bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancement of Heat Transfer Characteristics in an Absorber Tube of a Solar-Based Energy System Using Nanofluids
Authors: Alashkar Adnan , Gadalla Mohamed
Published: March 2016

In this present paper, nanoparticles are dispersed into a base fluid, their effect on the thermophysical properties and overall heat transfer coefficient of the fluid inside a circular tube representing an absorber tube of a Parabolic Trough Solar Collector (PTSC) is studied. Different models are used to predict the effective density, specific heat capacity, viscosity and thermal conductivity of the nanofluids. For the analytical analysis, Alumina (Al2O3), Copper (Cu) and Single Wall Carbon Nanotubes (SWCNT) nanoparticles are dispersed into Therminol VP-1 oil. The resulting nanofluids are compared in terms of their thermophysical properties, their convective heat transfer characteristics and their overall heat transfer coefficient. Moreover, the effect on increasing the volume fraction on the properties and the heat transfer coefficient is studied. The computational analysis results show that the thermal conductivity increases with the increase of the volume fraction. In addition Therminol/SWCNT showed the highest thermal conductivity enhancement of 98% for a volume fraction of 3%. Further, the overall heat transfer coefficient increases with the increase of volume fraction, and Therminol/SWCNT showed the highest enhancement with 72% compared to Al2O3/Therminol and Cu/Therminol that showed an enhancement of 29% and 43% respectively.
Tribology as an Enabler for Innovation in Surface Generation Processes
Authors: Subramanian K. (Subbu) , Jain Anant , Rajagopal Vairamuthu , Bhushan Brij M.
Published: March 2016

Surface generation processes involve convergence of both machining and tribological interactions between the tool and the work. Abrasive finishing is one among the many families of surface generation processes, of which grinding process is a sub-set. In a typical grinding process, six different interactions can be identified at the grinding zone resulting in surface generation. Of these six interactions one is governed by the principles of machining, while the other five are governed by the principles of tribology. Thorough analysis of these interactions helps to characterize and understand the role of both tribological mechanisms and machining interactions in a typical grinding process. Moreover, these interactions offer the grinding process a flexibility which has resulted in a series of process innovations over decades transforming the grinding process into a high material removal rate machining process as well as an ultra-fine finishing process. Historical developments as well as recent process innovations are presented in this review paper along with the common frame work for their analysis using a set of microscopic interactions applicable in all these cases.
Parametric Study on the Effect of Partial Charge on Water Infiltration Behavior in MFI Zeolites
Authors: Vaartstra Geoffrey A. , Humplik Tom , Wang Evelyn N. , Maroo Shalabh C.
Published: March 2016

This work analyzes the infiltration behavior of water into sub-nanometer MFI zeolite pores using molecular dynamics simulations. Infiltration simulations are run for a range of partial charge values on the zeolite atoms. Infiltration behavior is compared to partial charges to verify dependence and determine critical charge above which infiltration becomes severely inhibited even at high pressures. Attraction energy is calculated and correlated to the observed infiltration behavior. The critical partial charge of Si∼1.8 occurs when the water-zeolite interaction energy becomes stronger than water-water attraction due to which water molecules get stuck and infiltration is significantly reduced.
Load Distribution in Barefoot Running Shoes
Authors: Gnagne Raoul , Barez Fred , Kao James , El-Hage Amer
Published: March 2016

Running is one of the most practiced sports around the world and it dates back to Ancient Greece. Running became an Olympic sport in 1896 and today is mostly performed for fun and to stay in shape. Nowadays, athletic shoe companies make claims on the performance of the type of shoes they manufacture. Some of their claims include shoes that allow free movements, fit like a glove, and are in complete harmony with human mechanics. The preceding characteristics are those of so-called barefoot running shoes. Robillard [1] explains that minimalist running shoes could be defined as those that provide limited or no support and only minimal protection, with the heel at the same level as the forefoot. Even though running may have been investigated, however, there is not enough analyses on barefoot running shoes. The objective of this study was to investigate the load distribution on the feet of a healthy running adult wearing barefoot shoes through experimental work and finite element analysis (FEA).

The methodology used in this study included experimental as well FEA. Tests were conducted with a 175-lb adult subject wearing a pair of minimalist shoes. Experimental data were collected and used to perform Finite Element Analysis. The barefoot shoes were modeled with an equivalent thickness of 0.453 inch, and the following parameters were experimentally determined such as the Young’s modulus of 467 psi, a density of 0.0025 lb/in3, and a Poisson’s ratio of 0.08.

The simulation results yielded a maximum compressive stress of 38.71 psi in the toe region. This stress level was approximately one-half of the stresses generated in the heel region of conventional sport shoes. This study, further, revealed the reduction of stresses at the heel region with barefoot shoes resulting in lower risk of pain and injury to the foot in the absence of impact transients ordinarily experienced with conventional shoes.
Pulsatile Primary Slurry Atomization: Effects of Viscosity, Circumferential Domain, and Annular Slurry Thickness
Authors: Strasser Wayne , Battaglia Francine
Published: March 2016

A central theme of our prior experimental and computational work on a transonic self-sustaining pulsatile three-stream coaxial airblast injector involved obtaining spectral content from compressible 2-D models and preliminary droplet size distributions from incompressible 3-D models. The three streams entail an inner low-speed gas, and outer high-speed gas, and an annular liquid sheet. Local Mach numbers in the pre-filming region exceed unity due to gas flow blockage by the liquid. Liquid bridging at somewhat regular intervals creates resonance in the feed streams. The effects of numerical decisions and geometry permutations were elucidated. The focus now shifts to compressible 3-D computational models so that geometric parameters, modeled domain size, and non-Newtonian slurry viscosity can be more elaborately explored. While companion studies considered circumferential angles less than 45°, specific attention in this work is given to the circumferential angles larger than 45°, the slurry annular dimension, and how this annular dimension interacts with inner nozzle retraction (pre-filming distance). Additional metrics, including velocity point spectral analyses, are investigated. Two-stream experimental studies are also computationally studied.

Multiple conclusions were drawn. Narrower annular slurry passageways yielded a thinner slurry sheet and increased injector throughput, but the resulting droplets were actually larger. Unfortunately the effect of slurry sheet thickness could not be decoupled from another important geometric permutation; injector geometry physical constraints mandated that, in order to thin the slurry sheet, the thickness of the lip which separates the inner gas and slurry had to be increased accordingly. Increased lip thickness reduced the interfacial shear and increased the thickness of the gas boundary layer immediately adjacent to the slurry sheet. This suppressed the sheet instability and reduced the resulting liquid breakup. Lastly, velocity point correlations revealed that an inertial subrange was difficult to find in any of the model permutations and that droplet length scales correlate with radial velocities.

As anticipated, a higher viscosity resulted in larger droplets. Both the incremental impact of viscosity and the computed slurry length scale matched open literature values. Additionally, the employment of a full 360° computational domain produced a qualitatively different spray pattern. Partial azimuthal models exhibited a neatly circumferentially repeating outer sheath of pulsing spray ligaments, while full domain models showed a highly randomized and broken outer band of ligaments. The resulting quantitate results were similar especially farther from the injector; therefore, wedge models can be used for screening exercises. Lastly, droplet size and turbulence scale predictions for two external literature cases are presented.
Application of a Hybrid RANS-LES CFD Methodology to Primary Atomization in a Coaxial Injector
Authors: Strasser Wayne , Battaglia Francine , Walters Keith
Published: March 2016

Non-zonal hybrid RANS-LES models, i.e. those which do not rely on user-prescribed zones for activating RANS or LES, have shown promise in accurately resolving the energy-containing and highly anisotropic large-scale motions in complex separated flows. In particular, the recently proposed dynamic hybrid RANS-LES (DHRL) approach, a method which relies on the continuity of turbulence production through the RANS-to-LES transition zone, has been validated for several different compressible and incompressible single phase flow problems and has been found to be accurate and relatively insensitive to mesh resolution. Time-averaged source terms are used to augment the momentum balance. An added benefit of the DHRL is the ability to directly couple any combination of RANS and LES models into a hybrid model without any change to numerical treatment of the transition region. In this study, an attempt is made to extend the application of this model to multiphase flows using two open literature coaxial two-stream injectors involving non-Newtonian liquids. For the first time, the new model has been successfully implemented in a multiphase framework, combining the SST RANS model with MILES LES approach. Favre averaging is used to ensure consistency between the momentum equations and the density fluctuations. It was found that the momentum source terms must be density weighted in order to ensure stability of the solution. Primary atomization findings with a stable model are encouraging. The spray character with the new model was somewhere between that of a RANS model and the LES result. Droplet sizes, which are indicative of the shear layer energy, for the RANS model were greater than the hybrid results, which were comparable to the LES result and matched the experimental expectation. Additionally, the new approach showed a liquid core breakup length close to that expected from the literature.
Dynamic Failure of Aluminum Alloy 2219-T8 Under High Strain Rate
Authors: Bolling Denzell , Olasumboye Adewale , Owolabi Gbadebo
Published: March 2016

The suitability of aluminum alloys in a vast majority of engineering applications forms the basis for the need to understand the mechanisms responsible for their deformation and failure under various loading conditions. The material investigated in this study is AA 2219-T8 aluminum alloy. Supplied by the NASA Research Center, with high strength to weight ratio and corrosive resistance. Containing a unique mixture of aluminum, copper, and other trace elements, this alloy has potential applications in multiple fields including aerospace, defense, and commercial industries. In this paper, the dynamic high strain rate impact deformation of the AA2219-T8 aluminum alloy was performed using the split Hopkinson pressure bars. The evolution of localized strain in the aluminum samples during the deformation process obtained using high speed digital cameras is reported. Microstructural analysis of deformed aluminum samples was also performed using optical microscopes in order to determine the influence of impact strain rate on localized strain along narrow adiabatic shear bands in the AA2219-T8 aluminum alloys. Results obtained indicate that peak flow stress in the deformed aluminum sample depends on the strain rate at which the deformation test was performed. The non-uniformity of the strain obtained using the digital image correlation as deformation time progresses shows two distinct areas of non-uniform strains that may be indicating potential sites for the formation of adiabatic shear bands in the tested samples.
Effect of Time Dependent Excitation Signals on Gating in Nanofluidic Channels
Authors: Boone C. , Fuest M. , Wellmerling K. , Prakash S.
Published: March 2016

Nanofluidic field effect devices feature a gate electrode embedded in the nanochannel wall. The gate electrode creates local variation in the electric field allowing active, tunable control of ionic transport. Tunable control over ionic transport through nanofluidic networks is essential for applications including artificial ion channels, ion pumps, ion separation, and biosensing. Using DC excitation at the gate, experiments have demonstrated multiple current states in the nanochannel, including the ability to switch off the measured current; however, experimental evaluation of transient signals at the gate electrode has not been explored. Modeling results have shown ion transport at the nanoscale has known time scales for diffusion, electromigration, and convection. This supports the evidence detailed here that use of a time-dependent signal to create local perturbation in the electric field can be used for systematic manipulation of ionic transport in nanochannels.

In this report, sinusoidal waveforms of various frequencies were compared against DC excitation on the gate electrode. The ionic transport was quantified by measuring the current through the nanochannels as a function of applied axial and gate potentials. It was found that time varying signals have a higher degree of modulation than a VRMS matched DC signal.
A Microscale Study of the Impact of Bubble Growth Dynamics on Surface Heat Flux in Microchannel Flow Boiling Process
Authors: Bigham Sajjad , Moghaddam Saeed
Published: March 2016

In this study, the physics of microscale heat transfer events at the wall-fluid interface during the growth of a moving bubble in a microchannel is analyzed. The study is enabled through development of a novel device that utilizes 53 microscale platinum resistance temperature detectors (RTDs) embedded in a composite substrate made of a high thermal conductivity material coated by a thin layer of a low thermal conductivity material. This sensors arrangement enables resolving the thermal field at the bubble-wall interface with unprecedented spatial and temporal resolutions of 40–65 μm and 50 μs, respectively. To prevent random bubble inception, a 300 nm in diameter cavity is fabricated using a focused ion beam (FIB) at the center of a pulsed function microheater. A detailed analysis of the surface heat transfer events and their relations to time scale of formation and dimensions of bubbles are conducted to decipher the underlying physics of the flow boiling process. Experimental results show that four mechanisms of heat transfer are active as a bubble grows and flows through the channel. These mechanisms of heat transfer are 1) microlayer evaporation, 2) interline evaporation, 3) transient conduction, and 4) micro-convection. The results suggest that the average surface heat flux enhances as the bubble grows in size resulting in expansion of the surface area over which the thin film evaporation mechanism is active. Above a certain bubble size, the average surface heat flux declines due to the formation of a dry region at the bubble-wall interface. Hence, the results indicate that there is an optimal bubble length at which the average surface heat flux is maximum.
The Effects of Fabrication Induced Residual Stress-Strain States on the Irradiation Performance of Monolithic Mini-Plates
Authors: Ozaltun Hakan
Published: March 2016

Effects of initial stress-strain states on irradiation performance of monolithic fuel plates were studied. The monolithic fuel plates consist of a high density low enrichment U-Mo fuel that is encapsulated in an Aluminum cladding. Because the fabrication involves multiple stages, there are concerns, if the irradiation performance of the plates is affected by the pre-irradiation stress-strain states. To investigate these concerns, a representative plate was evaluated for distinct initial stress-strain states. First, the foil preparation stage by co-rolling process was simulated. For this, a scaled version of the process was simulated to calculate the stress-strain profiles. These profiles were then used to incorporate initial states for the HIP process. Additional HIP simulations were also considered to evaluate the cases with stress-free foils prior HIP bonding. For the simulation of HIP process with initially stress-free co-rolled foils, several bonding temperatures were considered. Finally, the irradiation processes were simulated for all cases with distinct pre-irradiation stress-strain states. The stress-strain fields from the fabrication process were used to incorporate the initial states for the irradiation simulations. The resulted distortions, stress-strain fields and temperature profiles were extracted at the selected locations. Finally, a comparative evaluation was made to determine the sensitivity of the plate’s performance to the pre-irradiation stress-strain states. The irradiation simulations have revealed that the fabrication stresses in the fuel would be relieved relatively fast in reactor. The fuel foil would be essentially stress-free during irradiation. The stresses however, would develop at the shutdown stage. For the cladding material, the stresses continue to increase and additional plastic strains are generated as a result of fuel swelling. The study indicated that the stress-strain fields of the plates during irradiation are not affected by the initial stress state of the plates.
Synthesis and Characterization of Chitosan-Mg-Based Composite Scaffolds for Bone Repair Applications
Authors: Adhikari Udhab , Rijal Nava P. , Pai Devdas , Sankar Jagannathan , Bhattarai Narayan
Published: March 2016

Bone has a remarkable ability to regenerate and heal itself when damaged. Most minor injuries heal naturally over time, but when the defects are larger, they require a substrate to support the cell growth and guide the repair process. Bone grafting is currently done by using either an autograft, where the substrate is harvested from a suitable donor site within the patient’s body; or an allograft, where the substrate is harvested from a cadaver. However, both techniques have significant drawbacks. In autografting, significant complications tend to arise from donor site morbidity. In allografting, the issues are the risk of disease transmission, and the logistical difficulties in the local or even global matching process for donor tissue. A third approach, employing tissue-engineered scaffold materials, provides superior performance by helping to restore bone tissue functions during regeneration and by subsequent resorption of the graft material as new bone tissue forms. These bioactive scaffolds are porous and made of natural materials that are capable of harboring growth factors, drugs, genes, or stem cells. The objectives of this research are to synthesize biofunctional composite scaffold materials, based on chitosan (CS) and magnesium (Mg), for use in bone regeneration and to measure their physiochemical properties. Scaffolds were fabricated from the aqueous dispersions of starting materials by subsequent freezing and phase separation by the lyophilization process. A CS solution was prepared by dissolving CS in 2 % (v/v) acetic acid solution, whereas carboxymethyl chitosan (CMC) was dissolved in deionized water. The concentrations of CS and CMC (in a constant 1:1 weight ratio) ranged between 2% and 5 %. Various dry weight percentages of Mg gluconate (MgG) were added to the scaffolds by dissolving the MgG solution in the CS/CMC. SEM imaging showed the scaffolds to possess uniform porosity with a pore size distribution range of 100–150 μm. Micro CT analysis showed that the pores were distributed throughout the scaffold’s entire volume and they were highly interconnected. Compressive strengths of up to 340 kPa and compressive moduli of up to 5 MPa were obtained for these fabricated scaffolds. When introduced into a cell culture medium, these scaffolds were found to remain intact, retaining their original three-dimensional frameworks and ordered porous structures maintaining sufficient mechanical strength. These observations provide a new effective approach for preparing scaffold materials suitable for bone tissue engineering.
Chemical Equilibrium Model for Fixed-Bed Gasification to Assess Biomass Energy Content
Authors: Verdeza Arnaldo , Ahumada Luz , Bula Antonio
Published: March 2016

A chemical equilibrium model for fixed-bed gasification is developed, which allows the prediction of the syngas composition, the amount of residual coal or ash, as well as the amount of tars as a function of the gasification temperature and the elemental composition of the biomass and the tars. Moreover, the combustion heat of the gas fuel is calculated, as well as the conversion and process efficiency, in order to perform further analyses which allow the determination of energy potential for different types of biomass under several conditions of moisture and equivalence ratio of gasifying agent. Performance of the proposed model is compared to prediction of some models which were found to be relevant in the literature review. An assessment to the model is also carried out. For this purpose, a case-study is performed for African palm (Elaeis guineensis) shells using a commercial gasifier. Experimental data obtained from the biomass used in the case-study are used to feed the model and perform the assessment. Actual results and model predictions (results) are compared varying the equivalent relation between 0.05 and 0.65, and the moisture content form biomass between 0 and 20%. This case is proposed as a benchmark case for further applications.
Influence of Materials Properties on the Irradiation Behavior of U-10Mo Monolithic Mini-Plates
Authors: Mohamed Walid , Roh Hee Seok
Published: March 2016

The DOE/NNSA Conversion [1] Program in the US aims to minimize the use of high enrichment uranium in civilian applications. This initiative is being approached by converting research and test reactors from the use of highly enriched uranium (HEU) to low enrichment uranium (LEU, <20% 235U) with high density of uranium to achieve stable operation of converted reactors. Among variety of fuel materials investigated to serve in the conversion process, U-Mo based alloys have shown stable and acceptable swelling response under typical operation conditions of research and test reactors.

For the conversion of high performance research reactors, a large number of irradiation experiments were conducted to evaluate the mechanical behavior of the U-10Mo monolithic mini-plate; however, it is difficult to investigate all design and operation variables with potential impact on the irradiation behavior of the fuel experimentally.

Thus, this study performed Finite Element Analyses (FEA) on a 3-D monolithic plate by changing material properties of components. The material properties considered in this study included thermal, mechanical, and irradiation specific properties of the fuel, cladding, and liner. Among FEA results, higher Young’s modulus of cladding material caused a significant decrease in all stress values in the three sections of the monolithic mini-plate. On the other hand, variation in the Young’s modulus of Zr-liner showed the minimal effect on the overall mechanical response of the monolithic mini-plate. Results showed that increasing the yield stress of the cladding material directly caused a increase in the maximum stress observed in the cladding section by almost 40 %. Considering the thermal properties of materials in the monolithic plate, maximum and minimum stress in fuel foil were found to either increase or decrease in proportional with the coefficient of thermal expansion of the fuel material. However, variation in the coefficient of thermal expansion in the cladding section caused a remarkable increase in peak stresses in the fuel foil.

While mechanical and thermal properties of the foil, liner, and cladding sections are known, other irradiation-dependent properties such as coefficient of irradiation creep of U-10Mo are not firmly determined to date. The mechanical response of L1P756 is being simulated with different values of the coefficient of irradiation creep and the observed “bulging” in the plate will be compared to available post-irradiation measurements. Thus, it will be possible to determine an accurate value of irradiation creep coefficient of U-10Mo which in turn would allow predicting its mechanical behavior under different irradiation conditions.
Lifecycle Cost Analysis for Better Air Conditioning Choice in Kuwait Residential Sector
Authors: Almutairi Hamad H. , Dewsbury Jonathan , Lane-Serff Gregory F.
Published: March 2016

Residential air conditioning consumes a huge amount of the produced electrical power from fossil fuel power plants in Kuwait. Energy availability and the consequences on Kuwait’s expenditure associated with producing electricity is a hot topic in this oil producing country. The predominant air conditioning type in Kuwait’s residential sector is packaged direct expansion. An intention to shift to chilled water air conditioning system for future’s houses was announced as a promising solution to save energy. This work is presented to demonstrate how lifecycle cost analysis can be performed to underline tentative issues before shifting to a new air conditioning system for houses in Kuwait. No previous attempts have been made to assess the feasibility of chilled water air conditioning system for houses in Kuwait based on lifecycle cost analysis. The work considered the air conditioning requirements for a block of six typical houses as a baseline for the evaluation. The total cooling load of the studied block of houses was used to estimate the annual electrical energy associated with each air conditioning alternative. This was made by the help of DOE EnergyPlus thermal simulation engine through its interface with DesignBuilder software. Actual financial inputs were penetrated in the analysis; which includes installation, operation and maintenance costs for each studied air conditioning alternative. It was found that chilled water system can conserve about 40% of the annual electrical energy required to operate packaged direct expansion air conditioning. But, due to high installation cost, chilled water system is not cost effective for consumers. The outcomes from the lifecycle cost analysis indicated that it would be cost effective for the government to subsidy the installation of chilled water systems for consumers. This will help to conserve electrical energy associated with conventional systems that are currently in use.
Experimental Investigation on Compact Heat Exchanger in Aluminum Foam
Authors: Cirillo Luca , Manca Oronzio , Marinelli Lorenzo , Nardini Sergio
Published: March 2016

In this paper an experimental investigation on forced convection in a compact heat exchanger made up with an aluminum foam plate of 212.5mm × 212.5mm with a thickness of 40 mm and a single array with five circular tubes is presented. The foam has a porosity of 0.93 with 20 pores per inch and the tubes in aluminum have internal and external diameters equal to 9.5 mm and 12.5 mm. The test rig consists of an open air channel and a closed water cycle and the aluminum foam plate is placed inside the channel. The performances of the compact heat exchanger are evaluated for assigned hot water mass flow rate and different hot water inlet temperatures and air mass flow rate.

Results are given in terms of heat transfer rates and pressure drops as a function of air velocity and Reynolds numbers. The evaluation of dimensionless, thermal resistance, Colburn factor and Nusselt number is performed for different air mass flow rates and hot water inlet temperatures. The performance evaluation criteria is considered in terms of ratio between the heat transfer rate inside the heat exchanger and the pumping power of the air fan.
The Study on Shear Thinning Behavior of the Magnetorheological Fluid Under High Velocity Flow
Authors: Hu M. , Wang J. , Shen T. , Liu B. , Wang J. H.
Published: March 2016

As a kind of smart materials, the magnetorheological fluid (MRF) has a promising application for its excellent properties. In this paper, the shear thinning of the magnetorheological fluid (MRF) is analyzed from two aspects, firstly, the relation between the viscosity of MRF and the pressure difference between the inlet and the outlet of the tube is obtained based on the HB model; and then, the shear mechanism of shear thinning is analyzed from microcosmic viewpoint, by which the model of the shear thinning is established. What’s more, a effective method for calculating the MRF viscosity is proposed based on the hydrodynamics. The research result is verified by the experiments.
Experimental Investigations on DI Diesel Engine With Low Heat Rejection Combustion Chamber With Carbureted Ethanol and Crude Jatropha Oil
Authors: Rao Vencherla V. R. Seshagiri , Krishna Maddali V. S. Murali , Reddy T. Kishen Kumar , Srikanth D. , Murthy P. V. Krishna
Published: March 2016

It has been found that the vegetable oils and alcohols (ethanol and methanol) are promising substitute fuels for diesel fuel, because they are renewable in nature. However drawbacks associated with crude vegetable oil (high viscosity and low volatility) and ethanol (low cetane number and low energy content) which cause combustion problems in CI engines, call for engine with hot combustion chamber. Investigations were carried out on single–cylinder, four–stroke, water cooled, 3.68 kW direct injection diesel engine at a speed of 1500 rpm to evaluate the performance of a engine with medium grade low heat rejection (LHR) combustion chamber. It consisted of an air gap insulated piston and an air gap insulated liner fuelled with crude jatropha oil and carbureted ethanol with varied injection timing and injector opening pressure. Carbureted ethanol was inducted into the engine through a variable jet carburetor. This carburetor was installed at the inlet manifold of the engine and ethanol was inducted at different percentages of crude vegetable oil at full load operation on mass basis. Aldehydes (measured by dinitrophenyl hydrazine method), particulate emissions and oxides of nitrogen were measured at full load operation of the engine. With maximum induction of ethanol, engine with LHR combustion chamber showed improved performance over conventional engine at 27°bTDC and optimized injection timing.
A Novel Neck Support Design to Alleviate Worker Neck Pain
Authors: Yee Christina A. , Kazerooni Homayoon
Published: March 2016

Neck pain is common among occupations like dentistry and office work because workers in these professions tend to hold their necks in static flexion for extended periods of time. But there are few products available to help alleviate workers’ neck pain while still allowing them to carry out their daily tasks in varying environments. For example, office workers can use products like ergonomic chairs and desks to help promote proper posture, but these arrangements restrict workers to workspaces equipped with their necessary equipment and proper setup. Meanwhile, in the medical field, products like loupes, lights, and ergonomic workbenches are available to enhance visibility and reduce workers’ neck flexion angles. But these products have yet to fully eliminate the problem of neck pain especially in occupations like dentistry where static neck flexion is common. Therefore, the goal of this project is to develop a new neck support technology which alleviates neck pain caused by static neck flexion while still allowing workers full mobility and functionality in their workplace. Our design decreases muscle loading on the neck during neck flexion by reducing the moment on the neck using a device which acts as a “headrest” to support the head. In turn, the device redistributes forces to the upper body while still allowing full range of motion to the user. More specifically, our design applies an opposing force to the user’s forehead during neck flexion via a force generator attached to a headband which is attached to the head. The force generator is anchored to the upper body to permit use in varying environments without the need for special equipment or setups. We confirmed our design decreases muscle loading by building a prototype then performing surface electromyography (EMG) testing which showed not just a statistically significant reduction in neck muscle activity using one-way analysis of variance, but more distinctly a unanimous decrease in neck muscle activity during neck flexion for all seven test subjects with an overall average decrease of 60% among all subjects and 80% for certain subjects. Once we confirmed our design’s effectiveness in reducing neck muscle activity during static neck flexion which implied the ability to reduce neck strain, we improved our prototype’s functionality and aesthetics based on test subject feedback, our own observations, and dentists’ comments. Then, we performed workplace testing on two dentists with one dentist’s work focused mainly on hygiene while the other dentist’s work focused mostly on dental procedures. Overall, both dentists offered helpful feedback from different dental field perspectives for future prototype improvements with regards to comfort and functionality. They also provided promising comments regarding their visions for future device use which included training dental students on proper posture and applications in other occupations like office work and surgery.
Adaptive Multigrid Methods for Extended Fluid-Structure Interaction (eXFSI) Problem: Part I — Mathematical Modelling
Authors: Ebna Hai Bhuiyan Shameem Mahmood , Bause Markus
Published: March 2016

This contribution is the first part of three papers on Adaptive Multigrid Methods for eXtended Fluid-Structure Interaction (eXFSI) Problem, where we introduce a monolithic variational formulation and solution techniques. In a monolithic nonlinear fluid-structure interaction (FSI), the fluid and structure models are formulated in different coordinate systems. This makes the FSI setup of a common variational description difficult and challenging. This article presents the state-of-the-art of recent developments in the finite element approximation of FSI problem based on monolithic variational formulation in the well-established arbitrary Lagrangian Eulerian (ALE) framework. This research will focus on the newly developed mathematical model of a new FSI problem which is called eXtended Fluid-Structure Interaction (eXFSI) problem in ALE framework. This model is used to design an on-live Structural Health Monitoring (SHM) system in order to determine the wave propagation in moving domains and optimum locations for SHM sensors. eXFSI is strongly coupled problem of typical FSI with a wave propagation problem on the fluid-structure interface, where wave propagation problems automatically adopted the boundary conditions from of the typical FSI problem at each time step. The ALE approach provides a simple, but powerful procedure to couple fluid flows with solid deformations by a monolithic solution algorithm. In such a setting, the fluid equations are transformed to a fixed reference configuration via the ALE mapping. The goal of this work is the development of concepts for the efficient numerical solution of eXFSI problem, the analysis of various fluid-mesh motion techniques and comparison of different second-order time-stepping schemes. This work consists of the investigation of different time stepping scheme formulations for a nonlinear FSI problem coupling the acoustic/elastic wave propagation on the fluid-structure interface. Temporal discretization is based on finite differences and is formulated as an one step-θ scheme; from which we can consider the following particular cases: the implicit Euler, Crank-Nicolson, shifted Crank-Nicolson and the Fractional-Step-θ schemes. The nonlinear problem is solved with Newton’s method whereas the spatial discretization is done with a Galerkin finite element scheme. To control computational costs we apply a simplified version of a posteriori error estimation using the dual weighted residual (DWR) method. This method is used for the mesh adaptation during the computation. The implementation is accomplished via the software library package DOpElib and deal.II for the computation of different eXFSI configurations.
A Finite Element Formulation for the Analysis of Horizontally-Curved Thin-Walled Beams
Authors: Afnani Ashkan , Niki Vida , Erkmen R. Emre
Published: March 2016

In this study, a finite element formulation is developed for the elastic analysis of thin-walled curved beams. Using a second-order rotation tensor, the strains of the deformed configuration are calculated in terms of the displacement values and the initial curvature. The principle of virtual work is then used to obtain the nonlinear equilibrium equations, based on which a finite element beam formulation is developed. The accuracy of the method is confirmed through comparisons with test results and shell-type finite element formulations and other curved beam formulations from the literature. It is also shown that the results of the developed formulation are very accurate for cases where initial curvature is very large.
Iterative Solvers for Meshless Petrov Galerkin (MLPG) Method Applied to Large Scale Engineering Problems Challenges
Authors: Singh Rituraj , Singh Krishna M.
Published: March 2016

In recent years, significant research effort has been invested in development of mesh-free methods for different types of continuum problems. Prominent amongst these methods are element free Galerkin (EFG) method, RKPM, and mesh-less Petrov Galerkin (MLPG) method. Most of these methods employ a set of nodes for discretization of the problem domain, and use a moving least squares (MLS) approximation to generate shape functions. Of these methods, MLPG method is seen as a pure meshless method since it does not require any background mesh. Accuracy and flexibility of MLPG method is well established for a variety of continuum problems. However, most of the applications have been limited to small scale problems solvable on serial machines. Very few attempts have been made to apply it to large scale problems which typically involve many millions (or even billions) of nodes and would require use of parallel algorithms based on domain decomposition. Such parallel techniques are well established in context of mesh-based methods. Extension of these algorithms in conjunction with MLPG method requires considerable further research. Objective of this paper is to spell out these challenges which need urgent attention to enable the application of meshless methods to large scale problems. We specifically address the issue of the solution of large scale linear problems which would necessarily require use of iterative solvers. We focus on application of BiCGSTAB method and an appropriate set of preconditioners for the solution of the MLPG system.
A New Singularity-Free Formulation of a Three-Dimensional Euler-Bernoulli Beam Using Euler Parameters
Authors: Fan W. , Zhu W. D. , Ren H.
Published: March 2016

In this investigation, a new singularity-free formulation of a three-dimensional Euler-Bernoulli beam with large deformation and large rotation is developed. The position of the centroid line of the beam is integrated from its slope, which can be easily expressed by Euler parameters. The hyper-spherical interpolation function is used to guarantee that the normalization constraint equation of Euler parameters is always satisfied. Hence, each node of a beam element has only four nodal coordinates, which is significantly fewer than an absolute node coordinate formulation (ANCF) and the finite element method (FEM). Governing equations of the beam and constraint equations are derived using Lagrange’s equations for systems with constraints, which are solved by an available differential algebraic equation solver. The current formulation can be used to calculate the static equilibrium and dynamics of an Euler-Bernoulli beam under arbitrary concentrated and distributed forces. While the mass matrix is more complex than that in an absolute nodal coordinate formulation, the stiffness matrix and generalized forces are simpler, which is amenable for calculating the equilibrium of the beam. Several numerical examples are presented to demonstrate the performance of the current formulation. It is shown that the current formulation can achieve the same accuracy as the FEM and ANCF with a fewer number of coordinates.
Degradation Evaluation on Sensor Network Optimization in Fault Diagnosis Process
Authors: Salehpour Oskouei Farzin , Pourgol-Mohammad Mohammad
Published: March 2016

Degradation process directly impacts the system operational state. It is necessary to consider this effect on system failure for developing a precise model for system condition determination. Reliability prediction based on degradation modeling is an efficient method to determine life duration for some highly reliable components or systems under rare failure event occurrences. Sensors, (potentially high reliable components) are exposed to different environmental conditions accelerating their degradation rate. This study is aimed to evaluate the sensor reliability affecting the monitoring process. First, a sensor characteristic is selected through which the degradation process is affected. Then a degradation model is developed to calculate the sensor time to failure. For studying the sensor reliability effect on monitoring process, sensors are considered as system components. It is assumed that the failure of component will occur only when both the component and related sensor fail together. Considering this phenomena, sensors are added to the system in parallel form. Then, functional model of each scenario is developed. Cutsets of each scenario is extracted and the probability of top event is calculated. The scenario with less top event probability is selected as the optimal one.
Impact Resistance of Liquid Body Armor Utilizing Shear Thickening Fluids: A Computational Study
Authors: Khalili Fardin , De Paoli Federico , Guldiken Rasim
Published: March 2016

Since the creation of advanced knives and firearms with high rates of speed, safety has always been a vital issue for armed forces. A disadvantage of a regular fabric Kevlar is that, although it has an effective resistance against the impact of low-speed bullets, it reveals its weakness in the case of a stab wound and high-speed bullets. Under these circumstances, a new executable technology of fibers that improves the ballistic performance of the materials utilized in body armors is an essential necessity to build high quality and protective vests which are perfectly bulletproof. The purpose of this study is to investigate the physics and concepts of shear thickening fluids and perform a computational CFD simulation of liquid body armors which consist of a combination of polyethylene glycol liquid and nanoparticles of silica. A model of multiphase flow environment with STFKevlar, as a representative of the non-Newtonian shear thickening fluid (STF), is simulated in STAR-CCM+ in order to analyze the behavior of STFs under impact and performance of novel liquid body armors. In the current simulation, Eulerian multiphase flow and volume of fluid (VOF) are applied to generate three discrete regions and determine the volume fraction of each phase including gas, non-Newtonian liquid and solid which represent air, STFKevlar and bullet, respectively. Moreover, dynamic fluid body interactions (DFBI) and overset mesh are utilized to consider the interactions between the regions and forces applied. In this study, the properties of the bullet are based on characteristics of a regular pistol bullet, and it approaches the STFKevlar with the constant speed of 400 m/s. The results show that the non-Newtonian material is initially at equilibrium state and while the bullet approaches the STFKevlar, it acts like a shear thinning fluid. As a high-speed bullet nears the STFKevlar, it absorbs the significant amount of energy that is applied by the bullet. Consequently, the bullet stops penetrating the STFKevlar in a very small fraction of time due to the considerable increase in viscosity. As the shear rate increases over a certain critical value, viscosity increases remarkably which is the main characteristic of shear thickening transition and finally, it reaches to its maximum value of viscosity in approximately 8 × 10−5sec. In addition, a bullet applies a considerable amount of force on any Kevlar due to its high velocity and kinetic energy; however, the high resistant STFKevlar is approved as a high quality and protective vests which stops the bullet in 6 × 10−4sec.
Wireless Multi-Axial Force Sensing Shoe for Gait Abnormalities Monitoring
Authors: Gu Gwang Min , Kim Jung
Published: March 2016

Measurements of sequential Ground Reaction Force (GRF) can provide quite useful information for monitoring of gait abnormalities during activities in daily life. Measuring sequential GRF in conventional approach using force plates is difficult due to the limited number of force plates. Therefore, we developed a fully untethered GRF sensing system having the low height (12 mm) and the capability of sensing simultaneously shear and normal GRF. The biaxial force sensing shoe showed the excellent repeatability (0.6 %) under long-term periodic loading condition for two hours. Comparison experiments with commercially available film type force sensors, FSR (Interlink) and Flexiforce (Tekscan), were performed under walking condition for twenty minutes. Owing to the high repeatability of the proposed system, variabilities of swing time and stance time of user were investigated with two subjects, a healthy subject and a foot-drop patient. We suggested three diagnostic measures in consideration of conventional approaches — variability for gait symmetry, center of pressure distribution for balance, and ratio of shear and normal GRFs for foot pronation.
Experimental Investigation of Oscillation Controlled Heat Transport Tubes
Authors: Guler Omer F. , Aktas Murat K.
Published: March 2016

The oscillatory flows are widely used to enhance heat transfer or as an alternative cooling technique. The oscillatory flows in liquids have the potential of augmenting heat transfer as demonstrated in literature. The subject needs to be investigated in order to fully understand the thermal transport mechanism and affecting parameters. In this investigation, heat transfer in an oscillatory pipe flow of water was studied, experimentally for low frequency regime flow conditions. Major research tasks are; setting up of the experimental apparatus, parametric experimental investigation of the convective heat transfer in oscillatory pipe flow and data reduction and analysis. An experimental apparatus was designed and constructed for the experimental investigation. The equipment consist a capillary pipe bundle connecting a cold fluid and a hot fluid reservoir. The effects of the maximum displacement amplitude of the vibrations and vibration frequency on the heat transfer were analyzed with a parametric study. Significant effect of oscillatory flow on the thermal transport compare to pure diffusion was measured. The heat transfer is greatly enhanced as vibration displacement increase. The results of the present investigation will be useful in choosing optimum operation parameters for cooling applications utilizing oscillatory flows.