bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of electrical discharge machining electrode via laser cladding
Authors: Tang Y. , Fuh J.Y.H. , Lu L. , Wong Y.S. , Loh H.T. , Gupta M.
Published: November 2002

The feasibility of building copper‐based electrodes for electrical discharge machining (EDM) via laser cladding is investigated as an application of rapid prototyping (RP). Two material systems‐Cu/W (with and without nickel) and Cu/B4C (with and without nickel) in certain compositions are selected for the experimental investigation. The laser claddings are realised via a 3000 W CO2 laser with suitable parameters. The micro‐structures of the electrodes are analysed with a SEM. The performance of the EDM electrodes is examined in terms of machining rate and wear rate.
A conceptual model for selecting and evaluating third‐party reverse logistics providers
Authors: Meade Laura , Sarkis Joseph
Published: November 2002

The selection of third‐party logistics providers is an intriguing practical and research question. With the development and advancement of reverse logistics concepts and practice, the selection of partners for the specific function of reverse logistics support becomes more important. This paper is one of the first to address this issue. The factors that play an important role in selecting a third‐party reverse logistics provider; such as a focus on end‐of‐life product organizational roles (e.g. recycling, reuse, etc.), differ from some traditional factors for supplier selection. How these new factors can be included for the selection of a partner is modeled within a decision‐making framework.
From commodity marketing to category management: insights from the Waitrose category leadership program in fresh produce
Authors: O’Keeffe Michael , Fearne Andrew
Published: November 2002

Looks at how Waitrose deals with commodity marketing and category management by examining its category leadership strategy, which aims to reduce costs and align its network to the needs of the consumer. Seeks to shed light on how this was achieved and the key lessons to be learned from this procurement strategy. Concludes that the category leadership strategy requires a fundamental shift in the role of the retailer and supplier as well as a redesign of the performance measurement systems, but once these are achieved there are significant and guaranteed rewards.
A general framework of supply chain contract models
Authors: Wang Charles X.
Published: November 2002

A supply chain is two or more parties linked by a flow of goods, information, and funds. When one or more parties of the supply chain try to optimize their own profits, system performance may be hurt. Supply chain contract is a coordination mechanism that provides incentives to all of its members so that the decentralized supply chain behaves nearly or exactly the same as the integrated one. We have seen a vast literature on supply chain contracts recently. However, little work has been done on the relationships of those supply chain contract models. In this paper, we provide a general framework that synthesizes existing results for a variety of supply chain contract forms.
POS and EDI in retailing: an examination of underlying benefits and barriers
Authors: Margaret Weber Mary , Prasad Kantamneni S.
Published: November 2002

During the past 20 years, US retailing has gone through a period of unprecedented change as consumer demands and competition have intensified. This change is being further stimulated by the development of e‐commerce. Study of successful retailers indicates that a retailer’s ability to successfully carve out and defend a competitive position in the marketplace depends, to a great extent, on its ability to make investments in and utilize information. The study described in this paper examined the use of technology in retailing. The purpose of this paper is to examine the underlying factors explaining why retailers adopt POS and EDI. The results indicate that retailers are adopting these technologies to achieve direct, indirect, and strategic benefits. These benefits take the form of improved inventory management, reductions in costs, and increased flexibility of response to customer demands.
The “locus of value”: a hallmark of chains that learn
Authors: Collins Ray , Dunne Tony , O’Keeffe Michael
Published: November 2002

The concept of knowledge as a strategic asset of a firm underpins the idea that the “learning” in a learning organisation can be a source of competitive advantage. The principles of learning organisations can also be applied to integrated supply chains, where they demonstrate the same potential to improve competitive advantage. Product flows in chains are linear, but relationships in chains may exist in clusters or nodes that are non‐linear because they involve more than two chain participants. Within these relational nodes, firms have enhanced prospects of learning from one another, and in the process they can create more value than could otherwise be possible. When added value is created through joint learning, a “locus of value” exists. We propose that a locus of value is the hallmark of a learning chain. It improves competitiveness and is difficult to emulate by competitors.
Simulations and supply chains: strategies for teaching supply chain management
Authors: Sparling David
Published: November 2002

The Beer Game is one of the most popular simulations used to introduce students to the challenges of managing supply chains. While the basic simulation serves as a useful introduction to the problems, it does not take the next step of helping students or managers plan to surmount those problems and manage an efficient supply chain. This paper suggests a strategy for taking that next step, helping students move toward solutions of supply chain problems. The strategy builds supply chain teaching modules or an executive development program around modified Beer Game simulations. This paper also provides the tools for accomplishing both an introductory and a more advanced simulation. These simulation‐based programs have proved highly effective and popular in undergraduate, graduate and executive development programs.
Managing the mental and emotional aspects of retirement
Authors: Butters Jean
Published: November 2002

Retirement may cause different mental and emotional reactions at different times to different individuals. Through the identification and management of these emotions, retirees tend to enjoy this hard earned leisure more. How the individual relates to and interacts with society plays a big role in the emotions associated with retirement. People retire differently and some believe men retire differently from women. This may be due to man’s involvement in his work identification and woman’s instinctive role as nurturer. The young retirees should view retirement as an opportunity to revisit a childhood dream, take risks, learn new things, and stay active.
Obstacles to distance training and education in corporate organizations
Authors: Berge Zane L.
Published: November 2002

While distance education is on a fast growth curve currently, there are many barriers that must be overcome. The results reported here are from persons working in corporate organizations (n=448). Takes the perspective that various organizations are at different stages or levels of capabilities with regard to distance education. The research questions reported are: do distance educators in the corporate sector perceive different barriers depending upon the maturity of their organization’s capabilities in distance education; and as the organization’s distance education competency as a whole matures, will the overall number or intensity of perceived barriers to distance education be reduced? The evidence from the responses to this survey indicates that there is a relationship between an organization’s level of capability in distance education and the barriers to distance education reported by respondents for some but not all barriers. The analysis of this survey also supports the proposition that corporate trainers and educators perceive fewer, or less intense, barriers in organizations that are more capable delivering distance education.
Moving to problem‐based learning in the NZ engineering workplace
Authors: Stonyer Heather , Marshall Lex
Published: November 2002

New Zealand’s future has been linked to the growth of a “knowledge economy”, specifically the growth, development and integration of scientific and technological advancement in our economy, through new and existing enterprises. Consequently, NZ must address how current and future generations of science, engineering and technology practitioners (at all levels) will have opportunities to develop the requisite skills and knowledge they need to contribute fully to “knowledge” enterprises. Reflecting on the current NZ industry‐based engineering training, an analysis of the factors contributing to the levels of training is presented. In response and with a view to improve the culture of training and learning in NZ enterprises, a shift from the standardised training approaches often associated with unit standards, to adopting a “problem based learning” model for workplace training is proposed. The implications for educating workplace trainers to deliver workplace training based on this model are also discussed.
Managing and developing online education: issues of change and identity
Authors: Wallace Michelle
Published: November 2002

When a workgroup of educators determines to develop an online teaching capability, a number of fundamental change issues become apparent. For the manager, the issues relate to effecting a change process that is inclusive, sustainable and strategic. For the educators, the issues relate to their pedagogy, work practices and the power relations of the group, challenging their identities as academics. This paper examines the learning and development of one work group engaged in innovation and critiques its processes and outcomes in the light of some theories of organisational and individual change and the construction of work identity. Recommendations are made for sustainable change in similar contexts.
Managing the issue of learning relevance in the formulation of corporate learning strategies
Authors: Dealtry Richard
Published: November 2002

Previous articles in this series, on the evolution of the corporate university as a dynamic future state business development platform, have described processes and methodologies for achieving both organisation and strategic learning re‐orientation for success. “Managing the corporate university learning curve”, in particular revealed the innovative nature and challenge facing corporate university executives in their quest to achieve customised structures, flexible learning processes and time durable intellectual properties in a new or amended company educational paradigm, defined as model 3. This derivative model espoused business excellence, focused business education processes and timely executive action. A key dynamic strand in the evolution of the corporate university concept in model 3 was identified as the “management of learning” strand. Takes an overview on the current state of the art in corporate learning management and the issue tensions that can arise in the preparation of a progressive and satisfying learning strategy. Relates to the main issues surrounding the energising of learning in organisations, the consequences of corporate learning policy and an outline methodology for appraising the main determinants of corporate learning strategy.
Learning from Bristol: reflections from a health economist
Authors: Ferguson Brian A.
Published: November 2002

The Kennedy Report will almost certainly become a defining moment in the history of UK healthcare. On the whole the NHS is poor at learning from history and there is a wealth of important information to be drawn from the report and the whole experience of Bristol. This article distils the essential clinical governance messages that risk being lost. While many of the issues can be viewed from an economic perspective, much of what is required is a change in attitude across whole health economies. The contribution that economics can make is to design appropriate incentive mechanisms to bring about desired behavioural change. It can also continue to promote informed debate on the proper meaning of efficiency and to highlight the features required for an appropriate and effective regulatory framework.
Nomenclature issues in aseptic preparation of medicines
Authors: Gandy Rob , Kershaw Karen , Beaumont Ian
Published: November 2002

Nomenclature is of fundamental importance in healthcare. Different professionals interpret different terms in different ways. This has implications for measurement, clinical governance, risk management and any comparative studies where clear definitions are not predetermined. A project to determine how aseptic dispensing activity in pharmacies and clinical areas should be measured found this to be the case, primarily between nurses and pharmacists. It was essential to have consistently used terms and definitions for the purposes of the project. A preliminary list was audited with senior staff in clinical areas to ascertain local views and practices. Commonly used alternatives and other relevant terms were identified. The results were validated by a multidisciplinary workshop to determine a final list. Evaluation of these and wider examples highlights the many implications and the need for the issue to be directly addressed, particularly in a multi‐professional environment.
Clinical governance and education: the views of clinical governance leads in the south west of England
Authors: Clark Christopher E. , Smith Lindsey F.P.
Published: November 2002

This qualitative study examined the views of clinical governance leads in South West England on the development of clinical governance, and its relationship to education in primary care. Information was obtained from semi‐structured interviews with clinical governance leads, and supplementary methods were used to confirm key findings. Four principal themes emerged: education, support, barriers, and evolution. Education is central to achieving the clinical governance agenda. There is a range of educational needs within primary care and these must be integrated into practice professional development plans, which will be shaped by national and local priorities. A need for PCG clinical governance tutors to support this process emerged. A range of supporting mechanisms was identified, as were barriers: principally inadequate resources and a rigid agenda imposed from above. Existing educationalists will need to change their role within the new structures, and this should be an evolutionary rather than a revolutionary process.
A multi‐district model for the management of disease‐modifying treatments in multiple sclerosis
Authors: Ford Helen L. , Johnson Michael , Fear Jon
Published: November 2002

This paper’s objective is to develop a model for the appropriate and equitable use of disease‐modifying treatments in multiple sclerosis. The prevalence and incidence of multiple sclerosis was established in Leeds. A specialist multiple sclerosis team with two consultant neurologists and a multiple sclerosis support nurse was based at one centre. The team co‐operated with purchasers to develop a model of care. This included a referral protocol, strict prescribing criteria, counselling and education of patients, the use of patient‐centred outcome measures and training and feedback to other neurologists. A total of 217 people with multiple sclerosis were assessed from April 1997 to March 2000. Our experience suggests that a centralised multi‐district clinic developed by close collaboration between clinicians and health purchasers and operating under agreed rules is a feasible and effective model for the managed introduction of new treatments to the NHS.
Use of a proforma for reporting staging CT scans of the thorax
Authors: Keeling‐Roberts Christopher S.
Published: November 2002

The aim of this study was to devise a simple proforma for reporting staging CT scans of the thorax, to ensure that all essential information is included on the report, in a logical manner, and that a TNM classification and tumour stage is given. Once the design of the proforma had been agreed, its utilisation and effectiveness was audited. In an initial six month period, every proforma filled in had resulted in a TNM classification being given, although in only 20 out of 40 (50 per cent) had a tumour stage been given. In a subsequent six month period, 39 out of 44 patients (89 per cent) with lung cancer undergoing a staging CT scan had proformas completed, and a TNM classification and tumour stage given (95 per cent CI is (0.75, 0.96)). Therefore, a proforma can be a useful aid to reporting staging scans, and is an effective method of ensuring that tumours are staged as fully as possible, radiologically. In addition, relevant information is presented in a clear format that allows accurate collection of data for audit purposes.
A structured examination in labour improves documentation
Authors: Paul Sudipta , Rowlands David J.
Published: November 2002

A structured sticker for examination of women in labour was introduced at Arrowe Park Hospital in 1998 to improve documentation of examination findings. This study was undertaken to assess whether the use of the sticker improved documentation of examination findings and second, compliance of sticker use. A retrospective analysis was performed on 64 cases randomised by random number generated on Arcus Quickstat from 470 women who were induced by prostaglandin during 1 January 1998 to 31 December 1998 at Arrowe Park Hospital. Women were induced by prostaglandin were chosen as the study population to obtain data from early labour. A total of 229 examinations were performed in these areas. Statistical analysis was undertaken on Arcus Quickstat, and χ2 and Fisher’s exact tests were applied to check for statistical significance.
Learning by doing: training general practitioners to be appraisers
Authors: Wall Debbie , Conlon Maurice , Cullen Ron , Halligan Aidan
Published: November 2002

Effective appraisal is one of the key underpinning systems to allow the practical implementation of clinical governance. Between March and July 2002, over 800 GPs have attended the national GP “Training the Appraisers” Programme, funded by the Department of Health, and run by the NHS Clinical Governance Support Team (CGST) in partnership with Edgecumbe Consulting Ltd. The one day programme, which includes practical “real life” appraisal sessions for GPs, is well on the way to meeting its remit of training 900 GP appraisers (an average of three appraisers per PCT) in 2002. Once they have completed the course, trained appraisers can begin the process of conducting the first round of appraisals in their local primary care organisations. The GP Appraisal Programme recognises the potential of an effective system of appraisal to develop over time, so that patients can be confident that their family doctor is supported in taking regular, structured steps to ensure they are identifying and fulfilling their professional development needs and thereby enhancing the delivery of high quality care.
Using clinical risk management processes to develop the national service framework for coronary heart disease
Authors: Cowan P. Jane
Published: November 2002

This article discusses the role of clinical risk management in the implementation of the National Service Framework for Coronary Heart Disease (NSFCHD). It considers the practical difficulties faced in meeting NSF standards, and proposes a combined, complementary approach involving primary and secondary care. While the NSF makes no explicit reference to clinical risk management, the risk manager has an important role to play in ensuring that an adverse event reporting system is in place and its role fully accepted by clinicians. From a medico‐legal standpoint, a commitment to auditing outcomes and maintaining good clinician‐patient communication is viewed as essential. It concludes that doctors’ and patients’ interests are best served by clinicians adopting a clinical risk management approach to implementing the NSFCHD.
Analysis of Possibility of Pressure Tube Cold Pressurization During ECCS Injection for a Small Break LOCA
Authors: Mukhopadhyay D. , Gupta S. K. , Venkat Raj V.
Published: November 2002

ECCS is designed to keep the reactor fuel temperatures within safe limits. The paper describes an additional criterion for Indian pressurized heavy water reactors (IPHWRs) evolving from the need to avoid a small break loss of cooling accident (LOCA) developing into a more severe accident. During a small break loss of coolant accident (LOCA) in PHWRs, the hydro-accumulators ride on the system and inject emergency coolant. The atmospheric steam discharge valves (ASDVs) open and cool the system due to energy discharge. In addition, the pressure control system tends to maintain the pressure. Depending on the system design, this could lead to cold pressurization of the system. This paper examines this issue.
Investigating the Interaction Behavior Between Two Arbitrarily Oriented Surface Cracks Using Multilevel Substructuring
Authors: Moussa Walied A.
Published: November 2002

The existence of arbitrarily oriented multiple cracks is a common problem in brittle materials. Some of these materials, such as ceramics, are used in mechanical and aerospace structures that suffer from aging. Because of that, such structures have shown some signs of sudden partial or total failure. The interaction and coalescence of multiple cracks may significantly affect the designed lives of aging structures. Knowledge of the growth behavior of interacting cracks is still limited. In this paper, a novel submodeling meshing algorithm is used to construct different cases of arbitrarily oriented identical surface cracks in a plate subjected to remote tension. These cases are solved using finite element analysis (FEA) and covered a wide range of crack geometries. The stress intensity factors (SIFs) and the energy release rates (G) for these cracks are calculated as a function of their relative orientation and the position along the interaction crack-front. In this paper, the studied ratio of crack depth to plate thickness, a/t, and to crack length, a/c, are kept at 0.2 and 0.3, respectively. Where possible, a comparison of the 3-D results with 2-D ones is also considered.
Design Procedures for an FRP Stub-Flange Joint
Authors: Estrada H. , Parsons I. D.
Published: November 2002

The design procedures for an innovative fiber-reinforced polymer (FRP) stub-flange joint are presented. The joint is intended for use with filament-wound pipes, and was developed to address some of the problems associated with current FRP joints. Detailed design guidelines for proportioning the joint are presented in this paper. The design calculations are relatively simple and compare well with more detailed finite element calculations.
Shape Sensitivity Analysis of Linear-Elastic Cracked Structures Under Mode-I Loading
Authors: Chen Guofeng , Rahman Sharif , Park Young Ho
Published: November 2002

A new method is presented for shape sensitivity analysis of a crack in a homogeneous, isotropic, and linear-elastic body subject to mode-I loading conditions. The method involves the material derivative concept of continuum mechanics, domain integral representation of the J-integral, and direct differentiation. Unlike virtual crack extension techniques, no mesh perturbation is needed in the proposed method. Since the governing variational equation is differentiated prior to the process of discretization, the resulting sensitivity equations are independent of any approximate numerical techniques, such as the finite element method, boundary element method, or others. Since the J-integral is represented by domain integration, only the first-order sensitivity of displacement field is needed. Two numerical examples are presented to illustrate the proposed method. The results show that the maximum difference in calculating the sensitivity of J-integral by the proposed method and reference solutions by analytical or finite-difference methods is less than three percent.
The Mixed-Mode Fracture Analysis of Multiple Embedded Cracks in a Semi-Infinite Plane by an Analytical Alternating Method
Authors: Chang Chih-Yi , Ma Chien-Ching
Published: November 2002

An efficient analytical alternating method is developed in this paper to evaluate the mixed-mode stress intensity factors of embedded multiple cracks in a semi-infinite plane. Analytical solutions of a semi-infinite plane subjected to a point force applied on the boundary, and a finite crack in an infinite plane subjected to a pair of point forces applied on the crack faces are referred to as fundamental solutions. The Gauss integrations based on these point load fundamental solutions can precisely simulate the conditions of arbitrarily distributed loads. By using these fundamental solutions in conjunction with the analytical alternating technique, the mixed-mode stress intensity factors of embedded multiple cracks in a semi-infinite plane are evaluated. The numerical results of some reduced problems are compared with available results in the literature and excellent agreements are obtained.
Finite Element Simulation of the Tightening Process of Bolted Joint With a Bolt Heater
Authors: Fukuoka Toshimichi , Xu Quantuo
Published: November 2002

The tightening operation with a bolt heater has advantages surpassing those of other tightening methods. Currently, a bolt heater is mainly applied to tighten huge bolts that cannot be clamped by other means, and the tightening operation is usually supported by the expertise of skilled workers. In this paper, a numerical approach is presented to aim at a broader use of bolt heater technique by elucidating the tightening mechanism. The effects of thermal contact resistance existing around a bolted joint are taken into account for a better accuracy in the numerical analyses. Based on the numerical results obtained, a series guideline to help the tightening operation when performed by less skilled workers is proposed.
Limit Loads for Layered Structures Using Extended Variational Principles and Repeated Elastic Finite Element Analysis
Authors: Pan L. , Seshadri R.
Published: November 2002

Layered structures are used in industry due to their better cost-to-strength and weight-to-strength performance compared with conventional structures. This paper presents a simple and systematic procedure to estimate the limit load for those layered structures that can undergo plastic collapse. The extended Mura’s variational principle is used in conjunction with repeated elastic finite element analyses (FEA). The elastic parameters are modified in order to ensure that the repeated analyses lead to a stress distribution close to the limit state. The secant modulus of a given element within the finite element discretization scheme is employed to simulate the plastic flow parameter μ0, and rapid convergence of estimated multipliers to the exact value is achieved. By using the notion of “leap-frogging” to limit state, improved lower-bound values of limit loads have been obtained. The method has been applied to layered cylinders and beams.
Limit Load Estimation Using Plastic Flow Parameter in Repeated Elastic Finite Element Analyses
Authors: Pan L. , Seshadri R.
Published: November 2002

The procedures described in this paper for determining a limit load is based on Mura’s extended variational formulation. Used in conjunction with linear elastic finite element analyses, the approach provides a robust method to estimate limit loads of mechanical components and structures. The secant modulus of the various elements in a finite element discretization scheme is prescribed in order to simulate the distributed effect of the plastic flow parameter, μ0. The upper and lower-bound multipliers m0 and m′ obtained using this formulation converge to near exact values. By using the notion of “leap-frogging” to limit state, an improved lower-bound multiplier, mα, can be obtained. The condition for which mα is a reasonable lower bound is discussed in this paper. The method is applied to component configurations such as cylinder, torispherical head, indeterminate beam, and a cracked specimen.
Evaluation of Pressure Side Film Cooling With Flow and Thermal Field Measurements—Part I: Showerhead Effects
Authors: Cutbirth J. Michael , Bogard David G.
Published: November 2002

The goal of this study was to determine how showerhead blowing on a turbine vane leading edge affects of the performance of film cooling jets farther downstream. An emphasis was placed on measurements above the surface, i.e., flow visualization, thermal field, and velocity field measurements. The film cooling performance on the pressure side of a simulated turbine vane, with and without showerhead blowing, was examined. Results presented in this paper are for low mainstream turbulence; high mainstream turbulence effects are presented in the companion paper. At the location of the pressure side row of holes, the showerhead coolant extended a distance of about 3d from the surface (d is the coolant hole diameter). The pressure side was found to be subjected to high turbulence levels caused by the showerhead injection. Results indicate a greater dispersion of the pressure side coolant jets with showerhead flow due to the elevated turbulence levels.
Evaluation of Pressure Side Film Cooling With Flow and Thermal Field Measurements—Part II: Turbulence Effects
Authors: Cutbirth J. Michael , Bogard David G.
Published: November 2002

This study focused on the film cooling performance on the pressure side of a turbine vane subjected to high mainstream turbulence levels, with and without showerhead blowing. Whereas previous studies have measured the adiabatic effectiveness and heat transfer at the surface of the airfoil, the goal of this study was to examine the flow and thermal fields above the surface. These measurements included flow visualization, thermal profiles, and laser Doppler velocimetry. For comparison, adiabatic effectiveness was also measured. A mainstream turbulence level of Tu∞=20%, with integral length scale of seven hole diameters, was used. Particularly insightful is the discovery that the large-scale high mainstream turbulence causes a lateral oscillation of coolant jet resulting in a much wider time average distribution of coolant. Even with high mainstream turbulence, showerhead blowing was found to still cause a significantly increased dispersion of the pressure side coolant jets.
Correlation of Film-Cooling Effectiveness From Thermographic Measurements at Enginelike Conditions
Authors: Baldauf S. , Scheurlen M. , Schulz A. , Wittig S.
Published: November 2002

Adiabatic film-cooling effectiveness on a flat plate surface downstream of a row of cylindrical holes is investigated. Highly resolved two-dimensional surface data were measured by means of infrared thermography and carefully corrected for local conduction and radiation effects. These locally acquired data are laterally averaged to give the streamwise distributions of the effectiveness. An independent variation of the flow parameters blowing rate, density ratio, and turbulence intensity as well as the geometrical parameters streamwise ejection angle and hole spacing is examined. The influences of these parameters on the lateral effectiveness is discussed and interpreted with the help of surface distributions of effectiveness and heat transfer coefficients presented in earlier publications. Besides the known jet in cross-flow behavior of coolant ejected from discrete holes, these data demonstrate the effect of adjacent jet interaction and its impact on jet lift-off and adiabatic effectiveness. In utilizing this large matrix of measurements the effect of single parameters and their interactions are correlated. The important scaling parameters of the effectiveness are shaped out during the correlation process and are discussed. The resulting new correlation is designed to yield the quantitatively correct effectiveness as a result of the interplay of the jet in crossflow behavior and the adjacent jet interaction. It is built modularly to allow for future inclusion of additional parameters. The new correlation is valid without any exception within the full region of interest, reaching from the point of the ejection to far downstream, for all combinations of flow and geometry parameters.
Floquet Modal Analysis of a Teetered-Rotor Wind Turbine
Authors: Stol Karl , Balas Mark , Bir Gunjit
Published: November 2002

This paper examines the operating modes of a two-bladed wind turbine structural model. Because of the gyroscopic asymmetry of its rotor, this turbine’s dynamics can be quite distinct from that of a turbine with three or more blades. This asymmetry leads to system equations with periodic coefficients that must be solved by the Floquet approach to extract the correct modal parameters. A discussion of results is presented for a series of simple models with increasing complexity. We begin with a single-degree-of-freedom system and progress to a model with seven degrees-of-freedom: tower fore-aft bending, tower lateral bending, tower twist, nacelle yaw, hub teeter, and flapwise bending of each blade. Results illustrate how the turbine modes become more dominated by the centrifugal and gyroscopic effects as the rotor speed increases. Parametric studies are performed by varying precone angle, teeter stiffness, yaw stiffness, teeter damping, and yaw damping properties. Under certain levels of yaw stiffness or damping, the gyroscopic coupling may cause yaw and teeter mode coalescence, resulting in self-excited dynamic instabilities. Teeter damping is the only parameter found to strictly stabilize the turbine model.
Heat Flux Reduction From Film Cooling and Correlation of Heat Transfer Coefficients From Thermographic Measurements at Enginelike Conditions
Authors: Baldauf S. , Scheurlen M. , Schulz A. , Wittig S.
Published: November 2002

Heat transfer coefficients and the resulting heat flux reduction due to film cooling on a flat plate downstream a row of cylindrical holes are investigated. Highly resolved two-dimensional heat transfer coefficient distributions were measured by means of infrared thermography and carefully corrected for local internal testplate conduction and radiation effects. These locally acquired data are processed to lateral average heat transfer coefficients for a quantitative assessment. A wide range variation of the flow parameters blowing rate and density ratio as well as the geometrical parameters streamwise ejection angle and hole spacing is examined. The effects of these dominating parameters on the heat transfer augmentation from film cooling are discussed and interpreted with the help of highly resolved surface results of effectiveness and heat transfer coefficients presented earlier. A new method of evaluating the heat flux reduction from film cooling is presented. From a combination of the lateral average of both the adiabatic effectiveness and the heat transfer coefficient, the lateral average heat flux reduction is processed according to the new method. The discussion of the total effect of film cooling by means of the heat flux reduction reveals important characteristics and constraints of discrete hole ejection. The complete heat transfer data of all measurements are used as basis for a new correlation of lateral average heat transfer coefficients. This correlation combines the effects of all the dominating parameters. It yields a prediction of the heat transfer coefficient from the ejection position to far downstream, including effects of extreme blowing angles and hole spacing. The new correlation has a modular structure to allow for future inclusion of additional parameters. Together with the correlation of the adiabatic effectiveness it provides an immediate determination of the streamwise heat flux reduction distribution of cylindrical hole film-cooling configurations.
Effect of Nonuniform Inlet Conditions on Endwall Secondary Flows
Authors: Hermanson K. S. , Thole K. A.
Published: November 2002

Exit combustor flow and thermal fields entering downstream stator vane passages in a gas turbine engine are highly nonuniform. These flow and thermal fields can significantly affect the development of the secondary flows in the turbine passages contributing to high platform heat transfer and large aerodynamic losses. The flow and thermal fields combine to give nonuniform total pressure profiles entering the turbine passage which, along with the airfoil geometry, dictate the secondary flow field. This paper presents an analysis of the effects of varying total pressure profiles in both the radial and combined radial and circumferential directions on the secondary flowfields in a first-stage stator vane. These inlet conditions used for the first vane simulations are based on the exit conditions predicted for a combustor. Prior to using the predictions, these CFD simulations were benchmarked against flowfield data measured in a large-scale, linear, turbine vane cascade. Good agreement occurred between the computational predictions and experimentally measured secondary flows. Analyses of the results for several different cases indicate variations in the secondary flow pattern from pitch to pitch, which attributes to the rationale as to why some airfoils quickly degrade while others remain intact over time.
Unsteady Rotor Heat Transfer in a Transonic Turbine Stage
Authors: Didier F. , De´nos R. , Arts T.
Published: November 2002

This experimental investigation reports the convective heat transfer coefficient around the rotor of a transonic turbine stage. Both time-resolved and time-averaged aspects are addressed. The measurements are performed around the rotor blade at 15, 50, and 85% span as well as on the rotor tip and the hub platform. Four operating conditions are tested covering two Reynolds numbers and three pressure ratios. The tests are performed in the compression tube turbine test rig CT3 of the von Karman Institute, allowing a correct simulation of the operating conditions encountered in modern aero-engines. The time-averaged Nusselt number distribution shows the strong dependence on both blade Mach number distribution and Reynolds number. The time-resolved heat transfer rate is mostly dictated by the vane trailing edge shock impingement on the rotor boundary layer. The shock passage corresponds to a sudden heat transfer increase. The effects are more pronounced in the leading edge region. The increase of the stage pressure ratio causes a stronger vane trailing edge shock and thus larger heat transfer fluctuations. The influence of the Reynolds number is hardly visible.
St and cf Augmentation for Real Turbine Roughness With Elevated Freestream Turbulence
Authors: Bons Jeffrey P.
Published: November 2002

Experimental measurements of skin friction cf and heat transfer (St) augmentation are reported for low speed flow over turbine roughness models. The models were scaled from surface measurements taken on actual, in-service land-based turbine hardware. Model scaling factors ranged from 25 to 63, preserving the roughness height to boundary layer momentum thickness ratio for each case. The roughness models include samples of deposits, TBC spallation, erosion, and pitting. Measurements were made in a zero pressure gradient turbulent boundary layer at two Reynolds numbers (Rex=500,000 and 900,000) and three freestream turbulence levels (Tu=1%, 5%, and 11%). Measurements at low freestream turbulence indicate augmentation factors ranging from 1.1–1.5 for St/Sto and from 1.3–3.0 for cf/cfo(Sto and cfo are smooth plate values). For the range of roughness studied (average roughness height, k, less than 1/3rd the boundary layer thickness) the level of cf augmentation agrees well with accepted equivalent sandgrain ks correlations when ks is determined from a roughness shape/density parameter. This finding is not repeated with heat transfer, in which case the ks-based St correlations overpredict the measurements. Both cf and St correlations severely underpredict the effect of roughness for k+<70 (when ks, as determined by the roughness shape/density parameter, is small). A new ks correlation based on the rms surface slope angle overcomes this limitation. Comparison of data from real roughness and simulated (ordered cones or hemispheres) roughness suggests that simulated roughness is fundamentally different from real roughness. Specifically, ks values that correlate cf for both simulated and real roughness are found to correlate St for simulated roughness but overpredict St for real roughness. These findings expose limitations in the traditional equivalent sandgrain roughness model and the common use of ordered arrays of roughness elements to simulate real roughness surfaces. The elevated freestream turbulence levels produce augmentation ratios of 1.24 and 1.5 St/Sto and 1.07 and 1.16 cf/cfo compared to the Tu=1% flow over the smooth reference plate. The combined effects of roughness and elevated freestream turbulence are greater than their added effects suggesting that some synergy occurs between the two mechanisms. Specifically, skin friction augmentation for combined turbulence and roughness is up to 20% greater than that estimated by adding their separate effects and 8% greater than compounding (multiplying) their separate effects. For heat transfer augmentation, the combined effect of turbulence and roughness is 5% higher than that estimated by compounding their separate effects at high freestream turbulence (Tu=11%). At low turbulence (Tu=5%), there is a negative synergy between the two augmentation mechanisms as the combined effect is now 13% lower than that estimated by compounding their separate effects.
Combined 3-D Flow and Heat Transfer Measurements in a 2-Pass Internal Coolant Passage of Gas Turbine Airfoils
Authors: Chanteloup D. , Juaneda Y. , Bo¨lcs A.
Published: November 2002

A study of the flow and heat transfer in a stationary model of a two-pass internal coolant passage is presented, which focuses on the flow characteristic effects on the wall heat transfer distribution. Results are given in the upstream fully developed region. Heat transfer measurements were made with a transient technique using thermochromic liquid crystal technique to measure a surface temperature. The technique allows full surface heat transfer coefficient measurements on all the walls. Flow measurements were made with a stereoscopic digital PIV system, which measures all three-velocity components simultaneously. The coolant passage model consists of two square ducts, each having a 20 hydraulic diameter length. The ducts are connected by a sharp 180 deg bend with a rectangular outer wall. 45 deg ribs are mounted in a staggered arrangement on the bottom and top walls of both legs. The height of the ribs is equal to 0.1 hydraulic diameters. They are spaced 10 rib heights apart. The flow and heat transfer measurements were obtained at one flow condition with an inlet flow Reynolds number, based on the hydraulic diameter, of 50,000. The paper presents detailed measurement results of the flow characteristics and of the heat transfer distribution in the upstream straight leg of the passage and describes how the main and secondary flows influence the heat transfer distribution in the fully developed regions of the channel.
Modification of the NACA 632-415 Leading Edge for Better Aerodynamic Performance
Authors: Bak Christian , Fuglsang Peter
Published: November 2002

Double stall causes more than one power level when stall-regulated wind turbines operate in stall. This involves significant uncertainty on power production and loads. To avoid double stall, a new leading edge was designed for the NACA 632-415 airfoil, an airfoil that is often used in the tip region of wind turbines. A numerical optimization tool incorporating XFOIL was used with a special formulation for the airfoil leading edge shape. The EllipSys2D CFD code was used to analyze the modified airfoil. In theory and in wind tunnel tests, the modified airfoil showed smooth and stable stall characteristics with no tendency to double stall. Also, both theory and wind tunnel tests showed that the overall aerodynamic characteristics were similar to NACA 632-415 except for an increase in the lift-drag ratio below maximum lift and an increase in maximum lift. The wind tunnel tests showed that dynamic stall and aerodynamic damping characteristics for the modified airfoil and the NACA 632-415 airfoil were the same. The modified airfoil with leading edge roughness in general had better characteristics compared with the NACA 632-415 airfoil.
Separated Flow Transition Under Simulated Low-Pressure Turbine Airfoil Conditions—Part 1: Mean Flow and Turbulence Statistics
Authors: Volino Ralph J.
Published: November 2002

Boundary layer separation, transition and reattachment have been studied experimentally under low-pressure turbine airfoil conditions. Cases with Reynolds numbers (Re) ranging from 25,000 to 300,000 (based on suction surface length and exit velocity) have been considered at low (0.5%) and high (9% inlet) free-stream turbulence levels. Mean and fluctuating velocity and intermittency profiles are presented for streamwise locations all along the airfoil, and turbulent shear stress profiles are provided for the downstream region where separation and transition occur. Higher Re or free-stream turbulence level moves transition upstream. Transition is initiated in the shear layer over the separation bubble and leads to rapid boundary layer reattachment. At the lowest Re, transition did not occur before the trailing edge, and the boundary layer did not reattach. Turbulent shear stress levels can remain low in spite of high free-stream turbulence and high fluctuating streamwise velocity in the shear layer. The beginning of a significant rise in the turbulent shear stress signals the beginning of transition. A slight rise in the turbulent shear stress near the trailing edge was noted even in those cases which did not undergo transition or reattachment. The present results provide detailed documentation of the boundary layer and extend the existing database to lower Re. The present results also serve as a baseline for an investigation of turbulence spectra in Part 2 of the present paper, and for ongoing work involving transition and separation control.
Predicting Transition Without Empiricism or DNS
Authors: Johnson Mark W.
Published: November 2002

A numerical procedure for predicting the receptivity of laminar boundary layers to freestream turbulence consisting of vortex arrays with arbitrary orientation has been developed. Results show that the boundary layer is most receptivity to those vortices which have their axes approximately in the streamwise direction and vortex wavelengths of approximately 1.2 δ. The computed near wall gains for isotropic turbulence are similar in magnitude to previously published experimental values used to predict transition. The new procedure is therefore capable of predicting the development of the fluctuations in the laminar boundary layer from values of the freestream turbulence intensity and length scale, and hence determining the start of transition without resorting to any empirical correlation.
The Use of Sweep and Dihedral in Multistage Axial Flow Compressor Blading—Part II: Low and High-Speed Designs and Test Verification
Authors: Gallimore Simon J. , Bolger John J. , Cumpsty Nicholas A. , Taylor Mark J. , Wright Peter I. , Place James M. M.
Published: November 2002

This paper describes the introduction of 3-D blade designs into the core compressors of the Rolls-Royce Trent engine series with particular emphasis on the use of sweep and dihedral in the rotor designs. It follows the development of the basic ideas in a university research project, through multistage low-speed model testing, to their application to the high pressure engine compressor. An essential element of the project was the use of multistage CFD and some of the development of the method to allow the designs to take place is also discussed. Part I of the paper concentrated on the fundamental university-based research and the methods development. Part II describes additional low-speed multistage design and testing and the high-speed engine compressor designs and tests.