bluuebunny/crossref_metadata_2025 huggingface dataset:
Smooth muscle signalling pathways in health and disease
Authors: Kim H. R. , Appel S. , Vetterkind S. , Gangopadhyay S. S. , Morgan K. G.
Published: October 2008

Introduction

Mechanisms that regulate LC20 phosphorylation

Mechanisms that regulate the access of myosin to actin

Mechanisms that regulate cytoskeletal remodelling

Conclusions

Smooth muscle contractile activity is a major regulator of function of the vascular system, respiratory system, gastrointestinal system and the genitourinary systems. Malfunction of contractility in these systems leads to a host of clinical disorders, and yet, we still have major gaps in our understanding of the molecular mechanisms by which contractility of the differentiated smooth muscle cell is regulated. This review will summarize recent advances in the molecular understanding of the regulation of smooth muscle myosin activityviaphosphorylation/dephosphorylation of myosin, the regulation of the accessibility of actin to myosinvia theactin‐binding proteins calponin and caldesmon, and the remodelling of the actin cytoskeleton. Understanding of the molecular ‘players’ should identify target molecules that could point the way to novel drug discovery programs for the treatment of smooth muscle disorders such as cardiovascular disease, asthma, functional bowel disease and pre‐term labour.
Alveolar adenoma of the lung
Authors: SAK SERPIL DIZBAY , KOSEOGLU RESIT DOGAN , DEMIRAG FUNDA , AKBULUT HAKAN , GUNGOR ADEM
Published: October 2008

Alveolar adenoma is a rare and benign tumour of the lung that usually presents in asymptomatic patients as a coin lesion on chest radiography. Only 25 cases have been reported in the English medical literature. Alveolar adenoma has a characteristic multicystic histology and often resembles the normal lung parenchyma. Ultrastructural studies indicate that the epithelial cells lining the cysts are type‐II pneumocytes. Immunohistochemical analysis may aid in the characterization of alveolar adenoma and discriminate this condition from other types of benign lesions of the lung. An indolent clinical progression and absence of recurrence and metastasis after complete resection are the most important characteristics indicative of the benign nature of alveolar adenoma. Few studies have been conducted at the molecular level, such as by flow cytometry, with the objective of characterizing the biological nature of alveolar adenoma. Differential diagnoses include sclerosing hemangioma, papillary adenoma, lymphangioma, atypical adenomatous hyperplasia and bronchioloalveolar carcinoma. In this article we describe the immunohistochemical and flow cytometric features of this neoplasm in two male patients. Both the tumours showed a diploid DNA pattern with a low proliferation index. p53 test was found to be negative, and post‐operative follow‐up examinations at 22 and 32 months proved uneventful.
Giant angiolymphoid hyperplasia with eosinophilia on the chest
Authors: Trindade Felicidade , Haro Rosario , Requena Luis
Published: October 2008

Angiolymphoid hyperplasia with eosinophilia is a rare vascular proliferation characterized by single or multiple purplish, brownish papules and subcutaneous nodules, sometimes associated with pain or pruritus. This rare benign process occurs with a female predominance. Approximately 85% of the lesions occur in the skin of the head and neck; most of them are around the ear or on the forehead or scalp. Whether angiolymphoid hyperplasia with eosinophilia represents a benign neoplasm or an unusual reaction to varied stimuli, including trauma, the etiology remains unclear. Histopathologically, the lesions consist of a proliferation of blood vessels of variable size lined by large epithelioid endothelial cells and a variable inflammatory infiltrate of lymphocytes and eosinophils, sometimes with lymphoid follicle formation. The lesion is benign but may be persistent and is difficult to eradicate. We report on a case of a 58‐year‐old Caucasian man who presented a purplish pink dome‐shaped tumor of size up to 8 cm in diameter located on the chest. We emphasize this case considering the unusual dimensions of the lesion (8 cm diameter) and the atypical location on the chest.
A Question of Ethics: Research and Practice in Reproductive Health
Authors: RamaRao Saumya , Friedland Barbara , Townsend John W.
Published: October 2008

The intent of the ethical guidelines and regulations, developed over time, that govern research on human subjects is to ensure that research participants are well‐informed volunteers, protected from harm, ensured potential benefit, and enrolled in an egalitarian fashion. This study discusses ethical issues that researchers and program planners grapple with in the area of sexual and reproductive health. We illustrate the dilemmas that arise in the application of the ethical principles, how they have been addressed, lessons learned, and remaining challenges. The illustrations come both from research and from service‐delivery situations.
Routine Testing for HIV/AIDS in Sub‐Saharan Africa: A Philosopher's Perspective
Authors: Brockway George M.
Published: October 2008

This article summarizes some important arguments for and against instituting a routine testing regimen for HIV/AIDS in sub‐Saharan Africa. After reviewing these competing positions and noting their areas of agreement and disagreement, the author recommends an alternative way to solve the main sticking point between them, that is, how to test a large majority of the population while still respecting their human rights to autonomy and freedom from unnecessary harm. This article argues that the proposed solution would respect the rights to autonomy of the individual to a sufficient degree and stands a greater chance of being both practicable and effective than the alternatives.
Ethics, Ideology, and Reproductive Health Policy in the United States
Authors: Kulczycki Andrzej
Published: October 2008

The 1994 International Conference on Population and Development held in Cairo recognized the centrality of reproductive health to human rights and development. Progress on the Cairo agenda has slowed for numerous reasons, however. The United States, once an enthusiastic promoter of this agenda and still the world's leading reproductive health donor, has revised its reproductive health policies radically since the 2000 presidential election of George W. Bush. This study examines how policies have been reconfigured in five key reproductive health areas, sparking controversy both in the United States and internationally. These categories are the content of sex education, access to emergency contraception and to abortion services, condom effectiveness, and HIV/AIDS prevention. The analysis presented here elucidates how ideological considerations have superseded public health and ethical concerns and reflects on health and ethical consequences.
Phenyl hydroquinone, an Ames test‐negative carcinogen, induces Hog1‐dependent stress response signaling
Authors: Yamamoto Ayumi , Nunoshiba Tatsuo , Umezu Keiko , Enomoto Takemi , Yamamoto Kazuo
Published: October 2008

Recently, we have shown that phenyl hydroquinone, a hepatic metabolite of the Ames test‐negative carcinogen o‐phenylphenol, efficiently induced aneuploidy in Saccharomyces cerevisiae. We further found that phenyl hydroquinone arrested the cell cycle at G1 and G2/M. In this study, we demonstrate that phenyl hydroquinone can arrest the cell cycle at the G2/M transition as a result of stabilization of Swe1 (a Wee1 homolog), probably leading to inactivation of Cdc28 (a Cdk1/Cdc2 homolog). Furthermore, Hog1 (a p38 MAPK homolog) was robustly phosphorylated by phenyl hydroquinone, which can stabilize Swe1. On the other hand, Chk1 and Rad53 were not phosphorylated by phenyl hydroquinone, indicating that the Mec1/Tel1 DNA‐damage checkpoint was not functional. Mutations of swe1 and hog1 abolished phenyl hydroquinone‐induced arrest at the G2/M transition and the cells became resistant to phenyl hydroquinone lethality and aneuploidy development. These data suggest that a phenyl hydroqionone‐induced G2/M transition checkpoint that is activated by the Hog1–Swe1 pathway plays a role in the development of aneuploidy.
Junior doctor strike model of care: Reduced access block and predominant Fellow of the Australasian College for Emergency Medicine staffing improve emergency department performance
Authors: Thornton Vanessa , Hazell Wayne
Published: October 2008

Objective:  To describe the response and analyse ED performance during a 5‐day junior doctor strike.

Methods:  Data were collected via the patient information management computer system. Key performance indicators included percentage seen within maximum waiting times per triage category (TC), ED length of stay, emergency medicine patients who did not wait to be seen, hospital bed occupancy and access block percentage. Comparisons were made for the same 5 days before the strike (BS), during the strike (S) and after the strike.

Results:  Total doctor's shifts BS were 78.66 with 25% of these shifts being Fellow of the Australasian College for Emergency Medicine (FACEM) shifts. FACEM shifts were more common during the S period at 75% (P < 0.001). Total attendances (BS 631 vs S 596, P = 0.22) and TC percentages (P‐values for TC 1, 2, 3, 4, 5, respectively, 1.0, 0.55, 0.88, 0.97, 0.46) in the BS, S and after‐the‐strike periods were not significantly different. Despite fewer total doctor shifts, the FACEM predominant model of care during the strike resulted in better percentages seen within the maximum waiting times for TC3 (66%), TC4 (78%) and TC5 (86%) (all P < 0.001). There was a reduction in patients who did not wait to be seen (28 BS vs 5 S, P < 0.001), ED length of stay (admissions: BS 451 min vs S 258 min, P < 0.001; discharges: BS 233 min vs S 144 min, P < 0.02) and referrals to inpatient services (P = 0.02). This occurred with reduced bed point occupancy of 66% and a consequent reduction in access block.

Conclusion:  FACEM staffing and reduced access block were significant factors in improved ED performance.
Perceived Barriers and Benefits to Research Participation Among School Administrators*
Authors: Befort Christie , Lynch Rachel , James Rochelle L. , Carroll Shawna L. , Nollen Nicole , Davis Ann
Published: October 2008

Background:  Gaining access to conduct research in schools can be challenging, but little has been done to directly assess school administrators’ perceptions of research. The purpose of this qualitative study was to increase understanding of barriers and benefits of research participation as perceived by superintendents and principals in elementary, middle, and high school settings.

Methods:  Administrators (14 elementary, 14 middle, and 15 high school principals and 14 superintendents; total n = 57) were randomly selected from across a Midwestern state and were interviewed by phone following a semistructured guide of questions.

Results:  Six major themes were consistent across principals and superintendents and reached saturation. Themes indicated that administrators were interested in research projects that (1) provide tangible benefits to their school, (2) are consistent with their academic mission, (3) are not burdensome, (4) do not take place during state assessment time or other busy times, and (5) are credible and noncontroversial. Previous research experiences leave a lasting impression on administrators and influenced their future decisions.

Conclusions:  Findings indicate that researchers should carefully frame their research in terms of how it will directly benefit the school, keeping in mind that academic performance is the top priority for school administrators. Researchers should be very clear and realistic about the time commitments, how the research results will be provided, and how the study may be used to improve the school’s academic mission.
Favorable Cardiovascular Risk Factor Profile Is Associated With Reduced Prevalence of Coronary Artery Calcification and Inflammation in Asymptomatic Nondiabetic White Men
Authors: Michos Erin D. , Santos Raul D. , Narla Venkata , Pandey Shivda , Meneghelo Romeu , Carvalho Jose A. , Budoff Matthew J. , Blumenthal Roger S. , Nasir Khurram
Published: October 2008

Middle‐aged individuals with favorable levels of all major cardiovascular risk factors (CVRFs) have much lower age‐specific risks for incident cardiovascular disease (CVD). However, the relationship of the absence of CVRFs with subclinical CVD and inflammation is not well described. We classified 440 asymptomatic Brazilian men (aged 46±7 years) based on the number of CVRFs (smoking, systolic blood pressure ≥130 mm Hg, low‐density lipoprotein cholesterol ≥130 mg/dL, high‐density lipoprotein cholesterol <40 mg/dL, triglycerides ≥150 mg/dL, fasting glucose ≥100 mg/dL, and waist circumference >102 cm). Only 7% had no CVRFs, whereas 1, 2, 3, and ≥4 CVRFs were observed in 18%, 24%, 21%, and 29%, respectively. In age‐adjusted analysis, each lower CVRF profile was associated with lower odds of prevalent coronary artery calcium (odds ratio, 0.75; P=.002) and elevated white blood cell count (odds ratio, 0.70; P<.001). Our study supports the notion that a favorable CVD profile is associated with less underlying atherosclerosis and inflammation and further highlights the importance of primary prevention of CVRFs.
Directed evolution of Aspergillus niger glucoamylase to increase thermostability
Authors: McDaniel Allison , Fuchs Erica , Liu Ying , Ford Clark
Published: October 2008

Using directed evolution and site‐directed mutagenesis, we have isolated a highly thermostable variant of Aspergillus niger glucoamylase (GA), designated CR2‐1. CR2‐1 includes the previously described mutations Asn20Cys and Ala27Cys (forming a new disulfide bond), Ser30Pro, Thr62Ala, Ser119Pro, Gly137Ala, Thr290Ala, His391Tyr and Ser436Pro. In addition, CR2‐1 includes several new putative thermostable mutations, Val59Ala, Val88Ile, Ser211Pro, Asp293Ala, Thr390Ser, Tyr402Phe and Glu408Lys, identified by directed evolution. CR2‐1 GA has a catalytic efficiency (kcat/Km) at 35°C and a specific activity at 50°C similar to that of wild‐type GA. Irreversible inactivation tests indicated that CR2‐1 increases the free energy of thermoinactivation at 80°C by 10 kJ mol−1 compared with that of wild‐type GA. Thus, CR2‐1 is more thermostable (by 5 kJ mol−1 at 80°C) than the most thermostable A. niger GA variant previously described, THS8. In addition, Val59Ala and Glu408Lys were shown to individually increase the thermostability in GA variants by 1 and 2 kJ mol−1, respectively, at 80°C.
Shift of temporal responsivity curve of pattern reversal visually evoked potentials to lower frequencies in patients after recovery from optic neuritis
Authors: Okuno Takashi , Oku Hidehiro , Sugasawa Jun , Utsumi Takashi , Ikeda Tsunehiko
Published: October 2008

Purpose:  To investigate the responsivity of the visual system to pattern reversal stimuli of different reversal rates in optic neuritis patients after a full recovery of visual acuity.

Methods:  Thirty eyes with optic neuritis and 30 eyes of age‐matched normal controls were studied. Steady‐state pattern reversal visually evoked potentials (P‐VEPs) were recorded using reversal rates of 2, 10, 20 and 30 Hz. The relationship between the amplitudes of the P‐VEPs and reversal rate was analysed. The temporal responsivity curves of the two groups were compared.

Results:  The means ± standard deviations (SDs) of the P‐VEP amplitudes in the normal controls were 7.08 ± 2.97, 8.60 ± 2.37, 4.69 ± 1.99 and 2.11 ± 1.24 μV at reversal rates of 2, 10, 20 and 30 Hz, respectively. The comparable amplitudes from the recovered optic neuritis patients were 8.01 ± 2.45, 6.57 ± 2.54, 2.73 ± 1.76 and 0.94 ± 1.27 μV. The mean amplitude of the P‐VEPs elicited at a reversal rate of 2 Hz was not significantly different from that of normal controls. However, the amplitudes of the P‐VEPs at reversal rates of 10, 20 and 30 Hz were significantly smaller in the recovered optic neuritis patients than in the controls. In addition, the average maximum amplitude of the P‐VEPs was obtained at 10 Hz in normal subjects and at 2 Hz in the recovered optic neuritis patients.

Conclusion:  These results indicate that the peak of the temporal tuning curve of the P‐VEP shifts to lower frequencies in recovered optic neuritis eyes, and that the reduced amplitudes at higher frequencies seem to be characteristic of the visual system of patients with recovered optic neuritis.
Air/Water Two-Phase Flow Performance of Contra-Rotating Axial Flow Pump and Rotational Speed Control of Rear Rotor
Authors: Shigemitsu Toru , Furukawa Akinori , Watanabe Satoshi , Okuma Kusuo
Published: October 2008

An application of contra-rotating rotors, consisting of front and rear rotors rotating in the opposite direction from each other, has been proposed against a demand for developing a higher specific speed axial flow pump with a more compact structure, higher efficiency and higher cavitation performance. As axial flow pumps are used for standby operations of air-lock and air/water mixing discharge to prevent floods, air/water two-phase flow performance of the contra-rotating pump has to be also investigated. In the present paper, therefore, experimental results on air/water two-phase flow performance of a test pump with contra-rotating rotors are shown and compared with those of a conventional axial flow pump, consisting of a front rotor and a rear stator. Even under two-phase flow conditions head characteristic curve of the contra-rotating type has a more strongly negative slope than that of the conventional type. The contra-rotating type maintains higher head and higher efficiency even in the low flow rate range and vice versa in the high flow rate range. This result will be discussed by considering the change of outlet flow from front rotor due to two-phase flow with the help of observed air behavior in the rotors. Then effects of changes of rear rotor rotational speed different from front rotor speed, which is an advantage of the contra-rotating axial flow pump, on two-phase flow performance are examined. Under the condition of constant ratio of air to water flow rates, the head rise of the rear rotor linearly increases with rear rotor rotational speed. Air/water two-phase flow performance of the contra-rotating axial flow pump can be improved by this control procedure for the rear rotor rotational speed.
An Electronic Control Throttle for Torque and Stability Optimization
Authors: de Ojeda William , Pjellgren Christer
Published: October 2008

The design and performance of an inlet throttle mechanism composed of a spool and a direct acting solenoid is demonstrated to yield similar fuel injection characteristics, described by injection traces, as a pressure regulator placed in the output of a HEUI (hydraulic electronic fuel injector) pump with the added advantage of yielding torque savings of approximately 50% through the speed and load operation map in a typical automotive application. The paper details: the throttle mechanism, a variable gain area with a linear schedule designed for fine flow control followed by a high-gain to remedy cold start; the solenoid design, optimized to yield a constant force over the entire stroke for a given current level; and the close-loop feedback algorithm, characterized by a feed-forward term determined from bench testing at discrete pump speeds and loads. Testing shows the flow desired to collapse onto a single band correlating with duty cycle to the solenoid, a robust feature that enables the feed-forward term of the control system to be effective in adjusting to transient conditions. The paper includes comparisons at 1200, 2000 and 3000 pump rpm of the inlet throttle mechanism and of a pressure regulator applied to a HEUI pump in a system that comprises the pump, high-pressure accumulator and 8 fuel injectors. Time traces of pressure in the accumulator and rates of injected fuel at the cylinders indicate the inlet throttle device is slower to recover pressure following an injection event as expected, but only at lower operating speeds, which is due to the limited response of the pressure regulator at the higher speeds. The rates of injection traces show that there is no deterioration of the fuel injection characteristics.
Numerical and Experimental Investigation of Cavitation in a Pump
Authors: Gupta Amit , Kshirsagar J. T.
Published: October 2008

Cavitation in pumps is a well-known phenomenon that occurs when local static pressure approaches vapor pressure for the working fluid. The flowing fluid under this condition changes its phase from liquid to gas and form bubbles. These bubbles travel along with flowing fluid and reach a zone with relatively high pressure. As the pressure builds up, the size of the bubble reduces and at some stage bubbles collapse generating very high pressure locally that could damage the metallic blade surfaces. Extensive research activities are going to investigate cavitation phenomenon. At Kirloskar Bothers Ltd, a mixed flow pump was investigated thoroughly for its cavitation performance. The newly introduced Cavitation module in a CFD package, CFX, was used to predict the cavitation phenomenon for this pump. The performance of the pump was predicted first by using single-phase module. The overall performance prediction of the pump matched well with the measured results. The solver was switched over to account for cavitation study using multiphase flow phenomenon. The numerical approach brings out formation of vapor and growth of its volume fraction as the suction pressure is dropped. The paper describes both of these approaches and presents results in the form of impact of cavitation on overall performance of the pump. The vapor bubble formation and its volume fraction growth with reduction in suction pressure are brought out using numerical approach.
Vortex Transport in Separating Flows and Role of Vortical Structures in Reynolds Stress Production and Distribution
Authors: Yazdani Miad , Khakpour Yasmin
Published: October 2008

In this paper we will present some approaches on Reynolds stress production by vortex transport phenomena and nonlinear vorticity generation in momentum equation. First of all we represent a history of recent works to describe how fluid particle motions can be associated with Reynolds stress through either displacement or acceleration terms. In the next section we will describe how vortex stretching causes the Reynolds stress production and what is the dominant effect near and far from the boundary where viscous effects have to be considered. On the other hand, some vortex considered methodologies such as those synthesize boundary layer, as a collection of vortical objects seem to be inappropriate in general flow configuration. Therefore, there must be a moderate consideration in which both vortex and momentum transports come into account as it is done in LES. Furthermore since there exist open questions on Reynolds stress distribution in complex flows such as those with separation, our particular attention is paid to such effects due to vortical structures in separating flows. Further discussions include turbulence development caused by either vortex stretching or gradient terms that is determined by predominant conditions. However, it is seen that at the beginning, vorticity generators in Navier-Stokes equation contribute to dissipation effect. In addition, since such contribution corresponds to vorticity alignment, we investigate maximum vortex aligning and the effects of which causes the deviation of such alignment. The paper provides theoretical and numerical comparisons, where in the former, the vortical structure role is taken into account.
Separation Control of Aero Boundary Layer in Supercavitating Bodies and Its Effect on Pressure Drag Reduction
Authors: Khakpour Yasmin , Yazdani Miad
Published: October 2008

Supercavitation is known as the way of viscous drag reduction for the projectiles, moving in the liquid phase. In recent works, there is distinct investigation between cavitation flow and momentum transfer far away from the cavity surface. In fact such methodologies consider cavitation flow statically, rather than taking dynamic effects of overall flow into account. However, it seems that there is strong connection between overall flow and what takes place in the sheet cavity where a constant pressure distribution is assumed. Thereby, in order to configure the system conditions which may be cause of cavity perturbation and so system oscillation, we need to use proper methodologies in which turbulence shear stress effects and role of their distribution, are suitably come into account. Numerical simulation of supercavitating flows is pursued in this paper. The effect of air injection in the cavity as a means of stabilization is examined. A k-epsilon model is employed for the liquid flow region while a single-fluid two phase model is applied in the cavity region. Comparisons of several conditions exhibits that at very low cavitation numbers, constant pressure assumption fails particularly for gradient shaped profiles and separation is probable if the flow is sufficiently turbulent. Air injection into the NATURALLY FORMED supercavity is found as an effective way to prevent the probable separation and so significant pressure drag reduction up to 70% is observed. In addition, the position of injection plays a major role to control the aero boundary layer and it has to be considered.
On the Stability of Supercavitating Projectiles Based on Lagrangian Analysis
Authors: Khakpour Yasmin , Yazdani Miad
Published: October 2008

In this work, numerical simulation is used to study the stability enhancement of high speed supercavitating Shkval missile. Although supercavitation is known as one of the most effective methods for drag reduction, producing the cavity, either by ventilation or by cavitator at front of the body, may cause some instabilities on cavity surface and thus on the projectile’s motion. Therefore removing these instabilities comes as an important point of discussion. First of all, we calculate the sources of instabilities and measure respective forces and then present some approaches that significantly reduce these instabilities. One of these methods that could produce more stable supercavities is injecting of the air into the cavity unsteadily which varies through the projectile’s surface. This approach is provided by arrays of slots distributed on the projectile’s surface and unsteady injection is modeled over the surface. Furthermore, the position of ventilation, dramatically affects the stability like those in aerodynamics. In all approaches it is assumed that the supercavity covers the whole of the body, however the forces caused by the wakes, formed behind the body are taken into account. The calculation is performed at three cavitation numbers with respective velocities of 100 m/s, 150 m/s, 200 m/s.
Modeling Pneumatic Conveyor Duct Wear: A New Approach
Authors: Chand Prem , Saha A. C. , Chand Prafull
Published: October 2008

It was shown in one of our recent works [1] that, the apparently disconnected items like solid-gas flow phenomenon, duct wear and particle degradation are in fact beautifully connected involving all the three components of transfer processes — heat transfer, mass transfer and momentum transfer. This paper which basically is an extension of our work on Fluid Energy Mill [2] aims at predicting duct wear while transporting solids-gas mixture in pneumatic conveyor even in most difficult situations like flow through bends under interference situation. The paper elaborates the methodology used for wear prediction and highlights the effect of several parameters like material flow rate etc. on the nature and extent of the duct wear.
The LBE Simulation and PIV Experimental Study on a Novel Viscous Pump
Authors: Yang Fan , Liu Shuhong , Li Jinwei , Wu Yulin
Published: October 2008

A numerical study and PIV investigation of flow in a novel viscous-based pumping device appropriate for microscale applications is described. The device, essentially consisting of a rotating cylinder eccentrically placed in a channel, is shown to be capable of generating a net flow. The two shape cross-sections of cylinders, the circular and four semi-elliptic lobed contour are studied, which is the steady and unsteady flow problem, respectively. The lattice Boltzmann equation (LBE) simulations at low Reynolds numbers are carried out to study the influence of various geometric parameters, which the results are compared with the PIV experiment ones. The unified solid curved wall boundary condition based on interpolation and the balance of momentum on the wall of the LBE simulation is used in steady and unsteady flow, and the moving boundary condition is also used in the latter. The numerical results indicated that the more effective pumping and better performance is obtained with the decrease of Reynolds number, as well as the increase regular degree of cylinder cross-section.
Bubble Effect on the Structures of Weakly Turbulent Couette Taylor Flow
Authors: Mehel Amine , Gabillet Celine , Djeridi Henda
Published: October 2008

In industrial applications, rotating flows have been recognized to enhance mixing and transfer properties. Moreover, bubbly flows are also used to improve transfers. Therefore, it is interesting to study the effects of the dispersed phase on the structure of a Couette Taylor flow. Experiments are conducted for the quasi-periodic (Ta = 780) and the weakly turbulent (Ta = 1000) flow regimes. Bubbles (0.035 times as small as the gap) are generated by agitation of the upper free surface (ventilated flow). Larger bubbles (0.15 times as small as the gap) are generated by injection at the bottom of the apparatus and by applying a pressure drop (cavitating flow). Void fraction, bubble size and velocity, as well as axial and azimuthal velocity components of the liquid are investigated. For α>0.1%, there is evidence of bubble induced modifications of axial wavelength and liquid velocity gradients, depending on the bubble location in the gap and their size. For particular conditions of the flow, a premature transition to weakly turbulent flow is observed.
Computational Study of Unsteady Cavitating Vortex Flow in Axisymmetric Submerged Water Jet
Authors: Peng Guoyi
Published: October 2008

Unsteady cavitating and non-cavitating flows of high-speed submerged water jet have been investigated numerically by applying an approach based on the two-phase cavitation model to clarify the behavior of cavitating vortex flow in the near field of jet. The cavitation intensity is calculated by VOF method accounting for expanding and contracting of cavitation bubbles with the barotropic relation and the unsteady flow is calculated by RANS method employing the RNG k-ε turbulence model under the assumption of locally homogeneous two-phase flow. Computations are focused on the behavior of starting jet, and the validity is confirmed by comparing with experimental data. The result shows that a starting vortex ring is generated around the jet periphery, and develops with the vortex formation time. The relative standoff distance of ring-like cavity of cavitation bubbles generated in the starting vortex increases with the dimensionless vortex formation time similarly under different injection velocities.
An Updated Study of Recirculation at the Inlet of a Rotodynamic Impeller
Authors: Yedidiah S.
Published: October 2008

This paper presents an updated report of certain causes and effects of recirculation at the inlet of a rotodynamic impeller. It demonstrates how certain geometrical features of the inlet parts of the blades are affecting the pattern of the inlet-recirculation, and how this pattern is affected by the flow-rate. It demonstrates the effects of recirculation on the steepness of the QH-curve at reduced flow-rates, and the occasionally observed hysteresis within a certain range of partial flow-rates. Also, it discusses the manner in which recirculation is producing very intense instabilities at reduced NPSH, in axial-flow impellers and inducers. The conclusions arrived at are supported by results of test, reported in different papers. In addition of the above, it lists some of the uses of our present knowledge of the causes and effects of inlet-recirculation, which have been successfully applied in practice.
Entrainment in Free Jets
Authors: Sforza Pasquale M.
Published: October 2008

The mass flow passing through a plane normal to the mainstream direction of a free jet is the sum of the mass flow of the jet and that of the fluid entrained from surrounding ambient into which it issues. Manipulation of the instantaneous Navier-Stokes equations and the continuity equation yields an integro-differential equation for the instantaneous mass flow in the flow field. This equation is reduced to a form that suggests that jet entrainment may be viewed as a one-dimensional unsteady diffusion process with an integral source term arising from the gradient of forces in the axial direction of flow which are dependent, in general, on z and t. The small difference in the integrals of the net axial inertial force acting on the fluid in the volume defined by the limits of integration is balanced by an axial force arising from the viscous normal stress that is associated with axial rate of mass entrainment. Furthermore, it suggests that the kinematic viscosity of the fluid is the appropriate diffusion parameter. This formulation is used to assess the nature of the entrainment process in steady three-dimensional jets and to propose means for managing that process.
Numerical Study of Classification of Ultrafine Particles in a Gas-Solid Field of Elbow-Jet Classifier
Authors: Liang Shibin
Published: October 2008

Computational fluid dynamics (CFD) is applied to develop a novel submicron air classifier. Based on different inner structure sizes and positions in the elbow-jet classifier, the two-dimensional air flow field has been simulated by the Fluent software. The Coanda-effect plays a paramount role in the separation of ultrafine particles in the high-speed flow field of the elbow-jet classifier. The effects on the features of the Coanda element, i.e. a half-cylinder, have been analyzed and discussed. The trajectories of moving particles with different diameters in the channels and chambers of the classifier have been calculated under the velocity field simulation results obtained by the CFD analysis. The cut sizes of three products at the related outlets of the classifier are obtained based on the trajectories calculation of the particles and compared with the corresponding experimental results. The ground/classified experiment has been conducted by using the products outlet of a vortex jet mill as the particles feed of the elbow-jet classifier. The experimental results show that the external classifier for the vortex jet mill improves the classification of the mill significantly. The combination of the vortex jet mill with the external classifier provides a new choice of the grinding equipment for the multiple size products of fine/medium/coarse powders. A centrifugal channel has been added between the vortex jet mill and the elbow-jet classifier to improve the performance of the air classifier. Both numerical and experimental results show that the pre-distributed feed powders at the exit of the centrifugal channel have a strong effect on the fine powders separation and a less effect on the coarse powders separation.
Turbulence Dissipation by the Oscillation of Microbubbles
Authors: Brown Neal A.
Published: October 2008

With the objective of interfering with the Reynolds stress transfer of momentum to the sublayer, the loss factor is derived for turbulence dissipation by the resistive oscillation of microbubbles in the buffer layer region of a turbulent boundary layer in water. The rectilinear motion of a single bubble is examined under the influence of pressure gradients in its vicinity. It is presumed that both turbulence pressures and velocities can be represented by wavenumber-frequency spectra. Stokes drag is assumed for the bubble. The loss factor is found to be independent of the magnitudes of the fluctuating pressures and velocities. In addition to the spatial density of bubbles, the loss factor is found to depend only on a Reynolds number-like parameter involving the product of the frequency with the square of the bubble radius. The Reynolds parameter dependence has a form similar to that of a simple resonant response, although it is clear that no actual resonance is involved. With three diameters bubble spacing, the peak value of the loss factor is found to be approximately 2% at a parameter value of nine. The apparent bandwidth of the loss factor response is about one decade, suggesting that the phenomena is not “finely tuned”. For turbulence with typically large wavenumbers, very large spatial decay rates are suggested.
Preconditioning Method for Very-Slow Flows With Heterogeneous Condensation in a Mixing T-Junction Channel
Authors: Sakakura Kei , Sasao Yasuhiro , Yamamoto Satoru
Published: October 2008

The purpose of this study is to develop a numerical method for simulating condensate flow problems observed in industrial processes. The preconditioning method developed by our group is applied to the calculations of very-slow flows assuming heterogeneous condensation in a mixing T-junction channel which dry and moist air streams flowing into the channel are mixed together. A classical condensation model simplified by our group is used for evaluating condensation with heterogeneous nucleation. As shown in the calculated results, condensation in a T-junction pipe was variously influenced by the mixing type, such as stratified, turned jet, and wall jet flows. A notable difference in temperature distributions was also found with and without condensation due to the release of latent heat when condensation occurs.
Density Ratio and Turbulence Intensity Effects in Microbubble Drag Reduction Phenomenon
Authors: Skudarnov P. V. , Lin C. X.
Published: October 2008

Two-dimensional single phase computational fluid dynamics (CFD) model of microbubble-laden flow over a flat plate was used to assess the role of mixture density variation in microbubble drag reduction for high Reynolds number flows. The model consisted of Reynolds-averaged Navier-Stokes (RANS) transport equations, a standard k-ε turbulence model, and a convection-diffusion species transport model. Performance of the model was validated with available experimental data and numerical simulations of more advanced multiphase two-fluid model. A parametric study of density ratio and free stream turbulence intensity effects on drag reduction was carried out. The study indicated that the model taking into account only mixture density effect could still predict drag reduction reasonably well. In addition to this, higher values of free stream turbulence intensity are predicted to result in lower drag reduction.
Blunt Trailing Edge Shear Wake Development With Turbulent In-Flow Boundary Layers
Authors: Challa Dhanalakshmi , Klewicki Joe
Published: October 2008

Experiments are conducted to explore the structural mechanisms involved in the post-separation evolution of a wall-bounded to a free-shear turbulent flow. At the upstream, both the boundary layers are turbulent. Experiments were conducted in a two-stream shear-layer tunnel, under a zero axial pressure gradient shear-wake configuration. A velocity ratio near 2 was explored. Profile data were collected with a single wire probe at various locations downstream of the blunt separation lip. With this set of measurements, mean profile, axial intensity and measures of profile evolution indicate that the predominant shift from turbulent boundary layer to free shear-layer like behavior occurs between the downstream locations x/θ = 13.7 & 27.4, where θ is the upstream momentum deficit thickness on the low-speed stream. The shear wake width is observed to be nominally constant with the downstream position. Axial velocity spectra show that the transition from boundary layer flow to shear flow occurs earlier in high-speed stream when compared to low speed stream. Strouhal number, Sto, of initial vortex rollup based on initial momentum thickness was found to be 0.034, which is in very good agreement with the existing literature. Other measures are in good agreement with linear stability considerations found in the literature.
Determination of Total Shear Stress and Polymer Stress Profiles in Drag Reduced Boundary Layer Flows With Polymer Injection
Authors: Hou Y. X. , Somandepalli V. S. R. , Mungal M. G.
Published: October 2008

Two methods of recovering the entire total shear stress profile from incomplete velocity data in turbulent boundary layers are presented and validated for both DNS simulations and experimental measurements. The first method, an exponential-polynomial curve fit, recovers the whole total shear stress profile well by using the data from the outer part of the boundary layer (y/δ > 0.3). However, this curve fit is sensitive to the quality of the data. The second method, a new (1−y) weighted straight line fit, which is very simple and accurate, has been applied to current experiments of drag reduction in zero pressure gradient turbulent boundary layers with polymer injection. The total shear stress profile obtained from this fit is used to estimate the contribution of the polymer stress to the total shear stress.
Experimental Study of Jet Noise Characteristics of Series Connected Nozzles
Authors: Xu Qiang
Published: October 2008

Put abstract text here. A serial of experiments were conducted to study the noise radiated from a series connected nozzle pair. The experiment results are presented in this paper. This nozzle pair consists of two nozzles, one is called source nozzle, and the other is a secondary nozzle. In these experiments, the structure of source nozzle was fixed while that of secondary nozzle was changeable. The source nozzle is mounted on a pressure chamber which is connected to an air compressor. A steel tube is fixed at the tail of source nozzle. The secondary nozzle is connected to the other end of the tube. Throat size of secondary nozzle is larger then that of source nozzle. 15 types of nozzles with different expansion ratio, length of expand segment, and throat structure were used as the secondary nozzle. Jet noise pressure of these nozzle pairs was measured by 40AF Free Field Microphone. The frequency spectrum of jet noise from source nozzle with steel tube under different chamber pressures was calculated. The pressure range is from 0.1 to 1.2 MPa. This result is compared with those spectrums of nozzle pair with different secondary nozzle under different chamber pressures. The trend of peak frequency shifts for different nozzle pair and different chamber pressure is presented in this paper. The secondary nozzles make frequency peak shift from the source nozzle, especially in low frequency band. Different structure of secondary nozzle has different influence on the frequency characteristics of jet noise. Length of expand segment has greater influence on low frequency peak than other two factors. Joint time-frequency analysis is also used in analyze the change of frequency spectrum during throat size decreased under fixed chamber pressure and various spectrograms are also presented. In low frequency band, frequency peak remains during the change of source nozzle throat size. But in higher frequency band, the frequency peak shifts from low frequency to higher ones as the throat size decreases.
Recirculating Flow and Turbulence in a Low Aspect Ratio Dump Combustor
Authors: Karmakar S. , Kushari A.
Published: October 2008

Re-circulating flows are established in dump combustors at the dump plane due to the sudden expansion. However, given enough length, the separated flow at the dump plane attaches itself inside the combustor and a fully developed, non-circulating, attached flow field is established. But, if the length of the combustor is less than the free-stream reattachment length, then the flow does not re-attach inside the combustor. Instead, a portion of the flow is reflected from the exit section, causing stronger re-circulation that modifies the flow structure inside the combustor. This paper describes an experimental study of turbulent flow field inside a dump combustor for a range of flow Reynolds numbers. The focus of this effort is to study the interaction between the flow re-circulation and the large-scale turbulence. Detailed measurements of the wall pressure transients were taken using strain-gage pressure sensors. The fluctuating component of the pressure was isolated and analyzed. The signals were analyzed using FFT, Auto-Correlation and Cross-correlation to distinguish the re-circulating flow and the large-scale turbulence. The re-circulating flow, identified by low frequency fluctuations in pressure (∼ 0.5 Hz), was seen to be strongest inside the combustor almost half way through the combustor length. At the same time, the large-scale turbulence intensity (identified by high frequency fluctuations in the range of 460 Hz) level is seen to be lower inside the combustor than in the incoming pipe. This can be attributed to the turbulence cascading due to the re-circulating flow, which increases the small-scale energy and reduces the large-scale energy. These results show turbulence modulation due to re-circulating flow and can have far reaching applications in swirling turbulent flows.
An Investigation of the Flow and Global Performance in a Water-Jet Axial Flow Pump Based on CFD and Inverse Design Method
Authors: Gao Hong , Lin Wanlai , Ye Fangming
Published: October 2008

A new inverse design method based on non-constant distribution of circulation and axial velocity along the radial direction is used to design a pump impeller and a stator. The radial distribution of axial velocity at the design flow rate is calculated when an empirical radial distribution of circulation is given. CFD modeling of the global performance and the detailed flow field is performed using TASCflow software. A standard k-ε turbulence model combined with standard wall functions is used. A special mixing plane approach is employed to simulate the rotator-stator coupling flow field. The global performances of the water-jet pump, the radial distribution of velocity components at the exit of the impeller are also measured. Good agreement of the global performance, such as the pressure rise, the power and the efficiency, between CFD and experiment is obtained. The detailed velocity fields from inviscid analysis, CFD and experiment are compared and investigated.
CFD Investigation of Global Performance and Three Dimensional Flows in a Water-Jet Axial Flow Pump
Authors: Gao Hong , Lin Wanlai , Ye Fangming
Published: October 2008

The purpose of the present study is to investigate the global performance and three dimensional flow fields in a water-jet pump. TASCflow software is employed to simulate the rotator-stator coupling flow field. A standard k-ε turbulence model combined with standard wall functions is used. In order to investigate the effect of a rear stator on flow fields, the flows in two water-jet pumps with and without a rear stator are studied. The CFD predicted global performances are in good agreement with the experimental results. Then the flow fields, such as the pressure distribution on the blade surfaces, the axial and tangential velocities distribution, especially the radial loading distribution are investigated at different flow rates. In addition, the effect of a rear stator and different spacing between the rotor and the stator on the global performance and the flow fields of the water-jet pump are also investigated.