bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser applications in dentistry: A review of the literature
Authors: Cernavin Igor , Pugatschew Anthony , de Boer Niels , Tyas Martin J.
Published: May 2009

While there are many applications of lasers in dentistry, few have advantages over existing technology. To date, lasers should be considered to be an adjunct to conventional techniques. There are also considerations of cost and rapid obsolescence of current laser equipment. The possible adverse effects of lasers on the tissues adjacent to those being irradiated, to users and to patients must also be considered.
An investigation of discomfort experienced by dental therapists and assistants at work
Authors: Visser Jodie L. , Straker Leon M.
Published: May 2009

Dental therapists and assistants frequently experience musculoskeletal complaints associated with their work. In order to plan and implement programmes aimed at reducing the number of these complaints, the level and location of physical discomfort experienced by dental workers at work was documented to identify potential problem areas associated with dental practice.
Hygienist employment and the presence of periodontal notations in general dental practice patient records
Authors: Brown Louise F. , Keily Pamela A. , Spencer A. John
Published: May 2009

Available data suggest that the provision of periodontal ly related services in general dental practices is low. However, studies indicate that the employment of dental hygienists is associated with increased provision. One method of measuring is by examination of notations in patient treatment records. As part of a project assessing the effectiveness of professional education in changing the provision of periodontal services, 2280 records, comprising 60 randomly selected records of dentate adult patients who had received a dental examination in the previous 6 months were audited in each of 38 practices, 13 of which employed hygienists. Entries of a periodontal nature were classified under 3 categories: diagnostic, preventive and treatment. The presence or absence of each item on each record was recorded. Diagnostic services were notated infrequently overall, but practices employing hygienists had a significantly lower number of records with no diagnostic notations. Preventive items were more frequently notated in practices employing hygienists. Treatment items were most frequently notated in both types of practices. Overall, 13 of the 23 items were recorded significantly more frequently in practices employing hygienists.
Some problems of dental treatment. Part 2. Treatment avoidance: Some differences between regular and irregular patients
Authors: Smyth John S.
Published: May 2009

Analysis of questionnaire data obtained from 54 irregular patients and 56 regular patients attending the Dental Department of the Lower Hutt Hospital and private practices in Lower Hutt and Wellington, New Zealand indicates that irregular patients are more anxious about dental treatment, value natural teeth less and find dental treatment more unpleasant than do regular patients. These and other survey findings on dental service utilization and dental anxiety suggest that the dental profession has a good deal of control over the way the public utilizes dental services. Most international surveys have found that less than 60 per cent of the population visits the dentist regularly, so there appears to be the potential for a substantial increase in regular use of dental services by the public. But, it is also likely that the longer an individual is remiss in regular dental care and the more teeth are lost, the more difficult conversion to regular visits will be.
An infected mandibular fracture. Case report
Authors: Thurnwald G. A. , Macleod A. W. Gordon
Published: May 2009

A case of an infected mandibular fracture is presented. A submandibular abscess appeared to arise from chronic pericoronal infection associated with a third molar tooth in the line of fracture. Treatment of the case is described followed by a short discussion on the aetiology and management of infected mandibular fractures. The importance of adequate first aid and prompt referral is stressed.
Shear bond strength of a resin composite to enamel etched with maleic or phosphoric acid
Authors: Hallett Kerrod B. , Garcia‐Godoy Franklin , Trotter Amanda R.
Published: May 2009

The purpose of this study was to evaluate the effect of 10 per cent maleic and 37 per cent phosphoric acid on the shear bond strength of Z100 composite resin with Scotchbond Multi‐Purpose adhesive to primary and permanent tooth enamel. Four groups of 20 teeth each were established: 1, permanent teeth, 10 percent maleic acid etched for 15 seconds; 2, permanent teeth, 10 per cent maleic acid etched for 30 seconds; 3, permanent teeth, 37 per cent phosphoric acid etched for 15 seconds; 4, primary teeth, 10 per cent maleic acid etched for 15 seconds. Five teeth from each group were randomly assigned for SEM examination of the etched enamel surface. Scotchbond Multi‐Purpose primer and adhesive were applied to the etched enamel surface of the remaining 15 teeth and cured following the manufacturer's instructions. Z100 composite resin was placed in a nylon cylinder and cured for two 40 second intervals. Following thermocycling, the specimens were sheared on an universal testing machine and debonded areas were examined visually with a stereo microscope and with SEM. The mean shear bond strengths in MPa were: 1,17.00; 2, 14.58; 3, 14.66; 4, 11.18. ANOVA and Student‐Newman‐Keuls analyses revealed no statistically significant difference among the groups. SEM examination showed the majority of specimens fractured at the adhesive‐resin interface.
Physiopathology of primary periodontitis associated with plaque. Microbial and host factors. A review. Part 2
Authors: Liébana J. , Castillo A.
Published: May 2009

To a considerable extent, host factors condition the initiation and progression of periodontitis. The integrity of the periodontal structures and the immune elements in the gingival fluid may act as a defensive barrier against microorganisms. However, immune over‐response may lead to tissue damage and bone resorption from anaphylactic reactions, immunocomplex reactions, type IV hypersensitivity, complement hyperactivation via the alternative pathway, or direct action of leukocytes and macrophages. Moreover, insufficient host response allows bacteria to escape control, allowing more rapid progression of the disease.
Attitudes and smoking habits of dentists in Victoria: 16 years on
Authors: Mullins Robyn
Published: May 2009

In 1977 a survey of Victorian dentists measured their smoking prevalence, and their attitudes to dealing with patients who smoked. In 1993 these questions were repeated as part of a telephone survey of Victorian dentists. From 1977 to 1993 their prevalence of daily smoking had dropped from 30 per cent to 6 per cent, and this was not attributable simply to an influx of younger dentists who had never smoked. Many of those who had graduated in 1977 or more recently had never smoked, but many of the earlier graduates had quit, and there was no difference in the current smoking prevalence of the two groups. There had also been a change in dentists' attitudes towards smoking patients, with more of the 1993 sample (55 per cent) than the 1977 sample (43 per cent) agreeing with the statement ‘I encourage all my patients to give up smoking wherever possible’. Again, the more experienced dentists were adopting the new behaviours, not just the more recent graduates. Even so, in 1993 nearly half the dentists waited until the patient either was affected by smoking, or asked for advice before raising the issue.
The prognosis of oral mucosal squamous cell carcinomas: A comparison of clinical and histopathological grading and of laminin and type IV collagen staining
Authors: Firth Norman A. , Reade Peter C.
Published: May 2009

Changes in the distribution of basement membrane components have been described in dysplastic lesions and in oral mucosal squamous cell carcinomas (OMSCC). The purpose of this study was to determine if these changes were related to pathological grade and if so, whether this had prognostic implications. Fifty formalin‐fixed, paraffin‐embedded specimens of OMSCC, with five or more years clinical follow‐up, were studied using an immunoperoxidase technique for the detection of the basement membrane components, laminin and type IV collagen. The immunoreactivity of each component was evaluated and semiquantitatively scored as minimal, moderate or extensive and the results compared with the tumour size, node involvement and metastasis (TNM) clinical staging system and histopathological features. OMSCC were characterized by minimal or moderate staining with small islands of neoplastic cells frequently lacking staining for laminin and type IV collagen. Deposition of these components decreased with increased histopathological grade and absence of staining was more commonly associated with a poor prognosis. In particular the pattern of type IV collagen staining frequently differed from laminin staining. Neither of these parameters offered an advantage over TNM clinical staging with regard to prognosis. It was concluded that variations in laminin and type IV collagen immunoreactivity occured in OMSCC and that high histopathological grade tumours with considerably diminished staining with anti‐laminin and anti‐type IV collagen carried a poor prognosis.
Identification and classification of species within the Streptococcus sanguis group
Authors: Willcox M. D. P.
Published: May 2009

A biochemical identification scheme has been produced that allows for the differentiation of nine distinct species within the Streptococcus sanguis group. The species are S. sanguis, S. gordonii, S. crista, S. oralis, S. parasanguis, S. defectivus, S. adjacens and S. mitis, which have been previously described, and a new species, S. australis; In addition two distinct subspecies, S. oralis subsp. corona and S. oralis subsp. mitior, have been identified. DNA‐DNA hybridization confirmed the separation of strains Into the species. A new type of peptidoglycan peptide linkage, lys‐ala‐gly was also found within this species S. parasanguis and S. australis that has not been observed within the streptococci previously. DNA fingerprinting was shown to be a useful method for discriminating between strains within species, but did not allow discrimination between species.
The strength of auto‐cured and light‐cured materials. The shear punch test
Authors: Mount G. J. , Makinson O. F. , Peters M. C. R. B.
Published: May 2009

This paper examines the versatility of the shear punch test as described by Roydhouse and suggests that it should be considered as an alternative to the present standard compressive strength test for glass ionomer cements and flexural strength for composite resins. The shear punch test can be used for examining small thin specimens, about 1.0 mm thick and 8.0 mm in diameter, of both auto‐cured and light‐cured restorative materials such as composite resins and glass ionomer cements. The preparation of the specimen is simple and does not require a precision mould or subsequent machining to size except that, after curing, it may need to be abraded gently to obtain flat parallel test surfaces. The test apparatus consists of a punch approximately 3.0 mm in diameter opposing a true fitting matching die. The specimen is supported over the die section and the punch is advanced through it in a compression cage. The formula used to calculate the shear strength allows for variation in specimen thickness and thus provides comparative data between materials. It also allows examination of the effects of variations in manipulation, maturation and storage of each material. It is suggested this test should be considered as an alternative to the present compression and flexural strength tests because it would provide a single strength test for a range of restorative materials being manipulated under a variety of circumstances. It is of particular significance for testing the light‐cured materials because it examines a specimen size below that of the diameter of the exit window of a normal clinical light curing unit and also at a thickness where depth of cure of the material is not a problem.
An African Success Story: Ghana's Cocoa Marketing System
Authors: Williams Tracy
Published: May 2009

Ghana's cocoa marketing system has performed impressively over the past decade. Cocoa production has reached record high levels. Farmers receive a relatively large share of export earnings. Product quality is world renowned, and it regularly exceeds the most stringent international standards. Exports are handled professionally and efficiently. International loans are repaid reliably. Internal marketing is relatively uncorrupt and effective. This is a home‐grown success story, under the stewardship of a state‐run marketing board – the Cocobod – which manages almost all aspects of the internal cocoa marketing process and maintains a monopoly on cocoa exports. Given the dismal history of African commodity marketing boards in general, and of Ghana's cocoa marketing board in particular, this success demands explanation. It was not the result of radical transformation but of relatively subtle changes in the system that maintained the undoubted benefits of a centralised monopoly while minimising its damaging consequences. Success resulted from (1) building on the underlying strength of certain elements in the system, notably quality control and export management, (2) an episode of well‐directed reform, and (3) effective policies and organisational structures that protected the farmers' share of the cocoa revenues over time and inhibited the Cocobod returned to the politicisation it suffered in the past. The case accords with the much‐touted but oft‐neglected lesson that both context and institutions matter for organisational performance. In particular, complementary contexts and institutions can produce valuable synergies. More substantively, it suggests that poorly performing organisations in Africa may be turned around without radical measures.
Investigation of Throughflow Hypothesis in a Turbine Cascade Using a Three-Dimensional Navier–Stokes Computation
Authors: Perrin G. , Leboeuf F.
Published: May 2009

The results of a computation, performed with a three-dimensional Navier–Stokes computation at ONERA, have been averaged in the blade-to-blade direction; the spatial fluctuations around the averaged flow variables have also been determined. It has then been possible to estimate all terms in the average components of the momentum equations. The comparison of the two-dimensional balances of these three equations shows that the shear stress plays a minor role in the momentum balance, except on the dissipation of the passage vortex kinetic energy downstream of the blade trailing edges. The kinetic energy of the spanwise component of the velocity spatial fluctuations has a very strong influence on the radial pressure gradient; it introduces a convection effect. This is a key effect for all these balances.
Effects of Criterion Functions on Intermittency in Heated Transitional Boundary Layers With and Without Streamwise Acceleration
Authors: Keller F. J. , Wang T.
Published: May 2009

Attempting to understand the mechanisms of momentum and thermal transports in transitional boundary layers has resulted in the use of conditional sampling to separate the flow into turbulent and nonturbulent portions. The choice of a proper criterion function to discriminate between the two flow conditions is critical. A detailed experimental investigation was performed to determine the effects of different criterion functions on the determination of intermittency for application in heated transitional boundary layers with and without streamwise acceleration. Nine separate criterion functions were investigated for the baseline case without pressure gradient and three cases with streamwise pressure gradient. Inherent differences were found to exist between each criterion function’s turbulence recognition capabilities. The results indicate that using a criterion function based on Reynolds shear stress, (∂uv/∂τ)2, for turbulent/nonturbulent discrimination in a heated transitional boundary layer is superior to a single velocity or temperature scheme. Peak values in intermittency for the early to midtransitional region were found to occur away from the wall at approximately y/δ = 0.3 for all cases. To match the universal intermittency distribution of Dhawan and Narasimha (1958), the minimum values of intermittency at y / δ ≈ 0.1 should be used as the representative “near-wall” values.
Experimental and Theoretical Investigations of Heat Transfer in Closed Gas-Filled Rotating Annuli
Authors: Bohn D. , Deuker E. , Emunds R. , Gorzelitz V.
Published: May 2009

The prediction of the temperature distribution in a gas turbine rotor containing closed, gas-filled cavities, for example in between two disks, has to account for the heat transfer conditions encountered inside these cavities. In an entirely closed annulus, forced convection is not present, but a strong natural convection flow exists, induced by a nonuniform density distribution in the centrifugal force field. Experimental investigations have been made to analyze the convective heat transfer in closed, gas-filled annuli rotating around their horizontal axes. The experimental setup is designed to establish a pure centripetal heat flux inside these annular cavities (hot outer, and cold inner cylindrical wall, thermally insulated side walls). The experimental investigations have been carried out for several geometries varying the Rayleigh number in a range usually encountered in cavities of turbine rotors (107 < Ra < 1012). The convective heat flux induced for Ra =1012 was found to be a hundred times larger compared to the only conductive heat flux. By inserting radial walls the annulus is divided into 45 deg sections and the heat transfer increases considerably. A computer program to simulate flow and heat transfer in closed rotating cavities has been developed and tested successfully for annuli with isothermal side walls with different temperatures giving an axial heat flux. For the centripetal heat flux configuration, three-dimensional steady-state calculations of the sectored annulus were found to be consistent with the experimental results. Nevertheless, analysis of unsteady calculations show that the flow can become unstable. This is analogous to the Be´nard problem in the gravitational field.
Darryl E. Metzger Memorial Session Paper: A Summary of the Cooled Turbine Blade Tip Heat Transfer and Film Effectiveness Investigations Performed by Dr. D. E. Metzger
Authors: Kim Y. W. , Downs J. P. , Soechting F. O. , Abdel-Messeh W. , Steuber G. D. , Tanrikut S.
Published: May 2009

The clearance gap between the stationary outer air seal and blade tips of an axial turbine allows a clearance gap leakage flow to be driven through the gap by the pressure-to-suction side pressure difference. The presence of strong secondary flows on the pressure side of the airfoil tends to deliver air from the hottest regions of the mainstream to the clearance gap. The blade tip region, particularly near the trailing edge, is very difficult to cool adequately with blade internal coolant flow. In this case, film cooling injection directly onto the blade tip region can be used in an attempt to directly reduce the heat transfer rates from the hot gases in the clearance gap to the blade tip. The present paper is intended as a memorial tribute to the late Professor Darryl E. Metzger, who made significant contributions in this particular area over the past decade. A summary of this work is made to present the results of his more recent experimental work, which was performed to investigate the effects of film coolant injection on convection heat transfer to the turbine blade tip for a variety of tip shapes and coolant injection configurations. Experiments are conducted with blade tip models that are stationary relative to the simulated outer air seal based on the result of earlier works that found the leakage flow to be mainly a pressure-driven flow, which is related strongly to the airfoil pressure loading distribution, and only weakly, if at all, to the relative motion between blade tip and shroud. Both heat transfer and film effectiveness are measured locally over the test surface using a transient thermal liquid crystal test technique with a computer vision data acquisition and reduction system for various combinations of clearance heights, clearance flow Reynolds numbers, and film flow rates with different coolant injection configurations. The present results reveal a strong dependency of film cooling performance on the choice of the coolant supply hole shapes and injection locations for a given tip geometry.
Measurements of the Flow Field Within a Compressor Outlet Guide Vane Passage
Authors: Carrotte J. F. , Young K. F. , Stevens S. J.
Published: May 2009

A series of tests have been carried out to investigate the flow in a Compressor Outlet Guide Vane (OGV) blade row downstream of a single-stage rotor. The subsequent flow field that developed within an OGV passage was measured, at intervals of 10 percent axial chord, using a novel design of miniature five-hole pressure probe. In addition to indicating overall pressure levels and the growth of regions containing low-energy fluid, secondary flow features were identified from calculated axial vorticity contours and flow vectors. Close to each casing the development of classical secondary flow was observed, but toward the center of the annulus large well-defined regions of opposite rotation were measured. These latter flows were due to the streamwise vorticity at inlet to the blade row associated with the skewed inlet profile. Surface static pressures were also measured and used to obtain the blade pressure force at three spanwise locations. These values were compared with the local changes in flow momentum calculated from the measured velocity distributions. With the exception of the flow close to the outer casing, which is affected by rotor tip leakage, good agreement was found between these quantities indicating relatively weak radial mixing.
Turbulence Intensity and Length Scale Measurements in Multistage Compressors
Authors: Camp T. R. , Shin H.-W.
Published: May 2009

This paper describes the measurement and processing of turbulence data from multistage low-speed compressors. Measurements were made at the same relative positions in three four-stage compressors, each having different levels of the design stage loading coefficient. A new method of data processing to calculate turbulence intensities and integral length scales is outlined. Using this method, integral length scales have been measured in turbomachinery flows for the first time. It is shown how the turbulence intensity and integral length scale vary with position in the blade passage, with changing flow coefficient and with the value of the design stage loading coefficient. The results have been used to specify representative inlet conditions for experimental rigs and to improve the application of CFD turbulence models to turbomachinery modeling.
Monitoring of Aerodynamic Load and Detection of Stall in Multistage Axial Compressors
Authors: Ho¨nen H. , Gallus H. E.
Published: May 2009

The unsteady flow in a single-stage axial flow compressor at different operating conditions has been investigated with hot-wire and hot-film probes to find out the influence of the aerodynamic compressor load on the periodic fluctuations. These results are compared with measurements in the last stages of a multistage high-pressure compressor of a gas turbine for normal operation and under stall conditions. From the patterns of the frequency spectra of the measuring signals a parameter for the detection of the approach to the stability line of a compressor is derived. A method for the on-line monitoring of the aerodynamic load is presented. Based on these results a monitoring system has been developed. First experiences with this system, applied to two multistage compressors, are reported.
A Reduced Order Model of Unsteady Flows in Turbomachinery
Authors: Hall K. C. , Florea R. , Lanzkron P. J.
Published: May 2009

A novel technique for computing unsteady flows about turbomachinery cascades is presented. Starting with a frequency domain CFD description of unsteady aerodynamic flows, we form a large, sparse, generalized, non-Hermitian eigenvalue problem that describes the natural modes and frequencies of fluid motion about the cascade. We compute the dominant left and right eigenmodes and corresponding eigenfrequencies using a Lanczos algorithm. Then, using just a few of the resulting eigenmodes, we construct a reduced order model of the unsteady flow field. With this model, one can rapidly and accurately predict the unsteady aerodynamic loads acting on the cascade over a wide range of reduced frequencies and arbitrary modes of vibration. Moreover, the eigenmode information provides insights into the physics of unsteady flows. Finally we note that the form of the reduced order model is well suited for use in active control of aeroelastic and aeroacoustic phenomena.
Euler Solutions for Transonic Oscillating Cascade Flows Using Dynamic Triangular Meshes
Authors: Hwang C. J. , Yang S. Y.
Published: May 2009

The modified total-variation-diminishing scheme and an improved dynamic triangular mesh algorithm are presented to investigate the transonic oscillating cascade flows. In a Cartesian coordinate system, the unsteady Euler equations are solved. To validate the accuracy of the present approach, transonic flow around a single NACA 0012 airfoil pitching harmonically about the quarter chord is computed first. The calculated instantaneous pressure coefficient distribution during a cycle of motion compare well with the related numerical and experimental data. To evaluate further the present approach involving nonzero interblade phase angle, the calculations of transonic flow around an oscillating cascade of two unstaggered NACA 0006 blades with interblade phase angle equal to 180 deg are performed. From the instantaneous pressure coefficient distributions and time history of lift coefficient, the present approach, where a simple spatial treatment is utilized on the periodic boundaries, gives satisfactory results. By using this solution procedure, transonic flows around an oscillating cascade of four biconvex blades with different oscillation amplitudes, reduced frequencies, and interblade phase angles are investigated. From the distributions of magnitude and phase angle of the dynamic pressure difference coefficient, the present numerical results show better agreement with the experimental data than those from the linearized theory in most of the cases. For every quarter of one cycle, the pressure contours repeat and proceed one pitch distance in the upward or downward direction for interblade phase angle equal to −90 deg or 90 deg, respectively. The unsteady pressure wave and shock behaviors are observed. From the lift coefficient distributions, it is further confirmed that the oscillation amplitude, interblade phase angle, and reduced frequency all have significant effects on the transonic oscillating cascade flows.
Darryl E. Metzger Memorial Session Paper: An Account of Free-Stream-Turbulence Length Scale on Laminar Heat Transfer
Authors: Dullenkopf K. , Mayle R. E.
Published: May 2009

The effect of length scale in free-stream turbulence is considered for heat transfer in laminar boundary layers. A model is proposed that accounts for an “effective” intensity of turbulence based on a dominant frequency for a laminar boundary layer. Assuming a standard turbulence spectral distribution, a new turbulence parameter that accounts for both turbulence level and length scale is obtained and used to correlate heat transfer data for laminar stagnation flows. The result indicates that the heat transfer for these flows is linearly dependent on the “effective” free-stream turbulence intensity.
Effects of Elevated Free-Stream Turbulence on Flow and Thermal Structures in Transitional Boundary Layers
Authors: Zhou D. , Wang T.
Published: May 2009

The effects of elevated free-stream turbulence on flow and thermal structures in transitional boundary layers were investigated experimentally on a heated flat plate. Detailed boundary layer measurements using a three-wire probe and wall heat transfer were made with free-stream turbulence intensities of 0.5, 3.8, 5.5, and 6.4 percent, respectively. The onset of transition, transition length, and the turbulent spot formation rate were determined. The statistical results of the streamwise and cross-stream velocity fluctuations, temperature fluctuation, Reynolds stresses, and Reynolds heat fluxes were presented. The eddy viscosity, turbulent thermal diffusivity, and the turbulent Prandtl number were calculated and related physical mechanisms are discussed.
Enhanced Heat Transfer and Shear Stress Due to High Free-Stream Turbulence
Authors: Thole K. A. , Bogard D. G.
Published: May 2009

Surface heat transfer and skin friction enhancements, as a result of free-stream turbulence levels between 10 percent < Tu > 20 percent, have been measured and compared in terms of correlations given throughout the literature. The results indicate that for this range of turbulence levels, the skin friction and heat transfer enhancements scale best using parameters that are a function of turbulence level and dissipation length scale. However, as turbulence levels approach Tu = 20 percent, the St′ parameter becomes more applicable and simpler to apply. As indicated by the measured rms velocity profiles, the maximum streamwise rms value in the near-wall region, which is needed for St′, is the same as that measured in the free stream at Tu = 20 percent. Analogous to St′, a new parameter, Cf′, was found to scale the skin friction data. Independent of all the correlations evaluated, the available data show that the heat transfer enhancement is greater than the enhancement of skin friction with increasing turbulence levels. At turbulence levels above Tu = 10 percent, the free-stream turbulence starts to penetrate the boundary layer and inactive motions begin replacing shear-stress producing motions that are associated with the fluid/wall interaction. Although inactive motions do not contribute to the shear stress, these motions are still active in removing heat.
Heat Transfer Measurements in an Annular Cascade of Transonic Gas Turbine Blades Using the Transient Liquid Crystal Technique
Authors: Martinez-Botas R. F. , Lock G. D. , Jones T. V.
Published: May 2009

Heat transfer measurements have been made in the Oxford University Cold Heat Transfer Tunnel employing the transient liquid crystal technique. Complete contours of the heat transfer coefficient have been obtained on the aerofoil surfaces of a large annular cascade of high-pressure nozzle guide vanes (mean blade diameter of 1.11 m and axial chord of 0.0664 m). The measurements are made at engine representative Mach and Reynolds numbers (exit Mach number 0.96 and Reynolds number 2.0 × 106). A novel mechanism is used to isolate five preheated blades in the annulus before an unheated flow of air passes over the vanes, creating a step change in heat transfer. The surfaces of interest are coated with narrow-band thermochromic liquid crystals and the color crystal change is recorded during the run with a miniature CCD video camera. The heat transfer coefficient is obtained by solving the one-dimensional heat transfer equation for all the points of interest. This paper will describe the experimental technique and present results of heat transfer and flow visualization.
Heat (Mass) Transfer and Film Cooling Effectiveness With Injection Through Discrete Holes: Part I—Within Holes and on the Back Surface
Authors: Cho H. H. , Goldstein R. J.
Published: May 2009

A jet stream entering a crossflow is investigated for injection through a single hole and an array of holes for blowing rates of 0.2 to 2.2. The naphthalene sublimation technique has been employed to study the local mass (heat) transfer in the injection hole and in the vicinity of the hole entrance. The Sherwood number is fairly uniform along the circumference of the inside hole surface even at the low blowing rate considered. This is quite different from the case without injection (zero blowing rate), when the Sherwood number is highly nonuniform. The transfer rate in the hole is weakly influenced by the crossflow and the zone, which is directly affected, is confined close to the hole exit (about 0.15 hole diameter in depth). The average Sherwood number is similar to that in the absence of crossflow except at low blowing rates. The Sherwood numbers on the hole entrance surface (backside) are the same as when there is no crossflow. Thus, the Sherwood numbers inside the hole and on the back surface can be closely approximated from experiments without crossflow.
Buoyancy-Affected Flow and Heat Transfer in Asymmetrically Heated Rotating Cavities
Authors: Long C. A. , Morse A. P. , Zafiropoulos N.
Published: May 2009

Finite-volume predictions are presented for the convective heat transfer rates in a rotating cavity, formed by two corotating plane disks and a peripheral shroud, and subjected to a radial outflow of cooling air. The heating of the disks is asymmetric, the air entering the cavity through a central hole in the cooler (upstream) disk. The predicted Nusselt number distributions for each disk are compared with unpublished data from the University of Sussex for dimensionless mass-flow rates in the range 2800 ⩽ Cw ⩽ 14,000 and rotational Reynolds numbers, Reθ, up to 5.2 × 106. A single-grid elliptic procedure was used with turbulent transport represented via a low-Reynolds-number k–ε model and the turbulence Prandtl number concept. In comparing the predicted and measured convective heat fluxes, it is important to consider the radiative heat exchange between the disks. This is estimated using a conventional view-factor approach based on black-body emission. Under conditions of asymmetric heating, rotationally induced buoyancy forces can exert significant effect on the flow structure, the induced motion tending to oppose that imposed by the radial outflow. Indeed, flow visualization studies have revealed that, as the rotational Reynolds number is increased (for a fixed value of Cw), the flow in the source region initially becomes oscillatory in nature, leading eventually to the onset of chaotic flow in which the usual Ekman layer structure does not persist in all angular planes. The extent to which the effects of such flow behavior can be captured by the steady, axisymmetric calculation approach used here is questionable, but it is found that the turbulence model (used previously for the prediction of heat transfer in symmetrically heated cavities) still leads to good (± 10 percent) predictive accuracy for the heated (downstream) disk. However, the predicted Nusselt numbers for the cooler (upstream) disk generally show little accord with experimental data, often signifying heat flow into the disk instead of vice versa. It is concluded that the modeling of the turbulent heat transport across the core region of the flow is erroneous, especially at high rotational Reynolds numbers: This is attributed to overestimated turbulence energy production in that region due to the action of the radial-circumferential component of shear stress (νw). Adoption of an algebraic-stress model for this shear stress is partly successful in removing the discrepancies between prediction and experiment.
Swirl Brake Effect on the Rotordynamic Stability of a Shrouded Impeller
Authors: Baskharone E. A.
Published: May 2009

The swirling motion of the shroud-to-housing leakage flow in pumps is known to have an adverse impact on the impeller rotordynamic stability. Swirl brakes, under such circumstances, would enhance the stability margin by reducing or, ideally, eliminating, the prerotation at the leakage passage inlet station. The numerical analysis outlined in this paper provides a quantitative means of predicting the effectiveness of such devices. The computed results also illustrate the mechanism with which the fluid/rotor interaction, with the aid of a typical brake, is altered towards relative overall rotordynamic stability. This is done through a comparative examination of the pressure perturbation distribution over the shroud surface for a wide range of backward and forward impeller-whirl frequencies. The conclusions in this study are consistent with recent experimental findings and have important design implications.
The Influence of Film Cooling on the Efficiency of an Annular Nozzle Guide Vane Cascade
Authors: Day C. R. B. , Oldfield M. L. G. , Lock G. D.
Published: May 2009

This paper examines the effect of aerofoil surface film cooling on the aerodynamic efficiency of an annular cascade of transonic nozzle guide vanes. A dense foreign gas (SF6/Ar mixture) is used to simulate engine representative coolant-to-mainstream density ratios under ambient conditions. The flowfield measurements have been obtained using a four-hole pyramid probe in a short duration blowdown facility that correctly models engine Reynolds and Mach numbers, as well as the inlet turbulence intensity. The use of foreign gas coolant poses specific challenges not present in an air-cooled cascade, and this paper addresses two. First, a novel method for the determination of mass flow from pneumatic probe data in a heterogeneous gas environment is presented that eliminates the need to measure concentration in order to determine loss. Second, the authors argue on the grounds of dimensionless similarity that momentum flux ratio is to be preferred to blowing rate for the correct parameterization of film cooling studies with varying coolant densities. Experimental results are presented as area traverse maps, from which values for loss have been calculated. It is shown that air and foreign gas at the same momentum flux ratio give very similar results, and that the main difference between cooled and uncooled configurations is an increase in wake width. Interestingly, it is shown that an increase in the momentum flux ratio above the design value with foreign gas coolant reduces the overall loss compared with the design value. The data have been obtained both for purposes of design and for CFD code Validation.
A Numerical Investigation of Transonic Axial Compressor Rotor Flow Using a Low-Reynolds-Number k–ε Turbulence Model
Authors: Arima T. , Sonoda T. , Shirotori M. , Tamura A. , Kikuchi K.
Published: May 2009

We have developed a computer simulation code for three-dimensional viscous flow in turbomachinery based on the time-averaged compressible Navier–Stokes equations and a low-Reynolds-number k–ε turbulence model. It is described in detail in this paper. The code is used to compute the flow fields for two types of rotor (a transonic fan NASA Rotor 67 and a transonic axial compressor NASA rotor 37), and numerical results are compared to experimental data based on aerodynamic probe and laser anemometer measurements. In the case of Rotor 67, calculated and experimental results are compared under the design speed to validate the code. The calculated results show good agreement with the experimental data, such as the rotor performance map and the spanwise distribution of total pressure, total temperature, and flow angle downstream of the rotor. In the case of Rotor 37, detailed comparisons between the numerical results and the experimental data are made under the design speed condition to assess the overall quality of the numerical solution. Furthermore, comparisons under the part-speed condition are used to investigate a flow field without passage shock. The results are well predicted qualitatively. However, considerable quantitative discrepancies remain in predicting the flow near the tip. In order to assess the predictive capabilities of the developed code, computed flow structures are presented with the experimental data for each rotor and the cause of the discrepancies is discussed.
Computation of Separated-Flow Transition Using a Two-Layer Model of Turbulence
Authors: Papanicolaou E. L. , Rodi W.
Published: May 2009

A model for predicting transition in flows with separation is presented in this study. The two-layer model of turbulence is employed, along with a suitably defined intermittency function, which takes appropriate values in the laminar-, transitional- and turbulent-flow regions. Correlations derived from measurements are used for this purpose. Two test cases were selected: the flow over a long horizontal body with semi-circular leading edge and the flow over the backward-facing step of small height (expansion ratio of 1:1.01). In the former, oncoming flows with a free-stream turbulence level encountered in practical applications was considered (0.2–5.6 percent) whereas in the latter the corresponding level was much lower. The Reynolds numbers, based on the diameter in the first case and on the step height in the second, lie in the range of 1600–6600, in which limited numerical investigations were previously available and where bubbles with laminar separation and turbulent reattachment are expected. The predictions were found to compare well with the corresponding measurements, both in terms of the lengths of the separation and the transition regions and of velocity and turbulence intensity profiles at various stream-wise locations. The results show that, for the transition criterion chosen, in all cases transition is completed downstream of the reattachment point and that the rate at which it is completed increases with the free-stream turbulence level.
Redesign Auto Door Using Modularization and Ultra Light Steel Auto Body Structure
Authors: Haider I. , Ali S. A. , Oriet L. P. , Nooks J. A.
Published: May 2009

This paper presents redesign of a car body for material weight reduction for the cost saving by material as well as fuel efficiency improvement. ULSAB (Ultra Light Steel Auto Body Structure) concept is used for weight reduction in redesigning process. Modularization is used for redesigning to reduce parts cost. Four factors: cost of modules, cost of assembly, common design and weight of the car are considered. Comparison for the material cost, weight and assembly time has been done for proposed design and existing design. Redesign car shows efficient fuel consumption car. Automotive sector could reduce their total manufacturing cost per vehicle by using modularization in design. The customers will get cheaper and fuel efficient car.
Approximated Fundamental Frequency for Thin Circular Plates Clamped or Pinned at the Edge
Authors: Weiss George
Published: May 2009

Calculating the exact solution to the differential equations that describe the motion of a circular plate clamped or pinned at the edge, is laborious. The calculations include the Bessel functions and modified Bessel functions. In this paper, we present a brief method for calculating with approximation, the fundamental frequency of a circular plate clamped or pinned at the edge. We’ll use the Dunkerley’s estimate to determine the fundamental frequency of the plates. A plate is a continuous system and will assume it is loaded with a uniform distributed load, including the weight of the plate itself. Considering the mass per unit area of the plate, and substituting it in Dunkerley’s equation rearranged, we obtain a numerical parameter K02, related to the fundamental frequency of the plate, which has to be evaluated for each particular case. In this paper, have been evaluated the values of K02 for thin circular plates clamped or pinned at edge. An elliptical plate clamped at edge is also presented for several ratios of the semi–axes, one of which is identical with a circular plate.
Method for the Early Development of a Bayesian Prior Time-to-Failure Distribution for an Evolutionary Product Design
Authors: Baun Ward O.
Published: May 2009

This paper describes a method for the development of a Bayesian prior time-to-failure distribution used as an early estimate of the reliability of a new product which is an evolution of a previous ancestor design. In new product development, it is desirable to estimate the reliability of that new product as early as possible in the development program, in order to quantify future financial risks as a result of service costs, and to facilitate risk-based decision-making. It is difficult to make these reliability estimates sufficiently early in the development cycle to be of use in decision-making because of a lack of information. However, this “lack of information” is often a perception only, particularly when a new design is an evolution of a previous design. Making use of the reliability-related knowledge from an ancestor design can improve the accuracy of reliability predictions of the evolutionary design before testing of that design even commences. The method proposed is as follows. First, develop the list of failure mechanisms for the new product. Second, develop the time-to-failure distribution parameters for each of those mechanisms from ancestor product data, including the uncertainty inherent in each of those parameters. Third, develop a list of all changes being made in the new product design which will affect the reliability of the new design for a particular failure mechanism. Fourth, quantify the impact of each design change as an improvement factor distribution. Fifth, combine the ancestor product time-to-failure distribution parameters and the improvement rate factors using propagation of uncertainty rules to produce an estimate of the time-to-failure distribution parameters for the evolutionary product for each mechanism. Lastly, use Bayes’ rule to incorporate new information as the design process progresses. This method will allow estimates of new product reliability to be made earlier in the product development cycle. In making these estimates, this method will formally use pertinent reliability-related information from the previous generations of a product, and information on the impact of proposed design improvements. The method is architected in a manner that facilitates a structured approach to capturing and managing changes in the state of knowledge regarding the reliability of the new product which occur as the design process progresses. As new information arrives during the design process, in the form of either new field reliability information from the ancestor design, or on the demonstrated effectiveness of design improvements, that information can be formally entered into the model, and the reliability predictions for the product of interest can be updated to reflect that new state of knowledge.
Design and Testing of Gears With Non-Standard Profile
Authors: Zak P. , Dynybyl V.
Published: May 2009

This paper introduces a sophisticated methodology that guides the design of the non-standard geometry of cylindrical gearwheels, methodology for the evaluation of operation life depending on flank damage (pitting) in shortened lifetime tests of gearwheels and also number of other research results. The methodology for the design of gearwheels modifications is solved by using FEM system and takes into account real geometry of the whole gearbox and its component. Processed samples designs are tested in experimental testing stand and compared with samples which are designed using DIN 3990 standard Method B. The test results serves for verification of created designs. The back-to-back test-rig allowing smooth control of virtual power up to 785 kW (1053 HP) is also described. The methodology for evaluation of pitting area is solved by using digital documentation and automatic evaluation of damaged tooth flank surface.