bluuebunny/crossref_metadata_2025 huggingface dataset:
Intracellular mediators of JAM‐A–dependent epithelial barrier function
Authors: Monteiro Ana C. , Parkos Charles A.
Published: June 2012

Junctional adhesion molecule‐A (JAM‐A) is a critical signaling component of the apical junctional complex, a structure composed of several transmembrane and scaffold molecules that controls the passage of nutrients and solutes across epithelial surfaces. Observations from JAM‐A–deficient epithelial cells and JAM‐A knockout animals indicate that JAM‐A is an important regulator of epithelial paracellular permeability; however, the mechanism(s) linking JAM‐A to barrier function are not understood. This review highlights recent findings relevant to JAM‐A–mediated regulation of epithelial permeability, focusing on the role of upstream and downstream signaling candidates. We draw on what is known about proteins reported to associate with JAM‐A in other pathways and on known modulators of barrier function to propose candidate effectors that may mediate JAM‐A regulation of epithelial paracellular permeability. Further investigation of pathways highlighted in this review may provide ideas for novel therapeutics that target debilitating conditions associated with barrier dysfunction, such as inflammatory bowel disease.
Relevance of endothelial junctions in leukocyte extravasation and vascular permeability
Authors: Vestweber Dietmar
Published: June 2012

Inflammation and immune surveillance rely on the ability of leukocytes to leave the blood stream and enter tissue. Cytokines and chemokines regulate expression and the activation state of adhesion molecules that enable leukocytes to adhere and arrest at sites of leukocyte exit. Capturing and arrest is followed by the transmigration of leukocytes through the vessel wall—a process called diapedesis. The review will focus on recently published novel approaches to determine the route that leukocytes take in vivo when they migrate through the endothelial layer of blood vessels. This work has revealed the dominant importance of the junctional pathway between endothelial cells in vivo. In addition, recent progress has improved our understanding of the molecular mechanisms that regulate junctional stability, the opening of endothelial junctions during leukocyte extravasation, and the induction of vascular permeability.
Transference of Atmospheric Hydroxyl Radical to the Ocean Surface Induces High Phytoplankton Cell Death
Authors: Llabrés Moira , Dachs Jordi , Agustí Susana
Published: June 2012

Hydroxyl radical (OH), the main atmospheric oxidant at the global scale, is believed to play an important role in the dynamics of dissolved organic matter in the sea. Herein, we provide evidence, on the basis of seven experiments performed in contrasting ecosystems (subtropical NE Atlantic and Antarctic waters), of high fluxes of atmospheric OH into the surface oceanic layer, particularly during afternoon events. The experiments demonstrated a tight negative relationship between phytoplankton abundance and the concentration of OH in surface seawater, with acute cell death during afternoon atmospheric OH influx events. The effect of OH radical was higher for picophytoplankton organisms, with Prochlorococcus showing the highest decay rate and the shortest half‐life among the phytoplankton populations habiting the ocean surface layers. Our results provide evidence for a high toxicity of atmospheric‐derived OH radical to phytoplankton of the surface layer of the ocean.
Exploring young people's expectations of a youth mental health care service
Authors: Watsford Clare , Rickwood Debra , Vanags Thea
Published: June 2012

Client expectations about mental health services relate to the client's and the therapist's role, the therapeutic process and therapeutic outcomes. Research with adults shows that such expectations affect service engagement and clinical outcomes.

Aim: The present study investigated expectations for adolescents and young adults, which have not been adequately investigated and may partly explain the reluctance of young people to seek professional help.

Methods: Participants included 20 young people aged 12–24 attending their initial session at a youth mental health service, who were interviewed immediately prior to their initial session. Data were analysed using qualitative methods to draw main themes around each of the four expectancy types.

Results: Overall, the strongest theme was that young people were unsure of what to expect from attending a mental health service. The key theme for expectations of their role as a client was readiness for therapy, and for the therapist's role the key themes were who they expected to see, the directiveness and likeability of the therapist, and the type of help they expected they would receive. The young people expected that the therapy process would involve simply talking and expected their engagement to be dependent on how much they liked their first few sessions. Outcome expectations were non‐specific and the theme of hopefulness was most evident.

Conclusion: As unrealistic and unmet expectations can lead to poorer engagement and outcomes in therapy, the study highlights a need for young people to be better informed about what to expect when coming to mental health services.
The addition of sitagliptin to ongoing metformin therapy significantly improves glycemic control in Chinese patients with type 2 diabetes*†
Authors: YANG Wenying , GUAN Yanfen , SHENTU Yue , LI Zhi , JOHNSON‐LEVONAS Amy O. , ENGEL Samuel S. , KAUFMAN Keith D. , GOLDSTEIN Barry J. , ALBA Maria
Published: June 2012

Background:  The present study was conducted to evaluate the efficacy, safety and tolerability of sitagliptin added to ongoing metformin therapy in Chinese patients with type 2 diabetes (T2DM) who failed to achieve adequate glycemic control with metformin monotherapy.

Methods:  After a metformin titration/stabilization period and a 2‐week, single‐blind, placebo run‐in period, 395 Chinese patients with T2DM aged 25–77 years (baseline HbA1c 8.5%) were randomized (1:1) to double‐blind placebo or sitagliptin 100 mg q.d. added to ongoing open‐label metformin (1000 or 1700 mg/day) for 24 weeks.

Results:  Significant (P < 0.001) changes from baseline in HbA1c (−0.9%), fasting plasma glucose (−1.2 mmol/L), and 2‐h post‐meal plasma glucose (−1.9 mmol/L) were seen with sitagliptin compared with placebo. There were no significant differences between sitagliptin and placebo in the incidence of hypoglycemia or gastrointestinal adverse events. A small decrease from baseline body weight was observed in the placebo group compared with no change in the sitagliptin group (between‐group difference 0.5 kg; P = 0.018).

Conclusions:  The addition of sitagliptin 100 mg to ongoing metformin therapy significantly improved glycemic control and was generally well tolerated in Chinese patients with T2DM who had inadequate glycemic control on metformin alone.
William Cowper: A Religious Melancholic?
Authors: BUIE DIANE
Published: June 2012

This article re‐evaluates the account of the mental turmoil expressed by the poet William Cowper in his spiritual autobiography Adelphi. The article considers Adelphi in the context of eighteenth‐century theological works written on the subject of religious melancholy prior to its being penned. It suggests that Cowper may have feigned the illness and provides evidence that Cowper borrowed heavily from such works in order to portray himself as a religious melancholic. The article argues that religious melancholy was a well‐recognised illness in the eighteenth century and that it was exploited because of the tolerance shown towards sufferers.
A Neutered Beast? Representations of the Sons of Tipu Sultan –‘The Tiger of Mysore’– as Hostages in the 1790s
Authors: WILLCOCK SEAN
Published: June 2012

In 1792 the British took two young Indian princes as hostages to guarantee that their father, Tipu Sultan, would meet the terms of his surrender. This article analyses the art works that emerged in response to that event, arguing that this seemingly triumphal imagery was an ambivalent phenomenon in which can be found significant undercurrents of anxiety over the morality of the capture of children. I suggest that the hostage imagery's recourse to paternalistic motifs in fact demonstrates the crises of legitimacy that paternalism encountered as it attempted to establish itself as a moral incarnation of an increasingly aggressive imperial power.
Real‐time PCR as an effective technique to assess the impact of phoresy by Paenibacillus sp. bacteria on Steinernema diaprepesi nematodes in nature
Authors: CAMPOS‐HERRERA R. , EL‐BORAI F. E. , DUNCAN L. W.
Published: June 2012

Quantitative real‐time PCR (qPCR) is a powerful tool to study species of cryptic organisms in complex food webs. This technique was recently developed to detect and quantify several species of entomopathogenic nematodes (EPNs), which are widely used for biological control of insects, and some natural enemies of EPNs such as nematophagous fungi and the phoretic bacteria Paenibacillus sp. and Paenibacillus nematophilus. A drawback to the use of primers and TaqMan probes designed for Paenibacillus sp. is that the qPCR also amplified Paenibacillus thiaminolyticus and Paenibacillus popilliae, two closely related species that are not phoretically associated with EPNs. Here, we report that the detection of Paenibacillus sp. DNA in nematode samples was two orders of magnitude greater (P < 0.001) when the bacterium was added to soil together with its EPN species‐specific host Steinernema diaprepesi than when it was added concomitantly with other EPNs or with species of bacterial‐feeding nematodes. Just 6% of samples detected trace amounts of P. thiaminolyticus and P. popilliae exposed to the same experimental conditions. Thus, although the molecular assay detects Paenibacillus spp. DNA in nonphoretic associations, the levels are essentially background compared to the detection of Paenibacillus sp. in association with its nematode host.
Interaction of Campylobacter spp. and Human Probiotics in Chicken Intestinal Mucus
Authors: Ganan M. , Martinez‐Rodriguez A. J. , Carrascosa A.V. , Vesterlund S. , Salminen S. , Satokari R.
Published: June 2012

Campylobacter is the most common cause of bacterial food‐borne diarrhoeal disease throughout the world. The principal risk of human contamination is handling and consumption of contaminated poultry meat. To colonize poultry, Campylobacter adheres to and persists in the mucus layer that covers the intestinal epithelium. Inhibiting adhesion to the mucus could prevent colonization of the intestine. The aim of this study was to investigate in vitro the protective effect of defined commercial human probiotic strains on the adhesion of Campylobacter spp. to chicken intestinal mucus, in a search for alternatives to antibiotics to control this food‐borne pathogen. The probiotic strains Lactobacillus rhamnosus GG and Propionibacterium freudenreichii ssp. shermanii JS and a starter culture strain Lactococcus lactis ssp. lactis adhered well to chicken intestinal mucus and were able to reduce the binding of Campylobacter spp. when the mucus was colonized with the probiotic strain before contacting the pathogen. Human‐intended probiotics could be useful as prophylactics in poultry feeding for controlling Campylobacter spp. colonization.
Perceived facial adiposity conveys information about women's health
Authors: Tinlin Rowan M. , Watkins Christopher D. , Welling Lisa L. M. , DeBruine Lisa M. , Al‐Dujaili Emad A. S. , Jones Benedict C.
Published: June 2012

Although several prominent theories of human facial attractiveness propose that some facial characteristics convey information about people's health, empirical evidence for this claim is somewhat mixed. While most previous research into this issue has focused on facial characteristics such as symmetry, averageness, and sexual dimorphism, a recent study reported that ratings of facial adiposity (i.e., perceptions of fatness in the face) were positively correlated with indices of poor physical condition in a sample of young adults (i.e., reported past health problems and measures of cardiovascular fitness). These findings are noteworthy, since they suggest that perceived adiposity is a potentially important facial cue of health that has been overlooked by much of the previous work in this area. Here, we show that ratings of young adult women's facial adiposity are (1) better predicted by their body weight than by their body shape (Studies 1 and 2), (2) correlated with a composite measure of their physical and psychological condition (Study 2), and (3) negatively correlated with their trait (i.e., average) salivary progesterone levels (Study 3). Together, these findings present further evidence that perceived facial adiposity, or a correlate thereof, conveys potentially important information about women's actual health.
Children's recognition of emotions from vocal cues
Authors: Sauter Disa A. , Panattoni Charlotte , Happé Francesca
Published: June 2012

Emotional cues contain important information about the intentions and feelings of others. Despite a wealth of research into children's understanding of facial signals of emotions, little research has investigated the developmental trajectory of interpreting affective cues in the voice. In this study, 48 children ranging between 5 and 10 years were tested using forced‐choice tasks with non‐verbal vocalizations and emotionally inflected speech expressing different positive, neutral and negative states. Children as young as 5 years were proficient in interpreting a range of emotional cues from vocal signals. Consistent with previous work, performance was found to improve with age. Furthermore, the two tasks, examining recognition of non‐verbal vocalizations and emotionally inflected speech, respectively, were sensitive to individual differences, with high correspondence of performance across the tasks. From this demonstration of children's ability to recognize emotions from vocal stimuli, we also conclude that this auditory emotion recognition task is suitable for a wide age range of children, providing a novel, empirical way to investigate children's affect recognition skills.
Thin-Walled Rods With Semiopened Profiles
Authors: Kobelev V.
Published: June 2012

The analysis of thin-walled rods with semiopened cross-section is performed in this article. An essential characteristic for this class of thin-walled beamlike structures is their closed but flattened profile. The unusual shape of semiopened thin-walled beams allows the efficient optimization due to wide variability of shapes. One popular application of the theory of semiopened thin-walled beams is the twist beam of the semisolid suspension.
Stochastic Harmonic Function Representation of Stochastic Processes
Authors: Chen Jianbing , Sun Weiling , Li Jie , Xu Jun
Published: June 2012

An approach to represent a stochastic process by the combination of finite stochastic harmonic functions is proposed. The conditions that should be satisfied to make sure that the power spectral density function of the stochastic harmonic function process is identical to the target power spectral density are firstly studied. Then, two kinds of stochastic harmonic functions, of which the distribution of the amplitudes and the random frequencies are different, are discussed. The probabilistic characteristics of the two kinds of stochastic harmonic functions, including the asymptotic distribution, the one-dimensional probability density function, and the rate of approaching the asymptotic distribution, etc., are studied in detail by theoretical treatment and numerical examples. Responses of a nonlinear structure subjected to strong earthquake excitation are investigated. The studies show that the proposed approach can capture the target power spectral density exactly with any number of components. The reduction of the components provides flexibility and reduces the computational cost. Finally, problems that need further investigations are discussed.
Dynamic Switching Study on Fluidic Component of Fluidic Sprinkler
Authors: Wang Chao , Li Hong , Chen Chao , Tu Qin , Yun Qianglong
Published: June 2012

The fluidic sprinkler controlled by clearance is a new type of water-saving and energy-conservation sprinkler. Different from traditional impact rotating sprinkler, a fluidic component is applied in the fluidic sprinkler, which serves not only as a discharge substance, but also as a driving mechanism instead of a complicated impact-drive mechanism. The mutual conversion between straight spray state and stepping state makes the sprinkler running. The investigation of the flow inside the fluidic component in the switching process and the stepping frequency of the sprinkler are the foundations to learn the law of fluidic control and to optimize the performance of the fluidic sprinkler. This paper carries out the simplified prototype of the fluidic component, measures the pressure distribution on the side wall under static attachment state and the pressure fluctuations during the dynamic switching process. The discrepancy between the results indicates that, previous researches on static attachment state are not applicable in switching process. The simulation of dynamic switching is carried out by UDF self-programming method with the experimental results as boundary conditions. The transient flow in the dynamic switching process is studied roughly. The distributions of the pressure, velocity, turbulence kinetic energy have been obtained.
Modeling of Pin Fin Heat Sinks Based on Volume Averaging Theory
Authors: Zhou Feng , DeMoulin George W. , Geb David J. , Catton Ivan
Published: June 2012

In this paper, a consistant model is developed to describe transport phenomena in a pin fin heat sink that take into account the scales and other characteristics of the medium morphology. The specific geometry of the heat sink is accounted for in such a way that the details of the original structure are replaced by their averaged counterparts. Equation sets allowing for turbulence and two-temperature or two-concentration diffusion are obtained for non-isotropic porous media with interface exchange. The equations differ from known equations and were developed using a rigorous averaging technique, hierarchical modeling methodology, and fully turbulent models with Reynolds stresses and fluxes in the space of every pore. The transport equations are shown to have additional integral and differential terms. These terms are closed experimentally from available data for pin fin morphology. The resulting equation set is relatively simple and is descretized using the finite difference method. Such computational algorithm is fast running, but still able to present a detailed picture of themperature fields in the airflow as well as in the solid structure of the heat sink. The calculated friction factor and thermal resistance are compared with experimental data to verify the porous model and validate the numerical code. The results calculated by the code agrees with the experimental data quite well, which offers possibility for multiple parameter optimization using Design of Experiment (DOE) to achieve high cooling capabilities.
Calculation of Nano-Sized Particle Catcher by Ultrasonic Vibration
Authors: Nishino Shinichi , Ochi Mitsuaki , Kofu Kenji
Published: June 2012

Particles on the plate vibrated by ultrasonic were gathered on the node of vibration plate. Similar to this phenomenon, if two plates are set with parallel, a plate is vibrated by ultrasonic and acoustic pressure distribution is produced between the vibration and reflection plate, nano-sized particles might be collected from the air flow and air is cleaned. Although ultrasonic was applied for the liquid and remove particles, but this has not been researched for air. Then the purpose of this study is to calculate the acoustic pressure distribution between the vibration and reflection plate by using CFD, and investigate the nano-sized particle motion in acoustic pressure distribution. When standing wave between plates is calculated, acoustic wave generated by ultrasonic vibration was reflected at the reflection plate. In the case of CFD, standing wave could not be calculated because these waves disclaim each other and wave generated by a plate doesn’t reach at the other plate. Therefore acoustic wave is also produced at reflection plate, duplicate these waves from vibration and reflection plates, and standing wave between plates were obtained. About investigation for the nano-sized particle motion in acoustic pressure distribution, particles were injected into calculation domain. Particles which have the same diameter and density with influenza virus were applied in this calculation. Examination of particle’s motion and efficient condition on dust catch were calculated in case of changing parameter, for example, amplitude and frequency of vibration plate, velocity of flowing particles, concentration of particles in the flow and so on.
Two Phase Flow Simulation for Nucleate Boiling Heat Transfer Calculation in Waterjacket of Diesel Engine
Authors: Mohammadi Arash , Hashemi Hossein , Jazayeri Ali , Ahmadi Mahdi
Published: June 2012

Basic understanding of the process of coolant heat transfer inside an engine is an indispensable prerequisite to devise an infallible cooling strategy. Coolant flow and its heat transfer affect the cooling efficiency, thermal load of heated components, and thermal efficiency of a diesel engine. An efficient approach to study cooling system for diesel engine is a 3D computational fluid dynamics (CFD) calculation for coolant jacket. Therefore, computer simulation can analyze and consequently optimize cooling system performance, including complex cooling jacket. In this paper a computational model for boiling heat transfer based on two-phase Mixture model flow is established. Furthermore, the phenomenon of nucleate boiling, its mathematical modeling, and its effect on heat transfer is discussed. Besides, the static, total and absolute pressure, velocity and stream lines of the flow field, heat flux, heat transfer coefficient and volume fraction of vapor distribution in the coolant jacket of a four-cylinder diesel engine is computed. Also, comparison between experimental equation (Pflaum/Mollenhauer) and two-phase Mixture model for boiling hat transfer coefficient is done and good agreement is seen. In conclusion, it is observed that at high operating temperatures, nucleate boiling occurs in regions around the exhaust port. Numerical simulation of boiling heat transfer process of cooling water jacket and temperature field in the cylinder head of the diesel engine is compared with the data measured on the engine test bench. The calculated results indicate that this method can reflect the impact of boiling heat transfer on water jacket rather accurate. Therefore, this method is benefit to improve the computational precision in the temperature field computation of a cylinder head.
Optimum Network Sizing for Delivering Different Media
Authors: Xia Liang , Deng Shiming , Chan Ming-yin
Published: June 2012

This paper aims at fundamentally finding optimal shape of networks used in delivering different distribution networks from one supplier plant to a number of end-users in order to minimize power loss in delivery process under a constraint of total flow volume. A general equation is developed for evaluating the power loss for different shape networks. Based on the equation, a parameter, γ, is deduced which can be applied to define the volume flow into three classifications. For each flow classification, the optimal shape network will be discussed. Results indicate that the radial shape will be optimum when γ ≥ 1. When γ<1, an optimal tree shape network is deduced for evenly distributed end-users on a square.
Unstable Operation of a Mixed-Flow Pump and the Influence of Tip Clearance
Authors: van Esch Bart , Cheng Li
Published: June 2012

Many mixed-flow and axial flow pumps exhibit a so-called unstable head curve. Due to the risk of instabilities this flow region is usually avoided during pump operation. This paper presents experimental and numerical research on the relation between the instability in the head curve and the magnitude of unsteady hydraulic forces. It is found that there is a strong influence of the extend of the clearance gap between impeller blades and casing. The spectral content of the forces shows evidence of rotating instabilities. It indicates that not only instability of the head curve and unsteady forces are interrelated, but also rotating instabilities play a role in this phenomenon. Results of CFD calculations are presented as well, showing the difficulties in simulating the flow under such conditions.
Continuous Spectrum of the Rotordynamic Forces on a Four Bladed Inducer
Authors: Torre Lucio , Pasini Angelo , Cervone Angelo , d’Agostino Luca
Published: June 2012

The paper illustrates the results of an experimental campaign conducted in the CPRTF (Cavitating Pump Rotordynamic Test Facility) at ALTA S.p.A., aimed at characterizing the rotordynamic forces acting on a whirling four-bladed, tapered-hub, variable-pitch inducer, designated as DAPAMITO4. The roles of the imposed whirl motion of the rotor, flow coefficient, cavitation number and liquid temperature have been investigated. A novel experimental technique, consisting in measuring the continuous spectra of the forces as functions of the whirl ratio, has been developed and validated. This technique gives the possibility of extracting valuable information from the experiments by clearly identifying the qualitative and quantitative behavior of the forces, and is therefore useful to catch the unlikely foreseeable complexity of the rotordynamic forces and their consequences on the stability of axial inducers.
A Novel Approach to Simplification of NPSH(r) CFD Calculation
Authors: Strongin Mikhail
Published: June 2012

Present work proposes approach that significantly shortens the calculation time for NPSH(r). This time is comparable with time for the head calculations. Most cavitation models take into account phase change, bubble dynamics, turbulent pressure fluctuations, etc. In this case multiphase flow model must be used. This work presents some simplifications, based on the physical nature of cavitation on the pump impeller, which significantly (10–50 times) reduces the calculation time of NPSH (r). The main idea of proposed procedure is to determine the liquid vapor (cavitation) zone simply from steady state calculation of one phase incompressible flow without taking into account multiphase effects. Based on absolute pressure distribution it is easy to determine areas with absolute pressure lower then saturated liquid vapor pressure for given liquid conditions. Consequently it is possible to consider the steady state location of liquid vapor (cavitation) on the impeller vanes. So this zone may simply be expelled from the flow domain. For many pump related cases, these zones are very close to cavitation areas, and give main impact on the head of the pump. Commercial Fluent 12.1.4 code is used for calculations. Proposed procedure for NPSH(r) calculation is in good agreement with test data for different types of pumps and may be used as a tool to shorten a design process for new pumps.
Flow Measurements in a Transparent Centrifugal Pump by Using 3-D PIV Technique
Authors: Yang Hua , Zhou Ji-ren , Tang Fang-ping , Liu Chao , Xu Hao-ran
Published: June 2012

With the development of laser measurement technique, LDV (Laser Doppler Velocimeter) and PIV (Particle Image Velocimetry) have been widely used to measure the flow fields. Comparison with LDV, PIV is a multiple point measurement technique and the flow fields can be measured convenient. Nowadays, 2-D (two Dimensional) PIV have been used to investigate the flow fields in the centrifugal pump, while 3-D (three Dimensional) PIV is seldom to be used. The reason is that the calibration for 3-D PIV in a small space of centrifugal pumps in very difficult. In this paper, a special water tank was used for 3-D PIV calibration in rotation impeller. The 3-D transient relative velocity in one impeller passage at three axial sections were obtained, when the pump run under the design flow rate. The radial component velocity Wr showed a concave distribution except R = 45 mm. With the increase of radius, the circumference location of minimum Wr moved from the pressure side to the suction side and the tangential component velocity Wθ on the suction side decreases, while on the pressure side increases gradually. The PIV measurement error was investigated based on the mass conservation equation. The maximum error of the PIV measurement was 3.14%, it showed that the test results have higher accuracy and the measured data was reliable.
Numerical Simulation and Stereo PIV Test of Inner Flow in a Double Blades Pump
Authors: Wang Kai , Liu Houlin , Yuan Shouqi , Tan Minggao , Wang Yong , Dong Liang
Published: June 2012

A double blades pump is widely used in sewage treatment industry, while at present the research on the internal flow characteristics of the double blades pump is very few. So, the CFD technology and the stereo PIV test technique are applied to study the inner flow in a double blades pump whose specific speed is 110.9. The commercial code FLUENT is used to simulate the inner flow in the double blades pump at 0.6Qd, 0.8Qd, 1.0Qd, 1.2Qd and 1.4Qd. The RNG k-ε turbulence model and SIMPLEC algorithm are used in FLUENT. According to the results of the three-dimensional steady numerical simulation, the distributions of velocity field in the impeller are obtained at the five different operating conditions. The analysis of the numerical simulation results shows that there is an obvious vortex in the impeller passage at off-design conditions. But the number, location and area of the vortex are different from each operation condition. In order to validate CFD simulation results, the stereo PIV is used to test the absolute velocity distribution in the double blades pump at Jiangsu University. The distributions of three-dimensional absolute velocity field at the above five different operating conditions are obtained by the PIV test, and the measured results are compared with the CFD simulation results. The comparison indicates that there are vortexes in impeller passages of the double blades pump under the five operating conditions. But as to the area of the vortex and the relative velocity values of the vortex core, there are some differences between the experiment results and the numerical simulation results. The research work can be applied to instruct the hydraulic design of double blades pumps.
Complete Pump Characteristics and 4-Quadrant Representation Investigated by Experimental and Numerical Approaches
Authors: Gros Laurent , Couzinet Anthony , Pierrat Daniel , Landry Luc
Published: June 2012

The hydraulic performances of the centrifugal pumps are well-known as long as considering normal pump operating conditions but the abnormal operating conditions as energy dissipators or as turbines are less studied. The complete pump characteristics can be reported on a single four-quadrant representation and can be used to predict the behaviour of the machine during the transient operations or to explain the accidental scenarios. This study which is supported by the French manufacturers aims to explore the four quadrant operating conditions of a testing centrifugal pump using experimental and numerical approaches. In the one hand, the experimental test rig afford to perform a series of constant-speed runs varying from negative to positive values in the normal or reverse direction. The range of flowrates is included between −200 to +300 per cent and differs following the rotational speeds. Head, efficiency and torque are measured for all cases, negative or positive discharges. On the other hand, numerical modelling of the same centrifugal pump is performed. CFD computations for a large range of flow rates are analysed. According to the operating conditions, steady state or transient rotor-stator approaches are used to obtain realistic predictions and a discussion concerning the domain of validity of steady state modelling is proposed. Finally, the pump behaviour in the four quadrants obtained by the transient numerical simulations based on two equation turbulence models are in good agreement with the experimental results.
Hydrodynamic Design of the Volute of a Centrifugal Pump Using CFD
Authors: Torabi Rouhollah , Nourbakhsh S. Ahmad
Published: June 2012

The objective of this paper is to develop the shape of an existing volute so that the radial forces in off-design condition become minimum. For this purpose 3-D inverse design method based on the 3-D viscous flow calculations was applied to re-design the geometry of the volute of a low specific speed pump. Various aspects of the geometry change independently to achieve the best one which produces less radial force in off design conditions. Measurements included time-averaged values of velocity and static pressure at a large number of locations in the volute.
A New High-Precision Solver to Predict Pressure Fluctuations in Centrifugal Pumps
Authors: Solis Moise´s , Khelladi Sofiane , Bakir Farid
Published: June 2012

The appearance of CFD codes in the field of Turbomachines has made a valuable contribution in understanding various physical phenomena and in improving the design of the pump. Thus, the application of numerical simulations combined with experimental tests has allowed to improve efficiency and to reduce manufacturing costs. In some industrial applications, the noise from the pumps during their operation should be reduced to respect certain acoustic criteria. One cause of this noise is the strong interactions between the rotating and stationary parts that generate pressure fluctuations within the flow which are propagated inside the machine and then toward to the environment. On the other hand, the research efforts to reduce these fluctuations concern mainly geometrical modifications (radial gap, splitter blades, volute shape) that have been tested through numerical and experimental tests. Nowadays, the requirements in terms of precision lead us to develop new and original techniques to model the fluid physics inside the pump. So, the accurate prediction of the pressure fluctuations is very sensitive and many considerations are essential for this purpose such as the correct choice of the boundary conditions, turbulence model, mesh quality and discretization schemes. For the current CFD codes, it is very difficult to achieve derivation schemes with very high order of accuracy for unsteady cases. This paper presents a new high order finite volume method to calculate the pressure fluctuations which is based on Moving Least Squares approximations. The navier-stokes solver is validated in a 2D centrifugal pump geometry and compared firstly to numerical results from Fluent code and secondly to experimental results in order also to analyze the relation between 2D and 3D pressure fluctuations.
Velocity Field Measurements in Wake of a Straight-Bladed Vertical Axis Wind Turbine
Authors: Hara Yutaka , Suzuki Takahiro , Ochiai Yuki , Hayashi Tsutomu
Published: June 2012

Small vertical axis wind turbine (VAWT) is promising for the development of wind energy in the built environment due to its insensitivity to yaw. In general, computer codes based on the blade element and momentum (BEM) theory, which have much less calculation time than CFD codes, are used for design and performance prediction of wind turbines. However, the results on small VAWTs obtained by the BEM theory often do not accord with the experimental results due to the low Reynolds number, the dynamic stall effects, and so forth. The three-dimension nature of the flow field around the VAWT rotor may be one of the reasons for the discord. This study aims to elucidate the actual flow field around small VAWT. In this study, velocity field measurements were carried out in the wake of a small straight-bladed VAWT by using an ultrasonic anemometer. The measurements of the V and W velocity components showed the downwash and the blow-up, which proceeded toward the equator level and merged into the horizontal flow. Counter flow of the U component was also observed in the mainstream direction. The wake velocity profile simulated by using the Double-Multiple Streamtube (DMS) model based on the BEM theory showed a similar behavior to that of the measured wake. However, the high thrust coefficient estimated from the measured deficit in the U velocity component almost doubles the estimation by the BEM theory.
Numerical Simulation of Underwater Propulsor Using an Unstructured Overset Mesh Technique
Authors: An Sang Jun , Kwon Oh Joon
Published: June 2012

In the present study, the hydrodynamic characteristics of underwater propulsors have been numerically investigated using a RANS flow solver based on pseudo-compressibility. A vertex-centered finite-volume method was utilized in conjunction with 2nd-order Roe’s FDS to discretize the inviscid fluxes. The viscous fluxes were computed based on central differencing. The Spalart-Allmaras one equation model was employed for the closure of turbulence. A dual-time stepping method and the Gauss-Seidel iteration were used for unsteady time integration. An unstructured overset mesh technique was adopted to treat the relative motion between multiple bodies. Calculations were made for the DTRC4119 marine propeller at several advancing ratios. Additional calculations were also made for multiple-blade-row underwater propulsors. Reasonable agreements were obtained between the present results and the experiment for the pressure coefficients on the blade surface and the integrated blade loadings. The interaction between multiple blade rows and the thrust and torque distributions were also analyzed to investigate the performance of underwater propulsors.
Fluidic Components for Oscillating Water Column Based Wave Energy Plants
Authors: Dudhgaonkar Prasad V. , Jayashankar V. , Jalihal Purnima , Kedarnath S. , Setoguchi T. , Takao M. , Nagata S. , Toyota K.
Published: June 2012

A bidirectional (oscillating) air flow is central to energy conversion from wave to wire in an oscillating water column based wave energy plant. Several classes of bidirectional turbines, which operate with such an oscillating flow, have been designed and tested with limited efficiencies. A topology which uses fluidic diodes in conjunction with unidirectional turbines is shown to significantly improve the efficiency. The design and test results from several fluidic diodes for such an application are discussed. It is shown that a combination of a fluidic diode and the unidirectional turbine can achieve a very high impedance to reverse flow while having a high efficiency in the forward direction, over a wide range of flow coefficients.
Study on Open Cross-Flow Runner for Environmentally Friendly Nano-Hydraulic Turbine Utilizing Waterfall (Influence of Waterfall Thickness on the Runner Performance)
Authors: Yamazaki Masahiro , Oike Shingo , Iio Shouichiro , Ikeda Toshihiko
Published: June 2012

The aim of this investigation is to develop an open type cross-flow runner for environmentally friendly nano-hydraulic turbine utilizing extremely low head waterfalls. The waterfall condition is strongly affected by weather, so flow rate changes frequently. It causes a decrease in runner performance because it does not have any flow adjusting mechanisms. It is, therefore, important to evaluate the runner performance against the change of flow condition for stable power generation. This study focused on the influence of waterfall flowing position and its thickness on the runner performance. An open type cross-flow runner was applied for waterfall generation. As a result, we found that the runner characteristic varied with the waterfall condition. In particular, the waterfall thickness has great influence on the runner performance. The value of CPmax reaches the highest value of 0.61 at Q = 3.0×10−3 m3/s.
Numerical Analysis of Wing-Tip Flows and Aerodynamic Sound Generated From the Flows
Authors: Yamasari Kazuaki , Suzuki Yasumasa , Kato Chisachi , Ohnishi Masaaki , Yatuduka Kentaro , Taira Taneyuki , Fujita Hajime
Published: June 2012

We study the flow and the aerodynamic sound generated from the wing-tip using numerical analysis. The objective of this study is to clarify the contribution to level of sound generated from the wing-tip. We predicted the aerodynamic sound by the separation method based on Lighthill analogy. The model is a rectangular wing having NACA0012 profiles. The shape of wing-tip is blunt, which has sharp edges. The Reynolds number based on the chord length and uniform velocity is 2×105. The angle of attack is 9 degree which is the lifting condition. The flow around the airfoil is predicted by Large-eddy simulation of turbulent incompressible flow. Current results indicated that the simulated surface pressure distribution and pressure power spectrum agreed quantitatively with measured data. In this result, we calculated the Lighthill tensor from velocity and density of air. In addition we discussed the wing-tip vortex structure and its origin. The far field sound predicted by Lighthill tensor shows a similar tendency to the measured data. To investigate the contribution of the overall level around the airfoil with wing-tip, the far field sound was predicted by Lighthill tensor only around wing-tip. The aerodynamic sound level generated from wing-tip is small compared to the overall level of the sound all around airfoil, however it remains possible that contribute to particular frequency band.
Oscillation Caused by Vortex Cavitation in a Double-Suction Volute Pump
Authors: Tanaka Kazuhiro , Inoue Akira , Sato Toshiyuki , Nagahara Takahide , Fuchiwaki Masaki , Shimizu Fumio
Published: June 2012

This study highlights a mechanism of the vortex cavitation occurrence from the baffle plate, the end of the suction duct, in a double-suction volute pump and a relationship between pump oscillation and the cavitation occurrence. In this study, full 3D numerical simulations have been performed using a commercial code inside the pump from the inlet of suction duct to the outlet of delivery duct. The numerical model is based on combination of multiphase flow equations with the truncated version of Rayleigh-Plesset model predicting the complicated growth and collapse process of cavity bubbles. The vortex cavitation has the characteristic frequency based on the impeller rotation and has much influence on the pump oscillation, however at over discharge range the vortex cavitation does not collapse, because the cavitation runs into and combines with another cavitation generated in the impeller shroud, and the fixed frequency of the pump oscillation is reduced. The experimental investigations have also been performed on the cavitating flow to evaluate the numerical results and the both results agree well.
Formation of a Hollow Jet and its Breakup in Ambient Air
Authors: Vu Truong V. , Takakura Hideyuki , Wells John C. , Minemoto Takashi
Published: June 2012

An experiment investigation on the formation and breakup of a hollow jet issuing from a coaxial nozzle into ambient air has been carried out. The hollow jet consists of an outer jet of water that encloses an inner jet of argon gas. By varying the flow rate ratio of the inner jet to the outer jet, three different breakup patterns of hollow water jets are identified using two types of nozzles: (I) satellite formation, (II) single-core hollow drop formation, and (III) multi-core hollow drop formation. These patterns are mapped in a space of Weber number versus flow rate ratio, We – Q. Experimental results in pattern (II) show that increasing the flow rate ratio results in increasing the formation frequency, slightly increasing outer diameters of the hollow drops, and decreasing their wall thickness.
Study on the Collapse of Water Jet
Authors: Ikuta Ryuhei , Koizumi Yasuo , Yoshida Hiroyuki , Takase Kazuyuki
Published: June 2012

Collapse of a water jet flowing out from a nozzle to the atmosphere was examined. The diameters of nozzles used in the experiments were 3, 6 and 8 mm. The flow state of the water jet was recorded with a high speed video camera. The collapse length was derived from recorded images. When the flow velocity was quite low, the surface of the water jet was smooth and small perturbations appeared at the lower position of the water jet. As the flow velocity was increased, the position where the small perturbations appeared came close to the nozzle outlet. The perturbations grew as these went downstream and lumps of water were formed at the lower position. When the flow velocity was further increased, successive waves came around on the surface of the water jet. The collapse of the water jet occurred in such a state that the lump of water was torn off from the jet. When the water jet velocity was high, the jet turned into a dispersed flow and the collapse occurred. The agreement of the measured results and the predicted results was poor. It was considered that the instability of the surface of the water jet seemed important for the jet collapse in the present experimental range. The Kelvin-Helmholtz instability wave length was compared with the measured wave length on the water jet. When the wave length reached the Kelvin-Helmholtz instability wave length, the jet collapse occurred except the case that the transition to the dispersed flow caused the jet collapse. The air rolling into the water jet was not observed in the present experimental conditions. The two-phase region was not formed inside the water jet contrary to what is explained in the literature.
Encapsulation and Disintegration of a Gas-Cored Annular Liquid Jet
Authors: Yoshinaga Takao
Published: June 2012

Breakup and encapsulation phenomena are analytically investigated for a gas-cored compound liquid jet which consists of an inviscid and incompressible core gas and surrounding annular liquid. Applying the long wave approximation to both core and annular phases, a set of reduced nonlinear equations is derived for large deformations of the jet. Breakup of the jet is numerically examined in the reduced equations when the jet is semi-infinite and sinusoidal disturbances are fed at the end of the jet. It is found that there exit the most unstable frequencies of disturbances giving the shortest breakup time, which increase as the increase of input amplitudes and velocity ratios of the core to the annular phases, while increase or decrease depending upon the Weber numbers based on the annular phase. For small and medium Weber numbers, it is shown that the jet breaks up by pinching of the core phase and the capsule formation periods and sizes can be determined by the most unstable frequencies, which well agree with the results in the previous experiment and the existing phenomenological model. On the other hand, it is also shown for large Weber numbers that the jet breaks up by disintegration of the annular phase and fails to encapsulate the core gas.
Dynamics of Cell Pattern Formation in Internally Heated Convection Viewed From Local to Global Particle Image Thermometry
Authors: Abe Ryuta , Tasaka Yuji , Kumagai Ichiro , Murai Yuichi , Yanagisawa Takatoshi
Published: June 2012

Internally heated convection is a fundamental phenomenon, largely governing the dynamics of natural systems such as the atmosphere and Earth’s mantle. It also plays an important role in industrial applications. Here we have investigated the separation of the top thermal boundary layer in order to understand the cell enlargement and the dynamics of the cell pattern formation. To observe the development of the thermal boundary layer non-invasively, the temperature distribution of the vertical plane in a convective cell was visualized by particle image thermometry (PIT). Micro-encapsulated thermo-chromic liquid crystals (TLCs) were seeded in the test fluid and illuminated by a white light sheet, and scattering light was taken by a digital camera. For quantitative temperature measurement, we have calibrated the temperature changes with the variation of the hue color component. The development of the thermal boundary layer with respect to the Rayleigh number has been investigated. The results show the local Rayleigh number determined from the thickness of the thermal boundary layer, which increases towards a critical local Rayleigh number ∼600.