bluuebunny/crossref_metadata_2025 huggingface dataset:
Threshold Stress for Crack-Healing of Silicon Nitride Ceramics
Authors: Takahashi Koji , Ando Kotoji , Yoshida Shoko , Saito Shinji
Published: August 2008

Si3N4/SiC composite ceramics were hot-pressed in order to investigate the crack-healing behavior under stress. Semi-elliptical surface cracks of 100 μm in surface length were introduced on each specimen. The pre-cracked specimens were crack-healed under cyclic or constant bending stress of 5 Hz at healing temperatures of 1000° and 1200°C and the resultant bending strength and fatigue strength were studied. The threshold stress for crack-healing, below which the pre-cracked specimens recovered their bending strength, was investigated. The mechanisms of crack-healing in Si3N4/SiC under stress were also discussed.
Development of a Thermal Fatigue Screening and Evaluation Methodology for Pressurized Water Reactor Plants
Authors: Keller J. D. , Bilanin A. J. , Rosinski S. T.
Published: August 2008

Thermal cycling has been identified as a mechanism that can potentially lead to fatigue cracking in un-isolable branch lines attached to pressurized water reactor (PWR) primary coolant piping. A significant research and development program has been undertaken to understand the mechanisms causing thermal cycling and to develop models for predicting the thermal-hydraulic boundary conditions for use in piping structural and fatigue analysis. A combination of first-principles engineering modeling and scaled experimental investigations has been used to formulate improved thermal cycling modeling tools. This paper will provide an overview of the model development program, a summary of the supporting test program, and a description of the thermal cycling model structure. Benchmarking of the thermal cycling model against several PWR plant configurations is presented, demonstrating favorable comparison with cases where thermal stratification and cycling has been previously observed.
Spectra Thermal Fatigue Tests Under Frequency Controlled Fluid Temperature Variation: Development of Test Equipment and Preliminary Tests
Authors: Kasahara Naoto , Hasebe Shinichi , Kobaysashi Sumio , Ando Masanori , Kawasaki Nobuchika , Morita Hiroshi
Published: August 2008

High cycle thermal fatigue induced by fluid temperature fluctuation is one of the important issues in nuclear plants. JNC has proposed a fatigue evaluation method paying attention to temperature attenuation related with frequency of fluctuation. In order to clarify the frequency effect of fluid temperature fluctuation on the crack initiation and propagation, a sodium temperature controlled thermal fatigue test equipment (SPECTRA) was developed. This equipment is capable of preciously controlling sodium temperature variation under various frequencies with a constant flow rate. This performance was achieved by the control of electromagnetic pumps without mechanical valve operations. Specimens are long straight pipes where temperature fluctuation ranges gradually reduce from upstream to downstream. As preliminary tests, temperature measurement and fatigue experiments were conducted. Measured temperature was preciously controlled under various frequencies. Cracks were observed in upstream area of a specimen. From above results, capability of frequency controlled test by SPECTRA facility was confirmed.
A Structured Approach to Resource Allocation
Authors: Bott Terry F. , Eisenhawer Stephen W.
Published: August 2008

Allocating limited resources among competing candidates is an important problem in management. In this paper, we describe a structured and flexible approach to resource allocation using logic-evolved decision (LED) analysis. LED analysis uses logic models to generate an exhaustive set of competing alternatives and the inferential model that is used for preference ordering of these alternatives. The inferential models can use data in numerical, linguistic, or mixed forms; uncertainty in the evaluation results can be expressed using probabilistic- or linguistic-based methods. We illustrate the use of LED analysis for an allocation problem with numerical input data and for an allocation problem with only linguistic input data.
Reliability Analysis of the Tube Hydroforming Process Using Fuzzy Sets Theory
Authors: Li Bing , Metzger Don R. , Nye Tim J.
Published: August 2008

Tube hydroforming currently enjoys increasingly widespread application in industry, especially in the automotive industries, because of several advantages over traditional methods. Reliability analysis as a probabilistic method to deal with the probability of the failure of the structure or the system has been widely used in industry. A new reliability analysis approach for the tube hydroforming process using the fuzzy sets theory is presented in this paper. The stress of the hydroformed tube is related to several parameters, such as geometry, material properties, and process parameters. In most cases, it is difficult to express in a mathematical formula, and its relative parameters are not random variables, but the uncertain variables that have not only randomness but also fuzziness. In this paper, the finite element method is applied as a numerical experiment tool to find the statistical property of the stress directly by a fuzzy linear regression method. Based on the fuzzy stress-random strength interference model, the fuzzy reliability of the tube hydroforming process can be evaluated. A tube hydroforming process for cross-extrusion is then introduced as an example to illustrate the approach. The result shows that this approach can be extended to a wide range of practical tube hydroforming process.
Application of a Multi-Objective Optimization to Risk-Based Inservice Testing
Authors: Virulsri Juksanee , Sakai Shinsuke , Izumi Satoshi , Iwasaki Atsushi
Published: August 2008

This paper proposes a methodology to apply a multi-objective optimization to risk-based inservice testing with robustness. The multi-objective optimization is applied to solve the trade-off between maintenance costs and unavailability of a standby system and then assist in determining the robust solution. In order to obtain the most robust solution, the decision-making method for the multi-objective optimization in the viewpoint of robustness is proposed. The risk ranking and revising risk-ranking processes are then used to assist in finding the most optimal surveillance test interval based on risk management. The applicability of the proposed methodology is confirmed by case studies for a standby system of a simplified high-pressure injection system (HPIS) in a nuclear power plant’s pressurized water reactor (PWR). The results showed that the proposed methodology provides the effective scheme to achieve the most optimal surveillance test interval based on risk and robustness.
Laboratory Scale Experimental Simulation of a Pipe Rested on a Saddle Supporting System for Verification of Numerical Modeling
Authors: Blyukher Boris , Niezgoda Tadeusz , Malachowski Jerzy , Szymczyk Wieslaw , Ochelski St. , Kiczko A.
Published: August 2008

The paper presents results of preliminary experimental and numerical tests over research and development of the numerical, FEM (Finite Elements Method) based method of pipeline strain/stress condition assessment with the use of data possessed from inline inspection tool. At the beginning, the research is focused on an example of a typical flaw which may be detected in oil or gas transporting pipeline by Geometry Measuring Pipeline Intelligent Gauge (Geo-PIG) during inline inspection. Such a typical flaws are dents and folds in the pipe which rests on a supporting concrete block or other type of saddle supporting system. The research method is based on numerical simulation and analysis. But it must be verified experimentally. For the needs of experimental verification of the numerical method tests were conducted at laboratory scale. Artificial dents, folds, and ovalizations were created with the use of material strength testing machine for samples of weldless thin walled pipe rested on specialized stand, simulating a saddle supporting system. The process of buckling during the three-point bending test took place close to the middle support with visible local buckling in the pipe wall. The experiment was conducted under the strict control, enabling measurements of deformations and strains in selected points located on external surface of the pipe wall. Since the Military University of Technology (MUT in Warsaw) itself is not a provider of inline surveys with the use of Pipeline Intelligent Gauge PIG), the substitutive equipment was used for deformation measurements on tested pipes with so called “digitizing arm” which was the analogue of the real inline inspection tool. The use of 3D digitizing arm was successful. The data collected with the use of this tool are coherent and may be used for verifications of FEM modeling. The preliminary numerical test models for the experiment simulation are also presented. The only disadvantage of laboratory tests was that they do not allow to conduct investigation on pressurized pipe for technical as well as for safety reasons. Experimental research on deformations and strains conducted for bent pipes will allow verifying strains and stress distributions obtained from numerical calculations. This will allow improving methods of numerical simulations.
A Structural Integrity Evaluation for the Interference-Fit Flywheel of Reactor Coolant Pump
Authors: Park J.-S. , Song H.-C. , Yoon K.-S. , Choi T.-S. , Park J.-H.
Published: August 2008

In this study, stress analyses and structural integrity evaluations for an interference-fit flywheel assembly of reactor coolant pump are conducted. Finite element stress solutions of the flywheel assembly at the standstill, normal operation speed, design overspeed and joint-release speeds, are obtained. For evaluations of structural integrity of the flywheel with surface cracks, considering ductile and non-ductile fracture, stress intensity factors of a series of surface or edge cracks postulated are also obtained by using the finite element alternating method. In the analyses, release of deformation-controlled stresses caused by structural interactions with centrifugal loads during rotation is considered. Results of stress and fracture evaluations are presented, including the primary and secondary stresses, applied stress intensity factors and the fatigue crack growth rates in the flywheel disc. For the interference-fit flywheel design and material conditions investigated, it is found that fatigue crack growth rates of smaller surface cracks in the flywheel are negligible. The material resistance to non-ductile fracture in terms of material KIC and RTNDT is the governing factor for the structural integrity of the flywheel with larger surface cracks.
High Pressure Fluctuations Induced by Safety Valves Operating With Liquids at Very Low Lift
Authors: Dossena V. , Marinoni F. , Di Vincenzo S. , Boccazzi A. , Sala R.
Published: August 2008

This paper deals with the valve disc vibrations occurring during safety valve opening transient. These vibrations always induce pressure fluctuations that are not damped if pressure is not sufficiently increased. The tests, performed on three different safety valves, showed heavy pressure fluctuations in the valve inlet connecting pipe. For connecting pipe lengths over 0.7 m, excessive pressure fluctuations were measured even in the protected device. The analysis of vibration inception and development is presented, showing that the phenomenon is driven by an harmonic self-exited motion of the valve disc coupled to a standing wave system in the connecting pipe. Vibration frequencies always strongly exceeded the spring-disc natural frequency, meaning that the disc movement occurred between a fixed position of the stem head and the disc seat on the nozzle. No impact on this latter surface was ever detected. On the contrary, significant damages of the stem-disc coupling were observed. Finally, the influence of plant and valve parameters that affect the pressure fluctuation amplitude is presented and discussed.
Model for Vibration of Rotating Beams Supported by Flexible Foundation and Driven by DC Motor
Authors: Abed A. , Al-Bedoor B. O. , Al-Qaisia A. A.
Published: August 2008

This paper presents a mathematical dynamic model of a flexible arm-flexible-foundation manipulator driven by a DC motor. The mechanical system equations of motion are derived using the Lagrangian dynamics, the assumed modes method and the condition of inextensibility, the foundation flexiblility is represented by two linear springs in the vertical and the horizontal directions. The simple DC motor theory is borrowed and augemented to the mechanical model through the motor torque and hub angular velocity. The system produced is a nonlinear system that is electromechanically coupled and presented in state space. Simulation results showed the effects of root flexibility and the arm attachment angle on the system dynamics. The spectrums of the tip deflection and the armature current showed that the electrical current carries the arm vibration signature.
Developing an Efficient, Predictive, Risk Based Inspection/Maintenance Program for Recovery and Power Boilers
Authors: Peterson Rick
Published: August 2008

Risk Based Inspection (RBI) is intended to be a simple, logical, repeatable, documented method of determining equipment inspection frequencies and inspection scopes/methods. With consistent boiler tube thickness measurements, developed boiler tube engineering standards and well documented inspection/repair information, it is possible to set up an effective RBI program for predicting boiler component conditions and accurately plan boiler inspections/repairs far into the future. Inspection efforts are then concentrated, logically, on the documented ‘problem’ and high risk areas of the boiler. Inspection scopes and frequencies are reduced on the more benign, low risk areas. All boiler components will have documented and accepted justifications detailing how the component inspection scopes and frequencies were developed.
Application of Risk-Based Inspection and Maintenance Planning to a Range of Power Generation Equipment
Authors: Worswick David , Tan George , Badrol Ahmad
Published: August 2008

In general, benefits from adopting a risk-based inspection and maintenance (RBM) strategy for power generation plant may accrue from the following: • Increased plant reliability/availability leading to a reduction in unit operating cost and increased competitiveness. • Reduced cost exposure to future failure of equipment. • Reduced inspection and maintenance expenditure. • Justification for extended run periods between statutory inspections of plant. The particular benefit(s) derived depend primarily on the extent and appropriateness of the maintenance and inspection programs carried out previously. AEA Technology has developed a practical methodology and associated software for RBM planning of power generating plant. In conjunction with our clients, we have conducted numerous studies over the past five years covering a wide range of equipment. This paper briefly describes the RBM planning methodology and software, and summarizes a series of Case Studies to demonstrate its generic applicability, practicability and benefits. The Case Studies address the following equipment: • A steam turbine. • Fired boilers. • Hydro turbines. • A heat recovery steam generator.
Justifying the Use of High Integrity Pressure Protection Systems (HIPPS)
Authors: Marszal Edward M. , Mitchell Kevin J.
Published: August 2008

As chemical plants and petroleum refineries plan for future expansion, the capability of existing pressure relief systems to safely dispose of higher capacities is often a significant constraint. Current codes and standards now allow for the use of High Integrity Pressure Protection Systems (HIPPS) in lieu of increasing the capacity of emergency relief systems. There is a significant body of knowledge on how to design a HIPPS system once the requirement for one has been established. However, there is gap in knowledge of what situations allow for HIPPS and what practical steps can be taken to determine when a HIPPS is justified. This paper describes the analytical techniques that can be used by engineers to justify a design using instrumented protection in lieu of upgrading the relief system. A review of applicable requirements from codes and standards is included along with risk-based methods to ensure a HIPPS design is as safe as — or safer than — conventional relief design.
Thermal Interaction From Hot Liquid Entering a Cold Pipe
Authors: Galbally D. , Moody F. J.
Published: August 2008

There are many transient sequences in the energy industry where a hot or cold liquid enters a flow passage that is at a different temperature. Thermal energy is transferred by convection between the liquid and the boundary of the flow passage, causing both temperatures to change with time at all locations as the liquid column moves. This paper presents a theoretical analysis of transient heat transfer between an axial liquid flow at constant velocity V and the walls of the flow passage, which are in contact with constant temperature surroundings. A general nondimensional model that includes internal heat generation from the fluid flow is formulated and solved analytically for various cases such as obtaining the freezing point of a heated liquid material that solidifies after the flow passage extracts enough of its initial thermal energy. Analytical solutions for thin-walled pipes, temperature history at pipe entrance and temperature of the moving liquid front are also provided in this study. A simple numerical scheme is proposed in order to calculate liquid and passage wall temperatures at general points of the time-space domain where analytical solutions have not been obtained.
Investigation of Steam Desuperheater Waterhammer
Authors: Zysk Gregory
Published: August 2008

Steam supplied to an underground piping distribution network from a fossil fired boiler is desuperheated using water injection valves. Waterhammers occurred in the system, failing a valve on two separate occasions. Operations personnel also experience excessive high-level alarms at drain stations local to the valves. An investigation was conducted to determine the root cause of the valve failures and the cause of the excessive water in the steam system. Mitigating design changes were also proposed to solve these problems. Available analytical methods were shown to be effective in predicting waterhammer occurrence and magnitude. These methods can be used to evaluate the potential for waterhammer in similar systems with potential steam/water interaction.
Numerical Prediction of Homologous Curves for the SMART MCP
Authors: Kim Min-Hwan , Kim Jong-In , Kim Dong-Ok , Lee Jae-Seon , Park Jin-Seok
Published: August 2008

A procedure for generating preliminary homologous curves, which are used as an input for the safety analysis of SMART, was developed. A commercial code for the computational fluid dynamics was adopted as a tool for the procedure. To generate homologous curves, we define the homologous variables and construct a computational matrix. Computations were performed according to the matrix, and the results were compared and analyzed for the representative computational points among the matrix. A modification method to obtain the homologous curves from the results was suggested by using the similarity laws and the complete curves were generated. The curves were compared with available experimental data and the validity of the procedure was investigated.
Prediction of Foreign Object-Caused Fretting-Wear on Helical Tubes in the Single-Phase External Flow Field
Authors: Jo Jong Chull , Jhung Myung Jo , Kim Woong Sik , Kim Hho Jung
Published: August 2008

This paper presents the prediction of fretting-wear on helical tubes caused by foreign object in an operating helical coiled steam generator. The thermal-hydraulic conditions of both tube side and shell side flow fields are predicted by a general purpose computational fluid dynamics code employing the finite volume element modeling. Modal analyses are performed for the finite element modelings of helical tubes to get the natural frequency, corresponding mode shape and participation factor. The wear rate of helical tube caused by foreign object is calculated using the Archard formula and the remaining life of the tube is predicted. Also, discussed in this study are the effects of flow velocity, internal pressure, tube-to-foreign object contact angle, and vibration of the tube on the remaining life of the tube.
Underwater Explosion in a Pool and Damage Assessment: A Global Approach From Far-Field to Close Range
Authors: Loiseau O. , Cheval K. , Autrusson B.
Published: August 2008

The concern of this paper is the study of the effects of the detonation produced by an underwater explosive device. This work applies in particular to the study of some industrial pools, filled with water and a few meters deep. These pools are generally build so as to ensure a certain watertightness, this function being obtained for instance by the adjunction of an internal liner, a few millimeters thick and made of stainless steel. Here, we focus on the possible loss of this function both by the damage caused to concrete and the perforation of the liner. Those damages could be either due on one hand to the local deformations related to the global structure response and on the other hand to the local effects of the explosion. The first aspect has been investigated previously, using in particular the so-called “Method of Images (MOI)” (F. Delmaire-Sizes et al, 2001). The second aspect only occurs when the device is in a sufficiently close range so that the pressures produced by the detonation can cause volumetric damage into the materials. The starting point of this second phenomenon is investigated in the paper on the basis of a numerical model for concrete under high pressure and high strain rates (T. J. Holmquist, 1993). The second phenomenon comes in addition with the first one. An example is conducted showing how numerical simulations for the local analysis, coupling Eulerian and Lagrangian computations, complete the previous global analysis.
Work of Shaking Table
Authors: Minowa Chikahiro , Chiba Toshio
Published: August 2008

To improve the reliability of the structure under the severe earthquake, many shaking table tests have been conducted. In the shaking table tests, the test model on the shaking table was excited by the acceleration wave. In the shaking table test, it is important to account for the input energy and work by the shaking table on the test model. From an energy point of the view, the input energy of the shaking table test is discussed.
A Computational Approach to Assessing Blast Damage in Urban Centers Using AUTODYN
Authors: Cowler Malcolm S. , Quan Xiangyang , Fairlie Greg E.
Published: August 2008

Recent terrorist attacks have prompted considerable interest in predicting damage to structures that could result from explosive blasts in densely populated urban environments. This is a particular concern for government and military organizations wishing to improve the safety of facilities and insurance providers who want to quantify risks. Blast waves from explosions are characterized by a shock front propagating into the surrounding air, followed by an exponential decay in pressure. Structural damage can be caused by either the magnitude of the peak pressure or the impulsive loading over time. Thus, any assessment of damage requires accurate computation of the entire pressure history on the structure. Semi-empirical approaches, such as CONWEP, although able to predict free-field and single-reflected pressures accurately, are unable to account for the effect that the urban environment has on amplifying, dissipating or focusing the blast wave. This paper describes a numerical finite difference approach, using the non-linear dynamics program AUTODYN, which allows an accurate prediction of the pressure fields that develop as a blast wave propagates through an urban environment by recursively remapping the solution through numerical regions that expand to track the evolving shock front. Data for specific urban layouts can be imported into AUTODYN from geographic information system (GIS) services.
Peridynamic Modeling of Impact Damage
Authors: Silling S. A. , Askari E.
Published: August 2008

The peridynamic theory is an alternative formulation of continuum mechanics oriented toward modeling discontinuites such as cracks. It differs from the classical theory and most nonlocal theories in that it does not involve spatial derivatives of the displacement field. Instead, it is formulated in terms of integral equations, whose validity is not affected by the presence of discontinuities such as cracks. It may be thought of as a “continuum version of molecular dynamics” in that particles interact directly with each other across a finite distance. This paper outlines the basis of the peridynamic theory and its numerical implementation in a three-dimensional code called EMU. Examples include simulations of a Charpy V-notch test, accumulated damage in concrete due to multiple impacts, and crack fragmentation of a glass plate.
Elaboration and Introduction of the Methodics of Non-Destructive Inspection (Control) of Physical-Mechanical Properties of NPP Pressure Vessels
Authors: Bakirov M. , Potapov V. , Zabruskov N. , Vystavkin I. , Levchuk V.
Published: August 2008

Resource of reactor with PWR is defined, in the first instance, by foundation of integrity of the third physical barrier of safety. The third physical barrier of safety provides a reliable keeping of the coolant in the boundaries of NPP primary circuit. More than thirty year history shows, that reactor vessel is a weak spot in this barrier, the metal of the pressure vessel is subjected to intensive irradiation. The mechanism of operational damage of pressure vessel steel is represented in Fig. 1. This article describes the works, which were conducted by VNIIAES during the last years in the field of elaboration of specimen-free methods and means of inspection (control) of physical-mechanical properties of pressure vessels welds metal of NPPs with PWR. On the base of analysis of that factors, which exercise the most substantial influence on the irradiation embrittlement of pressure vessel materials and on the base of distribution of these factors by degree of significance, there were selected the most appropriate specimen-free methods of inspection: kinetic indentation and kinetic magnetising. It was presented the description of the specimen-free methods, devices and of the results of laboratory measurements, and also the description of the manufacturing procedure and the procedure of certification of the methods on full-scale slabs from WWER-1000 pressure vessel. In the article also is described the example of using of the specimen-free methodics by full-scale inspection (control) of the metal of reactor internal components and of pressure vessel of WWER-1000 of Rostov NPP Unit 1.
Corrosion Damages on Piping System and Problems of the Inspection Maintenance
Authors: Hara Yasuhiro , Yokono Yoshikazu
Published: August 2008

Petroleum and petrochemical industries in Japan, the post construction code of piping in 20021), the post construction code of vessels and drums were enacted by Japan Petroleum Institute (JPI) respectively. These codes include practice along with 6 JPI recommended practices established in 20032). This paper discusses mainly a diagnosis method for chemical plant piping showing the implementation process for maintenance of in-site piping units in Japan maintenance companies, taking also the API method that is being employed recently in Japan into consideration.
Corrosion of Aluminized Steel in Seawater
Authors: Kimoto Hiroki
Published: August 2008

The influence of flow rate of seawater on the corrosion rate of hot-dipped aluminized steel in seawater was investigated using the following galvanic couples: aluminum/carbon steel, aluminum/Fe-Al alloy, aluminum/stainless steel, Fe-Al alloy/carbon steel, Fe-Al alloy/stainless steel, and carbon steel/stainless steel. The corrosion rate of aluminum in all the couples was greater than that of aluminum not connected with other metals. The corrosion rates increased in the following order: aluminum/carbon steel > aluminum/stainless steel > aluminum/Fe-Al alloy. Aluminum connected with carbon steel had the greatest corrosion rate: seven times of the rate of aluminum that was not connected with other metals. The galvanic corrosion rate of carbon steel is 1.9 to 2.5 times greater than that of carbon steel that is not connected with other metals.
Assessing the Effects of Vibratory Loading on Pipelines Using Analysis and Monitoring Techniques
Authors: Alexander Chris , Runte Dave , Long Randy
Published: August 2008

This paper provides the methods and results associated with an engineering assessment for a project involving pile driving adjacent to an active 6-inch (152 mm) nominal diameter gas pipeline. The pile driving was associated with the expansion of the I-95 Highway located in Daytona Beach, Florida. The work involved analysis, metallurgical field evaluation, and measurement of strain and acceleration in the pipe during the pile driving. The analysis involved using finite element methods to predict stresses in the pipe using acceleration loads provided during a previous pile driving exercise. Using a range of soil stiffness values, the calculated bending stresses in the pipeline ranged from 50 to 2,000 psi (0.3 to 13.8 MPa). Even with the most compliant soils, the stress was relatively low compared to the hoop stress created by an internal pressure of 500 psi (3.4 MPa). The metallurgical field investigation involved careful inspection of the pipe quality, including field replication and determining the carbon content of one weld. The strain measurements indicated that the stress levels in the pipe were below design stress limits and that the short-term pile driving loads did not inflict serious injury to the line. Findings of the investigation indicated that the pipe had been well-maintained over its 40 year life and that no measurable corrosion was present. This project demonstrates the benefits derived in using a range of engineering disciplines and capabilities to ensure safety in conducting potentially-damaging activities adjacent to active gas pipelines.
Structural Integrity Assessment for Various Failure Modes Using a Risk-Based Maintenance Method
Authors: Horikawa Hiroyuki , Yoshikawa Masaki , Takasu Nobuo
Published: August 2008

In this paper, a newly developed system called RBM (Risk-Based Maintenance) is presented. The system is used to describe the structural integrity of buried pipeline based on the index of risk that is defined in the product of the failure frequency and the consequence. Various failure modes corresponding to each degradation mechanism are included, and the estimation of failure probability that the external load exceeds the structure resistance is carried out. As the result of trial evaluation compared with the past earthquake incident, it is in good agreement with actual damage of pipeline subjected to liquefaction and large ground deformation. Furthermore, the system enables operators to maintain the structural integrity for service life by providing the most optimized maintenance plan according to the risk level. The features of the quantitative risk evaluation approach and the benefits of the developed RBM system as a means of structural integrity assessment are also discussed.
Application of Unsteady Flow Analysis Using the Vortex Method to the Design of Pump Sumps
Authors: Yamamoto Yukihiro , Yoshida Tadashi
Published: August 2008

For reduce of cost to construct urban drainage pump station, the efforts to design compact and high-velocity pump sumps has been made. It is necessary to investigate the generation of harmful vortex to design such smaller pump sump, but model test is mainly used for the investigation. In the present paper, the vortex method is applied to the numerical simulation of unsteady and three-dimensional flow in suction pit of drainage pump station, and air-intake vortex and submerged vortex cavitation is investigated and predicted. In the first step, on extremely different two variables of velocity, frequency to generate vortex is found out from pressure fluctuation on the flow by the vortex method, and it is confirmed that calculated frequency is comparative close to experimental value.
Lobed Mixer Analysis for Design Assessment and Improvement
Authors: Reich Alton J. , Underwood Mark L.
Published: August 2008

Lobed mixers have been the subject of research and development since the 1950s. The turbulence driven nature of the mixing process has been difficult to capture using CFD analysis, and much of the work performed to-date has been via experimental studies. This paper presents some of the findings from an on-going project to utilize analysis to assess the performance of a lobed mixing device, and several potential geometry modifications.
Research of Revised Thermal Design Parameter Optimization With Response Surface Method Application for Fitness Function
Authors: Nakanishi Tohru , Okamoto Keishi , Koyamada Koji , Kotera Hidetoshi
Published: August 2008

For the thermal management of the electric products, the compact modeling method is commonly applied to the numerical analysis with the simplification of the each component used in the products, on the view point of the best thermal design. In the generation of the compact modeling, the method that the model parameters are optimized toward to the fitness between the temperature value of numerical analysis result and the actual hardware testing data, is conventionally used, with some monitored points which are given in advance. In this parameter optimization, the fitness function is to be 1 on the no (0) temperature difference between them at all monitored locations, and on the other hand, that is to be 0 if the temperature difference between them is infinite. However, it was found that this conventional method brought the fitness function shape of one sharp mountain, as the analysis result, and the method, that represented the fitness function with the quadratic polynomial, caused the important problem on the view point of the analysis quality if the Response Surface Method is used of the parameter optimization. Therefore in this research to resolve this problem, we suggest the method that the response surfaces, which are based on the heat conduction law, are composed for each monitored location, and the fitness function is given with these surfaces. This method is applied into some compact modeling and the benefit is verified. The meanwhile of the temperature difference between the numerical analysis result and the solution field is decreased half, and the divergence makes one-tenth decrease.
Nanotechnology: An Overview and Opportunities for Computational Modeling
Authors: Meyyappan M.
Published: August 2008

Nanotechnology is an enabling technology that is expected to have an impact on electronics, computing, data storage, materials and manufacturing, health and medicine, energy and environment, national security and other sectors. Fundamental to all this is development of nanostructured materials with novel and interesting properties. Examples include carbon nanotubes, inorganic nanowires, nanoparticles, quantum dots, dendrimers, etc. characterization of these nanomaterials and understanding their properties is the next important aspect of research in nanoscience and technology. Beyond these comes application development: devices, sensors, nanoelectromechanical systems (NEMS), composites, etc. to name a few. The talk will provide an overview of the above with carbon nanotubes (CNTs) and inorganic nanowires as nanomaterial examples.
Computational Analysis of Heat Transfer Enhancement Due to Rectangular Ribs in a Turbulent Duct Flow
Authors: Chaube Alok , Sahoo P. K. , Solanki S. C.
Published: August 2008

A computational analysis of heat transfer enhancement due to artificial roughness in the form of rectangular ribs has been carried out. A turbulence model is selected by comparing the predictions of different turbulence models with experimental results available in the literature. A detailed analysis of heat transfer variation within inter rib region is done by using the selected turbulence model. The analysis shows that peak in local heat transfer coefficient occurs at the point of reattachment of the separated flow as observed experimentally. The results predict a significant enhancement of heat transfer in comparison to that for a smooth surface. There is a good matching between the predictions by SST k-ω and experimental results.
A Pragmatic Coupling Strategy Between Commercial CFD and Structure Analysis Codes
Authors: Smith Brian L. , Dury Trevor V. , Ni Liping , Zucchini Alberto
Published: August 2008

The paper describes how a simple link has been established between the commercial Computational Fluid Dynamics (CFD) code CFX-4 and the two commercial structural analysis software packages ABAQUS and ANSYS. The interface has enabled separate, specialist groups to perform conjugate heat transfer and stress analysis computation within a common project, without the need to lease expensive interface software. The fluid/structure coupling operates primarily in steady-state mode, though transient coupling is possible at specified time intervals, provided there is no feed-back of the structural displacement on the thermal hydraulics. Illustrative examples are presented in the paper of how the coupled codes are being used to aid the design of a pilot spallation source target, and to analyze operational transients and accident sequences.
Simulation of a Magnetorheological Damper With a Combination of a Commercial CFD and FEA Code
Authors: Zschunke F. , Brunn P. O. , Steven M.
Published: August 2008

Magnetorheological fluids (MRFs) show a high but reversible rise of viscosity upon application of an external magnetic field. This effect can be utilized in controllable dampers, when a deep understanding of the mechanisms for this behavior is available. Today the design of dampers is still quite empiric so it is favorable to be able to simulate the damper geometries first. Measurements on MR dampers are shown and compared with the results of a combined simulation of the problem with a CFD code for the flow and a FEA code for the magnetic field distribution in the damper geometry. It is shown that the flow resistance of the orifices that corresponds to the damping force of the damper can be predicted with this simulation using a simple fluid model.
Modeling and Simulation of the Injection Compression Molding Process
Authors: Stoll Henning , Hofer Thomas , Fritz H.-G.
Published: August 2008

The Injection Compression Molding (ICM) technique allows the cost-effective production of complex, thin-walled polymer parts. ICM offers the possibility to direct laminate a decorative layer on the application (in-molding/back molding). Crucial to the quality of the application is the mold design and the process control. Errors in process control might be correctable later on, errors in the mold design mostly aren’t. To avoid this, computer aided calculations that describe the mold filling process are necessary. Fillflow®, a software developed at the Institut fu¨r Kunststofftechnologie (IKT), is capable of simulating several different compression/injection molding processes. This article describes the mathematical and numerical model used for Fillflow®, shows the structure of the software design and results from a verification with an industrial-sized automotive part.
Prediction of Ring Crevice Hydrocarbons Depending on Some Engine Parameters
Authors: Yildirim A. Murat , Gu¨l Zafer
Published: August 2008

The model consists of three major submodels. First is prediction of time-varying composition of combustion gases, second is modelling the release of the ring crevice HC’s during late expansion and exhaust stroke and the last one is a simple phenomenological approach for calculation of temperature variation with crank angle. Valve overlap period is excluded in the solution. It is necessary for 2d-solution. Continuity and Navier-Stokes equations are solved. But instead of energy equation, above mentioned phenomenological submodel is introduced for calculation of temperature. Oil film HC’s and postflame oxidation are excluded, as for the last, solution procedure enhances the period after which in cylinder oxidation ceases. Result are presented at the extend limited counterparts allow, due to the lack of common parameters adapted in different studies amongst plenty of them. HC versus engine speed, inlet pressure, equivalence ratio, compression ratio, ignition time and crank position at which combustion ends are plotted.
A Study of the Accuracy, Global Performance, and Computational Expenses of k–ε, k–ω, and RSM Turbulent Models for Flow in an Industrial Static Mixer
Authors: Rahmani Ramin K. , Keith Theo G. , Ayasoufi Anahita
Published: August 2008

Viscous liquids have to be homogenized in continuous operations in many branches of processing industries; and therefore, fluid mixing plays a critical role in the success or failure of many industrial processes. The use of static mixers has been utilized over a wide range of applications such as continuous mixing, blending, heat and mass transfer processes, chemical reactions, etc. Consequences of improper mixing include non-reproducible processing conditions and lowered product quality, resulting in the need for more elaborate downstream purification processes and increased waste disposal costs. This paper extends previous studies by the authors on an industrial helical static mixer and illustrates how static mixing processes of single-phase viscous liquids can be simulated numerically. It also intends to present an improved understanding of the turbulent flow pattern for single-phase liquids through the mixer. Three-dimensional finite volume simulations are used to study the performance of the mixer for a range of practical Reynolds numbers, using three different turbulent models: k–ε model, k–ω model, and RSM model. The accuracy, global performance and costs of the different turbulent models have been examined. The flow velocities, pressure drops, etc. are calculated for each model. The calculated pressure drop of each case is compared with experimental results. Using different tools, the mixing results obtained from the different models are studied and compared.
Multiscale CFD of the Flow, Heat and Mass Transfer Through a Porous Material With Application to Protective Garments
Authors: Sobera M. P. , Kleijn C. R. , Brasser P. , van den Akker H. E. A.
Published: August 2008

A multi-scale study of the performance of protective clothing has been performed by coupling various types of numerical simulation of flow, heat and mass transfer. At first, a detailed study of the turbulent flow at Re = 3900 around a circular cylinder, sheathed at some small distance by a porous layer, has been performed by means of Direct Numerical Simulations with a commercial unstructured finite volume based Computational Fluid Dynamics solver. This geometry is widely used in experiments to study the performance of fabric materials. From this DNS study, it was found that the flow underneath the clothing is laminar and periodic, with a velocity magnitude much smaller than the free stream velocity. Micro-scale Direct Numerical Simulations of the flow through the textile at the scale of individual fibres revealed a simple relation between textile porosity and permeability. A good agreement was found between flow and heat transfer predictions of Direct Numerical Simulations and from Reynolds Averaged simulations. From the latter, an engineering correlation for heat and mass transfer was deduced.
CFD Simulation of a Hydraulic Servo Valve With Turbulent Flow and Cavitation
Authors: Chen Q. , Stoffel B.
Published: August 2008

In this paper the internal flow in a hydraulic servo valve was investigated. The objectives of this research work were to investigate the turbulent flow and the cavitation phenomenon in the valve by using numerical simulation method in the form of CFD (Computational Fluid Dynamics). The geometry of this valve is described by a 3D model and hybrid mesh elements — tetrahedron and hexahedron — are applied to generate the necessary computational meshes for the further calculation. Using the CFD commercial code FLUENT, the internal flow was studied for the turbulent flow situation. In addition, cavitation phenomenon was also investigated with the multiphase model and standard k-ε turbulence model. Simulation results show that the flow in this valve is characteristically turbulent and the cavitation emerges actually in the small gap region between the spool and the valve base.
Immersive Visualization of Dynamic CFD Model Results
Authors: Comparato Joseph R. , Ringel Karen L. , Heath Daniel L.
Published: August 2008

With immersive visualization the engineer has the means for vividly understanding problem causes and discovering opportunities to improve design. Software can generate an interactive world in which collaborators experience the results of complex mathematical simulations such as computational fluid dynamic (CFD) modeling. Such software, while providing unique benefits over traditional visualization techniques, presents special development challenges. The visualization of large quantities of data interactively requires both significant computational power and shrewd data management. On the computational front, commodity hardware is outperforming large workstations in graphical quality and frame rates. Also, 64-bit commodity computing shows promise in enabling interactive visualization of large datasets. Initial interactive transient visualization methods and examples are presented, as well as development trends in commodity hardware and clustering. Interactive, immersive visualization relies on relevant data being stored in active memory for fast response to user requests. For large or transient datasets, data management becomes a key issue. Techniques for dynamic data loading and data reduction are presented as means to increase visualization performance.
Study of Energy Spectra of Turbulence by the Vortex Method
Authors: Ogami Yoshifumi
Published: August 2008

The energy spectra produced by the vortex method are studied. The strengths of the vortices are determined so that the energy spectra correspond to the given target spectra for two different integral scales. Velocity fluctuations produced by the simulation of vortex shear layer are obtained and energy spectra of these fluctuations are examined. It is found that in the case of the larger integral scale, the spectra almost agree with the target in the range up to the cut-off wave length, and that in the case of the smaller scale, the deviation of the spectra from the target is quite large.