bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Bi-Linear S-N Curve and Crack Growth Law on the Safety Analyses of Welded Joints of an Offshore Structure
Authors: Khan Rizwan A. , Ahmad Suhail
Published: July 2009

Design of welded structures for fatigue limit state is normally carried out by means of either linear or bilinear S-N curves which have been found adequate to predict crack initiation only. To properly assess the effects of design, fabrication, inspection and repair strategy for structure degradation due to crack growth, Fracture mechanics (FM) models need to be applied. In this paper, alternative S-N and FM formulations of fatigue are investigated. Probabilistic fracture mechanics approach predicts the fatigue life of welded steel structure in the presence of cracks under random spectrum loading. It is based on a recently proposed bi-linear relationship to model fatigue crack growth and incorporates a failure criterion to describe the interaction between fracture and plastic collapse. Uncertainty modeling, especially on fatigue crack growth parameters, is undertaken with the aid of recently published data in support of the bilinear crack growth relationship. Results pertaining to fatigue reliability and fatigue crack size evolution are presented using the Monte Carlo Simulation Technique, and emphasis is placed on a comparison between linear and bi-linear crack growth models. The bi-linear S-N curve and crack growth model are found to lead to higher fatigue life estimates and shows sensitivity to many other parameters in addition to the stress state of the component. These findings implicate inspection schemes for components of the marine structures to ensure minimization of the surprises due to wide scatter of the fatigue phenomenon in marine environment. Variations in system configuration, service life and coefficients of crack growth laws have been studied on the parametric basis.
Optimizing Limb Lengthening Using an Autodistractor and Force Measurement
Authors: Wee Jinyong , Rahman Tariq , Mackenzie William G. , Akins Robert , Levine David , Richardson Dean W. , Dodge George R. , Seliktar Rahamim
Published: July 2009

The procedure of limb lengthening is a common method for correcting limb length inequality. The lengthening procedure, however, can result in serious complications such as premature consolidation of bone and soft-tissue contractures. To avoid adverse effects, it is important to determine the safe limits of the lengthening procedure in terms of forces applied, rate of distraction, overall length added and effects of the procedure on associated tissue. In this study, we investigate the relationship between distraction speed and callus formation in the fracture gap and how this affects the distraction resisting force (DRF) and muscle adaptation. A new distraction system was designed to continuously measure the DRF during tibial lengthening using a unilateral fixator. Measurements were made in 2 sheep for 51 days and 38 days respectively. The first sheep acquired 5cm (25% of its original length) of new bone with various rates of distraction. The second sheep acquired 3.8cm (15% of its original length) of new bone with 1mm/day fixed rate of distraction. During the lengthening procedure, the DRF steadily increased as the callus was being formed in the distraction gap. In sheep1 the lengthening rate was increased from 1mm/day to 1.25mm/day at the lengthening day 36 to manage what was interpreted to be signs of early premature consolidation. The DRF decreased to 310N from 400N at the lengthening day 43. Radiographs taken at day 43 showed separation in the callus. During the 1.25mm/day lengthening the sheep lost ankle joint movement completely. The major muscles, long digital extensor (LDE), cranial tibial (CT), gastrocnemius and deep digital flexor (DDF) were collected from the operated and non-operated hind limbs. The result showed that LDE and CT were damaged while gastrocnemius and DDF were intact. In sheep2, the distraction rate was maintained at 1mm/day and it showed a similar increase of DRF up to 550N at the end of distraction (lengthening day 38). There was no visible joint restriction observed. None of the four muscles collected showed signs of the profound tissue damage noted in sheep1. Comparison of the DRF profile with radiological interpretation confirmed that the degree of callus formation was appropriate at DRF of 300 ∼ 500N. Additionally the ability of the muscle to adapt to the given length could be affected by the time when the rate was changed. Additional studies are underway to determine the optimal regimen including appropriate rates and forces.
Core Ignition Prediction With Moving Two-Phase Zone Boundaries
Authors: Hasan Dov , Nekhamkin Yuri , Wacholder Eitan , Elias Ezra
Published: July 2009

The interaction between a fuel rod metal clad and the surrounding steam in a nuclear reactor core under hypothetical accident conditions is considered using a thermal balance based model. This enables the calculation of the metal transient temperature and its rate of oxidation, which may possibly lead to ignition and rapid burning. The transient fluid thermal-hydraulic behaviour of the two phase region, as well as the propagation in space and time of its boundaries following a step change in the coolant inlet mass flow rate are solved using a one-dimensional, two-phase homogeneous flow model. The solution scheme consists of first solving the velocity field analytically followed by a numerical solution of the remaining balance equations for the density field. The transient location of the dry-zone region, as well as the other flow primary variables; i.e., vapour quality, and enthalpy are then directly obtained. Numerical results are illustrated based on input data of a partially uncovered AP600 type nuclear reactor core during a bottom-reflooding phase of a loss of coolant accident scenario.
Stability Analysis of the Parametric Roll Resonance Under Non-Constant Ship Speed
Authors: Galeazzi Roberto , Vidic-Perunovic Jelena , Blanke Mogens , Jensen Jo̸rgen Juncher
Published: July 2009

The aim of this work is to analyze the influence of a nonconstant ship speed on the onset and development of the parametric roll resonance. A 2-DOF nonlinear surge-roll model is set up and analyzed. Perturbation methods are also applied to evaluate the influence of dynamic variations of surge velocity on the onset of parametric roll. The theoretical results are illustrated and validated using a 4-DOF hydrodynamic and control theory model.
Modelling of Hard Broaching
Authors: Wegener Konrad , Vargas Guilherme E. , Kuster Friedrich , Pinto Fa´bio W. , Schnider Thomas
Published: July 2009

Hard broaching is a finishing process to correct geometrical deviations of internal profiles on hardened workpieces, typically using a hardened steel body overlaid with a single layer of metal-bonded diamond grits. The tool essentially has the opposite contour as the workpiece. The process is characterized by an oscillating movement of the broaching tool, while the tool is pushed sequentially deeper into the workpiece. During the retraction phase the chips are removed from the chip spaces. The tool consists of a roughing part and a finishing part to increase the surface quality and reduce the tolerances. For gaining a deeper understanding of the process and for its optimization a stochastic tool model is introduced, which takes into account the differing shape, size, orientation and position of the single grains. Specifications about the tool geometry and the diamond coating as well as process parameters are used as input. The model is capable to predict the active grains, the respective cutting areas, cutting forces and surface roughness of such a virtual image of the broaching tool, which is thus capable to be used to layout and optimize the shape, layer and process strategy of hard broaching. It further allows analyzing the effects of the feed per stroke on the process in dependence of different process and tool parameters. By the modeling a strategy for process optimization is derived. The influences of the optimization strategy on the process are presented and discussed.
Computer Simulation and Optimisation of Tissue Engineering Scaffolds: Mechanical and Vascular Behaviour
Authors: Almeida Henrique A. , Ba´rtolo Paulo J.
Published: July 2009

Additive biomanufacturing processes are increasingly recognised as ideal techniques to produce scaffolds for tissue engineering applications. These scaffolds must be biocompatible, biodegradable, with appropriate porosity, pore structure and pore distribution and optimal vascularisation, with both surface and structural compatibility. Surface compatibility means a chemical, biological and physical suitability to the host tissue. Structural compatibility corresponds to an optimal adaptation to the mechanical behaviour of the host tissue. Recent advances in tissue engineering field are increasingly relying on modelling and simulation. This paper proposes a novel computational tool combining structural, computational fluid dynamics and topological optimisation schemes, to predict and optimise both mechanical and vascular behaviour of scaffolds for soft and hard tissue applications, with different topological architectures and levels of porosity. This tool is particularly important to quantify the structural heterogeneity and scaffold mechanical properties with a designed microstructure subjected to either a single or a multiple load distribution. This computational tool enables the simulation of biological flows in vascular passages of scaffolds. The blood flow considered in this study is a complex fluid comprising a suspension of red blood cells, white blood cells and platelets within a newtonian plasma. A topological optimisation scheme is being developed to obtain the ideal scaffold topological architectures.
High Stiffness Closed-Form Kinematic Structural Design of a Low-Cost 4/5-Axis Micro/Meso-Scale Inverted High-Speed Machining Center
Authors: Mayor J. Rhett , Kimn Edward
Published: July 2009

The demand for miniaturized components is increasing in various industries, such as the biomedical, consumer electronics, optics and defense-related industries. The production of the micro/meso-scale components and parts in these industries is typically undertaken using MEMS-type photolithographic production techniques that have limitations in the materials and geometries that can be produced. However, numerous research efforts during the course of the last five to ten years have developed micro-scale EDM processes, micro-laser processes and micro-machining operations. In particular, the micro-machining processes have been demonstrated to provide a credible solution to the production of micro/mesoscale parts with complexes geometries in a broad range of materials. The development of mMTs is growing with the rapidly increasing demand for tighter tolerances. Traditionally, mMTs have been developed based on horizontal or vertical Cartesian co-ordinate machine tool structures. However, as the need for increased process flexibility and productivity is continuously being driven higher, there is a need to develop higher degree of freedom machining systems, including 4-axis and 5-axis machining centers. In this paper, the design of a low-cost, high-precision, high-speed 4/5-axis micro/meso machining center is presented as a cost-competitive alternative to existing open-form kinematics precision machining centers. A key departure from traditional machine tool design approach that has been adopted in this design is the utilization of closed-form kinematic structural design to create a high-stiffness, low-cost machine tool base. In addition, the lower thermal mass of the mMT base enhances rapid thermal washout in the structure and significantly reduces the thermal gradients in the structure. Consequently the thermal errors present in the structure are limited and simply and adequately handled using existing error compensation strategies. Initial results from an analytical and numerical investigation of the thermo-mechanical response of an innovative, kinematically closed-form inverted micro-machining center are presented. A coarse resolution parametric study was undertaken to evaluate the preferred preferred design space for maximum stiffness and minimum thermal distortion in low-cost, high precision, high-speed micro-machining centers. In addition, in order to facilitate part loading and unloading operations will be considered as a key design characteristic. A key result of this study has been the identification of a preferred design space for kinematic form selection, material selection and structural design options for increased rigidity, reduced thermal error and reduced production costs for flexible 4/5-axis micro/meso-scale machining centers. The proposed mMT design achieves a 3X increase in rigidity over a comparable tradition kinematically open horizontal mMT system.
Shape Knowledge Annotation for Virtual Product Sharing and Reuse
Authors: Catalano C. E. , Falcidieno B. , Attene M. , Robbiano F. , Spagnuolo M.
Published: July 2009

This paper explores a promising framework, the ShapeAnnotator, for the semantic annotation of 3D objects in the context of Product Design. The ShapeAnnotator provides the functionalities that allow the user to load a suitable formalization of relevant concepts and to annotate, or tag, a virtual product model, or its parts, with these concepts (markup). Moreover, the ShapeAnnotator provides tools that support the users in the identification and selection of the relevant parts in the virtual product model (segmentation toolbox). An ad hoc form feature ontology has been developed and a specific application scenario has been set up for the validation of the approach in the reverse engineering scenario. Through the ShapeAnnotator, objects can be described by semantic annotations and also its meaningful features can be explicitly described independently and further characterized by specific attributes and relations with other parts and/or features. The contextualization of the ShapeAnnotator for Product Design is the first step towards the integration of knowledge formalization and geometric reasoning techniques, which will support the interoperability in the Product Development Process.
Locating Impact on Thick Plates by Acoustic Wave Analysis
Authors: Kim Ho-Wuk , Lee Sang-Kwon
Published: July 2009

Loose parts in a steam generator of a nuclear power plant often impact the wall of the generator and become one of the damage sources in the nuclear power plant. In general, the steam generator of the nuclear power plant is structured by thick plates. This paper presents a novel approach to locating an impact load in a thick plate. The approach is based on an analysis of the acoustic waveforms measured by a sensor array located on the plate surface and theoretically obtained by either the exact elastodynamic or theory the approximate shear deformation plate theory (SDPT). For accurate estimation of the location of the impact source due to loose part, the time differences in the arrival times of the waves at the sensors and their propagation velocities are determined. This is accomplished through the use of a combined higher order time frequency (CHOTF) method, which is capable of detecting signals with lower signal to noise ratio compared to other available methods. The dispersion curves for multi modes of Lamb waves are calculated by using exact plate theory and SDPT. It is difficult to measure directly the group velocity for Lamb mode of acoustic waveform in the thick plate because they are dispersive waves. However, most of the energy in the wave is carried by the flexural waves (A0 mode); the group velocity of this mode is extracted by using the CHOTF technique for estimating the impact source location. The estimates are shown to be in excellent agreement with the actual locations and the technique is applied to the detection of the location of the impact load due to the loose part in a nuclear power plant.
Control of Ship Motion at Low Speed: Experiments With a Physical Tanker Model
Authors: Morawski Leszek , Vinh Nguyen Cong
Published: July 2009

The paper presents a system controlling ship motion at low speed. The control system makes use of three fuzzy logic controllers. They are: course keeping controller, longitudinal position keeping controller and transverse position keeping controller. Three controllers work independently to keep the ship hull centre at the reference point with the set course. The ship motion is controlled by tracing and following coordinates of the reference point. They change according to the assumed ship motion trajectory and speed. The ship control system use three propellers: bow thruster, stern thruster and the main propeller of the ship. The control signals (propellers powers) have the form of pulses with relevant amplitude and time duration. The pulsatory nature of the control signals was obtained by proper selection of the shape of the member functions in Mamdani-type controllers and the use of the bisector defuzzyfication method. The magnitude of the signal is changed in steps and plays the role of rough control while its duration is adjusted continuously and plays the role of fine control The control system was worked out in Matlab-Simulink with RTW, xPC-target toolboxes and tested on a scaled physical model of a tanker in the real lake environment. The system installed on model contain two PC computers and as the measured devices use DGPS RTK Leica system, ST20 Anschutz gyrocompass and Gill-windobserver. The paper discuss the controlling algorithm, along with the results of control system tests.
Challenges in Implementing Digital Aircraft Technologies
Authors: Klunover Avner
Published: July 2009

While 3D Model Geometrical Definition of a Product is quite a mature Technology, extending it to a full authority single Digital Product is still a major challenge especially for complex products such as Aircraft (A/C) and Cars. The real meaning of such definition is one unique Data-Base which includes all required information for all downstream applications during the whole Product Lifecycle, from Design through Manufacturing up to Logistic and Maintenance.
Engineering Education: Prospective Research Issues
Authors: Waks Shlomo
Published: July 2009

There exists an increasing gap between engineering developments and research on educating engineers. There is a need to investigate and develop pedagogical means for advancing engineering education. The problem stems from the fact that most engineering educators are concerned mainly with disciplinary engineering contents, while researchers in the educational domain concentrate on educational psychology and pedagogical aspects. There is not enough cooperation between engineering and education, thus avoiding the creation of synergetic interaction between the two domains in a given engineering education system or situation. This article deals with the question: what has to be investigated in engineering education in order to advance learning activities of students and updating engineers? We will analyze some issues, as they aroused during recent years in a series of research studies on engineering education around the world and in the Department of Education in Technology and Science at the Technion – Israel Institute of Technology. After analyzing the status of engineering education and emergence of relevant R&D activities, possible research questions are presented. For example: (1) How should the contents of an engineering curriculum be determined? By whom? (2) Is there a need for a recognized educational scholarship like that of the existing disciplinary scholarship? (3) Creativity and project work – what do engineering educators and students think about? (4) What are the conditions and means for advancing the learning process in a multimedia environment? (5) What are the pitfalls in using hypermedia during the learning process? (6) What is Self-Learning Regulation (SLR) and why is it an important issue in engineering education? Accordingly possible trends in engineering education research are proposed and discussed.
Generation of Residual Stresses in Composites
Authors: Barsanescu Paul , Grimberg Raimond , Carlescu Petru
Published: July 2009

The paper presents a new mechanical modeling of thermal mismatch residual stresses in composites. Some equations which can be easy used in order to calculate the three-dimensional state of residual stresses in fibers and matrix, in a unidirectional composite lamina, are carried out or adopted on the basis of a composite cylinder model, developed in Theory of Elasticity. Using these equations, residual stresses developed due to differential thermal shrinkage as it cools down from the high processing temperature to the ambient temperature can be predicted.
Operation of the Siemens SOFC Generators CHP100 and SFC5 in a Mechanical Factory
Authors: Verda Vittorio , Orsello Gianmichele , Disegna Gianni , Debenedictis Ferrante
Published: July 2009

Solid Oxide Fuel Cells (SOFCs) are a promising technology for distributed electricity generation and cogeneration. Most of the installations of SOFC are small size fuel cells (of the order of decades of watts or few hundred watts) in laboratories. There are very few installations of commercial scale SOFC plants. In this paper the operating results obtained with two SOFC plants are presented. These plants, whose nominal electric power is 100 kW and 5 kW respectively, produce heat and power to contribute to the energy requirements of the Turbocare factory in Torino, Italy.
Numerical Prediction of Efficiency, Cavitation and Unsteady Phenomena in Water Turbines
Authors: Josˇt Dragica , Lipej Andrej , Mezˇnar Peter
Published: July 2009

The paper presents numerical analysis of the flow in all types of water turbines. Analysis was performed by ANSYS CFX-11.0 computer code. A detailed analysis of complete radial and axial turbine is presented. On the basis of numerical results efficiency and cavitation are predicted and compared to the measured results obtained on test rigs in Turboinstitut. The paper presents also numerical analysis of the flow in a two jet Pelton turbine. The analysis was divided into two parts. At first a steady state analysis of the flow in the piping system with the jets at the outlet was performed. The second step was unsteady analysis of the runner with jets. The casing was not included in the domain of calculation. The predicted efficiency is compared to the measured values.
Design, Modeling and Functionality Allocation in Mechatronic Production Systems
Authors: Neugebauer Reimund , Drossel Welf-Guntram , Ihlenfeldt Steffen , Wabner Markus
Published: July 2009

This paper reviews current developments in mechatronic systems for metal cutting and forming machine tools. The integration of mechatronic modules to the machine tool and their interaction with manufacturing processes are presented. Sample mechatronic components for precision positioning and compensation of static, dynamic and thermal errors are presented as examples. The effect of modular integration of mechatronic systems on the reconfigurability and reliability of the machine tools is discussed along with intervention strategies during machine tool operations. The performance and functionality aspects are discussed through active and passive intervention methods. A special emphasis was placed on active and passive damping of vibrations through piezo, magnetic, and electro-hydraulic actuators. The modular integration of mechatronic components into the machine tool’s structure, electronic unit, and CNC software system is presented. The paper concludes with the current research challenges required to expand the application of mechatronics in machine tools and manufacturing systems.
Virtual Laboratory of Pneumatics Systems Building
Authors: Kosˇt’a´l Peter , Veli´sˇek Karol , Mudrikova´ Andrea
Published: July 2009

Virtual laboratory of pneumatic and electro pneumatic systems will be used for learning of pneumatic and electro pneumatic schemes design principles. Rapid changeable conditions on labour market are on one side connected with international countries integration and on the other side the conditions are connected with rapid technological development. These changeable conditions are so creating new pressure to the employee competitions. Labour power is an important development aspect of present day informatics society. This importance can be found on firm level as well as in global economic development use. Labours which are suitable and high qualified for these conditions can be found in groups of university educated graduates. Especially we are talking about graduates of economy and technical universities. This kind of graduates is very required on the labour market. Researches operating about employers requirements and also operating about student opinions to the university training are indicating that teaching schedules and education process are not creating for praxis requirements. That mean, that universities have to teach special practical knowledge and skills re-bound to the praxis and its needs.
Flexible Manufacturing Cell’s Clamping Fixture
Authors: Kosˇt’a´l Peter , Veli´sˇek Karol
Published: July 2009

In these days the increasing of cutting speed (decreasing of main cutting time) has no majority influence to the productivity increasing. For this reason we have to short additional times what has important influence mainly by repeated operations. Additional times shortening is one of main conditions used for productivity increasing and by decreasing of manufacturing costs. One possibility how to short additional times is use optimal clamping device, as well as automation of clamping operations. Using of proper clamping device will lead to the quality and productivity increasing as well as to the decreasing of manufacturing costs. Development of new generation manufacturing machines and manufacturing systems needs, that this kinds of machines have to be equipped by proper clamping devices. That why clamping fixtures are developing together with manufacturing machines. Such developed fixtures can be used also in manufacturing systems with high repeatability of production baths, but they are mainly assigned for one piece manufacture, for clamping of more complicated pieces. Intelligent fixtures are different from classical fixtures not only by its design, but also by its properties. Its development is connected with its design and designing of higher generation machines.
The Layout of Manipulation Effector
Authors: Tolnay Maria´n , Olsˇavsky´ Viktor , Brody Milan
Published: July 2009

The paper published in the anthology describes an automated selection and optimized layout of vacuum elements in manipulation effectors of industrial robots and manipulators. Computer aided selection provides the user with a complete proposal of the necessary number, size and layout of pneumatic suction cups for manipulation with flat parts of circular or rectangular shapes. The computation of the required size and number of suction cups is conditioned by safe manipulation with the object and layout optimation from the point of providing an allowable deflection of the component, the value of which is determined by the user. The paper presents the basic structure of end effectors and a brief comment on current situation in the area of gripper selection and design. In conclusion there are described possibilities of further completion of the computer aided system for vacuum gripper design.
Control of a Two-Stage Assemble-to-Order Manufacturing System Under Demand and Capacity Uncertainties
Authors: Ceryan Oben , Koren Yoram , Duenyas Izak
Published: July 2009

This paper focuses on the production and assembly control in a two-stage assemble-to-order (ATO) manufacturing system. An ATO manufacturing system keeps inventory only at the component level, and products are assembled only after a customer order is received. ATO systems have a widespread use in various industries where mass customization is popular. The motivation of the problem is due to the need for firms in this setting to effectively coordinate the production of components and allocate the assembly line capacity shared across many different products. We model component production lines and a downstream product assembly line with M/M/1 queues in order to identify optimal policies regarding a firm’s decision on how many components of each type to produce and how to prioritize orders for various products. We also propose an effective heuristic solution that is robust with respect to the number of product alternatives offered.
New Laser Technology in Turbine Blade Measurements
Authors: Shacham Danny
Published: July 2009

Mechanical touch probes on CMMs (Coordinate Measuring Machines) are the most common sensors used for blade inspection. Most Blade Measurements today are based on a mechanical probe. The amount of useful data that can be collected using the mechanical touch probe is limited. Since blades are characterized by complicated free form 3D geometry shapes, the traditional solution of touch trigger probes on a CMM is very limited both in hardware as well as in measurement software. One of the major challenges of blade measurement is the “blade alignment” — finding the blade position relative to the CMM and moving the coordinate system from the CMM to the blade. It is a tricky trail and error approach, unless one is using very high precision (and very expensive) mechanical jigs. The recent trend from the touch trigger probe to a mechanical (Analog) scanning probe is a step in the right direction, in terms of data collection rate; however it is still limited by some major fundamental characteristics of the mechanical analog sensor: a. A mechanical probe needs to maintain continuous contact with the surface and thus is limited in its scanning speed. b. By nature, the dynamic range of a mechanical probe is only a few hundred microns, which makes the scanning pattern, the alignment routine and the programming of the scan path more complicated. c. Programming a mechanical probe for a cross-section scanning operation requires operator skill and experience. d. The resolution and size of the features that can be scanned are limited by the diameter of the stylus, so features such as leading and trailing edges are not good candidates for any mechanical or analog probe measurements.
Modeling the Manufacturing Cost of Solid Oxide Fuel Cells
Authors: Bar-On Isa , Vincent Tracey S. , Koslowske Mark , Woodward-Hagg Heather K.
Published: July 2009

During the past years solid oxide fuel cells have been developed with improved power densities at reduced operating temperatures. These cells consist of additional layers beyond the traditional two electrodes and the electrolyte layer. Some of these layers are only several microns thin posing a manufacturing challenge for traditional high volume manufacturing processes like tape casting or screen printing. Our previously developed process based cost model has been updated to include the additional layers, to account for yield improvements for thinner layers, and to anticipate the effect of equipment and process development. These latter improvements are assumed to improve automation and process control. Our results indicate that for improved processes with high yields these cells can readily meet manufacturing cost targets.
Virtual Evaluation for Machine Tool Design
Authors: Mori Masahiko , Piner Zachary I. , Ding Ke , Hansel Adam
Published: July 2009

This paper presents the virtual machine tool environment Mori Seiki established for the evaluation of static, dynamic, and thermal performance of Mori Seiki machine tools. In this system environment, machining accuracy and quality are the main focus for each individual analysis discipline. The structural analysis uses the Finite Element Method (FEM) to monitor and optimize the static rigidity of the machine tool. Correlation between physical experiments and digital simulation is conducted to validate and optimize the static simulation accuracy. To accurately evaluate and effectively optimize dynamic performance of the machine tool in the virtual environment, the critical modal parameters such as damping and stiffness are calibrated based on experimental procedures which results in precise setup of the frequency response models. Computational Fluid Dynamic (CFD) analysis model is built in the environment so that the thermal perspective of the machine tool is evaluated and thermal deformation is monitored. This paper demonstrates compatibility of the digital simulation with physical experiments and success in integrating theoretical simulation processes with practical Mori Seiki machine tool development.
Three Dimensional Numerical Simulation of Flow Field Inside a Reversible Pumping Station With Symmetric Aerofoil Blade
Authors: Cheng Li , Liu Chao , Zhou Jiren , Tang Fangping , Jin Yan
Published: July 2009

The pumping station with symmetric aerofoil can achieve reversible pumping function. It can keep high reversible efficiency and its flow coefficient is approaching to normal one. At same time, it has the simple structure and is easy to operate and maintain. The flow inside reversible pumping station is very complex and dominated by three dimensional viscous effects. With the rapid progress of computational fluid dynamics, CFD has become an important tool to help to make full understanding of flow. In order to recognize the characteristic of pumping station, the control volume method is used to simulation the flow filed. The RNG k-ε turbulent model and SIMPLEC algorithm are applied to do analysis. Flow field inside symmetric aerofoil blade and passage of pumping station are analyzed in detail. Some computational data, such as computational contour of sections, streamline of pumping system, flow vectors of blade and pressure contour of blade for two different rotate directional, are given in the paper. On the based of the simulation results, efficiency prediction of the pumping station is applied. By calculating the useful power and the hydraulic efficiency at the 11 different discharge points, capabilities of pumping station are predicted. A set of model pumping station with a 300mm blade are made for test. Using the laboratory test loop of which the total uncertainty of measured efficiency is ±0.39%, the hydraulic performance is evaluated and demonstrated. The numerical performances agree well with experiment data.
Contributions Concerning the Power Optimization of the Pumping Stations
Authors: Alexandrescu Aurora C. , Alexandrescu Simona Adina O. , Alexandrescu Constantin Adrian O.
Published: July 2009

Profitability of water distribution activity depends largely on the relationships between operational capability and service costs, related to supplier’s performance, volume of distributed water and effective operating costs. The main variables that influence the total selling price are required investment value, specific consumption of electrical energy for pumping power, unit price of the electrical energy and total volume of monthly consumed water billed. The selection of rehabilitation and modernization measures must rely on market studies results that appropriately establish the quantities of water that may be distributed and billed. Present and future water requirements will be determined based on the analysis of actual operation data and on estimation of future trends in water consumption on national and international levels. The optimization calculation will use two target functions: total maximum efficiency and total electric power consumption required for transport of each cubic meter of supplied water, and cubic meter of sewage water, respectively. The mathematical methods may be improved by taking into account all active consumers in the network with simultaneous water requirements, at each moment of the day. Using several original mathematical algorithms, authors developed a computer program that calculates the functional parameters of the ensemble pumping station – hydrophore – pipe distribution network, as well as the available consumer parameters. This may be accomplished at each moment in time, depending on the number of active consumers simultaneously connected to the supply network, in the hypothesis of a minimum price of cubic meter of pumped water. This paper proposes a solution of the problem of reducing production costs for supplied domestic water, which directly affects the reduction of the electric power consumption.
Simulation of Airflow and Fuel Spray Through an Axial Swirler for Gas Turbine Applications
Authors: Kempenaar Joshua E. , Shollenberger Kim A. , Oskam Gareth W.
Published: July 2009

A computational fluid dynamics (CFD) simulation of the effects of an upstream blockage on the fuel spray and airflow through an axial swirler in an experimental gas turbine fuel injector has been conducted. Blockage was varied by means of varying the inside diameter of a restriction upstream of the entrance to the axial swirler. Fuel is injected as a jet in cross-flow through fuel nozzles located in axial swirler vanes. Fuel spray was modeled in the commercial CFD code Fluent 6.3.26 using the Lagrangian approach with the built-in Discrete Phase Model (DPM). Results are given for the TAB, Wave, and KH-RT break-up models. Preliminary simulations with the TAB break-up model were performed for a simple axisymmetric jet and compared to experimental results before simulating the axial swirler geometry. The axial swirler simulations predict that spray dispersion decreases and droplet size increases as the flow area of the blocker ring increases.
Modelling of Fluid Dynamics Interacting With Ductile Fraction Propagation in High Pressure Pipeline
Authors: Popescu M. , Shyy W.
Published: July 2009

This paper presents a computational model for describing the behavior of the fluid dynamics in a fractured ductile pipe under high pressure. The pressure profile in front of the crack tip, which is the main source of the crack driving source, is computed by using nonlinear wave equation. The solution is coupled with one dimensional gas flow analysis behind the crack, choked flow. The simulation utilizes a high order optimized prefactored compact–finite volume method for space discretization, and low dispersion and dissipation Runge-Kutta for time discretization. As the pipe fractures the rapid depressurization take place inside the pipe and the propagation of the crack induce waves which strongly influence the nature of the outflow dynamics. Consistent with the experimental observation, the model predicts the expansion wave inside the pipe, and the reflection and outflow of the wave. The model also helps characterize the propagation of the crack dynamics and fluid flows around the tip of the crack.
Wind Tunnel Tests on Flow-Induced Vibrations and Scattering of Japanese Slates
Authors: Okamoto Satoru
Published: July 2009

A series of wind tunnel tests was conducted on the vibration and scattering behavior of full-sized model of roof tiles, which were used widely for roofings of Japanese wooden dwellings. This study has investigated the nature and source of the vibrating and scattering behavior of roof tiles with the aim of providing a better insight to the mechanism. The roof tiles were set up on the pitched roof in the downstream of the flow from the wind tunnel. The vibrations for the roof tiles were measured by the Laser Doppler Vibrometry and the accelerometer, and the practical natural frequencies of the roof tiles were analyzed by the impulse force hammer test method. The motions of the vibration and scattering were observed by the high-speed video camera. Based on the consideration on the results of the measurements, there is a basic mechanism which can lead to flow-induced vibrations of the roof tiles. This mechanism is similar to that of the so-called fluttering instability, which appears as the self-excited oscillation in the natural mode of the structure at the certain critical flow speed. The values of the frequencies for the oscillating relate to the values of natural frequencies of the vibration.
URANS Modeling of Three Airfoils With Different Stall Mechanisms
Authors: Elkhoury M. , Najem J. , Nakad Z.
Published: July 2009

Capability of recently developed Menter (ME) and Modified Menter (MME) one-equation models in predicting prestall and poststall characteristics of three airfoils that exhibit different stall onset mechanisms is investigated. The Spalart-Allmaras (SA) turbulence model is also included to form a baseline against which both the ME and the MME models are assessed. The effects of subiteration, grid size, and time stepping on the predictive accuracy of the numerical scheme are addressed. However, transition effect is not accounted for and hence, all test cases are run fully turbulent. Significant differences in the flow predictions of all models are noticed in regions with massively flow separation.
Numerical Simulation and PIV Measurement on the Internal Flow in a Centrifugal Mini Pump
Authors: Shao Jie , Liu Shuhong , Yuan Huijing , Wu Yuliun
Published: July 2009

This paper reports on the internal flow of a centrifugal mini pump. The RNG k-epsilon turbulence model was employed to simulate the three-dimensional turbulent flow in the pump. To examine and certify the simulation results, a transparent acrylic centrifugal mini pump model which is suitable for PIV measurement has been developed. The tongue region and the passages region between blades were investigated using PIV. In order to eliminate the effect of refraction on the area close to the wall and increase the measurement accuracy, the fluorescent particles were scatted into the working fluid with the tracing particles. It is found from the calculation and PIV measurement results that there is a large area of recirculation flow near the tongue at low flow rate working conditions. The computationally predicted water head using the RNG k-epsilon turbulence model are in very good agreement with the experimentally measured water head and the mean velocity distributions at investigation area obtained by PIV and calculation showed a satisfactory agreement as well. Meanwhile, the results of PIV measurements show that the flow status in one passage is different to another. And for capturing the internal flow detail information, the RNG k-epsilon turbulence model is not very suitable.
Smoothed Profile Method for Particulate Two-Phase Flow
Authors: Luo Xian , Maxey Martin R. , Karniadakis George E.
Published: July 2009

We re-formulate and demonstrate a new method for particulate flows, the so-called “Smoothed Profile” method (SPM) first proposed in [1]. The method uses a fixed computational mesh, which does not conform to the geometry of the particles. The particles are represented by certain smoothed indicator profiles to construct a smooth body force density term added into the Navier-Stokes equations. The SPM imposes accurately and efficiently the rigid-body constraint inside the particles. In particular, while the original method employs a fully-explicit time-integration scheme, we develop a high-order semi-implicit splitting scheme, which we implement in the context of spectral/hp element discretization. We show that the modeling error of SPM has a non-monotonic dependence on the time step size Δt. The optimum time step size balances the thickness of the Stokes layer and that of the profile interface. Subsequently, we present several numerical simulations, including flow past three-dimensional complex-shaped particles and two interacting microspheres, which are compared against full direct numerical simulations and the force coupling method (FCM).
Numerical Modelling of Cavitation Erosion
Authors: Dular Matevzˇ , Coutier-Delgosha Olivier
Published: July 2009

The goal of the work is to develop an expert system for monitoring and control of cavitation in hydraulic machines and to research the possibility of cavitation erosion prediction using CFD tools only. The geometry in question is a simple single hydrofoil, which is exposed to the developed cavitating flow at different flow conditions. The work was divided in more parts: numerical simulation of cavitating flow, experimental evaluation of the simulation, measurements of cavitation erosion, development of cavitation erosion model and finally the prediction of cavitation erosion using solely CFD. A study of erosion effects of cavitation on simple single hydrofoil configurations in a cavitation tunnel was made. A thin copper foil, applied to the surface of the hydrofoils, was used as an erosion sensor. A pit-count method was used to evaluate the damage. The cavitation phenomenon on hydrofoils at different flow conditions (system pressure, flow velocity) was observed. The erosion model is based on the physical description of different phenomena (cavitation cloud implosion, pressure wave emission and its attenuation, micro-jet formation and finally pit formation), which are involved in the process of pit formation. The cavitating flow was simulated using an “in house” CFD code which uses barotropic state law. The code was previously tested on numerous experiments. For the present case the predictions of velocity profiles and pressure evolutions in the vicinity of the hydrofoil were compared to experimentally measured data. In all cases a very good correlation was obtained. The erosion model was implemented into the code. It used values of local pressure, local void fraction and flow velocity to determine the magnitude of damage at a certain point. The results of prediction were compared to the experimentally measured damage on the hydrofoil and it was shown that it is possible, for this simple case, to use solely CFD tools to predict cavitation erosion evolution in time, final extent and final magnitude with a very good accuracy.
Investigation of Switching Time and Pressure Head Effects on Hydro Magnetic Micro-Pump and Flow Controller
Authors: Esmaily Moghadam Mahdi , Shafii Mohammad Behshad
Published: July 2009

The significant importance of micro-scaled devices in medicine, lab-on-a-chip, and etc resulted in a vast variety of researches. The idea behind the novel hydro magnetic micropump and flow controller is that ferromagnetic particles, mixed and dispersed in a carrier fluid, can be accumulated and retained at specific sites to form pistons in a micro-tube using some external magnetic field sources along the micro-tube. This external magnetic field is related to some solenoids, which are turned on and off alternatively. Depending upon dragging speed of these pistons, which itself is a function of switching time, this device can be used to either increase (pumping) or decrease (valving) the flow rate of the carrier fluid. In this research the observations of pistons forming process and the related phenomena were investigated for different switching times in a pressure driven flow setup. In the first part of the experiments, the variation of flow rate versus switching time was investigated with nickel particles of less than 10 micron in diameter and (0.25gNi)/(100ccH2O) concentration in water at the optimum switching mode. In the next part, keeping all the parameters fixed, the effect of the pressure head variation on the flow rate was inspected.
Optimization of Fluid Flow in 3D Bipolar Plates
Authors: Wu Jianfei , Nie Jianhu , Chen Yitung
Published: July 2009

In order to enhance the performance of Polymer Electrolyte Membrane (PEM) hydrogen production or fuel cell, optimizing of water flow distribution between channels is a necessary and effective way. To achieve this, 3D numerical simulations of the water flow along bipolar plate were performed. One baseline design and other five types of modified bipolar plates were investigated, which are under one design conception with gradually increasing contact angles to the header axle. The simulation showed that the high velocity appears at the lateral channels and the most promising velocity distribution, in this design, appears at the last case, which has the largest contact angle with header line.