bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of Failure of a Fixed Beam Subjected to Impact Load Using Quadrilateral Discrete Element Method
Authors: Nair Rajesh P. , Lakshmana Rao C.
Published: October 2013

Discrete Element Method (DEM) is an explicit numerical scheme to model the mechanical response of solid and particulate media. In our paper, we are introducing Quadrilateral Discrete Element Method (QDEM) for the simulation of the separation of elements in fixed beam subjected to impact load. QDEM results are compared with other DEM results available in literature. Impact loads include two cases: (a) a half sine wave and (b) a penetrator hitting the fixed beam. Separation criteria used for the discrete elements is maximum principal stress failure criteria. In QDEM, convergence study for the response of fixed beam is obtained using MATLAB platform. Validation of quadrilateral elements in fixed beam is being carried out by comparing the results with empirical formula available in literature for the impact analysis.
An Enhanced Articulated Human Body Model Under C4 Blast Loadings
Authors: Tan X. G. , Kannan R. , Przekwas Andrzej J. , Ott Kyle , Harrigan Tim , Roberts Jack , Merkle Andrew
Published: October 2013

Previously we had developed an articulated human body model to simulate the kinematic response to the external loadings, using CFDRC’s CoBi implicit multi-body solver. The anatomy-based human body model can accurately account for the surface loadings and surface interactions with the environment. A study is conducted to calibrate the joint properties (for instance, the joint rotational damping) of the articulated human body by comparing its response with those obtained from the PMHS test under moderate loading conditions. Additional adjustments in the input parameters also include the contact spring constants for joint stops at different joint locations. By comparing the computational results with the real scenarios, we fine tune these input parameters and further improve the accuracy of the articulated human body model. In order to simulate the effect of a C4 explosion on a human body in the open field, we employ a CFD model with a good resolution and the appropriate boundary treatment to obtain the blast loading condition on the human body surface more accurately. The numerical results of the blast simulation are shown to be comparable to the test data. With the interface to apply the blast pressure loading from the CFD simulation on the articulated human body surface, the articulated human body dynamics due to the C4 explosions are modeled and the simulation results are shown to be physiological reasonable.
Modeling and Simulation of Adiabatic Shear Bands in AISI 4340 Steel Under Impact Loads
Authors: Owolabi Gbadebo , Odoh Daniel , Odeshi Akindele , Whitworth Horace
Published: October 2013

In this study, the effects of microstructure and strain rate on the occurrence and failure of adiabatic shear bands in AISI 4340 steel under high velocity impact loads are investigated using finite element analysis and experimental tests. The shear band generated due to impact load was divided into some set of elements separated by nodes using finite element method in ABAQUS environment with initial and boundary conditions specified. The material properties were assumed to be lower at the second element set in order to initialize the adiabatic shear bands. The strain energy density for each successive node was calculated successively starting from the first element where initial boundary condition, initial strain hardening constant, and stress resistance had been specified. As the load time is increased, its corresponding effect on the localized shear deformation and width of the adiabatic shear band was also determined. The finite element model was used to determine the maximum stress, the strain hardening, the thermal softening, and the time to reach critical strain for formation of adiabatic shear bands. Experimental results show that deformed bands were formed at low strain rates and there was a minimum strain rate required for formation of transformed band in the alloy. The experimental results also show that cracks were initiated and propagated along transformed bands leading to fragmentation under the impact loading. The susceptibility of the adiabatic shear bands to cracking was markedly influenced by strain-rates and the initial material microstructures. The numerical results obtained were compared with the experimental results obtained for the AISI 4340 steel under high strain-rate loading in compression using split impact Hopkinson bars. A good agreement between the experimental and simulation results are also obtained.
FEA Robustness Verification in the Modeling of 1-D Stress Wave Propagation for a Split Hopkinson Bar (SHB) Test
Authors: McCoy Michael L. , Moradi Rasoul , Lankarani Hamid M.
Published: October 2013

Impact loading on mechanical structures and components produces stress conditions that are large in magnitude and fluctuate with time which are difficult for the engineer to assess for design. The Stress Wave Propagation (SWP) is a classical methodology to account for these large stress levels. Due to the highly mathematical approach of stress wave theory along with consideration of boundary conditions interactions in the struck solid, the stress wave propagation method generates closed solutions to impact problems that are only 1-D in nature [1, 2]. In engineering practice, most mechanical problems are more complex than 1-D and thus numerical methods need to be applied to provide engineering solutions. The Finite Element Method (FEM) is a numerical technique that is commonly used in static and dynamic loading conditions to provide engineering solution to complex geometry and loading. In this paper, the FEM is examined to determine if this methodology is robust enough to accurately represent Stress Wave Propagation in solid mediums by the capturing wave propagation velocities, boundary reflections and transmissions along with large transient stress magnitudes using simple 2-D axisymmetrical elements. The most complex 1-D problem and perhaps the most practical solved problem by the Stress Wave Propagation is the Split Hopkinson Bar (SHB) test. The purpose of this test is to determine the dynamic strength of materials. A finite element (FE) model of an as-built SHB test apparatus was developed. In the same function as the strain gages, two nodes were used to extract the strain time histories from the FE model of the apparatus bars. It was found that the pseudo-strain gages of the FEA compared well to the SWP theory. The pulse magnitudes of strains, strain rates and stress were found extremely similar and exhibited magnitudes within 4% between SWP and direct examination.

This model replicating a dynamic impact event demonstrated that the FEA can be used to solve complex impact problems involving stress wave propagation with the use of simple 2-D axisymmetric elements reducing computation time.
Flexible Graphene Sensors Using Channel Circuit Electrodes for Explosive Detection
Authors: Green Steven , Song Sangyup , Lee Je Kyun , Kim Byungki
Published: October 2013

Presented is an explosives sensor using molded channel circuit (MCC) electrodes. The sensor consists of polyethylene terephthalate (PET) substrate with a pair of electrodes fashioned from silver paste. The electrodes are coated with grapheme to create a resistive sensor. Tests utilizing Dinitrotoulene 2,4 (DNT) showed the validity of the combination of graphene resistive layer and MCC electrodes as an explosive sensor.
Numerical Simulation of Forging Process of Spiral Bevel Gear
Authors: Lai Rong-Jer
Published: October 2013

In this paper different cold forging processes of spiral bevel gear are studied based on the patent analysis. First of all, various design concepts are analyzed and classified according to the type of raw material and the motion of die during the forming process. Then, focused on the bulk billet, the parameters such as the mode of die motion, the size and shape of initial billet, the speed of punch and the coefficient of friction are selected to study their effects on the cold forging process. Finally, following the Taguchi method, numerical simulations are carried out to find out the suitable combination of process parameters. Material flow, stress and strain distributions as well as forging load are analyzed.
Computation of Flow and Heat Transfer of a Blade Internal Cooling Passage With Truncated V-Shaped Ribs on Opposite Walls
Authors: Li Shian , Xie Gongnan , Zhang Weihong , Sundén Bengt
Published: October 2013

The inlet temperature of gas turbine engine is continuously increased to achieve higher thermal efficiency and power output. To prevent from the temperature exceeding the melting point of the blade material, ribs are commonly used in the mid-section of internal blade to augment the heat transfer from blade wall to the coolant. In this study, turbulent flow and heat transfer of a rectangular cooling passage with continuous or truncated 45-deg V-shaped ribs on opposite walls have been investigated numerically. The inlet Reynolds numbers are ranging from 12,000 to 60,000 and the low-Re k-ε model is selected for the turbulent computations. The complex three-dimensional fluid flow in the internal coolant passages and the corresponding heat transfer over the side-walls and rib-walls are presented and the thermal performances of the ribbed passages are compared as well. It is shown that the passage with truncated V-shaped ribs on opposite walls is very effective in improving the heat transfer performance with a low pressure loss, and thus could be suggested to be applied to gas turbine blade internal cooling.
Heat Transfer Enhancement in Micro-Domains Using Gas-Driven Liquid Film
Authors: Houshmand Farzad , Peles Yoav , Amitay Michael
Published: October 2013

A liquid film has been introduced upstream of a heater in a microchannel with gas flow, and the impact on the heat transfer performance has been investigated. The shear force exerted by the gas flow on the gas-liquid interface drives the film and drags it downstream, onto the heated area. Distilled water was injected through a 350 μm circular hole in a main stream of Nitrogen in a 220 μm deep and 1.5 mm wide rectangular microchannel to enhance the heat transfer from a 1 mm × 1 mm heater. Average heat transfer coefficient was studied for different gas and liquid flow rates and compared with single-phase flow. Significant improvement in heat transfer performance was observed while the pressure drop in the channel was not increased dramatically.
A Model for the Nonlinear Buckling of Human Aorta
Authors: Amabili Marco , Karazis Kostas , Mongrain Rosaire , Shahmansouri Nastaran
Published: October 2013

Human aortas are subjected to large mechanical stresses due to blood flow pressurization and through contact with the surrounding tissue. It is essential that the aorta does not lose stability by buckling for its proper functioning to ensure proper blood flow. A refined reduced-order bifurcation analysis model is employed to examine the stability of an aortic segment subjected to internal blood flow. The structural model is based on a nonlinear cylindrical orthotropic laminated composite shell theory that assumes three aortic wall layers representing the tunica intima, media and adventitia. The fluid model contains the unsteady effects obtained from linear potential flow theory and the steady viscous effects obtained from the time-averaged Navier-Stokes equations. Residual stresses due to pressurization are evaluated and included in the model. The aortic segment loses stability by divergence with deformation of the cross-section at a critical flow velocity for a given static pressure, exhibiting a strong subcritical behaviour with partial or total collapse of the inner wall. Subsequent analyses including the effect of geometric wall imperfections indicate that imperfections in the axial direction have a more profound effect on the stability of the aorta decreasing the critical flow velocity for buckling.
Towards Measuring Young’s Modulus by Electronic Probing
Authors: Chigullapalli Aarti , Clark Jason V.
Published: October 2013

We propose an accurate and precise method for measuring the Young’s modulus of MEMS with comb drives by electronic probing of capacitance. The electronic measurement can be performed off-chip for quality control or on-chip after packaging for self-calibration. Young’s modulus is an important material property that affects the static or dynamic performance of MEMS. Electrically-probed measurements of Young’s modulus may also be useful for industrial scale automation. Conventional methods for measuring Young’s modulus include analyzing stress-strain curves, which is typically destructive, or include analyzing a large array of test structures of varying dimensions, which requires a large amount of chip real estate. Our method measures Young’s modulus by uniquely eliminating unknowns and extracting the fabricated geometry, displacement, comb drive force, and stiffness. Since Young’s modulus is related to geometry and stiffness that we find using electronic measurands, we are able to express Young’s modulus as a function of electronic measurands. We verify our method by using it to predict the Young’s modulus of a computer model. We treat the computer model as we would treat a true experiment by depending only on its electronic measurands. We find good agreement in predicting the exactly known Young’s modulus in a computer model within 0.1%.
Numerical Study of the Mean and Filtered Characteristics of Turbulent Jets Impinging on Convex and Flat Surfaces Using LES
Authors: Benhacine Adra , Nemouchi Zoubir , Khezzar Lyes , Kharoua Nabil
Published: October 2013

A numerical study of a turbulent plane jet impinging on a convex surface and on a flat surface is presented, using the large eddy simulation approach and the Smagorinski-Lilly sub-grid-scale model. The effects of the wall curvature on the unsteady filtered, and the steady mean, parameters characterizing the dynamics of the wall jet are addressed in particular. In the free jet upstream of the impingement region, significant and fairly ordered velocity fluctuations, that are not turbulent in nature, are observed inside the potential core. Kelvin-Helmholtz instabilities in the shear layer between the jet and the surrounding air are detected in the form of wavy sheets of vorticity. Rolled up vortices are detached from these sheets in a more or less periodic manner, evolving into distorted three dimensional structures. Along the wall jet the Coanda effect causes a marked suction along the convex surface compared with the flat one. As a result, relatively important tangential velocities and a stretching of sporadic streamwise vortices are observed, leading to friction coefficient values on the curved wall higher than those on the flat wall.
Performance Analysis on SOFC-HCCI Engine Hybrid System
Authors: Park Sung Ho , Lee Young Duk , Kang Sang Gyu , Ahn Kook Young
Published: October 2013

Fuel cell systems are currently regarded as a promising type of energy conversion system. Various types of fuel cell have been developed and investigated worldwide for portable, automotive, and stationary applications. In particular, in the case of large-scale stationary applications, the high-temperature fuel cells known as the molten carbonate fuel cell (MCFC) and the solid oxide fuel cell (SOFC) have been used as a power source due to their higher efficiency compared to low-temperature fuel cells. Because SOFCs have many advantages, including a high power density, low corrosion, and operability without a metal catalyst, many efforts to develop a SOFC hybrid system have been undertaken. SOFC hybrid systems with a gas turbine or engine show improved system efficiency through their utilization of waste heat and unreacted fuel. Especially, the internal combustion engine has the advantage of robustness, easy maintenance, and a low cost compared to gas turbines, this type is more adaptable for use in a hybrid system with a SOFC. However, the engine should be operated stably at a high air fuel ratio because the SOFC anode exhaust gas has a low fuel concentration. The homogeneous charge compression ignition (HCCI) engine has both the advantages of SI and CI engines. Moreover, the lean burn characteristics of the HCCI engine make it a strong candidate for SOFC hybrid systems. The objective of this work is to develop a novel cycle composed of a SOFC and a HCCI engine. In order to optimize the SOFC-HCCI hybrid system, a system analysis is conducted here using the commercial software Aspen Plus®. The SOFC model is validated with experimental data. The engine model is developed based on an empirical equation that considers the ignition delay time. The performance of the hybrid system is compared with that of a SOFC stand-alone system to confirm the optimization of the system. This study will be useful for the development of a new type of hybrid system which uses a fuel cell and an optimized system.
Role of Plaque Morphology in Altering the Flow Characteristics in Diseased Coronary Artery
Authors: Moreno Carlos , Bhaganagar Kiran
Published: October 2013

Patient specific simulations of a single patient based on an accurate representation of the plaque in a diseased coronary artery with 35% stenosis are performed to understand the effect of inlet forcing frequency and amplitude on the wall shear stress (WSS). Numerical simulations are performed with unsteady flow conditions in a laminar regime. The results have revealed that at low amplitudes, WSS is insensitive to forcing frequency and is it in phase with Q. The maximum WSS is observed at the proximal region of the stenosis, and WSS has highest negative values at the peak location of the stenosis. For higher pulsatile amplitude (a > 1.0), WSS exhibits a strong sensitivity with forcing frequencies. At higher forcing frequency the WSS exhibits nonlinear response to the inlet forcing frequency. Furthermore, significant differences in the mean velocity profile are observed during maximum and minimum volumetric flow rates.
Characteristics of Turbulent Gas Flow in Microtubes
Authors: Hong Chungpyo , Matsushita Shinichi , Asako Yutaka , Ueno Ichiro
Published: October 2013

This paper presents results of an experimental investigation of turbulent gas flow in microtubes fabricated by wire cutting electrical discharge machining (EDM) in a stainless steel block. The micro-tube was designed with a main flow tube and five pressure ports, which lead to the pressure transducers. The average diameters of the main tubes were 320 μm and 369 μm. And the aspect ratio of length to the average diameter is about 190. The outlet of the tube faced to the atmosphere. The pressure distribution of turbulent gas flow in microtubes fall steeply and Mach numbers increase near the outlet with increasing the inlet pressure due to flow acceleration. Both Darcy friction factors and Fanning friction factors of turbulent flow were obtained under the assumption of isothermal flow and under the assumption of one dimensional adiabatic flow. The later data reduction was proposed in the companion paper [1]. Friction factors obtained under assumption of isothermal flow is compared with one obtained under the assumption of one dimensional adiabatic flow. The result shows that the obtained Darcy and Fanning friction factors were evaluated as a function of Reynolds number on the Moody chart.
Vibration Control of Relative Tool-Spindle Displacement for CNC Lathe With Pipe Frame Structure
Authors: Morimoto Yoshitaka , Suzuki Naohiko , Kaneko Yoshiyuki , Isobe Minoru
Published: October 2013

A new CNC lathe with a pipe frame bed has been developed. One requested improvement for machine tools is their downsizing by minimizing the number of mechanical parts. Some researchers aim to construct a desktop factory. This trend has been attracting a lot of attention lately in the industrial field. When a machine tool bed is designed using castings and/or welded steel plate structures to comply with this request, it is difficult to ensure space for chip evacuation because of the space limitations of solid body components. This led us to develop another type of structure for machine tools.

A pipe frame bed has the ability to solve this problem. As represented by bridge trusses and flexible space structures, truss structures are traditional and fundamental in their design. This structure is expected to have enough space between the truss bars to solve the space problem. However, rigidity is the most significant issue for machine tools. Therefore, the desired rigidity is ensured by the use of diagonal braces.

Based on this design concept, a CNC lathe whose frame consists of pipes, joints, and diagonal braces has been developed with enough rigidity and space utility for chip evacuation. From the viewpoint of machine tool usage, the rigidity and stable dynamic characteristics of the structure must be obtained. Then, real-time vibration control theory is applied to the relative displacement between the tool post and the spindle. Active vibration control is used to suppress specific relative vibration modes.

In this paper, the effects of vibration control are evaluated by comparing the relative vibratory motion between the tool post and the spindle. Over 50% suppression has been achieved by applying vibration control to the target vibration mode. Additionally, using this control, the machined profile has been improved, and the roundness and harmonic analysis of the workpiece showed over 30% improvement.
Hands-On Assessment During Computer Aided Engineering Education
Authors: Hallberg Peter , Ölvander Johan
Published: October 2013

This contribution discusses aspects and benefits from involving physical representations when teaching engineering design and Computer Aided Engineering at Linköping University, Sweden.

The paper presents a syllabus for a comprehensive introductory CAD course. The course is populated by some 300 students on the Mechanical Engineering Master’s and Bachelor’s programs, as well as the Design and Product Development Master’s program. Assessment is made via a project where the students are assigned to model and optimize a small catapult. The catapult is then produced, using cheap materials, by the hands of the students who modeled it. Finally, the catapult is validated by entering a contest, where it is judged in respect of accuracy, weight, and cost. The catapult assignment is constructed in such a way that the students are forced to seek individual ways of applying their newly acquired knowledge of the CAD tool. Some 100 catapults are produced but the material cost for each catapult is only about €4.

The low-cost nature of the catapults originates from research conducted at the Division of Machine Design at Linköping University, where the concept of Low-Cost-Demonstrators for enhancement of the conceptual design phase has been developed over the past decade. The results from this research point towards several benefits from using physical representations alongside the common digital tools during the early stages of the product development process. Furthermore, evaluation of parameters such as the students’ performance and their own opinions of the course show notable enhancement compared to previous courses.
A Coupled Ordinates Method for Convergence Acceleration of the Phonon Boltzmann Transport Equation
Authors: Loy James M. , Mathur Sanjay R. , Murthy Jayathi Y.
Published: October 2013

Sequential solution methods are commonly-used for solving the phonon Boltzmann transport equation (BTE) because of simplicity of implementation and low storage requirements. However, they exhibit poor convergence for low Knudsen numbers. This is because sequential solution procedures couple the phonon BTEs in physical space efficiently but the coupling is inefficient in wave-vector (K) space. As the Knudsen number decreases, coupling in K space becomes dominant and convergence rates fall. Since materials like silicon have K-resolved Knudsen numbers that span 3–4 orders of magnitude at room temperature, diffuse-limit solutions are not feasible for all K vectors. Consequently, non-gray solutions of the BTE almost always experience extremely slow convergence. In this paper, we develop a coupled-ordinates method for solving the phonon BTE in the relaxation time approximation. Here, inter-equation coupling is treated implicitly through a point-coupled direct solution of the K-resolved BTEs at each control volume. This implicit solution is used as a relaxation sweep in a geometric multigrid method. The solution procedure is benchmarked against a traditional sequential solution procedure for thermal transport in silicon. Significant acceleration, between 10 to 300 times, over the sequential procedure is found for heat conduction problems.
Experimental Study of Water Entry and Exit of a Circular Cylinder at Free Surface: An Educational Approach
Authors: Goharzadeh Afshin , Molki Arman
Published: October 2013

This paper outlines a proposed experimental setup for characterizing the vertical motion of a horizontal circular cylinder through a free surface. Both water entry and exit are studied. The proposed experimental setup will enhance the student’s learning of the hydrodynamic impact phenomena. The experimental study is based on the flow visualization of free surface and surrounding water during the cylinder’s motion. The fluid flow phenomenon around the submerged cylinder is investigated using high-speed digital imaging and Particle Image Velocimetry (PIV). The proposed experiment is used as part of an undergraduate mechanical engineering fluid mechanics course taught at a university, which aims to educate young male and female engineers for the local oil and gas industry and particularly for the companies involved in sponsoring the institution. The details of the flow visualization system and teaching strategy for implementing this experiment in a Mechanical Engineering curriculum is discussed.
Effects of the Nano Particle Concentration and Type on Natural Convection Heat Transfer From Horizontal Concentric Cylinder Systems Cooling in the Ambient Air
Authors: Demir Hakan , Atayılmaz Ş. Özgür , Ağra Özden , Teke İsmail
Published: October 2013

Natural convection heat transfer from horizontal concentric cylinders is studied experimentally and numerically. Concentric cylinder was formed with two cylinders made of copper, and the annulus was filled with water. Concentric cylinder system was located in the ambient air and the inner horizontal cylinder was kept at a constant temperature. Experimental study was carried out in a conditioned room which can be maintained at a stable required value and inside a sufficiently designed test cabin. The inner copper cylinder surface temperatures varied between 30 °C–50 °C and ambient temperature was 20 °C. On the basis of the experimental data average Nusselt numbers for the air side of the concentric cylinders were calculated and compared with numerical results. The effective thermal conductivity of the annulus was calculated by using the experimental data and numerical solution results and compared. Besides, heat transfer enhancement in horizontal annuli has been investigated for different nano particle concentrations. Water based nano fluid containing Al2O3 nano particles have been used. Isotherms and streamlines are presented in the annulus and the air side. Heat transfer rates under steady state conditions for different nano particle concentrations were compared and heat transfer enhancement was determined.
Aerodynamic Shape Optimization of a Pipe Using the Adjoint Method
Authors: Helgason Eysteinn , Krajnović Siniša
Published: October 2013

Shape optimization of an inlet pipe to an engine re-circulator cooler using the adjoint method is presented. The method uses surface sensitivities calculated from an adjoint flow field implemented in the finite volume CFD solver OpenFOAM® [1]. This method allows for computation of the whole sensitivity field with only two solver calls, a primal and an adjoint solver call. A RANS solver with the standard k-epsilon turbulence model applying standard wall functions was used for the primal flow solver. The adjoint surface sensitivities are calculated from the adjoint and the primal flow fields and give information about how the objective function is affected by normal motion of the surface. The surface sensitivities are coupled to a mesh morphing library in OpenFOAM diffusing the motion of the boundary nodes to the internal cells of the mesh. The resulting geometry gave a 6.5% decrease in the total pressure drop through the pipe.
The Effect of Creating Different Size Surface Patterns on Corrosion Properties of Nickel
Authors: Toloei Alisina , Stoilov Vesselin , Northwood Derek
Published: October 2013

Most common methods of decreasing the corrosion rate of metals use inhibitors, chemicals, coatings and surface modifiers. In this study a new method has been used to combat corrosion. This new approach is based on creating specific patterns on nickel surface. A pattern of holes with different diameters (D) and inter-hole spacings (L) were created through a laser ablation method on nickel sheet samples. Corrosion tests were carried out in a 0.5M H2SO4 solution. Scanning electron microscopy (SEM) was performed in order to compare the appearance of the samples before and after corrosion tests. Energy dispersive spectroscopy (EDS) technique showed chemical composition of materials inside and outside of the holes before and after the corrosion tests. As a result of the surface patterning a significant improvement of protective properties of nickel surface has been achieved. All patterned surfaces showed better corrosion resistance compared to the polished reference samples. In addition, it has been shown that for a few specific patterns the corrosion resistance can be increased by orders of magnitude compared to the polished reference samples.
Laminar-to-Turbulent Boundary Layer Prediction Using an Alternative to the Laminar Kinetic Energy Approach
Authors: Lopez Maurin , Walters D. K.
Published: October 2013

This paper presents a new model concept for prediction of boundary layer transition using a linear eddy-viscosity RANS approach. It is a single-point, physics-based method that adopts an alternative to the Laminar Kinetic Energy (LKE) framework. The model is based on a description of the transition process previously discussed by Walters (2009). The version of the model presented here uses the k-ω SST model as the baseline, and includes the effects of transition through one additional transport equation for v2. Here v2 is interpreted as the energy of fully turbulent, 3D velocity fluctuations, while k represents the energy of both fully turbulent and pre-transitional velocity fluctuations. This modelling approach leads to slow growth of fluctuating energy in the pre-transitional region and relaxation towards a fully turbulent model result downstream of transition. Simplicity of the formulation and ease of extension to other baseline models are two potential advantages of the new method. An initial version of the model has been implemented as a UDF subroutine in the commercial CFD code FLUENT and tested for canonical flat plate boundary layer test cases with different freestream turbulence conditions.
Aerodynamic Performance Prediction of Centrifugal Fan With Forward Curved Blades
Authors: Polanský Jiří , Gášpár Roman
Published: October 2013

The paper deals with a numerical study of complex 3D unsteady flow in the impeller and spiral casing of the forward curved blade of the centrifugal stage. Aerodynamic characteristics of eight different geometrical configurations of the impeller for squirrel cage and high pressure centrifugal fans are investigated. The CFD codes ANSYS 13 and OpenFoam are applied. In this study impact of the blade geometry to compressor characteristic is investigated and possibilities of efficiency, pressure coefficient and working range increasing of centrifugal fan are presented.
Numerical Analysis of Deposits and Corrosion Influence on a Centrifugal Compressor Performance
Authors: Aligoodarz Mohammad R. , Tehrani Mohammad Reza Soleimani , Karrabi Hadi , Roshani Mohammad R.
Published: October 2013

Turbo machineries including compressors performance degrades over the period of operation and deviates from design levels due to causes including dust entrance into the compressor, blades mechanical damage, erosion and corrosion. These lead to reduction in compressor performance, efficiency and pressure ratio. Subsequently gas turbine performance is affected since their operation sate is correlated. In this study the numerical investigation of common causes that determine geometric characteristics of a 2-stage centrifugal compressor running in a gas station, including blades fouling and corrosion is performed. 3D Numerical modeling is implemented along with utilization of Shear Stress Transport (SST) turbulence model and independency from the grids is verified.
Shape Effects on the Drag Force and Motion of Nano and Micro Particles in Low Reynolds Number Flows
Authors: Feng Zhi-Gang , Feng Yusheng , Andersson Maria
Published: October 2013

Particulate flows are commonly found in a variety of applications. For example, nanoparticles have been used in targeted drug delivery systems and improving heat transfer in nanofluids. Crucial to the development of technologies that incorporate nanoparticles is to understand the effect of a nanoparticle’s shape on its motion. The effect of shape on nanoparticles used in drug delivery, in particular, is a very active area of experimental investigation. Also, the determination of the coefficients of hydrodynamic forces or drag forces on nanoparticles of different shapes is crucial in designing effective nanoparticle-mediated therapies. In this study we present a resolved discrete particle method (RDPM), which is also called the Direct Numerical Simulation (DNS), to investigate the effect of shape on drag force in a vicious fluid. Three different shapes of particles are studied: a sphere, a probate ellipsoid, and an oblate ellipsoid. These particles have the same volume and are placed in contact with the bottom wall in simple shear flows. Their drag forces are computed numerically; it is found that the particle shape has a significant effect on the drag forces. In the case of a spherical particle, our results agree very well with the analytical results found in the literature. The motion of three particles of the same volume but different shape in a simple shear flows are also simulated. It shows that different particle shapes cause particles to experience different hydrodynamics forces, leading them to different velocities and paths.
Methodology for the Economic Viability of Companies in the Semantic Adaptation of Information Systems
Authors: Marcelino-Jesus Elsa , Sarraipa Joao , Antão Mário , Jardim-Goncalves Ricardo , Mendonça da Silva João
Published: October 2013

In the current globalized and competitive business world it has become increasingly more important that companies adapt their knowledge bases, in order to establish more dynamic business partnerships. However, one of the main problems found in the establishment of such partnerships has to do with the lack of interoperability between technologic systems, especially those related to the semantic of shared knowledge. The integration and sharing of the knowledge representation elements of companies, performs a key role in the research challenges in the business interoperability area.

The paper presents a methodology to analyse the economic viability of companies in the needed effort to the conception of a common knowledge base in their operational domain area, in order to stimulate interoperability in the business cooperation. These studies also have as objective to support the development of the thesis that argues that in the future, the capability to adapt the semantics of business information systems will promote collaboration between companies, providing them new business opportunities.
Steady and Unsteady Three-Dimensional Flows in Confined Configurations With Constant and Variable Inflow Velocity
Authors: Panahi Araz , Mateescu Dan
Published: October 2013

This paper presents a three-dimensional analysis of the unsteady confined viscous flows generated by the variations in time of the inflow velocities (fluctuations) which often are present during the operation cycle of various engineering systems, and have to be taken into account in the study of flow-induced vibration and instability of these systems. Time-accurate solutions of the Navier-Stokes equations for these unsteady flows are obtained with a numerical method developed by the authors, which is second-order accurate in space and time and is based on a finite difference formulation on a stretched staggered grid and uses artificial compressibility. A factored alternate direction implicit (ADI) scheme and a special decoupling procedure, based on the utilization of the continuity equation, are used to substantially enhance the computational efficiency of the method by reducing the problem to the solution of scalar tridiagonal systems of equations. This method is applied to obtain solutions for the benchmark unsteady confined flow past a downstream-facing step, generated by the harmonic variations in time of the inflow velocity. The formation of the flow separation regions is thoroughly analyzed in the paper, including the influence on the flow separations of the Reynolds number, and of the oscillation frequency and amplitude of the inflow velocity variations.
Analysis of Wind Turbine Blade Motion: Linear Formulation Including All Aeroelastic Load Couplings
Authors: Mohammad Fouad , Ayorinde Emmanuel
Published: October 2013

A wind turbine blade similar to a helicopter rotor blade has the structure of a pretwisted beam of a variable airfoil asymmetrical cross-section. A number of approximate theories have been developed by different researchers to study the dynamic behavior of the blade of a horizontal axis wind turbine. Some researchers include warping, but they do not include the blade’s pretwisting. Others include the axial and torsional loadings and the coupling among these loadings but they ignore the bending loading. The new contribution in this study is the consideration of all the extensional, torsional and flexural loadings with their couplings, variable airfoil cross sections with warping effects, shear deflection, rotary inertia and with or without blade’s pretwist to obtain a more accurate dynamic model. To the best knowledge of the authors the simultaneous inclusion of all these factors has not been done before. The aerodynamic loadings (lift, drag and pitch moment) were calculated at each time step for a 14m blade that has a linear decreasing NACA4415 airfoil cross section utilizing a time dependent set of parameters such as angle of attack, material and air density, wind and blade speed, flow angle, yaw, pitch angles. Assuming that deformation is small, the total strain energy and total kinetic energy and external work due to the aerodynamic loading acting on the blade were calculated and used in the Lagrange equations of motion where we obtained the stiffness, mass and damping matrices of the linear dynamic equations of motion. Then the unknown displacements and rotations u, v and w in the directions of x, y and z axes respectively, the bending rotations θ1, θ2 about the y and z axes respectively and the torsional rotation ϕ about the x axis, were solved using the Newmark implicit iteration scheme.
Examination of Wind Turbine Blade Dynamics Considering Large Deformation and Including All Aeroelastic Load Couplings
Authors: Mohammad Fouad , Ayorinde Emmanuel
Published: October 2013

Many researchers have studied the structural dynamics behavior of the blade of the horizontal axis wind turbine using different approximate theories where they considered some assumptions that other researchers ignored. In a previous study, the authors considered all the extensional, torsional and flexural loadings acting on the blade with their couplings, variable airfoil cross sections with warping effects, shear deflection, rotary inertia and with or without blade’s pretwist. That previous study was performed for the linear small displacement case. In the present study, the new contribution is considering all the inclusions of the previous study but for the nonlinear large deformation case instead of the small deformation case. To the best knowledge of the authors the simultaneous inclusion of all these factors has not been done so far. The external work that acts on the blade, the total strain energy and total kinetic energy for all the different load couplings were defined (all the important strain higher order terms are kept since large deformation is considered) and used to obtain the Lagrange equations of motion. Then the load vector R, mass and linear and nonlinear stiffness matrices were deduced from the derived Lagrange equations of motion to build the nonlinear dynamic equations of motion that was solved for the three unknown displacements in the directions of x, y and z axes and the three unknown rotations about the x, y and z axes at the required stations along the length of the given blade using the Newmark implicit iteration scheme for a 14m long pretwisted blade that has a linearly decreasing NACA4415 airfoil cross section from hub to tip.
Carbon Fiber Reinforced Graphene Nanocomposite to Enhance Fracture Toughness for Cryogenic Application
Authors: McLaughlin Adam , Lee Je Kyun , Song Sangyup , Kim Byungki
Published: October 2013

This paper presents the fracture toughness, KIC, of a carbon fiber composite reinforced with the nanoparticle known as exfoliated graphite or graphene at room temperature and at cryogenic temperature. The measured KIC increased as mass fraction of graphene increase at room temperature and at cryogenic temperature for the composite with mass fraction of graphene of 0, 0.01, 0.1, 0.7, and 0.8.
Numerical Simulation and Experimental Investigation of Gas-Powder Flow in Inner Powder Delivery System
Authors: Liu Shuang , Kong Fanrong , Shi Shihong , Kovacevic Radovan
Published: October 2013

The powder concentration distribution is a key factor which affects the powder catchment efficiency, laser attenuation and, consequently, the molten pool morphology in laser cladding. A cladding technique (via a hollow laser beam with a central powder delivery system), called inner powder feeding, is presented, which can greatly increase the powder utilization. According to the structure of laser head used for inner powder feeding, a three-dimensional numerical model is developed to simulate the gas-powder flow. The influences of the carrier gas flow rate, the shielding gas flow rate, and the geometry of the gas nozzle on powder concentration distribution are investigated. An observation system is developed to capture a particle distribution image. The gray values of the particle images show that their distributions coincide with the numerical results. The model also predicts the powder catchment efficiency. Single track deposition experiments are performed and the results are compared with a four-nozzle coaxial powder feeding system.
Aeroderivative Power Generation With Coke Oven Gas
Authors: Dicampli James , Madrigal Luis , Pastecki Patrick , Schornick Joe
Published: October 2013

A major environmental concern associated with integrated steel mills is the pollution produced in the manufacture of coke, an essential intermediate product in the reduction of iron ore in a blast furnace. Coke is produced by driving off the volatile constituents of the coal—including water, coke oven gas, and coal-tar—by baking the coal in an airless furnace at temperatures as high as 2,000 degrees Celsius. This fuses together the fixed carbon and residual ash. The coke oven gas (COG) byproduct, a combustible hydrogen and hydrocarbon gas mix, may be flared, recycled to heat the coal, or cleaned to be used as a fuel source to generate energy or used to produce methanol.

There are several inherent problems with COG as a fuel for power generation, notably contaminants that would not be found in pipeline natural gas or distillate fuels. Tar, a by-product of burning coal, is plentiful in COG and can be detrimental to gas turbine hot gas path components. Particulates, in the form of dust particles, are another nuisance contaminant that can shorten the life of the gas turbine’s hot section via erosion and plugging of internal cooling holes.

China, the world’s largest steel producing country, has approximately 1,000 coke plants producing 200MT/year of COG. GE Energy has entered into the low British thermal unit (BTU) gases segment in China with an order from Henan Liyuan Coking Co., Ltd. The gas turbines will burn 100% coke oven gas, which will help the Liyuan Coking Plant reduce emissions and convert low BTU gas to power efficiently. This paper will detail the technical challenges and solutions for utilization of COG in an aeroderivative gas turbine, including operational experience. Additionally, it will evaluate the economic returns of gas turbine compared to steam turbine power generation or methanol production.
3D Ultrasound Elastographic Imaging and Characterization of Breast Cancer In Vivo
Authors: Sayed Ahmed , Layne Ginger , Abraham Jame , Mukdadi Osama
Published: October 2013

Breast cancer has a high mortality rate and caused about 13.7% of all cancer types deaths in women. Mammography imaging, having a good sensitivity to cancer, is used along with biopsy in a routinely manner, to differentiate between malignant and benign masses. Biopsy is an invasive procedure, and to reduce the necessity for performing it, ultrasound elastography was proposed. Elastography is a potential imaging technique to characterize breast masses, and to differentiate malignant from benign lesions, based on imaging estimated tissue strains under compression. This can result in lowering the number of unnecessary biopsies.

Using 3D elastography, lesion relative stiffness with the surrounding soft tissue is estimated at different compression levels, and used as a classification parameter to judge the malignancy of the lesion. In addition, elastography provided a means of emphasizing the strain difference of the lesion from the surrounding soft tissue, which can be used as an additional classification parameter. A pilot study on volunteered patients was performed, and results were compared with biopsy diagnosis as a reference. Initial elastography results showed good agreement with biopsy outcomes. Moreover, we constructed different strain elastograms including first principal, maximum shear and von Mises strains. Those new types of elastographic volumes incorporated the normal axial and shear strains together, which provided better distinction of the hard lesion from the soft tissue. In summary, the proposed elastographic techniques can be used as a noninvasive quantitative characterization tool for breast cancer, with the capability of visualizing and separating the masses in three dimensional space.
Influence of Flax Fibers on Properties of Starch-Based Composites
Authors: Elsayed Hamdy , Farag Mahmoud , Megahed Hassan , Mehanny Sherif
Published: October 2013

Eco-friendly “green” composites made from flax fibers and biodegradable corn starch-based matrix were successfully prepared by hot pressing. Thermoplastic starch (TPS) was obtained by blending native corn starch with glycerin and water. The plasticized starch was emulsified before being added to the previously NaOH-treated flax fibers. The flax content was varied from 20 to 80 wt%. The composites were preheated and then pressed at 5 MPa and 160°C for 30 minutes. Density measurements showed low porosity for all composites up to 50 wt% fibers. SEM investigation showed strong adhesion at fiber-matrix interface and good fibers wettability. Static tensile and flexural mechanical properties (stiffness and strength) of the composites appeared to increase with the fiber weight fraction increase up to 50 wt%. Increasing fiber content also improved composite stability in thermal degradation, water uptake and biodegradation. Some micromechanical models are used to study the tensile strength and modulus of the obtained composites such as the Kelly-Tyson and Halpin–Tsai equations. The present work shows that 50 wt% composite has competitive properties, qualifying this material to be affordable and appropriate for different applications.