bluuebunny/crossref_metadata_2025 huggingface dataset:
Quality Control and Monitoring of FRP Applications to Masonry Structures
Authors: Olivito R. S. , Zuccarello F. A.
Published: May 2008

Abstract:  The use of composite materials in strengthening and restoring interventions on existing structures is continuously increasing. During the last decades, many researchers have developed new strategies, technical solutions and analyses. In particular, the Italian CNR DT 200/2004 technical recommendations for the design and construction of strengthening techniques with fibre‐reinforced composite material (FRP) systems have been published to provide an aid to designers interested in the field of composite materials and to avoid their incorrect application. The Guidelines deal with different types of FRP applications both to masonry and reinforced concrete structures and take into account several tests for the quality control and monitoring of FRP installation. In the present study, the results of semi‐destructive and non‐destructive techniques conducted for the quality control and monitoring of FRP applications to masonry, according to CNR DT 200/2004 Guidelines, are reported. Pull‐off tests and shear‐tearing tests were performed on real brick and natural stone masonry buildings for the assessment of the quality of FRP application. Finally, non‐destructive tests were carried out to characterise the uniformity of FRP installation by means of thermographic tests. Different types of FRP fabrics have been adopted. The tests allowed the validation and assessment of procedures, methods and theoretical relationships suggested in the Guidelines.
Experimental Study of Effects of Process Parameters in Forge‐Welding Bimetallic Materials: AISI 316L Stainless Steel and 6063 Aluminium Alloy
Authors: Kong T. F. , Chan L. C. , Lee T. C.
Published: May 2008

Abstract:  Forge welding is a process that can overcome the limitations of friction welding and diffusion bonding for joining dissimilar metals, while still permitting a large amount of plastic deformation. However, the available information about forge welding of dissimilar metals is rare as most studies have focused on joining similar metals. This paper reports an investigation on effects of process parameters in forge‐welding bimetallic materials: AISI 316L stainless steel and 6063 aluminium alloy. Experiments were carried out under variations in process parameters, including forge‐welding temperature, amount of deformation and forging speed. The results showed that the forge‐welding temperature was the most significant process parameter and that this could highly influence the tensile strength of the joint. The quality joint was produced successfully. It could withstand the tensile strength of 111.3 MPa and this was comparable to the findings of other researchers. The diffusion zone of the joint was examined by the optical micrograph and elemental composition analysis. Intermetallic compounds were found in the diffusion zone, which was critical evidence for the validity of the experiment.
Intertextuality and the female voice after the Heroides
Authors: Lyne Raphael
Published: May 2008

Recent criticism of Ovid's Heroides has tried to attend properly to the female voices within the work. Effrosini Spentzou, in particular, has proposed a ‘lecture féminine’ that recognizes intertextuality as a male network working at the expense of women's expression. This essay explores the interaction of female speakers and intertextuality in early modern post‐Ovidian writing (by Donne, and Beaumont and Fletcher, with some reference to Shakespeare). In particular, it suggests ways in which literary women appear to find ways of making intertextuality serve their interests.
‘Perfectly Ovidian’? Dryden's Epistles, Behn's ‘Oenone’, Yarico's Island
Authors: Wiseman Susan
Published: May 2008

Taking as its starting point John Dryden's multi‐authored translation of Ovid's Heroides, Ovid's Epistles Translated by Several Hands (1680) this essay asks what seemed to readers to characterize the Heroides in Restoration England. The essay explores the modes of satire and pathos in the reception of Ovid in the period after the publication of Dryden's influential volume. First, it traces satirical reaction, asking about the possible invitation to satire present in Aphra Behn's ‘imitation’ of Ovid's epistle from Oenone to Paris because of Behn's lack of Latin. Second, it examines preceding translations and the characterization of the Heroides as suitable (and highly unsuitable) reading for women. Finally, it traces the use of the heroic epistle to discuss slavery in the eighteenth century. Exploring the story of Inkle and Yarico it suggests, tentatively, that the twin tendencies in the reception of the Heroides, satirical and pathetic, may both have worked to make available the form to articulate slavery.
Effects of Mirasol PRT treatment on storage lesion development in plasma‐stored apheresis‐derived platelets compared to untreated and irradiated units
Authors: Picker Susanne M. , Steisel Alexander , Gathof Birgit S.
Published: May 2008

BACKGROUND: The aim of this study was to examine the effects of a new riboflavin‐based pathogen reduction technology (PRT), the Mirasol PRT process (Navigant Biotechnologies) on platelet (PLT) storage lesion development.

STUDY DESIGN AND METHODS: A three‐arm in vitro study was conducted comparing cell quality of apheresis PLTs (n = 12 each) treated with Mirasol PRT (M) to untreated (C) and gamma‐irradiated units (X) collected from the same donors and stored for up to 7 days under equal conditions.

RESULTS: PLT count, lactate dehydrogenase, and K+ release of M units were not significantly different from C units, indicating retention of cell integrity during storage. The immediate effect (Day 1) of PRT treatment was a significant decrease in hypotonic shock response (M, 80.6 ± 7.8% vs. 89.2 ± 8.3%) and aggregation (M, 85.7 ± 15.2%/min vs. 111.8 ± 31.5%/min) as well as a significant acceleration of mitochondrial membrane depolarization (M, 1.43 ± 0.44% vs. 0.91 ± 0.27%) and P‐selectin expression (M, 38.4 ± 13.8% vs. 15.8 ± 7.7%) resulting in lower swirl scores on Day 5 (1.5 ± 0.7 vs. 2.7 ± 0.4). Significantly higher glucose consumption (60 ± 13 nmol/1012 cells/hr vs. 31 ± 9 nmol/1012 cells/hr) and lactate production rates (82 ± 17 nmol/1012 cells/hr vs. 40 ± 8 nmol/1012 cells/hr) caused higher acidity in treated units (pH on Day 5, 6.97 ± 0.15 vs. 7.42 ± 0.10). After PRT treatment, oxidative metabolism was still active and, from calculation of oxygen consumption (1.09 ± 0.23 nmol/min/109 PLTs), appeared to be up regulated relative to controls (0.76 ± 0.27 nmol/min/109 PLTs).

CONCLUSION: Although storage variables clearly showed the effects of PRT treatment, apheresis PLTs treated with Mirasol PRT retained cell quality during 5 days of storage without loss of mitochondria‐based oxidative respiration.
Nordic Luther Research in Motion
Authors: Holm Bo Kristian
Published: May 2008

Abstract:  Luther research in the Nordic countries is characterised by both continuation and discussion of its own legacy. Finnish Luther studies have a prominent position here, but are by no means the only actors in Nordic Luther research. Giving an overview of Nordic Luther research in the last decade, the article selects four main topics that have been the focus of special attention: politics and ethics, Communicatio idiomatum and Luther's view on language, Luther as preacher, and Luther and the gift. The article concludes with some comments on the continuing role of creation theology, so strongly emphasised in last century's Scandinavian Luther research.
Worship and the Eucharist in Luther Studies
Authors: Simon Wolfgang
Published: May 2008

Abstract:  In German as well as in international ecumenical discussions Luther's liturgical decision to delete most of the eucharistic prayer and emphasize the words of institution has been regarded as a problematic move. On the other hand, prominent Lutheran theologians continue to argue that this move is theologically sound, and that the ecumenical characterization of the Lord's Supper as the Eucharist is problematic because it stresses the human activity. This paper steers a middle course between these extremes, arguing that Luther's texts also show new possibilities for conceiving the sacrament in terms of thanksgiving and active response.
Do Antidepressants Work? Statistical Significance Versus Clinical Benefits
Authors: Johnson Blair T. , Kirsch Irving
Published: May 2008

Ours has been called the Prozac generation but, earlier this year, newspaper front page headlines screamed “Antidepressants don't work”. Our authors' reanalysis of drug trials was widely reported as implying that antidepressant drugs such as Prozac are overprescribed and useless. The truth, as Blair T. Johnson and Irving Kirsch explain, is more complex, and more interesting.
The Seventh Starling
Authors: Cavagna Andrea , Giardina Irene
Published: May 2008

A flock of starlings wheel overhead, thousands of birds rising, falling, turning as if of one mind. Birds move in flocks; fish in schools; insects in swarms. How do they do it? Can we study them to find quantitative answers or must we simply admire them?Andrea Cavagna and Irene Giardina do both.
Statistics with a Human Face
Authors: Bowman Adrian
Published: May 2008

How do you analyse a face?Adrian Bowman's statistics help children with cleft palates and show the symmetry behind the smile.
Panic now! Or Later?
Authors: Briscoe Simon
Published: May 2008

Simon Briscoe, author of a new book, Panicology, examines the role that data plays in media scare stories. Scary newspaper stories are scattered throughout this piece. Just how much ought we to be panicked by headlines?
Scatterplots Revisited
Authors: Reese Allan
Published: May 2008

How can a diagram present three or more variables at once?Allan Reese recommends keeping scatterplots two-dimensional—even if they represent higher dimensions of knowledge.
Six Sigma: An Opportunity for Statistics and For Statisticians
Authors: Coleman Shirley
Published: May 2008

Six Sigma is the name given to one of the most widely used methodologies for improving efficiency and profitability in manufacturing and production processes. Its users are trained in the basics of statistics, problem solving and project management. Shirley Coleman tells us that Six Sigma is an effective vehicle for introducing the statistics that have been available for years but have not been implemented.
Negishi–Solow efficiency wages, unemployment insurance and dynamic deterministic indeterminacy
Authors: Grandmont Jean‐Michel
Published: May 2008

This paper introduces efficiency wages designed to provide workers with incentives to make appropriate effort levels, and involuntary unemployment, along the pioneering lines of Negishi (1979), Solow (1979) and Shapiro and Stiglitz (1984), in a dynamic model involving heterogeneous agents and financial constraints as in Woodford (1986) and Grandmont et al. (1998). Effort varies continuously while there is unemployment insurance funded out of taxation of labor incomes. Increasing unemployment insurance is beneficial to employment along the deterministic stationary state, and can even in some cases lead to a Pareto welfare improvement for all agents, through general equilibrium effects, by generating higher individual real labour incomes, hence larger consumptions of employed and unemployed workers, and thus higher production. In contrast, the local (in)determinacy properties of the stationary state are opposite to those obtained in the competitive specification of the model: local determinacy (indeterminacy) occurs for elasticities of capital‐efficient labor substitution lower (larger) than a quite small bound. Increasing unemployment insurance is more likely to lead to local indeterminacy and, therefore, to generate dynamic inefficiencies due to the corresponding expectations coordination failures.
Sustainability of water management in Zaragoza city
Authors: Shirley‐Smith Chris , Cheeseman Chris , Butler David
Published: May 2008

This paper reviews the significant developments in water management that have occurred in Zaragoza, Spain in recent years. Action to achieve more sustainable water management was initiated by a local nongovernmental organisation (Ecodes) persuading and assisting the municipality to improve its delivery performance. Key successes, made by all sectors of the community, include the reduction of water use in the City by 1600 ML/year since 1995 despite significant population growth. The sustainability of the campaign is assessed within a recently devised PESTER framework which systematically addresses the key political, economic, social, technical, environmental and regulatory factors. This highlighted that a workable tariff system has now been achieved which is arguably fair to all, and that a balance has been achieved between local and nationally applicable water law. The main conclusion is that in order to achieve significant progress, it is vital to harmonise the energies, finances and above all commitment of all the main stakeholders.
Comparison of phosphorus removal between vertical subsurface flow constructed wetlands with different substrates
Authors: Tang X. Q. , Huang S. L. , Scholz M.
Published: May 2008

Phosphorus removal by constructed wetlands is a key strategy in diffuse pollution control. Phosphorus retention by experimental unplanted vertical‐flow constructed wetlands depends on substrate, influent quality and hydraulic residence time (HRT). The maximal phosphorus adsorption capacities of shale, gravel, ironstone and hornblende were 619.7, 89.05, 324.9 and 153.1 mg/kg, respectively, when the grain size ranged between 0.5 and 1.0 mm. Phosphorus adsorption capacities of shale, ironstone and hornblende were best explained by Langmuir adsorption isotherms. In comparison, Freundlich adsorption isotherms fitted gravel well. In separate column experiments with eutrophic Jin River water, shale showed better soluble reactive phosphorus (SRP) and total phosphorus (TP) retention performances than gravel, ironstone and hornblende. When the HRT was 2.2 days, the mean SRP removal rates were 96.7, 21.1, 33.6 and 33.0% for shale, gravel, ironstone and hornblende, respectively. Findings indicate that both SRP and TP removal rates increased when the HRT was prolonged.
The Bcl‐2 Antagonist HA14‐1 Forms a Fluorescent Albumin Complex that Can Be Mistaken for Several Oxidized ROS Probes
Authors: Kessel David , Price Michael , Reiners Jr John J.
Published: May 2008

The proapoptotic effects of the Bcl‐2 antagonist HA14‐1 are believed to derive from its affinity for the hydrophobic groove on Bcl‐2 and Bcl‐xL, thereby displacing proapoptotic factors, e.g. Bax and Bak. We have reported that HA14‐1 promotes the efficacy of low‐dose photodynamic therapy (PDT). A recent report proposed that the proapoptotic activity of HA14‐1 reflects its ability to generate reactive oxygen species (ROS) when incubated in an aqueous environment. This later study, like several other HA14‐1 investigations, relied on the use of fluorescent probes for ROS detection. We found that HA14‐1 reacts with the albumin in serum to yield a fluorescent product. After correcting for this effect, the putative formation of ROS by HA14‐1 could not be demonstrated with the fluorescent probes H2DCFDA, dihydroethidium or dihydrorhodamine. Indeed, the fluorescence excitation/emission spectra of HA14‐1 encompassed the excitation/emission wavelengths used to detect these ROS probes. Cells cultured in a medium supplemented with ovalbumin, instead of serum, underwent apoptosis following HA14‐1 addition, but did not exhibit fluorescence. Hence, HA14‐1 fluorescence was unrelated to its proapoptotic activity. We conclude that the enhancement of PDT by HA14‐1 reflects a pharmacologic effect, rather than its direct contribution of ROS.
Action Spectrum Conversion Factors that Change Erythemally Weighted to Previtamin D3‐weighted UV Doses†
Authors: Pope Stanley J. , Holick Michael F. , Mackin Steven , Godar Dianne E.
Published: May 2008

Many solar UV measurements, either terrestrial or personal, weight the raw data by the erythemal action spectrum. However, a problem arises when one tries to estimate the benefit of vitamin D3 production based on erythemally weighted outdoor doses, like those measured by calibrated R‐B meters or polysulphone badges, because the differences between action spectra give dissimilar values. While both action spectra peak in the UVB region, the erythemal action spectrum continues throughout the UVA region while the previtamin D3 action spectrum stops near that boundary. When one uses the previtamin D3 action spectrum to weight the solar spectra (Deff), one gets a different contribution in W m−2 than what the erythemally weighted data predicts (Eeff). Thus, to do proper benefit assessments, one must incorporate action spectrum conversion factors (ASCF) into the calculations to change erythemally weighted to previtamin D3‐weighted doses. To date, all benefit assessments for vitamin D3 production in human skin from outdoor exposures are overestimates because they did not account for the different contributions of each action spectrum with changing solar zenith angle and ozone and they did not account for body geometry. Here we describe how to normalize the ratios of the effective irradiances (Deff/Eeff) to get ASCF that change erythemally weighted to previtamin D3‐weighted doses. We also give the ASCF for each season of the year in the northern hemisphere every 5° from 30°N to 60°N, based on ozone values. These ASCF, along with geometry conversion factors and other information, can give better vitamin D3 estimates from erythemally weighted outdoor doses.
Comparability of the results of PT–INR with local MNPT and APTTR with MNAPTT on different coagulation analyzers in China
Authors: PENG L. , YAN C. , WU X. , NIE L.
Published: May 2008

The prothrombin time (PT), International normalized ratio (INR) and activated partial thromboplastin time (APTT) are the most used coagulation tests in China, where more than one type of automated coagulation analyzer is often used in the clinical laboratory. The PT–INR results of 109 samples were compared with local mean normal PT (MNPT) and APTT ratio (APTTR) with mean normal APTT (MNAPTT) on two different coagulation analyzers in the same laboratory. The two different coagulation analyzers showed no significant difference (P > 0.05) in PT and INR determination, but there was a significant difference (P < 0.01) for APTT. The INR with local MNPT and APTTR with MNAPTT, obtained with the ACL Futura and CA 510, showed much better agreement; 98.8% (82/83) of bias for INR with local MNPT was less than 15% compared with 90.4% (75/83) of bias for INR; and 100% of bias for APTTR (62/62) was less than 15% compared with only 6.5% (4/62) of bias for APTT. Meanwhile, there was no significant difference (P = 0.865) for APTTR with MNAPTT compared with APTT (P = 0.002) between the ACL Futura and CA 510. In conclusion, these analyzers showed very poor agreement for both the PT and APTT, but the calculation of ratios significantly improved agreement.
Red blood cell microcytosis and hypochromia in the differential diagnosis of iron deficiency and β‐thalassaemia trait
Authors: URRECHAGA E.
Published: May 2008

Iron deficiency anaemia (IDA) and β‐thalassaemia are the most common causes of microcytic anaemia. Some indices have been defined to quickly discriminate this diseases based on red cell parameters obtained from automated blood cell analyzers, and can be effective for use as a preliminary screening tool to allow the reflex HbA2 analysis, when a proper cut‐off is chosen. Advia 2120 (Siemens Medical Solutions Diagnostics) directly measures volume and haemoglobin concentration of individual red cells, and quantifies the percentage of microcytic, normocytic, macrocytic, hypochromic, normochromic and hyperchromic red cells. Because of the inverse behaviour of the % microcytic and % hypochromic red cells in β‐thalassaemia trait and in IDA the ratio between these two values was computed and its discriminant efficiency assessed. The aim of the study was to assess the predictive value of the new index % microcytic/% hypochromic ratio in the differential diagnosis of β‐thalassaemia compared with Mentzer index, currently used in our Laboratory. Sensitivity, specificity and total efficiency of both indices were calculated for a set of 110 IDA patients and 150 β‐thalassaemia carriers. Discriminant efficiency was similar for both indices.
Vitreomacular traction and exudative age‐related macular degeneration
Authors: Schulze Stephan , Hoerle Steffen , Mennel Stefan , Kroll Peter
Published: May 2008

Vitreomacular traction resulting from lacking, incomplete or anomalous posterior vitreous detachment is suspected to play a crucial role in the pathogenesis of different forms of age‐related macular degeneration (AMD) along with the known mechanisms. It is probable that the fundamental pathomechanisms of AMD formation have already begun by the time tractional forces lead to a change for the worse. Vitreomacular traction alone is perhaps not able to induce AMD. It would seem sensible to consider vitreous changes when diagnosing and treating AMD patients because of the high coincidence of vitreomacular traction and choroidal neovascularization (CNV) and the often successful treatment of other diseases of the vitreoretinal interface by vitrectomy. The concept of the pathogenesis of AMD should therefore be extended to include the influence of the vitreous, especially where therapeutic concepts such as pharmacological vitreolysis and vitreous separation have been established as causative treatment of late forms of AMD.
The Rotordynamic Forces on a Centrifugal Pump Impeller in the Presence of Cavitation
Authors: Franz R. , Acosta A. J. , Brennen C. E. , Caughey T. K.
Published: May 2008

An experiment in forced vibration was conducted to study the fluid-induced rotor-dynamic force on an impeller whirling along a trajectory eccentric to its undeflected position in the presence of cavitation. The prescribed whirl trajectory of the rotor is a circular orbit of a fixed radius. The force measured is a combination of a steady radial force due to volute asymmetries and an unsteady force due to the eccentric motion of the rotor. These measurements have been conducted over a full range of whirl/impeller speed ratios at different flow coefficients without cavitation for various turbomachines. A destabilizing force was observed over a region of positive whirl ratio. The range of flow conditions examined for a centrifugal impeller in a spiral volute has been enlarged to include cavitation. Compared to the non-cavitating condition, cavitation corresponding to a head a loss of three percent did not have a significant effect upon the unsteady force. However, a lesser degree of cavitation at the design point increased the destabilizing force for a particular set of whirl ratios.
Intermittency and Length Scale Distributions in a Plane Turbulent Plume
Authors: Chandrasekhara M. S. , Ramaprian B. R.
Published: May 2008

Previous studies have shown that normalized Reynolds shear stress and turbulent heat fluxes in asymptotic plane turbulent plumes are significantly higher than in asymptotic plane turbulent jets. This paper describes an attempt to relate this increase to the length scales in the flow. Hot/cold interface intermittency and integral-length-scale distributions were measured in both these flows. The interface-intermittency distributions were found to be bell-shaped in the plume in contrast to a nearly top-hat shape in a jet, thus providing confirmation of the role of buoyancy in generating larger scales in plumes. These larger scales cause the integral length of turbulence in the plume to increase by nearly 15 percent relative to the non-buoyant jet.
A Study on Vortex Shedding From Spheres in a Uniform Flow
Authors: Sakamoto H. , Haniu H.
Published: May 2008

Vortex shedding from spheres at Reynolds numbers from 3 × 102 to 4 × 104 in a uniform flow was investigated experimentally. Standard hot-wire technique were used to measure the vortex shedding frequency from spheres in a low-speed wind tunnel. Flow-visualization experiments were carried out in a water channel. Important results from the investigation were that (i) the variation of the Strouhal number St (=fD/U0, U0: freestream velocity, D: diameter of the sphere, f: vortex shedding frequency) with the Reynolds number (= U0D/v, v: kinematic viscosity) can be classified into four regions, (ii) the Reynolds number at which the hairpinshaped vortices begin to change from laminar to turbulent vortices so that the wake structure behind the sphere is not shown clearly when a Reynolds number of about 800 is reached, and (vi) at Reynolds numbers ranging from 8X102 to 1.5X104, the higher and lower frequency modes of the Strouhal number coexist.
An Experimental Study of the Flow Downstream of a Circular and Tapered Cylinder
Authors: Eibeck P. A.
Published: May 2008

The flow downstream of the intersection of both a circular and a tapered cylinder with a flat plate was examined at ReD = 1.3 × 105 using surface visualization, five-hole-probe anemometry, and flow visualization. A pair of large, counter-rotating swirls with common flow away from the wall and with centers over one diameter away from the wall was present downstream of both obstacles. It is suggested that the large, swirling pair are formed in the near wake of an obstacle that is exposed to symmetrical channel flow. A pair of smaller counter-rotating vortices with common flow toward the wall was observed embedded in the wall-shear flow eight diameters downstream of the tapered cylinder. This implies that the legs of the horseshoe vortex system only propagate downstream behind the streamlined obstacle shape.
Studies on Unsteady Pressure Fields in the Region of Separating and Reattaching Flows
Authors: Govinda Ram H. S. , Arakeri V. H.
Published: May 2008

Experimental studies on the measurement of pressure fields in the region of separating and reattaching flows behind several two-dimensional fore-bodies and one axisymmetric body are reported. In particular, extensive measurements of mean pressure, surface pressure fluctuation, and pressure fluctuation within the flow were made for a series of two-dimensional fore-body shapes consisting of triangular nose with varying included angle. The measurements from different bodies are compared and one of the important findings is that the maximum values of rms pressure fluctuation levels in the shear layer approaching reattachment are almost equal to the maximum value of the surface fluctuation levels.
Application of Momentum Integral Methods and Linearized Potential Theory for Predicting Separation Bubble Characteristics
Authors: Stropky D. M. , Djilali N. , Gartshore I. S. , Salcudean M.
Published: May 2008

A new viscous-inviscid interaction procedure of the semi-inverse type has been developed to predict two-dimensional separated flows. The method is applied to incompressible flow over an external backward-facing step, using linearized potential theory for the inviscid region and a simple modification of Pohlhausens’ momentum-integral method in the viscous region. The modified Pohlhausen method, which approximates the reverse flow region with a region of “dead-air,” is first tested without the viscous-inviscid procedure to predict fully developed laminar and turbulent flow in a plane symmetric sudden expansion. Comparisons are made with experimental data, other calculation methods, and finite difference predictions using a modified version of an elliptic code (TEACH-II). Reasonable predictions of the sudden expansion and backward-facing step flows are obtained, provided that the step-height to boundary-layer thickness ratio is large enough for the Pohlhausen type velocity profiles to be effective. The relative simplicity of the zonal equations coupled with the viscous-inviscid interaction procedure makes the present calculation method computationally attractive. The method should also prove useful in more complex separated flow situations, such as bluff-body aerodynamics.
Experimental Study of Casing Boundary Layers in a Multistage Axial Compressor
Authors: Venkateswaran S.
Published: May 2008

Measurements of the casing boundary layers were obtained in a four-stage, low speed axial flow compressor, to verify the ‘law of the wall’ applicability to these complex flows. Some of the available shear stress models of the two-dimensional flows have been examined towards the quantitative assessment of skin friction. The shear stress prediction obtained from the Ludwieg-Tillmann relation applied to the streamwise or untwisted profile agreed closely with the measured shear stress by the hot wire. The skin friction was fairly constant for rotor and stator flows and was close to the flat plate values. The boundary layer profiles exhibited a well pronounced semi-logarithmic region with the universal constants of the law of the wall far removed from the standard two dimensional values, especially for rotor flows. Stator flows showed signs of similarity to two dimensional flows.
Convective Gaseous Diffusion in Steady Axisymetric Cavity Flows
Authors: Parkin B. , Ravindra K.
Published: May 2008

Theoretical results on gaseous convective turbulent diffusion in steady axisymmetric flows are found to compare well with experimental results already in the literature. The investigation starts with the formulation of a highly idealized “slug-flow” model of the process for a quick estimate of the importance of turbulent boundary layer convection and for a comparison of previously published experimental and analytical results which had revealed order-of-magnitude discrepancies between calculated and measured air diffusion rates. Next, an existing two-dimensional convective diffusion model is adapted to axisymmetric cavity flow. Good agreement between experimental and calculated mass flow rates is found with a proper choice of turbulent diffusively from a Launder-Spaulding mixing-length model. The adapted “wrap around” model predicts a concentration boundary-layer thickness of the order of the cavity radius at the cavity terminus. Consequently, an axisymeetric analysis is also presented. From this it is found that the important part of the gaseous mass flow into the cavity occurs near the very front of the cavity where the concentration gradients are most severe. Downstream flow regions near the cavity are thereby depleted of dissolved air and the resulting concentration gradients are greatly reduced. Therefore the mass flow rate through downstream cavity surfaces are relatively unimportant and the simpler wrap around calculation can give useful engineering estimates of total mass flow rates.
Vortex Shedding From a Bluff Body Adjacent to a Plane Sliding Wall
Authors: Arnal M. P. , Goering D. J. , Humphrey J. A. C.
Published: May 2008

The characteristics of the flow around a bluff body of square cross-section in contact with a solid-wall boundary are investigated numerically using a finite difference procedure. Previous studies (Taneda, 1965; Kamemoto et al., 1984) have shown qualitatively the strong influence of solid-wall boundaries on the vortex-shedding process and the formation of the vortex street downstream. In the present study three cases are investigated which correspond to flow past a square rib in a freestream, flow past a rib on a fixed wall and flow past a rib on a sliding wall. Values of the Reynolds number studied ranged from 100 to 2000, where the Reynolds number is based on the rib height, H, and bulk stream velocity, Ub. Comparisons between the sliding-wall and fixed-wall cases show that the sliding wall has a significant destabilizing effect on the recirculation region behind the rib. Results show the onset of unsteadiness at a lower Reynolds number for the sliding-wall case (50 ≤ Recrit ≤100) than for the fixed-wall case (Recrit≥100). A careful examination of the vortex-shedding process reveals similarities between the sliding-wall case and both the freestream and fixed-wall cases. At moderate Reynolds numbers (Re≥250) the sliding-wall results show that the rib periodically sheds vortices of alternating circulation in much the same manner as the rib in a freestream; as in, for example, Davis and Moore [1982]. The vortices are distributed asymmetrically downstream of the rib and are not of equal strength as in the freestream case. However, the sliding-wall case shows no tendency to develop cycle-to-cycle variations at higher Reynolds numbers, as observed in the freestream and fixed-wall cases. Thus, while the moving wall causes the flow past the rib to become unsteady at a lower Reynolds number than in the fixed-wall case, it also acts to stabilize or “lock-in” the vortex-shedding frequency. This is attributed to the additional source of positive vorticity immediately downstream of the rib on the sliding wall.
A Theoretical and Experimental Study of the Characterization of Bubbles Using Light Scattering Interferometry
Authors: Bren˜a de la Rosa A. , Sankar S. V. , Weber B. J. , Wang G. , Bachalo W. D.
Published: May 2008

The present work details the theoretical and experimental research undertaken to determine the size and morphology of bubbles, and their dynamic characteristics such as velocity, number density, and volume flux using light scattering interferometry. The approach is based on the measurement of the phase difference of the interference fringe pattern which is produced when a particle passing through the probe volume defined by the intersection of two laser beams scatters light and interferes in the surrounding medium. Detailed analytical/numerical modeling of the phase Doppler approach using Mie scattering theory and the geometrical optics approximation resulted in optimum light scattering collection angles and calibration curves for bubble diagnostics. Using several techniques to generate a steady stream of monosize bubbles in the range from 6 μ to 1800 μm in diameter, the measurements obtained using the phase Doppler method were compared with direct photography yielding an agreement of better than 95 percent. The morphology of spheroidal bubbles was also investigated by placing the transmitting and receiving optical units at specified locations with respect to the scatterers. It is believed that this theoretical and experimental work has given the phase Doppler method general validity as applied to bubble diagnostics and promises to become a powerful research tool in the study of two phase flows.
Experimental and Analytical Study of Flow Diversion Beyond an Underexpanded Nozzle
Authors: Hansen E. C.
Published: May 2008

A steady-state flow apparatus was used to investigate the process of gun gas diversion through a single hole perforated disk diverter. The amount of diverted flow was found to depend on the distance between the nozzle and the diverter disk and the ratio of nozzle pressure to diverter exit pressure. Experimental studies used nitrogen and carbon dioxide as the working fluids to show the effect of specific heat ratio. At ratios of nozzle pressure to ambient pressure ranging from 4 to 60 diversion efficiencies of 50 to 99 percent were produced. A one-dimensional analytic gas flow model was developed. Results of the analytic model paralleled the experimental data for pressure ratios over 10.
Fluid Flow Through a Porous Medium Channel With Permeable Walls
Authors: Khodadadi J. M. , Kroll J. T.
Published: May 2008

A theoretical study of the fully developed fluid flow through a porous medium channel bounded by two permeable walls is presented. In the absence of inertia effects, a closed-form analytic solution to the volume-averaged momentum equation is obtained. The velocity profiles are illustrated for several combinations of the porous medium shape parameter and the blowing Reynolds number. The variations of the maximum velocity and the boundary frictional drag coefficient are also discussed.
On Laminar Wakes Behind a Circular Cylinder in Stratified Fluids
Authors: Hwang Robert R. , Lin S. H.
Published: May 2008

Finite-difference techniques based on boundary-fitted coordinates have been developed to study the flow of a stably stratified viscous fluid past a circular cylinder. A time-dependent approach is used and an implicit solution is applied in the implementation of vorticity-stream function formulation. All field equations are approximated using central differences and solved simultaneously at each time step by the SOR iteration. Results show that the stratification tends to retard the vortex shedding from the two sides of the cylinder and to narrow down the wake behind the cylinder. With increasing stratification, the drag exerted by the fluid on the cylinder at first decreases and then increases. These solutions also indicate that the periodic configurations of the oscillatory character of the wake flow decrease with the increase of stratification.
Flow Past Circular Cylinder With Different Surface Configurations
Authors: Leung Y. C. , Ko N. W. M. , Tang K. M.
Published: May 2008

Measurements of the mean pressure distributions and Strouhal numbers on partially grooved cylinders with different groove subtend angles were made over a Reynolds number range of 2.0×104 to 1.3×105 which was within the subcritical regime of smooth cylinder. The Strouhal number, pressure distributions, and their respective coefficients were found to be a function of the groove subtend angles. In general, a progressive shift of the flow regime to lower Reynolds number was observed with higher subtend angle and a subtend angle of 75 deg was found for optimum drag reduction. With the configuration of asymmetrical groove surface, lower drag, and higher lift coefficients were obtained within the same Reynolds number range. Wake traverse and boundary layer results of the asymmetric grooved cylinder indicated that the flows at the smooth and groove surfaces lied within different flow regimes and a downward shift of the wake.
Effect of Passenger Car’s Rear Deck Geometry on Its Aerodynamic Coefficients
Authors: Katz J. , Dykstra L.
Published: May 2008

The effects of aerodynamic modifications near the rear deck of a passenger-car based race car were investigated experimentally. The modifications were evaluated on a quarter-scale wind tunnel model and included a rear spoiler and a wing. The experimental results indicate that these devices alter the flow field on the vehicle’s body resulting in considerable negative lift coefficients. Also, this aerodynamic interaction is sensitive to rear wing location and when properly placed the total lift owing to the rear wing, combined with its effect on the vehicle’s body, can amount to twice the lift of the isolated wing.
Prediction of Confined Three-Dimensional Impinging Flows With Various Turbulence Models
Authors: Liou T. M. , Hwang Y. H. , Chen L.
Published: May 2008

This paper deals with three-dimensional, turbulent, confined impinging flows. Various turbulence models are examined with reported laser-Doppler velocimetry data and flow-visualization photographs. The turbulence models considered are the k–ε, k–ε with the Richardson number correction for swirling and recirculating flows (k–ε w/scm), algebraic Reynolds stress (k–ε–A), and modified k–kl models. The k–ε and k–ε–A models are found to be superior to the k–ε w/scm and modified k–kl models in predicting the main flow characteristics. The k–ε–A model provides a better quantitative agreement with the experimental data than can be achieved with the k–ε model, however, less computational effort is spent with the k–ε model than with the k–ε–A model. Also, the effect of the inlet velocity profile on the characteristics of the confined impinging flows is addressed in this study.
Boundary-Layer Transition in Accelerating Flows With Intense Freestream Turbulence: Part 1—Disturbances Upstream of Transition Onset
Authors: Blair M. F.
Published: May 2008

Hot-wire anemometry was employed to examine the laminar-to-turbulent transition of low-speed, two-dimensional boundary layers for two (moderate) levels of flow acceleration and various levels of grid-generated freestream turbulence. Flows with an adiabatic wall and with uniform-flux heat transfer were explored. All of the experimental test cases resulted in bypass-mode transitions, a conclusion based upon the observance of spots upstream of the theoretical minimum critical Reynolds number (three cases) or, for one case, upon the evidence that T-S mode amplification played no apparent role in the transition. Data obtained for the preonset stage indicate that the streamwise-component fluctuation-amplitude distributions, frequency distributions and outer-region waveforms of these bypass-mode transitions were similar to those reported in the literature for low-freestream-turbulence transitions. Within the zone upstream of the first appearance of turbulent spots: (1) The near-wall (Y<δ/2) fluctuations were predominantly low-frequency (frequency approximately 1/5 of that of the most amplified T-S disturbances). (2) The maximum streamwise-component fluctuations occurred over the altitude band 0.3<Y/δ<0.4. (3) Very strong negative “spikes” in streamwise velocity were observed, just upstream of spot initiation, at boundary-layer altitudes near Y/δ=0.6.
Numerical Solution of the Incompressible Boundary-Layer Equations Using the Finite Element Method
Authors: Schetz J. A. , Hytopoulos E. , Gunzburger M.
Published: May 2008

A new approach to the solution of the two-dimensional, incompressible, boundary-layer equations based on the Finite Element Method in both directions is investigated. Earlier Finite Element Method treatments of parabolic boundary-layer problems used finite differences in the streamwise direction, thus sacrificing some of the possible advantages of the Finite Element Method. The accuracy and computational efficiency of different interpolation functions for the velocity field are evaluated. A new element especially designed for boundary layer flows is introduced. The effect that the treatment of the continuity equation has on the stability and accuracy of the numerical results is also discussed. The parabolic nature of the equations is exploited in order to reduce the memory requirements. The solution is obtained for one line at a time, thus only two levels are required to be stored at any time. Efficient solvers for tridiagonal and pentadiagonal forms are used for solving the resulting matrix problem. Numerical predictions are compared to analytical and experimental results for laminar and turbulent flows, with and without pressure gradients. The comparisons show very good agreement. Although most of the cases were tested on a mainframe, the low requirements in CPU time and memory storage allows the implementation of the method on a conventional PC.
An Inverse Inner-Variable Theory for Separated Turbulent Boundary Layers
Authors: Das D. K.
Published: May 2008

An integral method is presented for computing separated and reattached turbulent boundary layers for incompressible two-dimensional flows. This method is a substantial improvement over the inner-variable approach of Das and White (1986), which was based on a direct boundary layer scheme that had several shortcomings. In this new approach, the integral equations have been completely reformulated so that the theory now proceeds in an inverse mode using displacement thickness as input. This new formulation eliminates the need for the second derivative of velocity distribution, which in the past has always been a source of error in all previous inner-variable approaches. Other significant additions are: (a) a single pressure gradient-wake correlation from a large amount of experimental data; and (b) replacement of the wake parameter from the final equations with a more stable parameter, wake velocity. Derivations of integral equations and their final working expressions, in both dimensional and nondimensional forms, are presented in detail. Predictions by this theory for skin friction, freestream velocity, momentum thickness, velocity profile and separation, and reattachment points agree well with experimental data. Sensitivity studies display that the theory is stable against variations in initial conditions, input distributions, and the pressure gradient-wake correlation.
Prediction of Rotor Dynamic Destabilizing Forces in Axial Flow Compressors
Authors: Colding-Jorgensen J.
Published: May 2008

It has been shown by Thomas (1958) and Alford (1965), that axial flow turbo-machinery is subject to rotor dynamic destabilizing gas forces produced by the circumferential variation of blade-tip clearance when the rotor is whirling. However, the magnitude and direction of these forces have yet to be clarified. For example, it is still uncertain, under which circumstances the rotor whirl direction will be forward, and when it will be backward, with respect to the rotation. In the present paper, a simple analysis of the perturbed flow in an axial compressor stage with whirling rotor is presented, based on the actuator disc analysis of Horlock and Greitzer (1983), and the gas force on the rotor is calculated on this basis. It appears that in the normal operation range of an axial compressor, the whirl direction is predicted to be forward always. Backward whirl is predicted to take place only at very low flow rates, well below the normally expected stall limit. Experimentally, forces were indeed found in direction of backward whirl for low flow rates, and in direction of forward whirl for high flow rates, in the results reported by Vance and Laudadio (1984), as analyzed by Ehrich (1989). While this experimental evidence supports the present theory qualitatively, a direct comparison of the measured and predicted destabilizing force has yet to be carried out.
Some Unsteady Fluid Forces on Pump Impellers
Authors: Miskovish R. S. , Brennen C. E.
Published: May 2008

Spectral analyses of all the forces and moments acting on a typical centrifugal pump impeller/volute combination are presented. These exhibit shaft frequencies, blade passing frequencies, and beat frequencies associated with a whirl motion imposed on the shaft in order to measure rotordynamic forces. Among other features the unsteady thrust was found to contain a surprisingly large blade passing harmonic. While previous studies have explored the magnitudes of the steady fluid-induced radial forces and the fluid-induced rotordynamic forces for this typical centrifugal pump impeller/volute combination, this paper presents information on the steady bending moments and rotordynamic moments due to the fluid flow. These imply certain axial locations for the lines of action of the radial and rotordynamic forces. Data on the lines of action are presented and allow inferences on the sources of the forces.
The Effect of Blade Manipulator in Fully Developed Pipe Flow
Authors: Mah Y. A. , Khoo B. C. , Chew Y. T.
Published: May 2008

Experiments were carried out in applying the concept of passive device called BLADEs (boundary-layer alteration devices) to fully developed pipe flow to assess its feasibility as a drag reduction device. The results of both the volumetric flow rate measurement and the pipe wall pressure distribution taken far downstream show that there is a net increase in drag with the device. With BLADES in tandem arrangement, there is a further net increase in drag which is contrary to its counterpart in boundary layer flow. Although the wall shear stress measurement following the device indicates some reduction in local drag, its magnitude of reduction is much smaller than that seen in the equivalent boundary flow. All these results suggest little possibility of any useful application of BLADEs to pipe flow.