bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-Intrusive Devices Applied to Sedimentation and Consolidation
Authors: Pham Van Bang Damien , Brisset Patrick
Published: June 2012

This paper presents two non-intrusive techniques to measure the time evolution of the vertical profile of concentration during batch settling test. The first one is a Magnetic Resonant Imaging (MRI) vertical prototype used on Gironde estuary. The second is an X-ray ‘home-made’ prototype used on Seine estuary. Both are used to observe the sedimentation and the consolidation processes of natural cohesive sediments. They provide the movement of the supernatant/suspension interface and the isoconcentration lines of the process. A space-time based method is proposed to close the governing equation.
Measurements of the Vorticity Behind a Circular Cylinder in a Uniform Stream
Authors: Inoue Yoshihiro , Suwa Naoki , Yamashita Shintaro
Published: June 2012

The present study is designed to experimentally investigate the flow field past a circular cylinder in a uniform stream. The circular cylinder was set across an open test section of water channel. Experiments were conducted with Reynolds number based on a cylinder diameter of 120 to 800, and the flow field was visualized by the hydrogen-bubble method and visualization of the flow velocity pattern in the lateral direction was made by using an ultrasonic velocity profiler (UVP). Fluctuating velocity fields, v(y, t), were measured. Changes in the deflection amount and width of the separated shear layer are indicated from intensity distributions of velocity fluctuation. According to the analysis based on the POD, it is clarified that the present flow fields may be represented by the reduced order model of the vortex structure. Integral of v(y, t) with respect to y is related with the averaged vorticity, and its time history indicates a stability of vortex shedding mode.
Experimental Investigation of Intermittent Gas-Liquid Flows on Solid Particle Transportation in Inclined Pipelines
Authors: Wang Liang , Goharzadeh Afshin , Rodgers Peter
Published: June 2012

Solid particle transport in pipelines by fluids is widely encountered in energy industry processes, such as oil production, drilling of horizontal and inclined wells and mining. In contrast to the intensive research effort that has investigated solid transport in horizontal pipelines, limited studies have been published on solid transportation mechanism generated from an initial stationary particle bed in inclined pipes. Consequently the underlying mechanisms responsible for pipe inclination influence on bed-load transport phenomena have not been extensively assessed, particularly for gas-liquid conveying of solid particles. This paper presents an experimental investigation on the influence hydraulic and two phase (gas-liquid) flows on sand dune transportation resulting from a stationary flat bed as a function of (i) pipe inclination, (ii) gas liquid flow rate and (iii) initial sand bed thickness. Experiments were undertaken in a laboratory environment using a 14 m long transparent Plexiglas loop of 24 mm internal diameter to permit optical access. The three phases used were water, air and sand. High speed digital photography was employed to study the flow phenomenon and characteristics of sand bed transportation for the analysis variables (i) to (iii) under consideration. For hydraulic conveying of solid particles, it was found that 1° upward pipe inclination had negligible influence on both the flow phenomenon and solid-liquid flow pattern transition. In contrast, for gas-liquid conveying of solid particles, pipe inclination resulted in considerably different transport phenomena relative to that observed for the horizontal orientation. Differences such as backward bed movement and enhanced particle suspension were observed, and found to be highly gas-liquid ratio dependent. These measurements provide fundamental insights into the influence of upward pipe inclination on bed-load mode solid transportation in a closed conduit.
Numerical Study on Deformation Behavior of a Fluid Particle Under Shear Flow
Authors: Suh Youngho , Lee Changhoon
Published: June 2012

In this work, we studied the deformation behavior of a droplet under the various flow conditions. The droplet deformation is calculated by a level-set method. In order to determine the acting force on a particle in shear flow field, we propose the feedback forces which can maintain particle position with efficient handling of deformation. Computations were carried out to investigate the deformation behavior of a droplet caused by the surrounding gaseous flow and the effect of the deformation on the droplet characteristics with various dimensionless parameters. Based on the numerical results, we observed that drag and lift forces acting on a droplet depend strongly on the deformation. Also, the present method is proven to be applicable to a three-dimensional deformation of droplet in shear flow, which cannot be properly analyzed by the previous studies. The drag and lift forces obtained from the present numerical method are favorably compared with the data reported in the literature.
Numerical Study of Impulse Actuation for Stall Control
Authors: Jee SolKeun , Lopez Mejia Omar D. , Moser Robert D.
Published: June 2012

The response of a stalled flow to a single impulse actuation is examined numerically to investigate the mechanism by which this actuation affects the flow. Delayed detached eddy simulation is used on a stalled NACA 4415 airfoil at an angle of attack of 20 degrees and Reynolds number Re = 570,000. A brief strong jet issues normal to the airfoil surface upstream of the nominal flow separation point of the airfoil, causing the boundary layer temporally reattached. This computation shows the detailed evolution of vortical structures generated by both the baseline flow and the impulse actuation. Initial vortices from the actuation convect downstream, interact with the separated shear layer, and dismantle the layer. After the collapse of the separated shear layer, the separation point moves aft and remains delayed for a much longer period than the actuation time, similar to experimental observation [1]. The jet is simply represented as a Dirichlet velocity boundary condition, which is found to be sufficient to represent the global effects of impulse actuation on the stalled flow.
High-Speed Visualization of the Oscillatory Supersonic Flow Over a Rectangular Cavity
Authors: Handa Taro , Miyachi Hiroaki , Kakuno Hatsuki , Ozaki Takaya
Published: June 2012

A mechanism of cavity-induced pressure oscillation in supersonic flows is not well understood in spite of a lot of former investigations. Especially, the process by which the pressure wave is generated and the path of the pressure wave propagating inside the cavity remain unclear. In order to clarify these, the oscillatory behaviors in the supersonic flow over a rectangular cavity are visualized by the schlieren method with a high-speed camera in the present study. The inlet Mach number of the flow is 1.68. The length and depth of the cavity are 14.0mm and 11.7mm respectively; i.e., the length-to-depth ratio of the cavity is 1.20. The pressure oscillation near the trailing edge of the cavity is also measured by use of the semiconductor-type pressure transducer simultaneously with the visualization. As a result, the pressure waves propagating inside as well as outside the cavity are successfully visualized. In addition, the relationship between the shear layer displacement, pressure wave generation and pressure oscillation at the trailing edge of the cavity are clarified experimentally.
Experimental and Numerical Analysis of Repairing a Triangular Shaped Airfoil
Authors: Etemadi F. , Mani M. , Etemadi M.
Published: June 2012

This article investigates the aerodynamic characteristics of repairing the airfoil with triangular damage by the measurement of aerodynamic coefficients improvement. For study of this model “two applied and numerical methods are used”. A full span NACA 641-412 airfoil is considered as test model. Using model is in five schematics: undamaged model, damaged model with upper, lower and full repair model. The used repair sheets are chosen based on the ABDR manuals. Effect of the repair on different shape of damage has performed by the quantity and quality results.
Control of Flight Altitude of a Small Flapping Robot by Wing Flapping Frequencies
Authors: Imura Tadatsugu , Fuchiwaki Masaki , Tanaka Kazuhiro
Published: June 2012

The purpose of this paper is clarifying the effect of wing motion for the flight of small flying robot without having tail wing. Specifically, we measured the body angle and flight velocity of flying small flying robot at different flapping frequency in range from 7.5 [Hz] to 10.5 [Hz], and clarified the effect of body angle for flight velocity in flights as flapping frequency changes. The small flying robot has large body angle in flight at high flapping frequency. The spatial vertical velocity increases because the body angle increases linearly despite of little change of flight velocity from viewpoint of robot as increasing flapping frequency. Moreover, for this flying robot, flying at larger body angle than body angle of 16 [deg.] is necessary condition for increasing spatial vertical velocity as flapping frequency changes. It indicates that the flight altitude of micro flapping robot is controllable by its flapping frequency.
Experimental Investigation of a Turbulent Boundary Layer Subjected to an Adverse Pressure Gradient
Authors: Nakamura Takanori , Kameda Takatsugu , Mochizuki Shinsuke
Published: June 2012

Experiments were performed to investigate the effect of an adverse pressure gradient on the mean velocity and turbulent intensity profiles for an equilibrium boundary layer. The equilibrium boundary layer, which makes self-similar profiles, was constructed using a power law distribution of free stream velocity. The exponent of the law was adjusted to −0.188. The wall shear stress was measured with a drag balance by a floating element. The investigation of the law of the wall and the similarity of the streamwise turbulent intensity profile was made using both a friction velocity and new proposed velocity scale. The velocity scale is derived from the boundary layer equation. The mean velocity gradient profile normalized with the height and the new velocity scale exists the region where the value is almost constant. The turbulent intensity profiles normalized with the friction velocity strongly depend on the nondimensional pressure gradient near the wall. However, by mean of the local velocity scale, the profiles might be achieved to be similar with that of a zero pressure gradient.
Modeling Carbon Black Aggregate Structure and Ionomer Coat for Optimum Design of PEFC Catalyst Layer
Authors: Inoue Gen , Fan Yun Peng , Matsuoka Takahiro , Matsukuma Yosuke , Minemoto Masaki
Published: June 2012

In present Polymer Electrolyte Fuel Cell (PEFC), the cathode oxygen reduction reaction (ORR) is dominant at high current density condition. In order to accelerate this reaction, oxygen, proton and electron, which move in void space, ionomer and carbon black (CB) or CNT respectively, have to be transferred at Pt surface smoothly. Accordingly, it is very important to know the transport phenomena in catalyst layer (CL) to design the optimum structure and to develop new materials. In order to investigate the transport phenomena in CL by applying calculation technique, in this study, heterogeneous CB aggregate structure was simulated by computer calculation as the first examination. In addition, ionomer coating condition and proton conductivity were examined. Furthermore oxygen, proton and electron transfer in 3D porous catalyst layer were calculated, and the effective reaction field was examined in various structure and ionomer condition.
Study on the Thermo-Hydrodynamic of a Dry Gas Seal in Helium Circulator for High Temperature Gas-Cooled Reactor
Authors: Lin Jianshu , Wang Hong
Published: June 2012

A comprehensive analysis method is proposed to resolve the problem of simulating a complex thermo-flow with two kinds of distinct characteristic length in the dry gas seal, and a conjugated simulation of the complicated heat transfer and the gas film flow is carried out by using the commercial CFD software CFX. By using the proposed method, a three dimensional of velocity and pressure field in the gas film flow and the temperature distribution within the sealing rings are investigated for three kinds of film thickness, respectively. A comparison of thermo-hydrodynamics of the dry gas seals is conducted between the sealed gas of air and helium. The latter one is used in a helium circulator for High Temperature Gas-cooled Reactor (HTGR). From comparisons and discussions of a series of simulation results, it will be found that the comprehensive proposal is effective and simulation results are reasonable, and the maximum temperature rise in the dry gas seal is within the acceptable range of HTGR safety requirements.
Numerical Investigation for the Effect of Blood Flow Rate and Asymmetric Bifurcation Angle on the Anterior Circulation Aneurysm Formation
Authors: Kim Soyoon , Ro Kyoungchul , Ryou Hong Sun
Published: June 2012

Most of aneurysms in the cranial cavity occur at the bifurcation of anterior circulation system. A cerebral aneurysm is easily ruptured, and it is fatal for most patients. Generally it is known that aneurysm occurs when arterial wall is deformed by high pressure or high wall shear stress (WSS). A blood flow pattern and the geometry and the blood vessel are important factors for aneurysm formation and the location. The transient interaction between blood flow and the arterial wall affects for simulating deformation of the blood vessel. Thus, numerical analysis is performed for various bifurcation angles and flow rate ratio in bifurcation artery with different diameters to predict the location of aneurysm by hemodynamic characteristics of blood flow. A bifurcation angle between the internal carotid artery and the anterior cerebral artery (ACA) increased, a region of high pressure moved to the bifurcated artery with larger bifurcation angle when ratio of blood flow rate is constant case. When the ratio of blood flow increased, the region of high wall shear stress moved to the side of large flow rate ratio. Our results showed that the high WSS or high pressure region occur at the location of aneurysm as mentioned in the clinical research. Thus, this indicates that the geometry of blood vessel and blood flow rate affect the location of the anterior circulation aneurysm.
Direct Numerical Simulation of Flow Past a Solid Particle: Influence of Streamline Curvature and Particle Non-Sphericity
Authors: Fukada Toshiaki , Omori Takeshi , Takeuchi Shintaro , Kajishima Takeo
Published: June 2012

Conventional point-particle models for fluid-solid two-phase flows are mainly based on the analysis of the fluid force on a sphere in a uniform stream or a homogeneous shear flow. Their applicability to the flows with (non-zero) streamline curvature and non-spherical particles is yet to be established. In particle segregation in curved flows, the effects of streamline curvature and particle shapes may become significant. In the present study, the hydrodynamic force on a single spherical/spheroidal particle in uniform and curved flow is investigated. The flow around a solid particle is simulated by an immersed-boundary method of a body force type, which has been developed by the authors. The results demonstrate that the spheroidal particle receives higher drag force than the spherical particle. On the other hand, though the effect of the streamline curvature on the fluid force is not clearly observed, the spherical particle rotates only in curved flow.
DNS of Conjugate Heat Transfer Phenomena With an Improved IB Method
Authors: Kang Seongwon
Published: June 2012

In the present study, the immersed boundary (IB) method is applied as a tool to solve a conjugate heat transfer problem in a turbulent flow around a circular cylinder. This problem involves complexities such as transition, turbulent natural convection, and interaction of fluid convection and solid conduction. In order to enforce the velocity boundary condition at the IB, a second-order reconstruction method is employed. In order to handle coupling of the temperature field between different materials, the fluid-solid interface is approximated as a group of adjoining Cartesian faces from heterogeneous material regions. A Hermite-type interpolation is applied to reconstruct the temperature field across the fluid-solid interface with a reduced error. This approach has been verified with a heat transfer problem with an analytic solution and shows an improved result compared to the previous method. For the turbulent conjugate heat transfer problem around a circular cylinder, the predicted local Nusselt number shows a good agreement with the previous experiment. The statistical data obtained from this simulation can be used for turbulence modeling of heat transfer problems around a bluff body.
Numerical Study of Mixing in a Droplet Moving Through a Winding Channel
Authors: Tanaka Mitsuru , Miyajima Yo , Mizutani Jun
Published: June 2012

Direct numerical simulations have been conducted for chaotic mixing inside an immiscible droplet moving through a winding channel or tube in order to clarify the detailed mechanism of the enhancement of mixing, which is useful for the design of efficient micro devices. An immersed-boundary method is used for simulating the flow inside the bending channel, while the PLIC-VOF algorithm is used for tracking the droplet interface. The molecular mixing is ignored and only the mixing due to the chaotic advection is considered by using passive tracer particles. By considering the relation between the flow structure and the mixing inside the droplet in two-dimensional computations, it is found that the quality of mixing strongly depends on the activity of the dipole structure of the flow inside the droplet, and that the activity depends on various parameters including the dimension and the shape of the winding channel. In a winding channel with a locally narrowed region, for example, circulating flows associated with the dipole are off-centered to reduce the efficiency of mixing. A three-dimensional computation shows that the quality of mixing is decreased in the edge regions of the droplet.
Multi Stage Axial Compressor Design and Performance Evaluation
Authors: Kang Young Seok , Park Tae Choon , Hwang Oh Sik , Yang Soo Seok
Published: June 2012

Recently, needs for Unmanned Air Vehicle (UAV) and small aircraft are increasing and demands for small turbo jet or turbo fan engines are also increasing. Then, size and weight are the two main restrictions in UAV or small aircraft propulsion system applications. One method for resolving such a problem is to increase the pressure rise per stage and to reduce the number of stages. Nowadays, matured compressor aerodynamic design techniques enable us to design highly loaded axial compressors. This paper covers from the design step of a highly loaded transonic axial compressor to the performance test result and its analysis. At the fore part of the paper, aerodynamic process of a multi stage axial compressor is introduced. To satisfy both of the mass flow and pressure rise, the compressor should rotate at a high rotational speed. Therefore the transonic flow field forms in the rotor stages and it is designed with a relatively high pressure rise per stage to satisfy its design target. Basically, one dimensional and quasi three dimensional compressor design were carried with compressor design codes. The compressor stage consists of 3 stages, and the bulk pressure ratio is 2.5. The first stage is burdened with the highest pressure ratio and less pressure rises occur in the following stages. Also it is designed that tip Mach number of the first rotor row does not exceed 1.3. The final design was confirmed by iterating three dimensional CFD calculations to satisfy design target and some design intentions. In the latter part of the paper, its performance test processes are briefly introduced. The performance test result showed that the overall compressor performance targets; pressure ratio and efficiency are well achieved. From the test results, we found some clues for further improvement and optimization of the compressor aerodynamic performance.
Unsteady Turbulent Simulation and Analysis of Pressure Fluctuation for High Temperature and High Pressure Centrifugal Pump
Authors: Liu Shuhong , Sha Yujun , Wu Yulin , Wang Baogang
Published: June 2012

The pressure fluctuation in the internal flow passage of centrifugal pump is a key factor affecting the stability of the hydraulic system, especially working at conditions of high temperature and pressure. In this paper, RNG k–ε turbulent model is adopted to simulate the unsteady flow through the whole flow passage of centrifugal pump working at temperature T = 300 °C and high pressure P = 280 bar. The pressure fluctuation is calculated at the predefined reference points in the different planes. By analyzing the results, it is found that: 1) the rotor-stator interaction between impeller and diffuser is the main cause for pressure fluctuation; 2) the dominant frequency of pressure fluctuation in the flow passage of impeller is the diffuser passing frequency; 3) the dominant frequency at the points of casing wall is almost the same, and the maximum amplitude is relatively small.
On the RANS Modeling of Turbulent Airflow Over a Simplified Car Model
Authors: Bella G. , Krastev V. K.
Published: June 2012

The need for reliable CFD simulation tools is a key factor for today’s automotive industry, especially for what concerns aerodynamic design driven by critical factors such as the engine cooling system optimization and the reduction of drag forces, both limited by continuously changing stylistic constraints. The Ahmed body [1] is a simplified car model nowadays largely accepted as a test-case prototype of a modern passenger car because in its aerodynamic behavior is possible to recognize many of the typical features of a light duty vehicle. Several previous works have pointed out that the flow region which presents the major contribution to the overall aerodynamic drag, and which presents severe problems to numerical predictions and experimental studies as well, is the wake flow behind the vehicle model. In particular, a more exact simulation of the wake and separation process seems to be essential for the accuracy of drag predictions. In this paper a numerical investigation of flow around the Ahmed body, performed with the open-source CFD toolbox OpenFOAM®, is presented. Two different slant rear angle configurations have been considered and several RANS turbulence models, as well as different wall treatments, have been implemented on a hybrid unstructured computational grid. Pressure drag predictions and other flow features, especially in terms of flow structures and velocity field in the wake region, have been critically compared with the experimental data available in the literature and with some prior RANS-based numerical studies.
Experimental Study of Roughness Influence on a Turbulent Pipe Flow
Authors: He´rout Benjamin , Giovannini Andre´ , Boisson Henri-Claude , Bensaid Riad , Lo Jacono David
Published: June 2012

The main goal of this study is to obtain experimental data to develop adapted hydraulic and thermal wall functions used by industrial CFD codes. An experimental study, based on a test rig designed to reproduce realistic flow characteristics, has been conducted in order to explore velocity and temperature profiles. Hydraulic characterization of turbulent pipe flow was conducted over a Reynolds number range of 20 000 to 90 000, with three different test sections, presenting an increasing sand grain roughness. The three components of the flow velocity were measured, using laser Doppler velocimetry, and particle image velocimetry. The results obtained give access to turbulent quantities, to non-dimensional velocity profiles and to velocity defect in the boundary layer. These results are considered sufficient to cover the hydraulic requirements of an adequate wall-function related to surface roughness.
Fractality in Turbulence
Authors: Salim S. M. Muztaba , Nicolleau F.
Published: June 2012

Fractality is, as we introduce it, an attribute relating to any object or system where the existence of self-similar replication of the whole is present in any order and scale. This can be realized in any turbulent flow due to the self-similar flow structures in its energy cascade. This intrinsic natural fractality is dominant in any turbulence energy cascade. In this paper, we report how this natural fractality is affected by a forced fractality externally superimposed on turbulent flow in a circular wind tunnel. The forced fractality was created by a fractal orifice plate. The time correlation and energy spectra showed that the forced fractality excites the natural fractality significantly and increases flow mixing. Simultaneously, we found that the fractal orifice plate is much more efficient than the classical orifice plate with equal flow area in terms of the flow mixing and deemed to be a better orifice flow meter than its classical counterpart.
Experimental Investigation on Effects of Surface Roughness Geometry Affecting to Flow Resistance
Authors: Ito Takahiro , Matsumoto Ayumu , Ito Toshihisa , Motozawa Masaaki , Iwamoto Kaoru , Kawashima Hideki , Ando Hirotomo , Senda Tetsuya , Kawaguchi Yasuo
Published: June 2012

Experimental investigation on effects of surface roughness geometry affecting to flow resistance has been carried out. The concentric cylinder device composed of outer cylinder and inner test cylinder was employed to the experiment. We prepared 24 different roughness models having various skewness of roughness profile as test inner cylinders. Surface of test cylinder has ridge and valley roughness whose shapes are isosceles right triangle V-shape. These ridge and valley are arranged at equal intervals. Therefore, RMS roughness of the surface and skewness of the surface roughness profile can be evaluated. In the experiment, inner cylinder is rotated but outer cylinder is stationary, torque of rotating inner cylinder was measured. Based on the torque measurement, we investigated the effect of skweness of the surface roughness on flow resistance. As a result, when the roughness profile has Gaussian distribution (skewness = 0), friction coefficient increases with increasing RMS roughness. Moreover, friction coefficient also increases with increasing skewness of surface roughness under same RMS roughness. In order to predict the friction coefficient from the geometric information of the surface, we estimated the equivalent sand grain roughness from surface roughness parameters. Results showed that it was clarified the relation among skewness of roughness profile, equivalent sand grain roughness and the root mean square of surface roughness.
PIV Measurements of Propeller Flow Field in a Large Cavitation Tunnel
Authors: Mori Takayuki , Kimoto Risa , Naganuma Kenji
Published: June 2012

Flow field around a marine propeller was measured by means of PIV technique in a large cavitation tunnel of the Naval Systems Research Center, TRDI/Ministry of Defense, Japan. Test section of the tunnel is 2m(W) × 2m(H) × 10m(L) and it contains 2000m3 of water. 2-dimensional PIV (2-D PIV) and stereo PIV (SPIV) measurements were made for a five-bladed highly skewed marine propeller. In the case of 2-D PIV measurements, high spatial resolution measurements were possible by seeding relatively small amount of tracer particles. Phase-averaged flow fields showed details on evolution of tip vortices. In the case of SPIV measurements, much larger amounts of tracer particles were required, and it was difficult to perform high resolution measurements. Phase averaged velocity profiles from SPIV measurements showed good agreement with 2-D PIV-measured results. PIV-measured results were compared with results of LDV measurements. Although PIV-measured velocity profiles showed fairly good agreements with LDV-measured results, some discrepancies were found at the blade tip region.
6 Degree of Freedom Motion Analysis of Surface Ship Models
Authors: Park Joel T. , Silver Andrew L. , Bishop Richard C.
Published: June 2012

A 6 degree of freedom (DOF) optical motion analysis system has been adapted for the measurement of surface ship model motion. The motions measured by the optical system are surge, sway, heave, roll, pitch, and yaw. Apparently, the calibration of the system is not traceable to a National Metrology Institute (NMI). Measurement results are compared to on-board instruments for the measurement of roll, pitch, and heave, which were calibrated prior to the test. Test results are presented for a Large Medium Speed Roll-on Roll-off (LMSR) ship model with a Transformable Craft (T-Craft) Surface Effect Ship (SES) in tandem connected by a ramp. The LMSR model was attached to a carriage in a rectangular wave-making basin. The results presented in this paper were conducted at a simulated Sea-State 4 and model speed of 0.372 m/s. The results were in reasonable agreement in pitch and roll where the instrument calibration uncertainties were between ±0.19° and ±0.67°, while the manufacturer’s specification is ±1.0°. Heave was measured near the stern by the optical system. The uncertainty in the correction to the center of gravity is estimated to be ±17 mm for the LMSR in comparison to the direct measurement of heave by a string pot at the cg, where the calibration uncertainty was ±1.3 mm.
Measurement of Ionized Particle Distribution in Axisymmetric Jet
Authors: Katoh Munamasa , Takamatsu Yuki , Yamada Shunsuke , Ishikawa Hitoshi
Published: June 2012

The aim of this study is to measure distribution of ionized particles in an axisymmetric jet. Recently, the effects of ionized particles, such as disinfection of bacteria and neutralizations of static electricity, are attracting much attention from many industry circles. Micro- and nano-size particles with electric charge are called “ionized particles” in this study. The ionized particles were usually carried to the objects in the air, which should be disinfected or neutralized, by a fluid force like an axisymmetric jet generated by a blower and a purge nozzle. High transportation of ionized particles improves the efficiency of the industrial products which use ionized particles. However, it is considered that behavior of ionized particle in axisymmetric jet is easily influenced by not only fluid force, but flow turbulence, Brownian motion and coulomb’s force. In this study, we measured ionized particle distribution in an axisymmetric jet by an ion count system which was a measuring device to count the number of ionized particles. The axisymmetric jet has an advantage of the high mass transportation and the diffusion capability by its flow characteristics. We conducted wind tunnel experiments to clarify the relationship between the axisymmetric jet and ionized particles. The experiment was performed in the flow velocity measurement by hot wire anemometer and the density measurement by an ion count system which was able to measure the number of ionized particle in the air. The results suggested that the behavior of ions in the jet was influenced by fluid force more than by the coulomb’s force. The aim of this study is to measure the distribution of ionized particles introduced into the axisymmetric jet.
Experimental and Numerical Analysis of the Cavitating Part Load Vortex Dynamics of Low-Head Hydraulic Turbines
Authors: Houde Se´bastien , Iliescu Monica S. , Fraser Richard , Lemay Se´bastien , Ciocan Gabriel D. , Descheˆnes Claire
Published: June 2012

The draft tube flow is a two-sided challenge for the operation of a hydraulic turbine. On one side, it is an important component for the performance of low to medium head turbines, where it can provide up to 40% of the extracted energy from the flow. On the other side, being a diffuser with a complex vorticity distribution at the inlet, vortex breakdown instability can occur at part load and generate a corkscrewed precessing vortex that can be associated with cavitation. The cavitating vortex rope, may generate undesired power output fluctuation and/or structural vibration. Therefore, draft tubes are much studied components but hard to tackle both numerically and experimentally. Within the framework of the AxialT project, the flow in the draft tube of a propeller turbine model operating at part load was studied using a combination of two-phase Particle Image Velocimetry (PIV) measurements and Unsteady Reynolds Averaged Navier-Stokes (URANS) simulations. The paper main focus is on the experimental methodology and results. It explains how Particle Image Velocimetry measurements were implemented, validated and post-treated to provide flow measurements in the draft tube cone at part load in the cavitating and non-cavitating regimes. It also describes various image processing techniques used to extract the velocity field around the cavitating vortex rope and to estimate the location of the water-vapour interface of the cavitating region. In the spirit of feeding experimental data to numerical simulations, an analysis of measured velocity profiles just under the runner is presented. Comparison between PIV measurements and preliminary URANS simulations is also illustrated.
Numerical Analysis of Super-Cavitating Flow Around a Two-Dimensional Cavitator Geometry
Authors: Park Sunho , Rhee Shin Hyung
Published: June 2012

Mostly for military purposes, which require high speed and low drag, super-cavitating flows around under-water bodies have been an interesting, yet difficult research subject for many years. In the present study, high speed super-cavitating flow around a two-dimensional symmetric wedge-shaped cavitator was studied using an unsteady Reynolds-averaged Navier-Stokes equations solver based on a cell-centered finite volume method. To verify the computational method, flow over a hemispherical head-form body was simulated and validated against existing experimental data. Through the verification tests, the appropriate selection of domain extents, cell counts, numerical schemes, turbulence models, and cavitation models was studied carefully. A cavitation model based on the two-phase mixture flow modeling was selected with the standard k-epsilon model for turbulence closure. The cavity length, surface pressure distribution, and the flow velocity at the interface were compared with experimental data and analytic solutions. Various computational conditions, such as different wedge angles and caviation numbers, were considered for super-cavitating flow around the wedge-shaped cavitator. Super-cavitation begins to form in the low pressure region and propagates downstream. The computed cavity length and drag on the body were compared with analytic solution and computational results using a potential flow solver. Fairly good agreement was observed in the three-way comparison. The computed velocity on the cavity interface was also predicted quite closely to that derived from the Bernoulli equation. Finally, comparison was made between the computational results and cavitation tunnel test data, along with suggestions for cavitator designs.
Numerical Investigations of Thermal Effects on the Interaction of Shock Waves With Bubbles
Authors: Jinbo Yoshinori , Takahira Hiroyuki
Published: June 2012

The present study deals with the collapse of nonspherical bubbles in a compressible liquid by taking the thermal diffusion into account. The ghost fluid method (GFM) is modified so as to consider the thermal diffusion through the bubble surface. The boundary condition for the temperature continuity at the interface is discussed for determining the values of the ghost fluids. The improved GFM is applied to the collapse of a single spherical bubble. The present results are in good agreement with those obtained from the equation of motion for a single bubble (Keller equation) coupling with the energy equation. The improved multigrid GFM is also applied to the interaction of a gas bubble with a strong shock wave. The non-spherical bubble collapse is simulated successfully by taking the thermal diffusion into account. The thermal boundary layers both inside and outside the bubble are captured with the present method although the thermal boundary layer in liquid is very thin. The bubble collapse due to the incident shock wave accompanies the formation of the liquid jets and shock waves leading to the high temperature field. The influence of thermal diffusion becomes more prominent when the initial bubble radius is small. It is shown that a large amount of heat outflows from the interior of the bubble to the liquid when the liquid jet hits the downstream surface of the bubble and the bubble rebounds. The increased thermal diffusion causes the decrease of the internal pressure and temperature in the bubble leading to more violent collapse.
On the Smoke Propagation of a Fire in a Tunnel With Concentrated Exhaust Ventilation
Authors: Tanaka Futoshi , Kato Masahiro , Majima Shouhei , Kawabata Nobuyoshi , Kikumoto Tomoki , Yamada Masahisa
Published: June 2012

In recent years, tunnel fire accidents of about 20 occur every year in Japan. The Nihonzaka and the Sakai tunnel fire accidents are as famous typical examples. When concentrated exhaust ventilation device is activated in such a tunnel fire, it is of concern that the people who take shelter receive damage from the fire smoke. When a tunnel fire occurs, the concentrated exhaust ventilation device is stopped in Japan. Therefore, the research on the use of concentrated exhaust ventilation device at a tunnel fire has not advanced in Japan. The purpose of this study is to clarify the smoke propagation when concentrated exhaust ventilation device is activated. The model tunnel in the scale of 1/5 was used in this study. Froude scaling law was used to make the experimental results of the model tunnel correspond to the real scale tunnel. The concentrated exhaust ventilation device installed on the model tunnel extracts the fire smoke from a chimney. The smoke distribution in the model tunnel was measured with smoke concentration meters. In the case that the exhaust ventilation device was activated, the smoke layer thickness of the downstream of the chimney thinned. However, in the upstream of the chimney, the smoke layer thickness did not change though the exhaust ventilation device was activated.
Optimization of Chemical Reaction Processes in Microreactors Using Reaction Rate Analyses
Authors: Asano Yukako , Togashi Shigenori , Endo Yoshishige
Published: June 2012

We applied microreactors to the three following reactions: a consecutive bromination reaction, the two-step Sandmeyer reaction, and an acetylation reaction including solvent effects. We obtained the reaction rate constants from few experimental data or quantum chemical calculations and optimized the reaction conditions such as the reaction times and temperature. We then experimentally validated them by microreactors. A consecutive bromination reaction, where the objective reaction was followed by the side reaction, was one of the processes. The reaction temperature played an important role in the effects of a microreactor. The yield of the objective product was improved by about 40% using a microreactor. The two-step Sandmeyer reaction was also applied, where the 1st-step reaction was followed by the 2nd-step reaction to produce the objective product. The 1st-step reaction had the diffusion-controlled process, while the 2nd-step reaction had the reaction-controlled one. The yield of the objective product was improved when microreactors were used and the reaction time for the 2nd-step reaction was set appropriately. Moreover, an acetylation reaction including solvent effects on reaction rates was considered and the solvent effects could be predicted from quantum chemical calculations. The calculation suggested that acetic acid with the larger electron-accepting property gave more stability to the species formed in the transition state. The reaction time was shortened using a microreactor, when the reaction process was changed from reaction-controlled to diffusion-controlled by changing the solvent used.
Numerical Modeling of Red Blood Cell Suspended in a Channel With Uniform Magnetic Field
Authors: Tatsumi Kazuya , Kuroki Ryo , Nishitani Kosuke , Arakawa Tomoki , Nakabe Kazuyoshi
Published: June 2012

Numerical simulations were carried out for the red blood cell (RBC) suspended in a stationary fluid. Elastic spring model were used to calculate the RBC membrane, and finite volume method was used to solve the flow field. The magnetic effect on the RBC was model by considering the anisotropic diamagnetic susceptibility of the phospholipids and transmembrane protein. The torque produced by these components at each element edge of the mesh generated on the cell surface was first calculated, and then the force applied to each node was evaluated. Experimental measurement of the RBC behavior in microchannels was also carried out under uniform magnetic field with the intensity of 8T using microscope and high-speed video camera to validate the present computation. The numerical simulation showed that the RBC rotates and orients so that the concave surface aligned parallel to the magnetic field. This behavior and the time that was required for the RBC to fully orient agreed well with the present experimental results. These results affirm not only the validity of the present method, but also the possibility of using microchannels to evaluate the magnetic characteristics of the RBCs.
Noninvasive Whole-Genome Sequencing of a Human Fetus
Authors: Kitzman Jacob O. , Snyder Matthew W. , Ventura Mario , Lewis Alexandra P. , Qiu Ruolan , Simmons LaVone E. , Gammill Hilary S. , Rubens Craig E. , Santillan Donna A. , Murray Jeffrey C. , Tabor Holly K. , Bamshad Michael J. , Eichler Evan E. , Shendure Jay
Published: June 2012

Sequencing of cell-free fetal-derived DNA from maternal plasma provides a noninvasive way to predict the fetal genome sequence.
Help—Plumber Needed
Authors: Methe Heiko
Published: June 2012

A cyclic peptide breaks up clogs in the kidneys of patients with multiple myeloma.
Meds Disturb Motor Development
Authors: Singh Manpreet K.
Published: June 2012

Intrauterine exposure to antipsychotic medication can decrease motor skills in infants.
Immunity Is But Skin Deep: Context Is Everything
Authors: Yipp Bryan G.
Published: June 2012

Epidermal Langerhans cells dictate specific immune responses of the skin resident memory T lymphocyte population in humans.
Adaptation of Human Parainfluenza Virus to Airway Epithelium Reveals Fusion Properties Required for Growth in Host Tissue
Authors: Palmer Samantha G. , Porotto Matteo , Palermo Laura M. , Cunha Luis F. , Greengard Olga , Moscona Anne
Published: June 2012

Paramyxoviruses, a family of RNA enveloped viruses that includes human parainfluenza virus type 3 (HPIV3), cause the majority of childhood croup, bronchiolitis, and pneumonia worldwide. Infection starts with host cell receptor binding and fusion of the viral envelope with the cell membrane at the cell surface. The fusion process requires interaction of the two viral surface glycoproteins, the hemagglutinin-neuraminidase (HN) and the fusion protein (F). We have previously shown that viruses with an HN/F pair that is highly fusogenic in monolayers of immortalized cells due to mutations in HN’s secondary sialic acid binding site are growth impaired in differentiated human airway epithelium (HAE) cultures and 
in vivo
. Here we have shown that adaptation of HPIV3 to growth in the lung is determined by specific features of HN and F that are different from those required for growth in cultured immortalized cells. An HPIV3 virus bearing a mutated HN (H552Q), which is fit and fusogenic in immortalized cells but unfit for growth in the lung, evolved into a less-fusogenic but viable virus in differentiated human airway epithelium. Stepwise evolution led to a progressive decrease in efficiency of fusion activation by the HN/F pair, with a mutation in F first decreasing the activation of F by HN and a mutation in HN’s secondary sialic acid binding site decreasing fusion activation further and producing a stable virus. Adaptation of HPIV3 to successful growth in HAE is determined by specific features of HN and F that lead to a less easily activated fusion mechanism.

IMPORTANCE
Human parainfluenza viruses (HPIVs) are paramyxoviruses that cause the majority of childhood cases of croup, bronchiolitis, and pneumonia worldwide, but there are currently no vaccines or antivirals available for treatment. Enveloped viruses must fuse their membrane with the target cell membrane in order to initiate infection. Parainfluenza virus fusion proceeds via a multistep reaction orchestrated by the two glycoproteins that make up its fusion machine. The receptor-binding hemagglutinin-neuraminidase (HN), upon receptor engagement, activates the fusion protein (F) to penetrate the target cell and mediate viral entry. In this study, we show that the precise balance of fusion activation properties of these two glycoproteins during entry is key for infection. In clinically relevant tissues, viruses evolve to acquire a set of fusion features that provide key clues about requirements for infection in human beings.
One heart, two cardiomyopathies
Authors: Vassiliou Vassilis , Agrawal Bobby , Ryding Alisdair
Published: June 2012

A 63-year-old woman with no previous medical problems presented with acute chest pain and an ECG consistent with an acute anterior myocardial infarction. At emergency angiography, she was found to have smooth unobstructed coronary arteries. On invasive left ventriculography, overall poor systolic function was noted with apical hypokinesis and basal hyperkinesis, consistent with Tako-tsubo phenomenon. Echocardiography demonstrated a hypertrophic left ventricle and left ventricular outflow obstruction due to systolic anterior motion of the mitral valve and moderate mitral regurgitation. Following appropriate management, she was discharged 6 days later. An outpatient MRI confirmed normalisation of the left ventricular systolic function; however, there was still significant left ventricular hypertrophy and dynamic obstruction. Although most patients presenting with chest pain and an ECG with ST elevation will have an acute coronary event, our patient had normal coronaries but both Tako-tsubo and hypertrophic cardiomyopathies.
Frontal sinus mucoceles presenting in the upper eyelid: an easily missed diagnosis
Authors: Ch'ng Soon Wai , Pillai Manju Bhaskaran , Morton Claire
Published: June 2012

Frontal sinus mucoceles are epithelium-lined mucus-containing sacs that are capable of bony expansion causing a spectrum of ophthalmological symptoms. If left untreated, they can erode the thin sinus wall causing life-threatening complications such as meningitis. We would like to alert the clinicians to this diagnosis that can be easily misdiagnosed. The first patient appeared to have an allergic blepharo-conjunctivitis that was not responding to topical and systemic medications. The second patient presented with recurrent preseptal cellulitis unresponsive to oral antibiotics. CT imaging of both patients revealed frontal sinus mucoceles. Both patients recovered well with sinus surgery. Management of these patients needed a close liaison with our ENT and radiology colleagues to warrant a good outcome.