bluuebunny/crossref_metadata_2025 huggingface dataset:
Etiological agents of superficial mycoses in Kayseri, Turkey
Authors: Kayman T. , Sarıgüzel F.M. , Koç A.N. , Tekinşen F.K.
Published: June 2012

Objective  In this study, we aimed to determine the prevalence of agents that cause superficial mycoses and clinical types of superficial mycoses in terms of age and gender in our region were aimed.

Methods  Five hundred samples of nails, skin and skin with hair taken from 476 children and adult patients pre‐diagnosed with superficial mycoses were examined by direct microscopy and cultural methods between October 2009 and October 2010.

Results  Fungal elements were determined in 212 (42.4%) of the samples by using direct microscopy. Fungal growth was detected in 111 (22.2%) cultures of the same samples. It was found that the most common agents in superficial mycoses were Trichophyton rubrum (43.7%), Candida spp. (28%) and less often, Aspergillus spp., Malassezia spp., Saccharomyces spp., Rhodotorula spp., Trichosporon spp. and Trichophyton verrucosum.

Conclusion  The significance of diagnosis by using direct microscopy and culturing together was again shown for the diagnosis of superficial fungal infections that follow a chronic course and affect the quality of life of patients. The most common agents in the superficial mycoses were T. rubrum. With this study, defining the aetiological agents of superficial mycoses in the Kayseri region is expected to contribute to the literature in terms of epidemiological data.
Methotrexate vs. fumaric acid esters in moderate‐to‐severe chronic plaque psoriasis: data registry report on the efficacy under daily life conditions
Authors: Inzinger M. , Weger W. , Heschl B. , Salmhofer W. , Quehenberger F. , Wolf P.
Published: June 2012

Objective  To compare the clinical efficacy of methotrexate (MTX) vs. fumaric acid esters (FAE) in psoriasis treated under daily life conditions.

Methods  Data were extracted from a registry (http://www.psoriasisregistry.at) of 272 adult patients with moderate‐to‐severe chronic plaque psoriasis treated primarily with MTX (n = 72) or FAE (n = 200) between 2004 and 2011. Data from all patients, including those who did not complete at least 3 months of monotherapy, were included in an intention‐to‐treat (ITT) worst‐case analysis.

Results  Thirty of 72 (41.7%) patients treated with MTX and 85 of 200 (42.5%) patients treated with FAE discontinued early, mainly due to side‐effects or lack of response. Among patients who completed at least 3 months of treatment, the response to primary treatment with MTX vs. FAE did not differ significantly at any time point. In the ITT worst‐case analysis at month 3, complete remission rate, PASI90, PASI75 and PASI50 rates were 6%, 7%, 24% and 39% in MTX‐treated patients vs. 1%, 5%, 27% and 44% in FAE‐treated patients. Overall mean PASI reduction score improved significantly in response to primary MTX and FAE treatment (by 10.6% and 12.6%, respectively) between 3 and 6 months (P = 0.0005; exact Wilcoxon test), but not between 6 and 12 months (P = 0.16). A subset of 32 patients who did not respond satisfactorily to primary treatment with FAE responded better to subsequent MTX therapy (P < 0.0001; paired Wilcoxon test).

Conclusions  As shown by retrospective analysis, the primary efficacy of FAE was similar to that of MTX under daily life conditions.
Determinants of Attitudes Toward Muslim Students Among Flemish Teachers: A Research Note
Authors: Agirdag Orhan , Loobuyck Patrick , Van Houtte Mieke
Published: June 2012

Muslims are now the second largest religious group in almost all Western countries and a large majority of Muslim citizens are children who attend schools. However teachers’ attitudes regarding the education of Muslim students are largely ignored by educational researchers. In this study, we investigate the determinants of teachers’ attitudes among Flemish (Belgian) teachers (N = 620). Regression analysis has revealed that female teachers, Muslim teachers, younger teachers, and teachers with a four‐year college degree have significantly more positive attitudes. Most interestingly, we found that teachers working in schools that enroll a larger share of Muslim students (greater than 50 percent) have more negative attitudes toward Muslim students than other teachers. The implications of these findings for educational policy are discussed.
Image statistics on the age perception of human skin
Authors: Arce‐Lopera Carlos , Igarashi Takanori , Nakao Keisuke , Okajima Katsunori
Published: June 2012

Background/purpose

Recent research on the age‐dependent changes of facial skin has analyzed their correlation with changes in image and colorimetric properties using mainly first‐ and second‐order statistics. The aim of this study is to reveal the importance of third‐order statistics and relate those image properties to skin age perception.

Methods

Photographs of the faces of 118 Japanese women ranging in age from 13 to 80 years were taken in a controlled environment. Subsequently, 10 Japanese subjects rated the age perception of skin patches from the cheek area of the original facial images.

Results

The age estimation of the skin patches was highly correlated with its chronological age proving that our skin patches contain enough information for age estimation. Also, the perceived age was significantly high correlated to color and lightness statistical values. Specifically, age perception was significantly high correlated with third‐order statistics of all channels in CIELAB1976.

Conclusion

Our results reveal the importance of higher order statistics for the development of nonintrusive skin quality assessments of the skin.
Aerobic exercise increases BKCa channel contribution to regulation of mesenteric arterial tone by upregulating β1‐subunit
Authors: Shi Lijun , Liu Bailin , Li Na , Xue Zhimin , Liu Xiaodong
Published: June 2012

New Findings

What is the central question of this study?

Calcium‐activated K channels (BK) play critical roles in regulating cellular excitability and vascular tone. Exercise‐training has beneficial effects on cardiovascular diseases which may result from an improvement of the vascular functions. However, the molecular targets and mechanisms underlying this action remain largely unknown in peripheral resistance arteries. This paper asks the question, do BK channels play a role in bringing about these changes?

What is the main finding and its importance?

This investigation is the first to demonstrate that aerobic exercise training increases the contribution of BK channels to regulation of vascular tone in mesenteric arteries. We found that it is mediated by upregulation of the Beta‐1 but not alpha1‐subunit protein to increase BK channel activity.

Substantial evidence has shown that exercise training produces numerous adaptations within the arteries. Large‐conductance Ca2+‐activated K+ (BKCa) channels are expressed broadly on smooth muscle cells and play an important role in the regulation of vascular tone. The present study was designed to investigate the mechanisms by which the BKCa channel underlies the exercise‐induced improvement of the vascular function in mesenteric arteries. Male Wistar rats (180–200 g) were trained for 12 weeks on a treadmill (EX group) and compared with age‐matched sedentary (SED) animals. Blood pressure and vascular contractility of mesenteric arteries were measured. Inside‐out patch‐clamp recording was applied on the freshly separated mesenteric smooth muscle cells to investigate the gating characteristics of BKCa channels. Western immunoblotting was performed to study expression levels of BKCa channel proteins. The maximal vascular contraction induced by noradrenaline (3 × 10−5m) was decreased after exercise training. Both TEA (3 × 10−3m) and iberiotoxin (3 × 10−8m) induced a significant increase of vessel tension in both SED and EX groups, but these effects were more pronounced in EX rats compared with SED animals. Inside‐out patch‐clamp recording showed that exercise training significantly increased the open probability, decreased the mean closed time and increased the mean open time and the sensitivity to Ca2+ and voltage without altering the unitary conductance. The expression of BKCaβ1‐ but not α‐subunit was significantly enhanced after exercise training. These data suggest that exercise training increases the contribution of the BKCa channel to the regulation of vascular tone in mesenteric arteries, which is possibly mediated by upregulating β1‐subunit protein to increase BKCa channel activity.
The dorsal motor nucleus of the vagus and regulation of pancreatic secretory function
Authors: Mussa Bashair M. , Verberne Anthony J. M.
Published: June 2012

New Findings

What is the Topic of this review?

This review describes new evidence for the control of pancreatic exocrine and endocrine secretion by the dorsal motor nucleus of the vagus. It describes the effects of several gastrointestinal peptides on pancreatic secretion and considers their sites of action in the vago‐vagal reflex pathway.

What advances does it highlight?

This review draws together recent electrophysiological, anatomical and pharmacological studies to provide a state‐of‐art view of the parasympathetic control of the exocrine and endocrine pancreas.

Recent investigation of the factors and pathways that are involved in regulation of pancreatic secretory function (PSF) has led to development of a pancreatic vagovagal reflex model. This model consists of three elements, including pancreatic vagal afferents, the dorsal motor nucleus of the vagus (DMV) and pancreatic vagal efferents. The DMV has been recognized as a major component of this model and so this review focuses on the role of this nucleus in regulation of PSF. Classically, the control of the PSF has been viewed as being dependent on gastrointestinal hormones and vagovagal reflex pathways. However, recent studies have suggested that these two mechanisms act synergistically to mediate pancreatic secretion. The DMV is the major source of vagal motor output to the pancreas, and this output is modulated by various neurotransmitters and synaptic inputs from other central autonomic regulatory circuits, including the nucleus of the solitary tract. Endogenously occurring excitatory (glutamate) and inhibitory amino acids (GABA) have a marked influence on DMV vagal output to the pancreas. In addition, a variety of neurotransmitters and receptors for gastrointestinal peptides and hormones have been localized in the DMV, emphasizing the direct and indirect involvement of this nucleus in control of PSF.
A Parallelized Algebraic Multi-Grid Matrix Solver
Authors: Zhao Xiang , Yang Zhi , Zhang Sijun , Chen Chien-Pin
Published: June 2012

Algebraic multi-grid (AMG) is increasingly used for large practical problems, its parallelization is highly demanded. A parallel algorithm to enhance the robustness and performance for AMG was proposed with regard to unique characteristics of partial differential equations governing fluid flows. A building strategy was developed to accomplish grid coarsening and build the hierarchy of multi-level grids. Moreover an agglomeration approach was proposed, which stems from the consideration of both the physical and mathematical properties of flow fields. The parallelized AMG has demonstrated excellent performances and strong enhancement on many cases.
CFD Analysis in a Non-Contact Holder
Authors: Tsukiji Tetsuhiro , Katsumata Shinsuke
Published: June 2012

There are many devices that use air flow characteristics. Recently an electric fan without propeller using air jet flow and a vacuum cleaner using swirling air flow have been developed by Dyson Ltd. Furthermore, as one of the applications of such air flow, a non-contact holder that can hold a body such as a work piece, disc etc., using low-pressure region generated by air flow without contact was developed by a Japanese company. Some bodies such as work piece are brought without contact with the holder. The mechanism to hold them is explained by Bernoulli’s theorem. However, systematic research has not been done in the present stage and the effect of the geometry of the non-contact holder on the holding force is not clear. In this paper, we calculated the flow in a non-contact holder and obtained the force to hold a body by CFD analysis. The effect of the deflector and inside geometry of the holder on the velocity and pressure distribution, and holding force is investigated. The deflector is a device fixed with the holder to increase the holding force using low-pressure region. CFD was done using both incompressible and compressible flow, and k-ε turbulent model was used. The calculated pressure distributions of a simpler model of the holder are compared with the previous experimental results to confirm our calculation method. The design policy of a non-contact holder is discussed based on the calculated results of velocity and pressure distributions and holding force. Consequently we show that the deflector is very useful to obtain high holding force and the concept to design the non-contact holder is required to get the holding force according to the weight of the body and to achieve high efficiency.
Numerical Flow Simulation in a Reciprocating Valveless Micropump With Parallel Geometry Nozzle-Diffuser
Authors: Ferna´ndez Joaqui´n , Marcos Alfonso , Barrio Rau´l , Blanco Eduardo , Parrondo Jorge L.
Published: June 2012

This work presents a numerical study of a nozzle/diffuser micropump under several frequencies of operation. The investigation focuses on the effects caused by two principal changes in the geometry: 1) a small duct portion included before the nozzle/diffuser element, with the purpose of inducing a fully developed flow, and 2) the size of the fluctuating chamber. As expected, the net flow rate of a nozzle/diffuser micropump increases with pumping frequency and also with the size of the fluctuating chamber. However, the duct before the nozzle/diffuser element causes more losses and a decrement in the net flow, though inducing a better flowing of the fluid into the nozzle.
Flow Field Investigation in a Water Treatment Reactor Using Computational Fluid Dynamics
Authors: Ahmed Saber , Rasul M. G. , Brown R. J. , Duran J. Esteban
Published: June 2012

The hydrodynamic behaviour of a novel flat plate photocatalytic reactor for water treatment is investigated using CFD code FLUENT. The reactor consists of a reactive section that features negligible pressure drop and uniform illumination of the photocatalyst surface to ensure improved photocatalytic efficiency. The numerical simulations allowed the identification of several design issues in the original reactor, which include extensive boundary layer separation near the photocatalyst support and regions of flow recirculation that render a significant portion of the reactive area. The simulations reveal that this issue could be addressed by selecting the appropriate inlet positions and configurations. This modification can cause minimal pressure drop across the reactive zone and achieves significant uniformization of the tested pollutant on the photocatalyst surface. The influence of roughness elements types has also been studied with a view to identify their role on the distribution of pollutant concentration on the photocatalyst surface. The results presented here indicate that the flow and pollutant concentration field strongly depend on the geometric parameters and flow conditions of the reactor.
Numerical Simulation of Low-Speed Two Phase Flows Based on Preconditioning
Authors: Niu Yang-Yao
Published: June 2012

This paper first applies flux vector type splitting method based on numerical speed of sound for computing incompressible single and multi-fluid flows. Here, a preconditioning matrix based on Chorin’s artificial compressibility concept is used to modify the incompressible multi-fluid Navier-Stokes Equations to be hyperbolic and density or volume fraction independent. The current approach can reduce eigenvalues disparity induced from density or volume fraction ratio and enhance numerical stability. Also, a simple convection-pressure flux-splitting method with high-order essentially non-oscillatory (ENO) type primitive variable extrapolations coupling with an ENO-MUSCL type volume fraction recompressed reconstruction within a mesh cell is used to maintain the preservation of sharp interface evolutions in multi-fluid flow simulation. Benchmark tests including a solid rotation test of a notched 2D cylinder, the evolution of spiral and rotational shapes of deformable circles, a dam breaking problem, the Rayleigh-Taylor instability and the cavitated flow problems are chosen to validate the current incompressible multi-fluid methodology.
Numerical Simulation of Three Dimensional Flow in Large Mixed-Flow Pump System
Authors: Yang Fan , Liu Chao , Tang Fangping
Published: June 2012

The three-dimensional flow inside a mixed-flow pump system was simulated by using CFX software. The Shear Stress Transport turbulent equation which combined k-ε and k-ω turbulent model was applied. The flow field in volute and discharge passage of the pump system was obtained and the hydraulic performances of the pump system were predicted. The velocity and pressure distribution in pump system were analyzed. From the calculation results it is evident that the flow in the double helix volute passage is a spiral movement combining axial and rotary flow; the static pressure distribution in the volute is symmetric; the uniformity of axial velocity distribution and velocity-weighted average swirl angle at the outlet section are relatively low; and static pressure distribution on pump blade surface is regular with higher static pressure on pressure side and lower one on the suction side. The axial forces decrease gradually with the decrease of lifting head and the radial forces decrease first and then increase. A model test of the pump system was conducted to verify the calculation results. The pressure fluctuation at certain sections of the pump system was measured from the model test. A good agreement was found for lifting head between calculated and measured results. While the deviation of the efficiency between calculated and measured results does exist in non design points which need to be improved.
New Centrifugal Pump in Very Low Specific Speed Range
Authors: Kagawa Shusaku , Kurokawa Junichi
Published: June 2012

In the range of very low specific speed, such as ns < 80 [min.−1, m3/min., m], or Ns < 533 [min.−1, USGPM, ft.], stable head-capacity curve is one of the most important issues. The head-capacity curve of a conventional closed impeller tends to be unstable with a positive slope characteristic in such a very low ns range. To solve this problem, a new type of centrifugal pump “J-groove pump” is proposed and tested in this study. The J-groove pump is composed of a rotating disk mounted with many shallow radial grooves and a circular casing. The experimental results reveal that the proposed J-groove pump is quite effective in the very low specific speed range. The pump head is about 1.2 times higher than that of a conventional centrifugal pump and the head-capacity curve is almost stable, though the efficiency becomes a little lower because of a large friction power of the stationary wall. The cavitation performance is also measured and is shown to be almost same as that of a conventional centrifugal pump. This pump is applicable to high speed pump, as it has no small clearance, high strength due to simple impeller configuration, and easy to assemble. In order to determine the internal flow characteristics of the J-groove pump, CFD simulation is carried out. It is revealed that the high head of the J-groove pump is caused by a strong vortex flow existing in both clearances near the impeller tip over the whole flow range.
Investigations of Unsteady Flow Field Characters in Axial Flow Pump Based on Numerical Simulation
Authors: Zhang De-sheng , Shi Wei-dong , Guan Xing-fan , Yao Jie
Published: June 2012

Investigations of the unsteady flow field characters in a axial-flow pump at different conditions are presented in the paper. The numerical simulation of the unsteady flow field is performed with FLUENT codes based on RNG k-ε model and SIMPLEC arithmetic. Numerical results show that the strong-coupling evolutions of static pressure and axial velocity distribution between rotor and stator in multi-conditions are periodic with the rotation of rotor. The interaction of stationary and rotating pressure field leads to periodic flow field distortions and induces pressure fluctuation. It is found that the maximum pressure amplitude of blade passing frequency occurs in the rotor inlet zone, but it deceases very fast backward to the stator. The dominant frequency at monitoring points located at rotor inlet, outlet and stator outlet, corresponds to the blade passage frequency. The axial velocity distortion resulting from the modulation of the interacting stationary and rotating flow field is affected by the blade numbers and thickness of both rotor and stator. The axial velocity has different distributions at different conditions, and the phase of it changes cyclically. However, the axial velocity distribution at stator outlet is also mainly affected by the stator blade numbers, but its phase does not change cyclically.
Study on Radial Forces of Centrifugal Pumps With Various Collectors
Authors: Pan Zhongyong , Li Junjie , Li Shuai , Yuan Shouqi
Published: June 2012

Numerical simulation is presented to study the steady and unsteady radial forces in a centrifugal pump with various collectors. The radial forces are obtained by integrating the pressure distribution around the impeller circumference. The calculated radial forces both time-dependent and independent at different flow rates caused by the collectors are compared. The results show that some conclusions do not consistent with the conventional experience as the collectors with double volute and vaned volute significantly decrease the radial forces and the radial force close a circle during the period of one blade passage passing. The combination of impeller and double volute is a trade-off design choice as it has significantly decreased the radial forces than that of single volute and its configuration is more compact than that of vaned collector.
Study on the Aerodynamic Performance of Small Axial Flow Counter-Rotating Fans
Authors: Liu Pin , Jin Yingzi , Wang Yanping , Qian Hongyu , Zhang Li
Published: June 2012

Small axial flow fans are used as cooling components for computers, electronic equipments and other electronic components. With the increasing power of electrical equipment, the demand for lower noise and higher ventilation of cooling fans to improve heat transfer effects is also increasing. Traditional methods of improving ventilation by raising the fan’s rotation speed causes a decrease in efficiency and an increase in noise. The researchers have found that higher pressure, ventilation and efficiency can be achieved in a small space by counter-rotating fans than single fans. In this paper, 3D simulation has been done on flow field of counter-rotating fans for heat exchange, and the method of large eddy simulation (LES) and FW-H acoustic model have been used to simulate the distribution of noise field. The frequency spectrum from different sound sources has been analyzed, and the optimal ranges of the distance and gap between rotors have been determined. All that will provide a theoretical basis for researches on their characteristics and structure design.
Aerodynamic Analysis for Camber Effect in Vertical Wind Turbine System
Authors: Kim Jinwook , Lee Dohyung , Han Junhee , Kim Sangwoo
Published: June 2012

The Vertical Axis Wind Turbine (VAWT) has advantages over Horizontal Axis Wind Turbine (HAWT) that it allows less chance to be degraded independent of wind direction and turbine can be operated even at the low wind speed. The objective of this study is to analyze aerodynamics of the VAWT airfoil and investigate the ideal shape of airfoil, more specifically cambers. The analysis of aerodynamic characteristics with various cambers has been performed using numerical simulation with CFD software. As the numerical simulation discloses local physical features around wind turbine, aerodynamic performance such as lift, drag and torque are computed for single airfoil rotation and multiple airfoil rotation cases. Through this study more effective airfoil shape is suggested based vortex-airfoil interaction studies.
Open Loop Dynamic Performance of Series Hydraulic Hybrid System With Hydrostatic Regenerative Braking
Authors: Ramakrishnan R. , Hiremath Somashekhar S. , Singaperumal M.
Published: June 2012

As gas prices rise and the green movement grows, more fluid power companies are working to develop hydraulic drive trains for large trucks to passenger cars and wind turbines. The hydraulic drive system is more effective and efficient than traditional hybrid systems because there is less energy lost between the engine and the wheels. Specially designed for stop-and-go vehicles, the system captures energy as the vehicle brakes. When the vehicle is restarted, the series hydraulic hybrid system puts the vehicle in motion. When the captured energy is depleted, then the engine kicks in. Here, the accumulator in the system is used to recover the kinetic energy without reversion of fluid flow. Variable displacement pump/motor unit is utilized for both driving and hydro-static regeneration mode. This paper gives an insight on dynamic simulation results obtained using LMS Amesim tool. The effect of various system parameters like pre-charge pressure and hydraulic pump/motor-pump maximum displacement on system output power is discussed. Varying pre-charge pressure of the accumulator shows significant improvement in the system output power. Maximizing the system output power indirectly leads to less fuel consumption and pollution reduction in hybrid vehicles.
Effects of Sway Motion and Flow-Induced Vibration on Vortex Structure Behind Flexible Rectangular Plate
Authors: Yonekura Masaki , Watanabe Kei , Yamada Shunsuke , Ishikawa Hitoshi
Published: June 2012

Vortex structure behind a flexible rectangular plate with sway motion and flow-induced vibration was experimentally investigated by wind tunnel experiment by using Particle Image Velocimetry (PIV). The flexible rectangular plate, which was made of a polyurethane block, was cantilevered on a flat plate. On the opposite end, top free end showed a sway motion in the downstream direction. Increasing sway angle, the top free end involved the flow-induced in-line vibration which has a small amplitude. This is a typical example of fluid-structure interaction problem. However more experimental research for the effects of the sway motion and the flow-induced vibration on vortex structure behind the rectangular plate is required. In this paper, we focus attention on the phase-averaged vortex structure when the amplitude of vibration is the largest and smallest case. PIV measurement was conducted to clarify the phase-averaged and the instantaneous vortex structure behind the swaying plate. We discussed the effect of sway motion and flow-induced vibration on vortex structure.
Influence of Water-Splash Formation by a Hydrophilic Body Plunging Into Water
Authors: Kubota Yoshihiro , Mochizuki Osamu
Published: June 2012

The objective of this study is to understand the relationship between water-splash formation and the surface conditions of bodies plunging into the water’s surface by considering hydrophilicity strength. A hydrophilic body (constructed with hydrogel), as well as an acrylic resin body, was created to understand the influence of hydrophilicity on splash formation. The strength of hydrophilicity was determined by investigating degrees of swelling. We obtained consecutive images of splash formation by using a high-speed CMOS camera. We show that water-splash formation is related to water-film formation by studying: 1) droplets formed at the film edge, 2) mushroom-or dome-type splashes caused by film impinging, and 3) crown-type splash caused by film separation. The strength of hydrophilicity affects the splash-formation process of the mushroom- and crown-type splashes. The difference in formation process is caused when the film velocity increases with hydrophilicity. As the film velocity increases with strong hydrophilicity, the film flow separates from the body surface and an air cavity forms. Crown-type splashes form with hydrophilic bodies because such film separation occurs. Moreover, the relationship between the strength of hydrophilicity and film velocity was examined empirically. These results indicate that the hydrophilic body does not alter the splash-formation process.
Influence of Dissolved Gas Concentration on Diameter and Number Density of Micro-Bubbles
Authors: Maeda Yasunari , Taya Chihiro , Hosokawa Shigeo , Tomiyama Akio , Ito Yoshihiro , Shibata Naoki
Published: June 2012

A micro-bubble generator based on a pressurized dissolution method can generate fine micro-bubbles with a high bubble number density. The mean diameter and the number density of micro-bubbles depend on the concentration of dissolved gas in the upstream region of a decompression nozzle. In this study, the mean diameter and the number density of micro-bubbles in the downstream region of the decompression nozzle are measured by using a phase Doppler anemometry (PDA) to examine effects of the dissolved gas concentration on the mean diameter and the number density of micro-bubbles generated by the pressurized dissolution method. Experiments are conducted for several dissolved gas concentrations in the upstream region of the decompression nozzle under bubble cavitation and sheet cavitation conditions in the decompression nozzle. The experimental results indicate that, (1) influence of the dissolved gas concentration on flow patterns in the decompression nozzle (bubble cavitation and sheet cavitation) is weak, (2) the Sauter mean diameter of micro-bubbles increases as dissolved gas concentration increases, (3) the gradient of Sauter mean diameter with respect to the dissolved gas concentration in a sheet cavitation case is higher than that in a bubble cavitation case, (4) micro-bubbles are generated even when the dissolved gas concentration is lower than the saturated concentration at the atmospheric pressure provided that a sheet cavitation takes place at the nozzle, and (5) the bubble number density increases with the dissolved gas concentration in bubble cavitation cases whereas it does not depend on the concentration in sheet cavitation cases.
Three-Dimensional Synthetic Aperture Imaging and Resolution of Multi-Phase Flows
Authors: Belden Jesse , Ravela Sai , Truscott Tadd T. , Techet Alexandra H.
Published: June 2012

Three-dimensional multiphase fluid flows demand advanced and innovative measurement systems in order to fully resolve the flow physics. Dense bubbly multiphase flows cannot be readily imaged by traditional, non-invasive flow measurement techniques due to the bubbles occluding optical access to the interior regions of the volume of interest. We present a novel technique for imaging these flows, which allows for determination of the 3D bubble distribution and bubble sizes despite the imaging challenges. By using synthetic aperture (SA) refocusing we are able to reparameterize images captured by an array of cameras to reconstruct a 3D volumetric map of the bubble field for every time instance. The SA refocusing technique has the unique ability, over conventional imaging methods, to see-through partial occlusions in the scene due to the configuration of the camera array and reconstruction algorithms, making it an ideal tool for resolving multiphase flows. Relatively dense bubbly flows can be resolved with good accuracy. We present fundamentals of the synthetic aperture methodology, a feature detection algorithm for extracting bubble size and location, and results from application of the technique to a bubble-entraining plunging jet.
Development of Dual-Layer PSP/TSP System for Pressure and Temperature Measurements in Low-Speed Flow Field
Authors: Moon Kil-Ju , Mori Hideo , Ambe Yuichiro , Kawabata Hiroaki
Published: June 2012

Pressure sensitive paint (PSP) and temperature sensitive paint (TSP) are useful measurement tools in measurement of pressure and temperature distribution on surfaces in airflows, and application of PSP and TSP in relatively low speed flow fields is highly demanded. However, temperature dependence of PSP will be the factor of an error in the pressure measurement, and therefore the temperature compensation is needed to obtain highly precise pressure distribution. To solve this problem, we apply new combining method. This is made by stacking up a PSP layer and a TSP layer. PSP emission and TSP emission can be separated each other using optical filters. Using this combining method, temperature distribution obtained by the TSP can be used for the temperature compensation of the PSP. In this research we call this combining method as “dual-layer PSP/TSP”. We clarify that the sensitivity of the dual-layer PSP/TSP in low-speed flow fields against pressure and temperature is comparable to that of mono-layer PSP or TSP, showing the feasibility of the dual-layer PSP/TSP for the measurement in low-speed flow fields with the gauge pressure below 1kPa and temperature in the range of 10–20°C (283–293K). We also clarify that, using dual-layer PSP/TSP method, the accuracy of pressure data obtained by PSP increases by compensation of temperature which is obtained by TSP.
Spectrum Analysis of the Taylor Vortex Flow With a Short Annulus Using the Ultrasonic Velocity Profiler
Authors: Kawai Hideki , Honma Tomoki , Kikura Hiroshige
Published: June 2012

Mild mixing effect is observed in the Taylor vortex flow (TVF) system in which the animal and plant cell walls are not disrupted as much as other bioreactor systems. These facts would be more important in developing a new bioreactor system, which plays an active role in the medical and bioindustrial fields. Although the mixing methods with an impeller are often used for an agitation in synthetic polymerization, the problem is that there exists a high shearing flow region just after the moving impeller. This region for instance, would cause the destruction of the alga cell when a microorganism in suspension is used as a bioreactor. The TVF is expected to reduce the local increase of these shearing forces because the device doesn’t have any impeller, and lead the bioreactor system to more uniform and stable states in the flow fields for cultivation or oxygen production. TVF in a single-phase flow with an infinite annulus is well known since it has a spectrum transition to turbulence and the oscillation is observed from the wavy vortex mode. Recent Takeda’s study has measured the precise spatiotemporal velocity fields by using the ultrasonic velocity profiler (UVP). On the other hand with a short annulus, we have various vortex modes generated due to the Ekman boundary layers occurred near the upper and lower solid boundaries. Each vortex mode also has the same spectrum transition such as wavy, modulated and soft turbulence modes. But the flow state seems much different from the infinite annulus. Present study measures the velocity profiles of the flow in TVF with a short annulus by using the UVP. We focus on not only the velocity profiles, but also the spectra in oscillation mode that occurs in different vortex modes. From the results, the spectra of the various oscillations are occurred with increase of Reynolds number, and seem different from those in the infinite annulus. This oscillation analysis would contribute to the basic knowledge of the mixing effect in solid-liquid flow when a microorganism in suspension is used as a bioreactor.
Direct Actuation of Small-Scale Motions for Enhanced Heat Transfer in Heated Channels
Authors: Hidalgo Pablo , Glezer Ari
Published: June 2012

Flow-effected, enhanced heat transfer in a high aspect ratio rectangular mm-scale channel that models a segment of a high-performance, air-cooled heat-sink is characterized. The present investigation reports a novel approach to enhanced cooling without increasing the channel’s characteristically low Reynolds number. Heat transport that is governed by the local heat transfer from the fin surface and by subsequent mixing with the core flow is significantly increased by deliberate shedding of unsteady small-scale vortices that are induced by the vibration of a miniature, planar piezoelectric reed. The present investigation focuses on the heat transfer and fluid mechanics that are associated with the small-scale motions induced by the reed. High-magnification particle image velocimetry (PIV) is used to characterize the interaction of the induced vortical structures with the channel flow. Performance enhancement by reed actuation is quantified in terms of increased power dissipation over a range of flow rates compared to the baseline flow in the absence of the reed. It is demonstrated that the channel’s coefficient of performance can be increased by a factor of 1.4 while accounting for the power to the reed and the changes in channel pressure drop.
Expanding of Fire-Ball and Subsequent Shock Wave Propagation by Explosives Detonation in Underwater
Authors: Kwak Ho-Young , Kang Ki-Moon , Ko Ilgon
Published: June 2012

A well known problem in hydrodynamics involves the sudden release of explosion energy, concentrated in a finite volume, to surroundings with uniform density. However, only similarity solutions which have no detailed information on the behavior of the fire-ball are available on this problem. In this study, we obtain a set of analytical solutions for the time dependent radius of expanding fire-ball after explosives detonation by solving continuity, Euler and energy equations with a “polytope” assumption for the fire-ball center. Subsequent spherical shock waves developed from the fire-ball in underwater are obtained by Kirkwood-Bethe hypothesis with Tait’s equation of state for water. The pressure waves emanating from the oscillating bubble in underwater, which has a notably different time scale from the shock wave generation, are obtained using the Rayleigh equation. The calculated results of period and the maximum radius of bubble developed from the fire-ball and the pressure wave from the oscillating bubble are similar to those observed.
Use of Wigner-Ville Transformations for Fluid Particles in Laser Doppler Flow Accelerometry
Authors: Chun Sejong , Kwon Hyu-Sang
Published: June 2012

Flow acceleration with Lagrangian description is crucial to understanding particle movements in turbulent jet flows or dissipation statistics in isotropic turbulence. Laser Doppler anemometry is regarded as a suitable experimental tool for measuring flow acceleration, because scattering particles generate trajectories in the measurement volume, which process gives rise to flow acceleration at a fixed measuring point with the Lagrangian description. The most useful algorithm for processing Doppler signals is either the quadrature demodulation technique (QDT) or the iterative parametric method (alternatively, the minimization of least squares, LSM) as in the literature. In the present study, another algorithm using the Wigner-Ville transforms (W-V) is introduced to give more accurate estimation of flow acceleration than the QDT or the LSM. Toward this end, five signal-processing algorithms, including the QDT, the LSM, the MC (maximization of correlation), and the W-V, were compared with each other in experiments with an impinging air jet flow with a cylindrical rod and a round free-air jet flow. Mean flow acceleration distribution in the streamwise direction was mainly investigated. Processing speeds for the above-mentioned signal-processing algorithms were checked to find the best algorithm, which has best performance with short processing time. The QDT was found to be an accurate algorithm with short processing time; however, the QDT was found to have limited applications to flows with large acceleration and high SNR. The MC was also found to be a good algorithm with moderate processing speed, which can be useful in flows with low SNR because the MC is an iterative parametric method. The W-V gave the most accurate values for flow acceleration; however, the processing time for this method was the slowest among the signal-processing algorithms.
Effect of Pressure Fluctuation at Nozzle Exit on Flapping Phenomena in a Two-Dimensional Jet
Authors: Shoji Yuichi , Terashima Osamu , Sakai Yasuhiko , Nagata Kouji
Published: June 2012

The flapping motion of the flow is one of the coherent structures in a two-dimensional turbulent jet. In past studies, the flapping phenomenon indicated that a pair of fluid lumps with the positive and negative streamwise velocity fluctuation exists on the opposite sides of the jet centerline, and the signs of the velocity fluctuation for those fluid lumps change alternately as the time advances. Additionally, it is known that the vortices at the jet exit are arranged symmetrically to the jet centerline and gradually become the alternate arrangement, and in the self-preserving region, the flapping phenomenon can be observed. However, the reason why the flapping phenomenon arises is not cleared yet. In this study, in order to clarify the influence of the velocity and pressure fluctuation on the arising of the flapping phenomenon, the characteristics of the velocity and pressure at near the jet exit are investigated. The measurements of the flapping phenomenon, the characteristics of the velocity and pressure at near the jet exit are conducted by using combined probe composed of an X-type hot-wire probe and a pressure probe, and at the same time, the measurements of streamwise velocity fluctuations at the two points in the self-preserving region are performed to determine the time when the flapping phenomenon is arising. The measured data are analyzed statistically by ensemble-averaging technique and conditional-sampling technique on the basis of the intermittency function for the flapping/non-flapping decision. The intermittency function is obtained by applying the wavelet transform analysis to the measured data by two I-type hot wire probes placed at the opposite side of the jet centerline in the self-preserving region. Measured and analyzed results show that the RMS value of the streamwise velocity fluctuation at the jet exit is clearly different according to whether flapping phenomenon arises or not. On the other hand, the RMS value of the pressure fluctuation at the jet exit is not influenced by the arising of the flapping phenomenon. In addition, the possibility that the arising of the strong negative pressure fluctuation at near the jet exit has an important role in the flapping phenomenon is shown.
Numerical Study on an Outlet Plenum of the PBMR
Authors: Ju Jae-Woo , Lee Sang-Moon , Kim Kwang-Yong
Published: June 2012

Parametric study on an outlet plenum of a PBMR type gas cooled nuclear reactor has been carried out using three-dimensional Reynolds-Averaged Navier-Stokes equations. Shear stress transport turbulence model is used for analysis of turbulence. Two geometric parameters are selected, namely, displacement on the horizontal line and angle of rotation about the center of gravity of the roof support block. Pressure drop and uniformity of flow distribution in the outlet plenum have been considered as the performance parameters of an outlet plenum of the PBMR. The results show that the performance parameters are affected considerably by the location of the roof support block.
HVAC Blower Aeroacoustics Predictions Based on the Lattice Boltzmann Method
Authors: Pe´rot Franck , Kim Min-Suk , Wada Koichi , Norisada Koji , Kitada Motohiro , Hirayama Shunsaku , Sakai Masaharu , Imahigasi Syoichi , Sasaki Noriya
Published: June 2012

Two centrifugal HVAC fan and casing geometries are experimentally and numerically investigated. Aerodynamic and acoustic measurements are performed at three operating conditions following an ISO standard procedure. Explicit and compressible CFD/CAA simulations based on the Lattice Boltzmann Method are performed for six configurations. From these simulations, flow information in term of pressure rise as a function of the mass flow rate and noise are obtained at the same time and compared to experiments. Additional post-processing is performed to have an insight on the origin and location of flow-induced noise sources.
Investigation of Aerodynamic Wheel Designs on a Passenger Car at Different Cooling Air Flow Conditions
Authors: Landstro¨m Christoffer , Lo¨fdahl Lennart
Published: June 2012

Passenger cars represent the largest part of all means of personal transportation today. Thus, it is important to work towards reduced energy consumption of cars if a sustainable mobility is to be achieved. This involves many aspects of vehicle engineering; one of them being aerodynamics. This study focuses on aerodynamic drag and the contributions from the wheels at different cooling air flow configurations. Wheels and wheel housings are important for the overall aerodynamic drag on passenger cars. It has been shown that as much as 25% of the aerodynamic drag originates from these components. Therefore, it is desirable to understand the flow structures related to the wheels and wheel housings, and how they interact with other important flow regions. This paper presents an investigation of the effects of wheel designs on aerodynamic drag at different cooling air flow configurations on a sedan type passenger car. Comparisons between numerical simulations and wind tunnel measurements are made for some of the configurations as well. Several additional wheel configurations were investigated numerically to further investigate the flow structures at the front and rear wheels. The numerical results show that the effects of radial wheel covering varied noticeably with cooling air flow configuration. In two of the configurations this resulted in a net drag increase with closed cooling air inlets. The best configuration with closed cooling air inlets generated an overall drag reduction of 29 drag counts compared with the numerical baseline with open cooling air inlets. In addition to the obvious drag reduction of closing the cooling air inlets, the main reasons for the additional decrease was limiting the drag increase at the front stagnation region and positive interference effects along the underbody and vehicle base.
Flow Past a Permeable Manipulator Ring Placed in a Turbulent Pipe Flow
Authors: Utsunomiya Koji , Nakanishi Suketsugu , Osaka Hideo
Published: June 2012

Turbulent pipe flow past a ring-type permeable manipulator was investigated by measuring the mean flow and turbulent flow fields. The permeable manipulator ring had a rectangular cross section and a height 0.14 times the pipe radius. The experiments were performed under four conditions of the open area ratio β of the permeable ring (β = 0.1, 0.2, 0.3 and 0.4) for Reynolds number of 6.2×104. The results indicate that as the open-area ratio increased, the separated shear layer arising from the permeable ring top became weaker and the pressure loss was reduced by increasing fluid flow through the permeable ring. When β was less than 0.2, the velocity gradient was steeper over the permeable ring and in the shear layer near the reattachment region. When β was greater than 0.3, the width of the shear layer showed a relatively large augmentation and the back pressure in the separating region increases. Further, the response of the turbulent flow field to the permeable ring was delayed compared with that of the mean velocity field, and these differences increased with β. The turbulence intensities and Reynolds shear stress profiles near the reattachment point increased near the wall region as β increased, while those peak values that were taken at the locus of the manipulator ring height decreased as β increased.