bluuebunny/crossref_metadata_2025 huggingface dataset:
Design Considerations for Compression Gas Driven Shock Tube to Replicate Field Relevant Primary Blast Condition
Authors: Sundaramurthy Aravind , Gupta Raj K. , Chandra Namas
Published: April 2014

Detonation of a high explosive (HE) produces shock-blast wave, noise, shrapnel, and gaseous product; while direct exposure to blast is a concern near the epicenter; shock-blast can affect subjects even at farther distances. The latter is characterized as the primary blast with blast overpressure, time duration, and impulse as shock-blast wave parameters (SWPs). These parameters in turn are a function of the strength of the HE and the distance from the epicenter. It is extremely important to carefully design and operate the shock tube to produce a field relevant SWPs. In this work, we examine the relationship between shock tube adjustable parameters (SAPs) and SWPs to deduce relationship that can be used to control the blast profile and emulate the field conditions.

In order to determine these relationships, 30 experiments by varying the membrane thickness, breech length (66.68 to 1209.68 mm) and measurement location was performed. Finally, ConWep was utilized for the comparison of TNT shock-blast profiles with the profiles obtained from shock tube.

From these experiments, we observed the following: (a) burst pressure increases with increase in the number of membrane used (membrane thickness) and does not vary significantly with increase in the breech length; (b) within the test section, overpressure and Mach number increases linearly with increase in the burst pressure; however, positive time duration increases with increase in the breech length; (c) near the exit of the shock tube, there is a significant reduction in the positive time duration (PTD) regardless of the breech length.
A Novel Approach for Compensating the Significance of Tubule’s Architecture in Urine Concentrating Mechanism of Renal Medulla
Authors: Sohrabi Salman , Nemati Mehr Seyyed Mahdi , Falsafi Pedram
Published: April 2014

Many theories and mathematical simulations have been proposed concerning urine concentrating mechanism (UCM). The WKM and region approach are the two most valuable methods for compensating the effect of tubule’s architecture in renal medulla. They both have tried to simulate tubule’s confinement within a particular region mathematically in one spatial dimension. In this study, continuity, momentum and species transport equations along with standard expressions for transtubular solutes and water transports on tubule’s membrane were solved numerically in three spatial dimensions which practically is the main significance of our novel approach. Model structure has been chosen as simple as possible to minimize the effect of other factors in tubule’s solute and water exchange. It has been tried to simulate the preferential interaction between tubules by introducing different diffusion coefficients for solutes in the intermediate media in order that changing this physical parameter directly could influence tubule’s confinement with respect to each other. The results have been discussed in detail and then the effect of solute’s diffusivity on UCM has been investigated subsequently. In overall, it has been found out that this simulation can validate the integrity of our proposed approach for further investigation in this field.
Solar-Powered Water Distillation System
Authors: Beitelmal Abdlmonem , Fabris Drazen , Kiriu Reece
Published: April 2014

Future water demand is predicted to increase while current resources are continuously depleted. In this paper, a standalone off-the-grid water purification system is designed to provide an economically sustainable model for delivering clean drinking water is presented. This system utilizes concentrated heat generated by solar parabolic troughs to boil brackish water for the distillation process. The water vapor is then condensed into clean drinkable water in a water collection tank. The process of designing and optimizing the solar-powered distillation system (Heat exchanger, boiler, parabolic troughs, tracking and control system, photovoltaic panels and vapor and the heat transfer fluid pumps) and specifically the process of fabricating the parabolic trough is presented and discussed in details. Two troughs were designed and fabricated each with an area of 1.5 m2 (16 ft2). Each trough provides approximately 125 watts/ft. Duratherm 450, a non-toxic, non-hazardous heat transfer fluid (HTF) is selected for the solar trough hot loop. Additional system performance analysis was conducted through experimental testing and through a virtual system model utilizing the Engineering Equation Solver (EES). EES is used to model the heat transfer process of the overall distillation system and a range of optimum HTF flow rates were determined. The experimental results show an increase in water temperature within the boiler for the new range of HTF flow rates. In addition, the results show that the solar troughs are more robust, less expensive to manufacture, operate at a higher temperature and provide a higher performance when compared to a system that utilizes thermal panels. The overall system manufacturing cost is approximately $6000, which includes tracking, a control system and other required distillation components. This system is designed to fit into a standard 20-foot shipping container for ease of transportation worldwide.
Studying the Intact, ACL-Deficient and Reconstructed Human Knee Joint Using a Finite Element Model
Authors: Vairis Achilles , Petousis Markos , Stefanoudakis George , Vidakis Nectarios , Kandyla Betina , Tsainis Andreas-Marios
Published: April 2014

The human knee joint has a three dimensional geometry with multiple body articulations that produce complex mechanical responses under loads that occur in everyday life and sports activities. Knowledge of the complex mechanical interactions of these load bearing structures is of help when the treatment of relevant diseases is evaluated and assisting devices are designed.

The anterior cruciate ligament in the knee connects the femur to the tibia and is often torn during a sudden twisting motion, resulting in knee instability. The objective of this work is to study the mechanical behavior of the human knee joint in typical everyday activities and evaluate the differences in its response for three different states, intact, injured and reconstructed knee. Three equivalent finite element models were developed. For the reconstructed model a novel repair device developed and patented by the authors was employed.

For the verification of the developed models, static load cases presented in a previous modeling work were used. Mechanical stresses calculated for the load cases studied, were very close to results presented in previous experimentally verified work, in both load distribution and maximum calculated load values.
Modelling and Simulation of Guide-Wire Interaction With Vasculature Using Constrained Multibody Dynamics
Authors: Chembrammel Pramod , Younus Habib Mohd , Kesavadas Thenkurussi
Published: April 2014

In this paper, we describe the mathematical modeling of guide wire dynamics for an intravascular surgical procedure as a problem of constrained multibody dynamics involving surface to surface interactions. The goal of this project is to develop a physics based real time simulator with haptics for the above procedure. The guide-wire is segmented into a finite number of massless and inextensible rods attached with spheres on either sides thus reducing the problem to that of the dynamics of rolling motion of spheres on the re-parameterized surface of vasculature under the action of unilateral constraints with associated Lagrange multipliers. The constrained problem is solved as LCP using Lemke’s method and stabilized using Baumgarte constrain stabilization. The parameters for the constrained violation stabilization are learned real-time using a method based on adaptive control theory. Simulations were performed on geometries representing different sections of vasculature. The results show that this method can be implemented on a full-scale three dimensional vasculature with a hardware interface for haptic feedback.
Conceptual Design by a Topology Consistent Skeletal Modeler With Convolution Surfaces
Authors: Ma Guohua , Crawford Richard H.
Published: April 2014

During the conceptual design stage, the design engineers usually sketch their design ideas. For those sketches, the skeleton of the design idea can be created with lower dimensional primitives like lines, arcs, etc. In this paper, we focus on skeletal modeling, which is an approach to creating solid models in which the engineer designs with lower dimensional primitives such as points, lines, and triangles. The skeleton is then “skinned over” to create the surfaces of the three dimensional object. Then the convolution surfaces are generated by convolving a kernel function with a geometric field function to create an implicit surface. We propose that skeleton, even it is simple, contains important design information, such as the geometric, topology that defines the design concept. It is very important to keep the topology of the skeleton and thus the important information that defines the design concept, i.e, the geometry of the product, the functionality of the product determined by the topology of the design. We assume that design engineers expect the topology of a skeletal model to be identical to that of the underlying skeleton. In this paper, the system is described and some examples are illustrated to use the skeletal based modeler.
Comparison Orthogonal Tube Turning Data Versus Finite Element Simulation Using LS Dyna
Authors: Chandrasekaran Vishnu Vardhan , Payton Lewis N.
Published: April 2014

The current study focuses on building a 2-Dimensional finite element model to simulate the orthogonal machining process under a dry machining environment in a commercially available FEA solver LS DYNA. One of the key objectives of this thesis is to carefully document the use of LS Dyna to model metal cutting, allowing other researchers to more quickly build on this work. Actual force data is obtained using an Orthogonal Tube Turning apparatus that has been statistically validated to an accuracy of 99+%. The work material used in this study is Aluminum 6061-T6 alloy. The tool material is tool steel, which is modeled as a rigid body. A Plastic Kinematic Material Hardening model is used to define the work material. Chip formation is based on the effective failure plastic strain. A constant coefficient of friction between the tool and work piece is used, obtained from the actual experimental results. The simulation is carried out with the same constant velocity, different rake angles and depth cuts as in the real world experiment. The cutting force and thrust force values obtained for each combination of rake angle and cut depth are validated against the experimental data obtained at Auburn University. The resulting model is considered valid enough to use for sensitivity analysis of the metal cutting process in aluminum alloy 6061-T6 in the university environment. The model is available publicly to any university from a website provided.
Implications of Increased Lower Extremity Movement Variability on Fall Susceptibility at Increased Stride Lengths During Locomotion
Authors: Nordin Andrew D. , Bailey Joshua P. , Dufek Janet S.
Published: April 2014

The purpose of this examination was to explore the effects of stride length (SL) perturbations on walking gait, relative to preferred walking (PW) and running (PR), via lower extremity range of motion (ROM) variability. ROM variability at the hip, knee, and ankle joints, in the sagittal and frontal planes were used in evaluating motor control of gait, where increased gait variability has been previously implicated in fall susceptibly.

Nine participants (5 male, 4 female; mean age 23.11±3.55 years, height 1.72±0.18m, mass 72.66±14.37kg) free from previous lower extremity injury were examined. Kinematic data were acquired using a 12-camera system (Vicon MX T40-S; 200Hz). Data filtering and interpolation included a low pass, 4th order, Butterworth filter (15Hz cutoff) and cubic spline. Five gait trials were completed for PW and PR, with subsequent SL manipulations computed as a percentage of leg length (LL). SL perturbations included 60%, 80%, 100%, 120%, and 140% of LL.

Kinematic analysis involved one stride (two steps) during each gait trial, assessing ROM at the hip, knee, and ankle from heel contact to toe-off for each limb, in the sagittal and frontal planes. Variability was expressed using coefficient of variation (%). Comparisons were made using 3×7 (joint × stride condition) mixed model ANOVAs, with repeated measures on stride condition (α = 0.05), using SPSS 20.0.

Differences in lower extremity ROM variability were detected among stride conditions in the frontal and sagittal planes (F[3.185,76.451] = 3.004, p = .033; F[4.595,110.279] = 2.834, p = .022, respectively). Greater ROM variability was observed at, and in excess of SLs of 100%LL relative to PW in the frontal plane (PW: 9.2±4.2%; 100%LL: 11.8±3.6%, p = .014; 120%LL: 13.5±5.8%, p = .046; 140%LL: 13.8±6.5%, p = .016), and between SLs of 80%LL and 120%LL in the sagittal plane (4.9±3.0%; 7.8±4.7%, p = .046, respectively). From this, PW appeared to occur within SLs of 60%LL to 80%LL, while SLs exceeding 100%LL resulted in increased lower extremity ROM variability. This may have consequences for fall susceptibility at increased stride lengths during walking. PR did not reveal significant variability differences (p>.05) compared to walking conditions in either the sagittal or frontal plane (7.5±5.0%; 12.8±7.7%, respectively), suggesting that running represents a separate, but stable gait pattern. In the sagittal plane, ROM variability was significantly lower at the hip (3.9±1.5%), relative to the ankle (8.4±1.6%, p<.001) and knee joints (7.4±2.6%, p = .001), suggesting that gait control may be more active at the ankle and knee joints. Future investigations should examine kinetic changes in gait when altering stride length.
Formation and Characterization of Co-Continuous Shear Thickening Fluid/Polymer Blends
Authors: Hong Yifeng , Yao Donggang
Published: April 2014

By synergistically combining distinct physical and chemical properties of different components, co-continuous polymer blending has become an important route to improve the performance of polymeric materials. Shear thickening fluid is a type of non-Newtonian fluid which has unique shear rate dependence and good damping properties. In this work, the authors combined the shear thickening fluid and a commodity polymer into a single system by forming a co-continuous blend via a melt processing technique. The processing window of such co-continuous blend was determined by referring to the thermal and rheological properties of raw materials and experimentally exploring various blending conditions. An increase of tanδ under dynamic mechanical analyzing testing was observed in the co-continuous blend compared with neat polymer as control, which indicated the enhancement of damping capabilities.
A Biomechanical Study of Directional Mechanical Properties of Porcine Skin Tissues
Authors: Huang Hsiao-Ying Shadow , Huang Siyao , Gettys Taylor , Prim Peter M. , Harrysson Ola L.
Published: April 2014

Skin is a multilayered composite material and composed principally of the proteins collagen, elastic fibers, and fibroblasts. The direction-dependent material properties of skin tissue is important for physiological functions like skin expansion. The current study has developed methods to characterize the directional biomechanical properties of porcine skin tissues. It is observed that skin tissue has a nonlinear anisotropy biomechanical behavior, where the parameters of material stiffness is 378 ±160 kPa in the preferred-fiber direction and 65.96±40.49 kPa in the cross-fiber direction when stretching above 30% strain equibiaxially. The results from the current study will help optimize functional skin stretching for patients requiring large surface area skin grafts and reconstructions due to burns or other injuries.
Mechanics of Air-Inflated Drop-Stitch Fabric Panels Subject to Bending Loads
Authors: Cavallaro Paul V. , Hart Christopher J. , Sadegh Ali M.
Published: April 2014

Rapid deployment and mobility of lightweight structures, namely inflatable structures, are of growing significance to the military and space communities. When deployment and rigidity are driven by pressure (for example, air or fluid) and materials such as textiles, elastomers and flexible composites are used, significant load carrying capacity per unit weight (or per-unit stowed volume) can be uniquely achieved. Specifically, the pressurized air directly provides the stiffness to support structural loads, thus eliminating the requirement for heavy metal stiffeners that are used in conventional rigid structures. However, the material and system behaviors are not sufficiently understood. Furthermore, predictive-performance analysis methods and test standards are not adequately established because the behaviors of inflatable fabric structures often involve coupled effects from inflation pressure such as fluid-structure interactions (FSI’s), thermo-mechanical coupling and nonlinear constitutive responses of the materials. These effects can restrict the use of conventional design, analysis and test methods.

This research explores the mechanics of air-inflated drop-stitch fabric panels subject to bending loads using analytical and experimental methods. Results of experimental four-point bend tests conducted at various inflation pressures are used to validate the analytical method. The predicted and experimental deflections, wrinkling onset moments, ultimate loads, pressure changes, etc. are compared and discussed.
Linked Product and Process Monitoring in Smart Factories Based on Federative Factory Data Management
Authors: Picard André , Anderl Reiner , Schützer Klaus , Moura Antonio Álvaro de Assis
Published: April 2014

In the context of Smart Factories chances and challenges for the use of Federative Factory Data Management (FFDM) arise. Within Smart Factories involved systems, products and resources are equipped with Cyber-Physical Systems (CPS). The seamless integration of these CPS devices into networks provides the possibility for FFDM on world wide access to factory data. The actuality, but also the amount of data on all levels of the Smart Factory is continuously increasing. The need for new methods and tools for the representation and the presentation of this factory data is required. Combining the web technologies in the FFDM-approach on the one hand and the integration of CPS of Smart Factories into FFDM on the other hand allow new possibilities for the usage of mobile internet devices in FFDM. In this paper the concept for the employment of a mobile internet device as instrument for the presentation of FFDM-data is described. Parallel an approach for the integration of CPS based devices into the FFDM is described. As a representative scenario the monitoring of linked product data and process data in route sheets visualized within a mobile internet devices is described afterwards. The presented concept is transferred to a first prototypical implementation.
Numerical Investigation of Metal-Foam Filled Liquid Piston Compressor Using a Two-Energy Equation Formulation Based on Experimentally Validated Models
Authors: Zhang Chao , Wieberdink Jacob H. , Shirazi Farzad A. , Yan Bo , Simon Terrence W. , Li Perry Y.
Published: April 2014

The present study presents CFD simulations of a liquid-piston compressor with metal foam inserts. The term “liquid-piston” implies that the compression of the gas is done with a rising liquid-gas interface created by pumping liquid into the lower section of the compression chamber. The liquid-piston compressor is an essential part of a Compressed Air Energy Storage (CAES) system. The reason for inserting metal foam in the compressor is to reduce the temperature rise of the gas during compression, since a higher temperature rise leads to more input work being converted into internal energy, which is wasted during the storage period as the compressed gas cools.

Liquid, gas, and solid coexist in the compression chamber. The two-energy equation model is used; the energy equations of the fluid mixture and the solid are coupled through an interfacial heat transfer term. The fluid mixture, which includes both the gas phase and the liquid phase, is modeled using the Volume of Fluid (VOF) method. Commercial CFD software, ANSYS FLUENT, is used, by applying its default VOF code, with user-defined functions to incorporate the two-energy equation formulation for porous media.

The CFD simulation requires modeling of a negative momentum source term (drag), and an interfacial heat transfer term. The first one is the pressure drop due to the metal foam, which is obtained from experimental measurements. To obtain the interfacial heat transfer term, a compression experiment is done, which provides instantaneous pressure and volume data. These data are compared to solutions of a zero-dimensional compression model based on different heat transfer correlations from published references. By this comparison, a heat transfer correlation which is most suitable for the present study is chosen for use in the CFD simulation.

The CFD simulations investigate two types of metal foam inserts, two different layouts of the insert (partial vs. full), and two different liquid piston speeds. The results show the influence of the metal foam inserts on secondary flows and temperature distributions.
Patient-Specific Aneurysms Rupture Prediction Using CFD Modelling With Strain Energy Function
Authors: Embong A. H. , Al-Jumaily A. M. , Mahadevan Giri , Sugita Shukei , Lowe Andrew
Published: April 2014

This paper proposes a new Patient-Specific Aneurysm CFD Model (PSAM) which is based on the energy strain function combined with dilated vessel wall stress-strain relationship to predict aneurysm rupture. The PSAM relies on the available mechanical properties and parameters obtained from a personalized model. A personalized model is developed based on instantaneous arterial deformations obtained from Doppler Ultrasound (US) images at 6–9 MHz. It is shown that PSAM has the ability to correlate the deformation wall energy based on continuous patient-specifics in predicting rupture.
Optimization of the Axial Porosity Distribution of Porous Inserts in a Liquid-Piston Gas Compressor Using a One-Dimensional Formulation
Authors: Zhang Chao , Simon Terrence W. , Li Perry Y.
Published: April 2014

A One-Dimensional (One-D) numerical model to calculate transient temperature distributions in a liquid-piston compressor with porous inserts is presented. The liquid-piston compressor is used for Compressed Air Energy Storage (CAES), and the inserted porous media serve the purpose of reducing temperature rise during compression. The One-D model considers heat transfer by convection in both the fluids (gas and liquid) and convective heat exchange with the solid. The Volume of Fluid (VOF) method is used in the model to deal with the moving liquid-gas interface. Solutions of the One-D model are validated against full CFD solutions of the same problem but within a two-dimensional computation domain, and against another study given in the literature.

The model is used to optimize the porosity distribution, in the axial direction, of the porous insert. The objective is to minimize the compression work input for a given piston speed and a given overall pressure compression ratio. The model equations are discretized and solved by a finite difference method. The optimization method is based on sensitivity calculations in an iterative procedure. The sensitivity is the partial derivative of compression work with respect to the porosity value at each optimization node. In each optimization round, the One-D model is solved as many times as there are optimization nodes, and each time the porosity value at a single optimization node is changed by a small amount. From these calculations, the sensitivity of changing the porosity distribution to the total work input (objective) is obtained. Based on this, the porosity distribution is updated in the direction that favors the objective. Then, the optimization procedure marches to the next round and the same calculations are completed iteratively until an optimum solution is reached. The optimization shows that porous media with high porosity should be used in the lower part of the chamber and porous media with low porosity should be used in the upper part of the chamber. An optimal distribution of porosity over the chamber is obtained.
Analysis of Thrombus Formation Process by Flow Induced High Shear Rate Using Optical Observation Method
Authors: Tamagawa Masaaki
Published: April 2014

This paper describes visualization of thrombus formation process on orifice flows by laser sheet beam and normal illumination. The aim is to investigate the effects of shear stress or shear rate on the thrombus formation or thrombus formation rate. It was found that the white thrombus formation rate is proportional to square root of shear rate, and the white thrombus is dominant when the shear rate is more than 450 (1/s).
Effect of Helical Vane Swirler Geometry on Heat Transfer Characteristics for Compressed Natural Gas/Air Swirling Flame Impinging on a Flat Surface
Authors: Chander Subhash , Singh Gurpreet
Published: April 2014

An experimental study has been conducted to investigate the effect of helical vane swirler geometry on heat transfer characteristics for compressed natural gas (CNG)/air swirling flame impinging on a flat surface. Effects of helical vane swirler geometric parameters like, length of helical insert (25 mm, 45 mm and 65 mm), depth of groove on the helical insert (2.5 mm, 3.5 mm and 4.5 mm) and number of helical vanes (8, 10 and 12), on heat transfer characteristics have been studied. All the inserts were having fixed helical vane angle of 45°. Also, the burner exit diameter was kept constant (d = 20 mm). Experiments were conducted at different dimensionless separation distances (6, 4, 3 and 2) for fixed values of Reynolds number (6000) and equivalence ratio (1.3). Significant variation in the heat flux profiles has been observed for different swirler inserts till the radial hump in heat flux. After the radial hump, almost in all cases, the heat flux lines merged together. These variations in the heat flux profiles were due to different level of swirling intensities produced by different swirlers at fixed value of the helical vane swirler angle. It was observed that the heating was comparatively more uniform at larger separation distances (H/d = 6). It has been concluded that defining swirl intensity only with the helical vane swirler angle would be incorrect for such type of swirlers. Other geometric parameters of the swirler like, number of vanes, length of the swirler and the depth of the groove should also be included in swirl intensity definition.
Computational Fluid Dynamic Analysis of Atomization Spray Cooling Nozzle Designs for Micromachining
Authors: Lunardelli Andressa , Wentz John E.
Published: April 2014

A recent development of cooling and lubrication technology for micromachining processes is the use of spray cooling. Atomization spray cooling systems have been shown to be more effective than traditional methods of cooling and lubrication for micromachining. Typical nozzle systems for atomization spray cooling incorporate the mixing of high speed air and atomized fluid. In a two-phase atomization spray cooling system, the atomized fluid can easily access the tool-workpiece interface, removing heat by water evaporation and lubricating the region by oil droplet spreading. The success of the system is determined in a large part by the nozzle design, which determines the droplet behavior at the cutting zone. In this study, computational fluid dynamics are used to investigate nozzle design and droplet delivery to the tool. An eccentric-angle nozzle design is evaluated through droplet flow modeling. This study focuses on the design parameters of initial droplet velocity, high speed air velocity, and the angle change between the two inlets. The system is modeled as a steady-state multiphase system without phase change. Droplet interaction with the continuous phase is dictated in the model by drag forces and fluid surface tension. The Lagragian method with a one-way coupling approach is used to analyze droplet delivery at the cutting zone. Following a factorial experimental design, deionized water droplets and a semi-synthetic cutting fluid are evaluated through model simulations. Statistical analysis of responses (droplet velocity at tool, tool positioning, and droplet density at tool) show that droplet velocity is crucial for the nozzle design and that modifying the parameters does not change droplet density in the cutting zone. Based on results, suggestions for future nozzle design are presented.
Prediction of Radiative Transport in Nonhomogeneous Combustion Gas Mixtures With a Wide Band G(K) Model
Authors: Liu Liping , He Jing
Published: April 2014

A wide band cumulative absorption coefficient distribution, g(k), model is adopted to predict radiative transport in combustion gas mixtures. Prior research has demonstrated similar accuracy of the model to the statistical narrow-band model and superiority to the exponential wideband model under isothermal and homogeneous conditions. This study aims to assess its usefulness in nonhomogeneous media. Sample calculations are performed in a 1D planar slab containing H2O/CO2 mixtures. The six-flux discrete ordinate method (S6-DOM) is employed to solve the radiative transfer equation (RTE), followed by an eight-point Gaussian quadrature of moments with zeroth-order fit. Predictions on the radiative source distribution along the slab and the net radiative flux at the walls are compared to the benchmark line-by-line calculation (LBL) and the statistical narrow-band correlated-k distribution model using the 7-point Gauss-Lobatto quadrature scheme (SNBCK-7). The differences between the g(k) model and LBL are below 5% for a large domain of the layer, with a CPU reduction by a factor of over 30 compared to SNBCK-7 and on the order of 104∼105 compared to LBL. The wide band g(k) model shows significant promise as an accurate and efficient tool to predict radiative transfer in nonhomogenerous media for combustion and fire simulations.
Three Dimensional CFD Analysis of Solar Air Heater for Enhancement of Thermal Performance Using Arc-Shaped Wire Turbulator
Authors: Karanth Vasudeva K. , Shivamallaiah Manjunath M. , Sharma Yagnesh N.
Published: April 2014

A literature review carried out by the authors reveals that that a CFD analysis has not been the focus of attention to evaluate the efficacy of turbulators for improving the thermal performance of solar air heaters. A three dimensional CFD analysis is carried out in the present work to augment the performance of solar air heater. Arc shaped wire turbulators (with forward and reverse curvature aligned with flow direction), V-shaped wire turbulators (with forward and reverse geometry with respect to the flow direction) and Straight turbulators are used in this study to improve the flow turbulence and thereby enhance the convective heat transfer to air. The numerical results are validated with experimental results for model without turbulator to calibrate the numerical methodology. The numerical results show that turbulators whether curved or straight are useful in enhancing the heat transfer rates. The Arc shaped turbulators have been found to provide better heat transfer coefficient value compared to that of straight and V-shape turbulators. Also interestingly, Reverse arc turbulators seems to provide better heat transfer coefficient value compared to forward arc turbulators. Further, V-angle has no significant effect for both forward and reverse V-turbulator configurations.
Simulation Study of Active Vibration Control of Cantilever Beam by Using State and Output Feedback Control Laws
Authors: Khot S. M. , Yelve Nitesh P. , Nair Raj
Published: April 2014

Undesired noise and vibrations have a detrimental effect in many areas. Hence the control of vibrations has become a relevant technological challenge. Active vibration control of structures using smart materials especially is in vogue. It involves sensing the motion of the structure using sensors, generating a control signal using a controller and applying a control force on the structure using actuators. To design the control system of any vibrating structure, the mathematical model of the system is required. However, it is not possible, to theoretically construct the model of complex structures. On the other hand, it is relatively simpler to model such systems in an Finite Element (FE) environment like ANSYS©. This paper deals with the extraction of the mathematical model of a cantilever beam from its FEA model. This procedure of extraction is applicable to any mechanical system under dynamics study. Then again, the matrices thus formed are usually very large and require a lot of computational time to process. Hence an attempt is made to construct the reduced model of the system which approximates the actual model to the desired extent. In this paper, the full model of the beam is reduced by discarding those modes which do not contribute to the overall response on the basis of their dc gains in MATLAB©. It is found that the frequency and transient responses of the full and reduced models match closely. Hence the reduced model may be used to represent the system instead of the full model with reasonable accuracy. Design of controller is attempted using the theory of state and output feedback control laws. The controller is modeled by calculating the optimal control gain by formulating an algorithm to solve the equations involved. The transient and frequency responses of the controlled full model and reduced models are then plotted. The procedure for designing controller described in this paper may be extended to any real world system.
Precision Shape Control of Laminated Membrane Reflector Based on the Photo/Piezoelectric Hybrid Actuation Method
Authors: Yue Hong-Hao , Long Yu-Fei , Jiang Jing , Deng Zong-Quan , Tzou Horn-Sen
Published: April 2014

According to the design requirement of large aperture, light mass and longevity, membrane reflectors have already become the developing direction for future space reflectors. In order to overcome membrane reflectors’ defect of low stiffness, active control for reflectors must be adopted to ensure the shape accuracy. This paper puts forward an active shape control method based on PVDF piezoelectric film for plane membrane reflectors: using in-plane laminated PVDF piezoelectric actuators to change the shape of the plane membrane reflector by activating the PVDF converse piezoelectric effect, so that active shape control can be achieved. In this paper, a plane membrane reflector model is built. Then shape error caused by thermal effect in medium earth orbit (MEO) and geosynchronous earth orbit (GEO) in which membrane reflectors mainly work is analyzed. After that the shape and layout of PVDF actuators is designed and the validity of the control method is verified by simulation. Lastly, the PLZT/PVDF hybrid drive theory is induced, and the possibility of distance control is demonstrated based on the photo/piezoelectric control strategy.
Lateral-Torsional Response Control of MR Damper Connected Buildings
Authors: Chandiramani Naresh K. , Motra Gokarna B.
Published: April 2014

Lateral-torsional seismic response control of two single-storey asymmetric plan buildings, interconnected using multiple magnetorheological (MR) dampers, is studied. LQR control is used to obtain desired control forces. The desired damper force, for the two-damper case studied herein, is obtained using least square minimization. Command voltages are predicted using either a Recurrent Neural Network (RNN) or a Clipped Voltage Law (CVL). Effective controllers are obtained based on performance criteria, by varying damper configurations. LQR-CVL and LQR-RNN prove considerably more effective than Passive-off control for response reduction of flexible building B1, but not so for rigid building B2. They yield a redistribution of base shear and torque between the buildings. When compared to Passive-on control their performance ranges from superior to comparable, except for torsional acceleration of B2 for which it is inferior. They yield considerable reduction in peak base shear/torque, and require much less power, compared to Passive-on control where saturation voltage is applied. LQR-RNN is somewhat more effective than LQR-CVL in response attenuation.
Boundary Element Analysis of Adhesion Considering van der Waals Force
Authors: Koguchi Hideo , Seki Kyohei
Published: April 2014

Recently, micro- and nano-machine for microelectromechanical systems (MEMS) and the mechanism of bio-adhesive pads and sensors attract great interest. Forces such as the van der Waals force affect the adhesion in nanoscale structures. Even if two bodies does not really contact, adhesion will happen as they approach each other. The adhesion occurs easily in micromachines, so several devices are required to prevent the adhesion. In the present paper, the van der Waals force is introduced into a boundary integral method (BEM) program for analyzing the adhesion in arbitrarily shaped bodies. The van der Waals force is described by a nonlinear function of the distance between two surfaces in close proximity, and the adhesion and repulsion forces vary greatly within the atom equilibrium distance, so the solution for the simultaneous equation in the BEM is hard to converge to an exact solution. In the present paper, we propose a method for converging to a solution, apply it to the adhesion problem between a cylinder and a flat substrate, and compare the solution with the previously published theoretical result. Furthermore, adhesive contact of a semicircular cylinder and a half domain with a wavy surface is analyzed, and the semicircular cylinder is moved to the horizontal direction of the domain. Then, stick-slip phenomenon can be observed and a variation of friction coefficient is discussed. In our analysis, a repeated boundary condition is introduced like a molecular dynamics analysis. So, the program can be used for evaluating the adhesion in a large system.
3D CFD Analysis of an Oil Injected Twin Screw Expander
Authors: Papes I. , Degroote J. , Vierendeels J.
Published: April 2014

Small scale Organic Rankine Cycle (ORC) systems have a big potential for waste heat recovery in the market. Due to the smaller volume flows inside these systems, non-conventional expansion technologies such as screw expanders become more interesting. Recent economic studies have shown the important role of screw machines in such cycles. However, in order to get a better understanding of the expansion behaviour in an ORC, appropriate simulation models of screw expanders are necessary. The flow inside an oil-injected twin screw expander is modeled in detail with 3D CFD (Computational Fluid Dynamics) calculations. These simulations are challenging because of the deforming domain and the narrow gaps between the screws or between a screw and the casing. The deforming mesh motion is handled by an in-house code which generates a block-structured grid with the help of the solutions of the Laplace problem. The oil-phase was modeled with an Eulerian multiphase model and the working fluid is treated compressible. The performance of the screw expander is strongly affected by the oil-injection which provides lubrication and a better sealing of the gaps. Therefore, the different types of leakages inside the screw expander are studied and monitored. As the result of the simulations, knowledge about the flow process and the losses inside the oil-injected screw expander is built up.
Non-FEA-Based Method as Means for Knowledge Based Assessment of Perceived Quality
Authors: Wagersten Ola , Wickman Casper , Söderberg Rikard
Published: April 2014

Fit and finish of vehicle split-lines is one important contributor to the final Perceived Quality (PQ) of the product. To achieve high PQ of split-lines, effects of geometrical variation has to be considered.

In early phases of the development chain the geometry models used for simulation and visualization have low level of detail. This limits the possibility to perform certain simulations that rely on a more complete detailed design. Consequently, alternative methods have to be considered to predict and simulate possible outcome in early phases concerning PQ issues.

This paper proposes how an existing non-FEA-based deformation method can support virtual assessment of the PQ of split-lines in early phases. The method is based on mesh morphing and has been implemented in a CAT-tool (Computer-Aided Tolerancing). Its strength lies in the simplicity of generating deformed shapes. The paper specifically focuses on how available knowledge regarding issues from previous projects can be used as input to the method, to predict part deviation and part behavior. The paper further presents industrial examples where the method has been applied. The results show that the proposed technique can be used as a complement to other simulation tools in early phases, where low level of detail on geometries limits the possibility to perform FEA (Finite Element Analysis) based simulations.
Thermal and Coupled Electromagnetic-Mechanical Analyses for the Development of a Dry Type Current Limiting Reactor
Authors: Choi Jangun , Park Sungwon , Kim Yonghan , Yang Heuiweon
Published: April 2014

In this paper, thermal and structural analyses based on numerical method have been conducted to develop a dry type current limiting reactor which can mitigate the fault current. The current limiting reactor is an effective device to reduce the breaking capacity of circuit breakers in spite of the growth of electric loads.

Temperature rise analysis of the dry type reactor is required and important to suppress the excessive temperature rise over temperature limit of an insulating material, and structural analysis for short current forces of the reactor is required to verify the structural integrity in fault current conditions. For the thermal stability of reactor, thermal-fluid analysis has been carried out to predict temperature rise of reactor winding.

Through the analyses, the optimal thickness of fiber-epoxy composite was determined to secure the structural integrity against the short current force by coupled electromagnetic-mechanical analysis. The numerical analyses results have been verified by conducting performance test for the prototype reactor.
Heat Transfer Studies in Thermally Conducting and Electrically Insulating Nano-Oils in a Natural Circulation Loop
Authors: Mohan Manu , Thomas Shijo , Taha-Tijerina J. , Narayanan T. N. , Sobhan C. B. , Ajayan P. M.
Published: April 2014

Mineral oil (MO), a dielectric insulating fluid, is commonly used as coolant and lubricant in various applications, such as in high voltage power transmission systems and machinery. The mode of heat transfer in most of these systems is natural convection. Prolonged operation at higher temperatures leads to the degradation of the dielectric coolant, which leads to diverse problems, such as shortage or breakdown of these devices and apparatuses. Increasing the heat transfer capability of the insulating fluid will minimize the energy consumption of the system, prolonging its useful life. It is proposed to improve the heat transfer performance of insulating fluid by the addition of hexagonal boron nitride (h-BN), which is synthesized and finally obtained in 2D-nanosheets through wet exfoliation technique, without affecting its electrical insulating property. h-BN was reported to have superb effect on thermal conductivity of MO (∼ 80% increase at 0.10wt.%) on addition at very low filler fraction [1], thermal stability of up to 800°C [2], and good electrical insulating properties due to its nature (electron band gap of approx. 4.5eV). The present work reports the application of nano-oil (MO + h-BN 2D-nanosheets) for enhanced heat dissipation. A rectangular thermosyphon loop was modeled as the thermal system in transformer. The aspect ratio of the loop and the positions of the heater and cooler were chosen according to the stability criterion so that the flow remains stable and unidirectional throughout the experiment. The effect on heat removal by varying the concentration of h-BN 2D-nanosheets (h-BNNS) in MO was measured and discussed.
High Speed Combustion Imaging in a Large Bore Gas Engine: The Relationship Between Pre- and Main Chamber Heat Release
Authors: Duong Jeudi , Wellander Rikard , Hyvönen Jari , Andersson Öivind , Richter Mattias , Johansson Bengt , Álden Marcus
Published: April 2014

An experimental study is carried out to investigate the combustion process in a Wärtsilä 34SG spark-ignited lean burn four-stroke large bore engine (bore 340 mm) by means of optical diagnostics when operating on natural gas. The main focus of this work is to gain knowledge about in-cylinder combustion phenomena when igniting a lean air/fuel mixture with pre-combustion chamber induced jets. Especially the origin of cyclic variability is of interest. The flame propagation process in a single cycle was captured using a high speed video camera. The analysis is based on apparent heat release rates in the pre-combustion chamber and main chamber, in order to find correlations with the imaged phenomena. The results show that the flame propagation inside the main chamber starts at the end of the pre-chamber combustion heat release and that variation in main chamber heat release does not correlate with variations in the pre-combustion chamber.
FEM Simulation of Swelling Elastomer Seals in Downhole Applications
Authors: Akhtar Maaz , Qamar Sayyad Zahid , Pervez Tasneem , Al-Jahwari Farooq Khalfan
Published: April 2014

Petroleum exploration and development industry is witnessing a rapid growth in the use of swelling elastomers. They are being used in new applications aimed at enhanced oil recovery through slimming of well design, zonal isolation, water shutoff, etc. Initially developed as a problem-solving strategy (for repair of damaged or deteriorating wells), swelling elastomers are now targeting major savings in cost and time through reduction in borehole diameter, reduced casing clearance, cementless completions, etc. Due to material and geometric nonlinearity, modeling and simulation of swelling elastomer applications becomes quite complex.

In this work, finite element simulation has been carried out to study swelling elastomer seal performance in downhole petroleum applications using the software ABAQUS. A hyperelastic model (that most closely resembles swelling elastomer behavior) is used for simulation of seal behavior. A series of experiments have been designed and performed to determine necessary material properties of a water-swelling elastomer as it gradually swells when exposed to saline water of two different concentrations at 50°C (to emulate field conditions of medium-depth oil wells). A large number of simulations are carried out to investigate sealing behavior against water salinity and swelling time. Sealing pressure at the contact surface between elastomer and formation (or outer casing) is studied for variations in seal length, seal thickness, compression ratio, water salinity, and swelling period. Results show that seal contact pressure increases with amount of swelling, seal length, and compression ratio; higher salinity environment results in lower sealing pressure; and more contact pressure is generated in the case of rock formation as compared to steel outer casing.