood. The socket structure has not been analyzed experimentally or theoretically from a mechanical standpoint. Therefore, this study aims to understand the dynamic response of socket and its interaction with the filiform hair. First, a 3D Finite Element Analysis (FEA) model, representing hair and hair-socket, has been developed. Then the dynamic analysis is conducted utilizing the appropriate load and boundary conditions based on the physical conditions that an insect experiences. These numerical analyses aid to understand the dynamic response of the hair and hair-socket system. The operating principles of the hair and hair-socket could be used for the design of highly responsive MEMS devices such as fluid flow sensors or micro-manipulators.
A Fast Running Model for Skeletal Impact Biomechanics Analysis
Authors: Tan X. G. , Przekwas Andrzej J. , Gupta Raj K.
Published: March 2016

Skeletal trauma occurs in many blunt, ballistic and blast impact events. Even though the personal body armors and protective equipment were effective in stopping the penetration of bullets or fragments, the resulting impact loading could lead to the significant injuries and fractures to the thoracic skeleton and extremities. The finite element (FEM) method, with its capability to handle complex geometries and nonlinear materials, are commonly used to analyze the tissue biomechanical responses and correlate the simulation results with the injury outcomes. However, it is very difficult to construct the three-dimensional (3D) FEM model for the skeletal biomechanics analysis because of the complex geometry and different materials involved. Moreover the simulation of 3D FEM model is computationally expensive because both small element size and high speed of sound in materials lead to very small time step in an explicit transient analysis. The simulation process is often not robust enough when the model experiences the large deformation. To shorten modeling and simulation times, we have developed a fast running model based on a novel nonlinear beam element for the skeletal impact biomechanics analysis. In contrast to the conventional beam elements, the kinematics of the developed beam element is free of rotational degrees of freedom (DOFs). The current beam element offers the desired constant lumped mass matrix for the large deformable explicit transient analysis. The realistic treatment of junctions and surface intersections among beams becomes straightforward. Furthermore the model can account for the irregular shape and different materials at beam cross sections by using the numerical integration. The sophisticated material models such as elastoplasticity can also be incorporated directly in the integration points. Thus the fast running model is suitable for the analysis of complex nonlinear composite structures such as the loading-carrying thoracic skeleton and extremities. The stereolithograph (STL)-based anatomical geometry of skeletal structure is used to extract the one-dimensional (1D) curved beam model and the associated beam cross sections. The anatomical surface of skeleton is also utilized for the calculation of transferred loads to the underlined beams. The 3D responses such as displacements and stresses from the fast running model are subsequently reconstructed on the anatomical surface for the visualization and skeletal trauma analysis. We demonstrate the efficiency of such modeling technique by simulating the rib cage and the lower extremity under the impact loadings. As compared to the 3D FEM model, the developed model runs fast and robust, and achieves good results without the need of laborious 3D meshing process.
A Constrained L2 Based Algorithm for Standardized Planar Datum Establishment
Authors: Shakarji Craig M. , Srinivasan Vijay
Published: March 2016

For years (decades, in fact) a definition for datum planes has been sought by ASME and ISO standards writers that combines the contacting nature of traditional surface plate mating with a means of balancing rocking conditions when there is a centrally positioned extreme point or edge on the datum feature. This paper describes a completely self-balancing method for datum plane establishment that matches traditional surface plate mating while automatically stabilizing rocker conditions. The method is based on a constrained L2 (L2) minimization, which, when seen mathematically, elegantly combines the desirable contact properties of the constrained L1 (L1) minimization with the stable properties of the unconstrained least-squares and does so in a manner that avoids the drawbacks of either of those two definitions. The definition is shown along with proofs of a mathematical development of an algorithm that relies on a strategically chosen singular value decomposition that allows for an elegant, robust solution. Concise code is included for the reader for actual use as well as to full clarify all the algorithmic details.

Testing has shown the definition defined here does indeed provide attractive balancing of full contact with rocker stability, leading to guarded optimism on the part of the key standards committees as an attractive default definition. Since both the ISO and ASME standardization efforts are actively working to establish default datum plane definitions, the timing of such a rigorously documented study is opportune.
Multiscale Modeling of Polymer/Graphite Interface
Authors: Iacobellis Vincent , Behdinan Kamran
Published: March 2016

This study presents the application of concurrent multiscale modeling to the simulation of failure at a polyimide/graphite interface. The model used was the previously developed bridging cell method for coupling atomistic to continuum formulations. Using the multiscale model, the work of adhesion and interfacial stress were obtained at multiple temperatures. Results agreed with experimental results obtained from the literature. Furthermore, the configuration of the polymer chains due to the presence of the graphite was investigated, where it was found that the density increased close to the material interface.
Dynamic Moving Load Identification Using Optimal Sensor Placement
Authors: Augustine Paul , Dhingra Anoop K. , Gupta Deepak K.
Published: March 2016

A structure in service can be subjected to static, dynamic or moving loads. Several situations in practice involve estimation of moving loads which induce vibrations in the structure on which they are applied. An accurate estimation of these loads will ensure product quality and reliability of the final design, and mitigate the cost of structural health monitoring systems. The moving nature of dynamic loads increases the computational difficulty of the problem. One of the types of Inverse Problems involves estimation of the applied load from measured structural response such as strain or accelerations.

Measuring response at a limited number of locations causes the unavailability of full set of structural response which can lead to inaccurate results. The unavailability of full structural response is mainly due to three reasons — (i) financial constraints limiting the number of sensors that can be used, (ii) inaccessibility of loading locations to place sensors, and (iii) sensor influence on structural response. The load recovered from such insufficient structural response data will be prone to errors. Ill-conditioning of the inverse problem can be eliminated by choosing optimum sensor locations on the structure, which leads to precise load estimate. No studies could be found which consider optimum sensor placement while recovering dynamic moving loads acting on a structure. In this paper, the recovery of the dynamic moving loads through measurement of structural response at a finite number of optimally selected locations is investigated. The developed algorithm is implemented using ANSYS APDL and MATLAB programming environment.

Optimum sensor locations are identified using the D-optimal design algorithm and strain gages are placed at those locations. An algorithm is developed to utilize the strain data measured at optimum locations to estimate the moving load. The developed algorithm is applied to three example problems. The first example deals with the case where two orthogonal dynamic moving loads are applied at the same location. The second example involves a specific vehicle-bridge interaction problem. The vehicle is approximated as a half model consisting of two axles, where the dynamic loads from axles are modeled as point loads which move together. In both the cases, the estimated dynamic moving loads matched closely with the applied loads. In third example, the algorithm is also tested by adding 5% noise to the input response data. Even with random noise present in input strain data, the load estimates are obtained with a high degree of accuracy. Compared to conventional algorithms for estimating moving loads, the developed method makes the dynamic moving load recovery procedure accurate and relatively easy to implement.
Women in Mechanical Engineering: The Gender (Im)balance by the Numbers
Authors: Mihalcea Rada , Moghe Pallavi , Burzo Mihai
Published: March 2016

In this paper, we take a close look at the participation of women in Mechanical Engineering, through an analysis of scientific publications in the field. Using a large dataset of over 100,000 publications from the ASME digital library, the paper creates a picture of the gender preferences associated with areas in the field of Mechanical Engineering. We find that while the average percentage of women in the field is generally low (15.6%), there are significant differences between the percentages of women in different categories, with areas such as biomechanical engineering, energy management, renewable energy, and nanotechnology attracting a larger than average proportion of women. Additionally, we also analyze the change in the number of authors in different areas over 20 years of research in the field, and observe a significant growth in recent years for both genders in the areas of biomechanical engineering, nanotechnology, and computational engineering.
Numerical Study for Data Center Cooling Using Active Tiles
Authors: Song Zhihang
Published: March 2016

The design of raised floor, hot/cold aisle data centers has become a widely used approach for data center cooling. However, more advanced cooling solution is still needed to achieve better managed airflow distributions and improved energy efficiency. The use of fan assisted floor tiles (i.e., active tiles) is being investigated as an evolution of Data Center cooling solutions to accommodate higher heat load demand. In this study, compact models of fan assisted tiles was imported into a basic hot aisle/cold aisle data center configuration built and analyzed using the computational fluid dynamics (CFD) technique. The significant thermal design aspects under numerical investigation include: fan curve, swirl settings, and under-floor pressure (with and without aisle containment). The flow features affected by the critical design variables are consequently compared and discussed. It might be concluded that appropriately designed fan assisted floor tiles might meet a promise of optimizing the cooling arrangement in data centers.
Fabrication of Polyacrylonitrile Nanofiber Membranes Functionalized With Metal Organic Framework for CO2 Capturing
Authors: Wahiduzzaman  , Khan Mujibur , Absar Saheem , Harp Spencer , Edwards Kyle , Takas Nathan
Published: March 2016

Crystalline particles known as Metal Organic Frameworks (MOF’s) are known for their large surface area and high adsorption and storage capacity for CO2 gas. Electrospun nanofibers are considered as ideal substrates for synthesizing the MOF particles on the fiber surface. In this project, Polyacrylonitrile (PAN) and a Cu-based MOF known as HKUST-1 were selected as substrate fibers and adsorbent particles respectively. A precursor solution of PAN polymer hybridized with HKUST-1 particles dissolved in Dimehtylformamide (DMF) is used as the primary component solution for electrospinning. SEM images of the electrospun fibers showed small MOF particles formation into the fiber structure. A secondary solvothermal process of MOF particles growing on the fibers was then executed to increase the amount of MOF particles for effectual gas adsorption. The secondary process consists of multiple growth cycles and SEM images showed uniform distribution of porous MOF particles of 2–3μm in size on the fiber surface. EDS report of the fiber confirmed the presence of MOF particles through identification of characteristic Copper elemental peaks of HKUST-1. Thermogravitmetric analysis (TGA) of HKUST-1 doped PAN fiber displayed 32% of total weight loss between 180°C and 350°C thus proving the as-synthesized MOF particles are thermally stable within the mentioned temperature range. A comparative IR spectroscopic result between the gas-treated and gas-untreated fiber samples showed the presence of characteristic peak in the vicinity of 2300 and 2400cm−1 which corroborates the assertion of adsorption of CO2 on the system. Further step involved is to investigate the gas adsorption capacity of the filter system in an experimental test bench. Non-dispersive Infrared (NDIR) CO2 sensors will be used at the gas inlet and outlet parts to measure the concentration of CO2 and determine the amount of gas uptake by the filter system.
Experiment Study of Cardboard Box Fire Behavior Under Dynamic Pressure in an Altitude Chamber
Authors: Tian Runhe , Liu Quanyi , Feng Rui , Chen Kewei , Yang Rui , Zhang Hui
Published: March 2016

Fires recently at low ambient pressure such as cruising airplane and high altitude airport have attracted great attention. Understanding fire behavior under low pressure is one of important fundamental problems for fire safety engineering design in forementioned environment. Observation of cardboard fires under dynamic pressure is of significant meaning to study continuous variation of fire behaviors of solid fuel during depressurization.

An altitude chamber of 2×3×4.65 m3 with a powerful pressure controlling system was designed to observe fire behavior of cardboard fires under dynamic pressure. In the chamber, two configurations of cardboard boxes filled with shredded office paper were tested under dynamic pressures at descent rates: 5.46kPa/min, 10.92kPa/min, and 19.68kPa/min for both configurations. Measured parameters in this study include flame temperature, radiative heat flux, and mass burning rate. The measurement data were analyzed to reveal depressurization effect on fire behavior.
Numerical Investigation of Data Center Raised-Floor Plenum
Authors: Beitelmal Abdlmonem H.
Published: March 2016

Data center raised-floor plenum effectiveness is numerically investigated using a computational fluid dynamics (CFD) package to determine the most appropriate data center raised floor plenum height (size). The current study considers raised floor plenum height between 30.5 cm and 152.4 cm (12–60 inch) with the standard 15.2 cm (6-inch) increment while maintaining the supply airflow rate constant. Three factors are considered for optimum plenum size: the individual airflow rate from each perforated tile, the level of airflow rates uniformity between different perforated tiles and the top rack inlet air temperature at 2.13 m (7-ft) above the raised floor. The results show that raised floor plenum with height of 76.2 cm (30-inch) or higher had the most uniform airflow rates through the perforated tiles and most uniform temperature across the top of the racks. The findings also indicate that the uniformity of the static pressure inside the plenum increases with plenum height. The current results show that data center plenums with height range of 76.2–91.4 cm (30–36 inch) are found to be the best option based on the current thermo-fluid considerations however thermo-economics analysis should be addressed in future work.
Stress Response of Germanium Electrodes During Lithiation/Delithiation Cycling
Authors: Nadimpalli Siva P. V. , Tripuraneni Rajasekhar
Published: March 2016

An in situ study of stress evolution of germanium as a lithium-ion battery electrode material is presented. Thin films of germanium are cycled in a half-cell configuration with lithium metal foil as counter/reference electrode, with 1M lithium hexafluorophosphate in ethylene carbonate, diethylene carbonate, dimethyl carbonate solution (1:1:1, wt. %) as electrolyte. Real-time stress evolution in the germanium thin-film electrodes during electrochemical lithiation and delithiation is measured by monitoring the substrate curvature using the multi-beam optical sensing method. Germanium thin film undergoes extensive inelastic deformation during electrochemical lithiation and delithiation similar to silicon. The peak compressive stress during lithiation in germanium was 0.6 GPa, which is almost half of the peak compressive stress of lithiated silicon. The tensile stress of lithiated Ge on the other hand was almost same as that of lithiated silicon, 1 GPa of peak stress. The stress response of the first cycle was slightly different from that of the second cycle, which is an indication of irreversible structural changes in the Ge electrode during the first cycle. The Ge thin films survived stresses as high as 1 GPa of tensile stress without developing any cracks while the Si films under same conditions showed extensive cracking, consistent with previous observations which claimed lithiated Ge to be tougher than lithiated Si.
Retracted: “Using Meta-Models as Fast and Accurate Predictors of a Reconfigurable Mould System” [ASME 2015 International Mechanical Engineering Congress and Exposition, Volume 2B: Advanced Manufacturing, Houston, Texas, USA, November 13–19, 2015, Conference Sponsors: ASME, ISBN: 978-0-7918-5736-6, Copyright © 2015 by ASME. Paper No. IMECE2015-50990, pp. V02BT02A010; 10 pages; doi:10.1115/IMECE2015-50990]
Authors: ASME
Published: March 2016

The above referenced paper has been removed from publication. June 8, 2016.

Copyright © 2016 by ASME
Heat Transfer From Separating and Non-Separating Suddenly Expanding Viscoplastic Flows
Authors: Hammad Khaled J.
Published: March 2016

Heat transfer from Bingham viscoplastic non-Newtonian flows through axisymmetric 1:5 and 1:2 sudden expansions has been studied numerically by solving the mass, momentum, and energy conservation equations. The non-dimensional yield stress, i.e. yield number, is found to have a significant impact on the flow and heat transfer behavior. Two distinct viscoplastic flow regimes are observed. For a given Reynolds number, increasing the yield number, results in transitioning from a recirculating to a non-recirculating viscoplastic flow regime. Substantial heat transfer enhancement exists downstream the expansion plane in the form of a peak heat transfer rate that is up to twice the downstream, fully developed, value. A single peak is observed for Newtonian and non-separating viscoplastic flows as opposed to two peaks in the case of separating viscoplastic flows. Peak heat transfer rates were found to substantially increase with the yield number and, to a lesser extent, with the expansion ratio.
Computational Study of Multiple Hydrokinetic Turbines: The Effect of Wake
Authors: Daskiran Cosan , Riglin Jacob , Oztekin Alparslan
Published: March 2016

Computational Fluid Dynamics (CFD) simulations have been conducted to investigate the performance of a predetermined propeller-based hydrokinetic turbine design in staggered and non-staggered placements for river applications. Actual turbine models were used instead of low fidelity actuator line or actuator disks for CFD simulations to achieve more reliable results. The k-ω Shear Stress Transport (SST) turbulence model was employed to resolve wall effects on turbine surface and to determine wake interactions behind the turbines. The wake interaction behind the upstream turbine causes significant drop on downstream turbine performance within non-staggered configuration. The upstream turbines in both staggered and non-staggered placement offers the same relative power of 0.96, while the relative power for downstream turbine is 0.98 for staggered installment and 0.16 for inline placement.
Effects of Layup and Matrix Toughness on Modeling Notched Carbon Fiber Panels in Out-of-Plane Bending
Authors: Suryan Levi J. , Daniels Mitchell A. , Parmigiani John P.
Published: March 2016

Predicting the damage progression behavior of fiber composites using finite element methods is an ongoing challenge in design of high performance structures. A common application of fiber composites is out-of-plane bending of a notched composite panel. This loading occurs, for example, in an aircraft fuselage near reinforcing members such as ribs or stringers. The material parameters used by the finite element package Abaqus that dictate damage progression behavior of fiber composites include 6 strength values which control when damage is initiated, and 4 energy parameters that control how damage propagates. The values of the initiation parameters (strengths) are often accurately known, however the values of the propagation parameters (energies) are often not accurately known. The consequences of these inaccuracies are not consistent. Current research indicates that accurate FEA results for out-of-plane bending always require accurate values for the material strengths. However the effect of inaccurate material propagation energy values can vary depending on composite laminate layup. Understanding how these effects vary and which values are important can help a designer select a material and/or determine which propagation energy values need to be accurately determined. This study uses the Abaqus implicit FEA solver to model center notched carbon fiber panels to explore the effect of ply orientation on the sensitivity of maximum load to values of matrix tensile propagation energy and matrix compressive propagation energy. Preliminary studies of this loading scenario showed that these values have significant effects on maximum load only for certain layups. Five different 20 ply layups were chosen for this study with varying number of plies oriented in the 90 degree direction. The 90 degree direction is defined as perpendicular to the bending stresses and parallel to the notch. For each layup, matrix compressive and tensile propagation energies were specified at ±20% from their nominal values to create two-level factorials. Each layup was also run using nominal values as a center point to assess linearity of the effects. Furthermore, damage propagation paths were compared to understand how damage propagation was being affected. This way, nonlinear effects of matrix propagation energy values on maximum load could be separated from any regime changes in damage propagation. The results of this study lend understanding to the finite element analyst on how layup affects the need for high-accuracy values of certain material properties. Accurate FEA results for some layups do not depend on accurate matrix propagation energy values. Having this in mind can save significant resources in the fiber composite design process by eliminating unnecessary destructive tests to determine material property values accurately.
Industry Partnership to Help Transform Liberal Arts Graduates to Advanced Manufacturing Careers
Authors: Zeid Ibrahim , Steiger-Escobar Susanne , Bograd Marina , Javdekar Chitra , Duggan Claire , Moussavi Shamsi , Sullivan Daniel , Kamarth Sagar
Published: March 2016

It is well recognized that manufacturing is making a comeback to the US, from the outsourcing that took place between 1980–2010. The need for advanced manufacturing careers is also well documented by many manufacturing organizations, substantiated by the report entitled “A National Strategic Plan for Advanced Manufacturing” which was released by the Executive Office of the President National Science and Technology Council’s in February 2012. The Association for Manufacturing Excellence (AME) points out that at the height of the recession, 32% of manufacturers reported that they had jobs unfilled because they could not find people with requisite skills. It is also well documented that liberal arts (BA) graduates suffer from mal-employment problems; they are either underemployed or unemployed. To solve this problem, this paper describes an innovative solution of transforming BA graduates to take on advanced manufacturing positions to meet the skilled workforce needs and fill these positions. This paper briefly describes the program, but focuses mainly on one aspect of it: industry partnerships. We describe the importance of industry partners to the proposed solution. We also discuss industry needs.
Perimeter Cooling Unit and Localized Row-Based Cooling Unit Transient Air Flow Effects Modeling and Characterization in Data Centers
Authors: Gao Tianyi , Geer James , Sammakia Bahgat G. , Tipton Russell , Seymour Mark
Published: March 2016

Cooling power constitutes a large portion of the total electrical power consumption in data centers. Approximately 25%∼40% of the electricity used within a production data center is consumed by the cooling system. Improving the cooling energy efficiency has attracted a great deal of research attention. Many strategies have been proposed for cutting the data center energy costs. One of the effective strategies for increasing the cooling efficiency is using dynamic thermal management. Another effective strategy is placing cooling devices (heat exchangers) closer to the source of heat. This is the basic design principle of many hybrid cooling systems and liquid cooling systems for data centers. Dynamic thermal management of data centers is a huge challenge, due to the fact that data centers are operated under complex dynamic conditions, even during normal operating conditions. In addition, hybrid cooling systems for data centers introduce additional localized cooling devices, such as in row cooling units and overhead coolers, which significantly increase the complexity of dynamic thermal management. Therefore, it is of paramount importance to characterize the dynamic responses of data centers under variations from different cooling units, such as cooling air flow rate variations.

In this study, a detailed computational analysis of an in row cooler based hybrid cooled data center is conducted using a commercially available computational fluid dynamics (CFD) code. A representative CFD model for a raised floor data center with cold aisle-hot aisle arrangement fashion is developed. The hybrid cooling system is designed using perimeter CRAH units and localized in row cooling units. The CRAH unit supplies centralized cooling air to the under floor plenum, and the cooling air enters the cold aisle through perforated tiles. The in row cooling unit is located on the raised floor between the server racks. It supplies the cooling air directly to the cold aisle, and intakes hot air from the back of the racks (hot aisle). Therefore, two different cooling air sources are supplied to the cold aisle, but the ways they are delivered to the cold aisle are different. Several modeling cases are designed to study the transient effects of variations in the flow rates of the two cooling air sources. The server power and the cooling air flow variation combination scenarios are also modeled and studied. The detailed impacts of each modeling case on the rack inlet air temperature and cold aisle air flow distribution are studied. The results presented in this work provide an understanding of the effects of air flow variations on the thermal performance of data centers. The results and corresponding analysis is used for improving the running efficiency of this type of raised floor hybrid data centers using CRAH and IRC units.
Dense Granular Flows as a New Heat Transfer Fluid for Concentrated Solar Power
Authors: Watkins Megan F. , Gould Richard D.
Published: March 2016

The increasing interest in concentrated solar power as a new form of renewable energy necessitates an improvement in overall system efficiency. Current heat transfer fluids employed to capture the concentrated heat demonstrate limited working temperature ranges. This study sought to investigate the use of dense granular flows as a possible new heat transfer fluid, as ceramic particles present virtually no restriction on working temperature. A bench-scale system simulating a single tube of a concentrated solar power central receiver was constructed and used to evaluate the heat transfer properties of the flow at low temperatures. Ceramic particles, 270μm in diameter, were gravity-fed through a vertical tube, resulting in granular flows with particle packing fractions of approximately 60%. Radial temperature profiles were measured and used to calculate the mean temperature of the fluid at different axial tube locations. The heat transfer coefficient was then calculated based on the input heat flux and measured wall and mean temperatures. The effect of the mass flow rate on the heat transfer coefficient was examined by using different orifices at the tube exit. As expected, the heat transfer coefficient increased with increasing flow rate. Heat transfer coefficients ranging from 330 to 380 W/m2-K were obtained for bulk temperatures ranging from 40 to 70°C. Previous works demonstrated comparable heat transfer coefficients at higher bulk temperatures. Thus, our preliminary heat transfer coefficient results demonstrate the potential of dense flows of ceramic particles for obtaining beneficial heat transfer properties at extremely high operating temperatures.
Design of a High Performance Polymer Thermoelectric Generator Using Radial Architecture
Authors: Menon Akanksha K. , Yee Shannon K.
Published: March 2016

Thermoelectric generators (TEGs) are solid-state heat engines consisting of p-type and n-type semiconductors that convert heat into electricity via the Seebeck effect. Conducting polymers are a viable alternative with intrinsic advantages over their inorganic counterparts since they are abundant, flexible as thick-films, and have reduced manufacturing costs since they can be solution processed. Furthermore, polymers have an inherently low thermal conductivity, thus affording them the option of forgoing some heat exchanger costs. Current examples of polymer TE devices have been limited to traditional flat-plate geometries with power densities on the μW/cm2 scale, where their potential is not fully realized. Herein, we report a novel radial device and evaluate the improved performance of polymer-based TEG based on this architecture. Analytical heat transfer and electrical models are presented that optimize the device for maximum power density, and we obtain the geometry matching condition for this radial device that maximizes the module figure-of-merit. Our radial architecture accommodates a fluid as the heat source and can utilize natural convection alone (due to heat spreading) to obtain high power densities of 1–3 mW/cm2 using state-of-the-art polymer TEs subjected to a temperature difference of 100 K.
Finite Element and Mechanical Modeling of Fatigue Behavior of Partial Vapor-Conditioned Viscoelastic Material
Authors: Hossain Mohammad , Rahim Khan A. S. M. Atiqur , Faisal Hasan , Tarefder Rafiqul
Published: March 2016

Past studies have shown that vapor conditioning to 100% Relative Humidity (RH) reduces the fatigue life of viscoelastic materials such as asphalt binder. However, it is not known how partial vapor conditions such as RH 25%, 49%, and 71% affect asphalt binder’s fatigue behavior. In addition, it is unknown which viscoelastic material parameter (i.e. viscus or elastic parameter) is responsible for damage in asphalt binder or Asphalt Concrete (AC) in general and what steps can be taken to reduce fatigue damage. In this study, films of asphalt binders were prepared and partially vapor-conditioned in enclosed chambers containing potassium acetate (25% RH), potassium carbonate (49% RH), and sodium chloride solutions (71% RH). Creep nanoindentation tests were performed on the vapor-conditioned asphalt film samples. The nano-creep test data are fitted using Burgers models. The Burgers model shows that elasticity increases and viscosity decreases as RH% increases. To this end, a Finite Element Method (FEM) model is developed in ABAQUS to examine the fatigue performance of the asphalt binder at 49% vapor-conditioned only. Using the spring and dashpot elements of Burgers model as FEM inputs, simulations are run. Results indicate that an increase in binder viscosity would reduce permanent deformation in the viscoelastic material.
3D Printing of Novel Gradient Osteochondral Scaffolds to Bridge the Gap Between Cartilage and Bone
Authors: Nowicki Margaret A. , Castro Nathan J. , Plesniak Michael W. , Zhang Lijie Grace
Published: March 2016

Osteochondral tissue has a graded structure spanning from the subchondral bone region beneath the joint surface to the hyaline cartilage region at the joint surface. Biological, physiological, and mechanical properties over the regions cross-section vary greatly; this provides a significant challenge for tissue-engineered structures addressing osteochondral defects. The objective of this research is to investigate the effects of scaffold pore structure on mechanical, biological, and physiological properties of 3D printed tissue engineered osteochondral scaffolds. Our results indicate that gradient pore structures improve both mechanical properties and cell performance when compared to homogeneously distributed pores and non-porous structures. This study also indicates that including nanocrystalline hydroxyapatite (nHA) into the hydrogel scaffold further improves cellular performance compared to both porous scaffolds without nHA and nonporous scaffolds.
Natural Convection and Entropy Generation in a Cavity Filled With Two Horizontal Layers of Nanofluid and Porous Medium in Presence of a Magnetic Field
Authors: Al-Zamily Ali , Amin M. Ruhul
Published: March 2016

A numerical analysis is performed to study the fluid flow, heat transfer and entropy generation inside a square cavity embedded with heat flux and subject to the horizontal magnetic field. The cavity is consist of two same width layers: first layer filled with nanofluid (Al2O3+water) and second one is saturated porous media filled with a same nanofluid. The uniform constant heat flux is applied partly at the base wall, and the other parts of the base wall are assumed adiabatic. The upper horizontal wall kept adiabatic, while the vertical walls are maintained at constant cold temperature. Finite element method based on the variational formulation is employed to solve the main equations.

The results of the present study are based on visualization of heat flow via isotherms and heatfunctions (heatlines), fluid flow via streamfunctions, and irreversibility via Bejan number. Comparisons with previously numerical and experimental published works are performed and the results are found to be in a good agreement. In this study, the effect of the main pertinent parameters, such as: nanoparticles volume fraction (0≤Φ≤0.15), Rayleigh number (104≤Ra≤107), Darcy number (10−1≤Da≤10−5), Hartmann number (0≤Ha≤60) on the fluid flow, heat transfer and entropy generation are investigated.

The results show that the effect of the Hartmann on Nusselt number increases as Darcy number increases especially at high Rayleigh number. Also, at Ra=107 and Φ=0.15, the percentage decreasing in Nusselt number due to present magnetic field (Ha=40) are 85.89% at Da=10−1, 87.12% at Da=10−3 and 98.69% at Da=10−5.