bluuebunny/crossref_metadata_2025 huggingface dataset:
SECONDARY WALL ASSOCIATED MYB1 is a positive regulator of secondary cell wall thickening in Brachypodium distachyon and is not found in the Brassicaceae
Authors: Handakumbura Pubudu P. , Brow Kathryn , Whitney Ian P. , Zhao Kangmei , Sanguinet Karen A. , Lee Scott J. , Olins Jennifer , Romero‐Gamboa Sandra P. , Harrington Michael J. , Bascom Carlisle J. , MacKinnon Kirk J‐M. , Veling Michael T. , Liu Lifeng , Lee Ji E. , Vogel John P. , O'Malley Ronan C. , Bezanilla Magdalena , Bartley Laura E. , Hazen Samuel P.
Published: July 2018

Grass biomass is comprised chiefly of secondary walls that surround fiber and xylem cells. A regulatory network of interacting transcription factors in part regulates cell wall thickening. We identified Brachypodium distachyon SECONDARY WALL ASSOCIATED MYB1 (SWAM1) as a potential regulator of secondary cell wall biosynthesis based on gene expression, phylogeny, and transgenic plant phenotypes. SWAM1 interacts with cellulose and lignin gene promoters with preferential binding to AC‐rich sequence motifs commonly found in the promoters of cell wall‐related genes. SWAM1 overexpression (SWAM‐OE) lines had greater above‐ground biomass with only a slight change in flowering time while SWAM1 dominant repressor (SWAM1‐DR) plants were severely dwarfed with a striking reduction in lignin of sclerenchyma fibers and stem epidermal cell length. Cellulose, hemicellulose, and lignin genes were significantly down‐regulated in SWAM1‐DR plants and up‐regulated in SWAM1‐OE plants. There was no reduction in bioconversion yield in SWAM1‐OE lines; however, it was significantly increased for SWAM1‐DR samples. Phylogenetic and syntenic analyses strongly suggest that the SWAM1 clade was present in the last common ancestor between eudicots and grasses, but is not in the Brassicaceae. Collectively, these data suggest that SWAM1 is a transcriptional activator of secondary cell wall thickening and biomass accumulation in B. distachyon.
Ultrasonography is more accurate than percutaneous palpation for identifying targeted thoracolumbar intervertebral disc spaces in dogs
Authors: Boursier Jean‐François , Fournet Alexandre , Bassanino Jean , Manassero Mathieu , Bedu Anne‐Sophie , Leperlier Dimitri
Published: July 2018

During minimally invasive spinal surgery, correct identification of the affected intervertebral disc space is critical. Percutaneous palpation is commonly used, but results may be unreliable. Fluoroscopy is the gold standard but can be cumbersome and exposes operators to ionizing radiation. Spinal ultrasound has been described in veterinary medicine and could be a feasible alternative. This prospective, methods comparison study mimicked a minimally invasive spinal surgery in 10 canine cadavers and compared the accuracy of ultrasound and percutaneous palpation for thoracolumbar intervertebral disc space identification, using fluoroscopy as the reference standard. For each experiment, a disc space was randomly chosen. Identification was then attempted using both percutaneous palpation and ultrasound. For ultrasound, a linear probe was used to guide the operator to the correct location. The time necessary to perform each method was recorded. Accuracies for each method were calculated and statistically compared. Effects of body condition score, location of the targeted thoracolumbar intervertebral disc space and learning curve for each method were also evaluated. Ultrasonographic identification was more accurate (96.7% vs. 76.7%; P < 0.03) but took longer (147 s vs. 29 s; P < 0.0001) than percutaneous palpation. Findings from this cadaver study indicated that percutaneous palpation alone had low accuracy for correctly identifying a targeted thoracolumbar intervertebral disc space and supported the use of ultrasound as a method for improving the accuracy. Future studies are needed to assess the method in clinical cases, especially in obese dogs and/or those in which the targeted site is distant from palpable anatomical landmarks.
Involvement of calvarial stem cells in healing: A regional analysis of large cranial defects
Authors: Durham Emily L. , Howie R. Nicole , Houck Reed , Oakes Brayden , Grey Zachary , Hall SarahRose , Steed Martin , LaRue Amanda , Muise‐Helmericks Robin , Cray James
Published: July 2018

Large craniofacial defects present a substantial clinical challenge that often requires the use of osteoconductive matrices and osteoinductive cues (i.e., bone morphogenetic proteins [BMP2]) to augment healing. While these methods have improved clinical outcomes, a better understanding of how the osteogenic fronts surrounding the defect, the underlying dura mater, and the cranial suture area contribute to healing may lead to more targeted therapies to enhance bone regeneration. We hypothesized that healing within a large bone defect will be precipitated from cells within the remaining or available suture mesenchyme abutting the edges of a murine critical sized defect. To investigate this hypothesis, 39 adult, wild‐type mice were randomly arranged into groups (9 or 10 per group) by time (4 and 8 weeks) and treatment (control, acellular collagen sponge alone, or acellular collagen sponge loaded with a clinically relevant scaled dosage of BMP2). The skulls were then subjected to microcomputed tomography and histological analysis to assess bone regeneration in regions of interest within the defect area. A regional assessment of healing indicated that BMP2 drives greater healing than control and that healing emanates from the surgical margin, particularly from the margin associated with undisrupted suture mesenchyme. Though BMP2 treatment drove an increase in cell presence within the healing defect, there was no regional orientation of craniofacial stem cells or vascularity. Overall, these data reinforce that osteoconductive matrices in conjunction with osteoinductive peptides result in better healing of large calvarial defects. This healing is characterized as emanating from the surgical margin where there is an abundant supply of vasculature and progenitor cells.
Trajectory of Manufacturing Industry in India since Post Reform Period
Authors: Pawar Sneha Sharad
Published: July 2018

Manufacturing has been an engine of growth in India in the seventies and eighties. After the 1991 reforms the engine appears to be slowing. This paper attempts to examine the reality behind the increased productivity by applying methods that measure productivity per factor and returns to scale. The analysis reveals that manufacturing output growth in post reform period is ‘input-driven’ rather than efficiency driven. The growth in manufacturing sector is dependent on the investment climate. The structural reforms since 1990s have made some progress. Despite recent setbacks, it is universally acknowledged that the reforms process in India cannot be reversed and sooner or later these reforms will be implemented. However, the long term competitive ability of Indian firms would depend on production efficiency. Production efficiency, in turn, is dependent on ability to develop, import and adapt new technologies among other factors. Hence, for achieving the efficiency the theories have been critically examined from Indian scenario and some measures have suggested in this paper.
The role of the paravertebral ganglia in human sympathetic neural discharge patterns
Authors: Klassen Stephen A. , Limberg Jacqueline K. , Baker Sarah E. , Nicholson Wayne T. , Curry Timothy B. , Joyner Michael J. , Shoemaker J. Kevin
Published: July 2018

Key Points

The mechanisms affecting recruitment patterns of postganglionic sympathetic nerves remain unclear. The divergent and convergent preganglionic innervation patterns of postganglionic neurons and the presence of differently sized postganglionic nerves suggest that the ganglia may participate in modifying the discharge patterns of single sympathetic postganglionic neurons innervating the skeletal muscle circulation.

Whether the ganglia affect the ordered behaviour of varying sized postganglionic sympathetic neurons in humans has not been studied.

Trimethaphan infusion produced an ordered pattern of action potential (AP) de‐recruitment whereby the firing of larger, low probability APs present at baseline was abolished first, followed by progressive decreased probability of smaller APs. Although integrated sympathetic bursts were no longer detected after several minutes of trimethaphan, firing of the smallest APs was detected.

These data suggest the ganglia affect the distribution of firing probabilities exhibited by differently sized sympathetic neurons.

The ganglia may contribute to sympathetic neural emission patterns involved in homeostatic regulation.

Do the ganglia contribute to the ordered behaviour of postganglionic neuronal discharge within the sympathetic nervous system? To further understand the functional organization of the sympathetic nervous system we employed the microneurographic approach to record muscle sympathetic nerve activity (MSNA) and a continuous wavelet transform to study postganglionic action potential (AP) behaviour during nicotinic blockade at the ganglia (trimethaphan camsylate, 1–7 mg min−1) in seven females (37 ± 5 years). Trimethaphan elicited a progressive reduction in sympathetic outflow characterized by fewer integrated bursts with decaying amplitude. Underlying trimethaphan‐mediated attenuations in integrated MSNA were reductions in AP incidence (186 ± 101 to 29 ± 31 AP (100 beats)−1) and AP content per integrated burst (7 ± 2 to 3 ± 1 APs burst−1) (both P < 0.01) in the final minute of detectable bursting activity in the trimethaphan condition, compared to baseline. We observed an ordered de‐recruitment of larger to smaller AP clusters active at baseline (14 ± 3 to 8 ± 2 active AP clusters, P < 0.01). Following cessation of integrated bursts in the trimethaphan condition, the smallest 6 ± 2 sympathetic AP clusters persisted to fire in an asynchronous pattern (49 ± 41 AP (100 beats)−1) in all participants. Valsalva's manoeuvre did not increase the incidence of these persistent APs (60 ± 42 AP (100 beats)−1, P = 0.52), or recruit any larger APs in six of seven participants (6 ± 1 total AP clusters, P = 0.30). These data suggest that the ganglia participate in the ordered recruitment of differently sized postganglionic sympathetic nerves.
Wake-Boundary Layer Interactions Behind a Square Cylinder for a Reynolds Number in Periodic Vortex Shedding Regime
Authors: Pal Arti , Sarkar Sudipto
Published: July 2018

Flow over a square cylinder in proximity to a wall for different gap-to-diameter ratios (G/D = 0 to 2, where G is the gap between the cylinder and flat plate and D is the side of the square cylinder) has been studied extensively for a Reynolds Number (Re = U∞D/v, where v is the kinematic viscosity of the fluid and U∞ is the free stream velocity) in the periodic vortex shedding regime. Ansys Fluent is used to solve two-dimensional (2-D), time dependent, incompressible Navier-Stokes equation by SIMPLE [1] algorithm implemented in finite volume method. Interesting flow features and changes in vortex dynamics can be seen by the present simulation, when the cylinder approaches very close to the plate. The boundary layer formed over the flat plate changes its characteristics for these low gap-ratios. Also the modification of the aerodynamic forces and the vortex shedding frequency are thoroughly described to understand the physics behind wake-boundary layer interaction at low Reynolds Number.
Design Optimization of a Mixed Flow Waterjet Pump for Performance Improvement Involving Cavitation
Authors: Huang Renfang , Luo Xianwu , Zhai Zhihong , Zhou Jiajian
Published: July 2018

A mixed-flow waterjet pump with a vaneless diffuser is treated to improve its hydraulic efficiency as well as cavitation performance. In order to conduct the design optimization, the authors apply a multiobjective strategy combined with design of experiments (DOE), computational fluid dynamics (CFD), inverse design method, surface response method (RSM) and non-dominated sorting genetic algorithm-II (NSGA-II). The hydraulic efficiency and the total vapor volume are selected as the optimization targets, and nine parameters are used to describe the blade shape with the same meridional section.

For numerical simulation, RANS method is applied with SST k-ω turbulence model and a mass transfer cavitation model based on the Rayleigh-Plesset equation. Optimal Latin hypercube design method is used in the design of experiments to uniformly sample in variation ranges and global optimization is then conducted by using non-dominated sorting genetic algorithm-II (NSGA-II) based on the input-target approximation functions built by the response surface model (RSM).

The optimization results demonstrate that both hydraulic efficiency and cavitation performance are improved at the design point through this multiobjective strategy. Based on analysis of the internal flows, secondary flows would be important contributor to the hydraulic loss as well as the nonuniform flow at impeller exit, and can be suppressed by adjusting the blade load along the hub or shroud by using the inverse design method.
Optimal Design of Impeller for Centrifugal Compressor Under the Influence of Fluid-Structure Interaction
Authors: Kang Hyun-Su , Song Yoo-June , Kim Youn-Jea
Published: July 2018

In this study, a method for optimal design of impeller for centrifugal compressor under the influence of flow-induced vibration (FIV) using fluid-structure interaction (FSI) and response surface method (RSM) was studied. Numerical simulation was conducted using ANSYS with various configurations of impeller geometry. Each of the design parameters was divided into 3 levels. Total 15 design points were planned by central composite design (CCD) method, which is one of the design of experiment (DOE) techniques. Response surfaces generated based on the DOE results were used to find the optimal shape of impeller for high aerodynamic performance. The whole process of optimization was conducted using ANSYS Design Xplorer (DX). Through the optimization, structural stability and aerodynamic performance of centrifugal compressor were improved.
Effect of the Accuracy Order of the Discretization Scheme on the Prediction Performance for the Turbulent Flow Structure Inside Fuel Assembly: Sensitivity Study
Authors: Lee Gong Hee , Cheong Ae Ju
Published: July 2018

Spatial discretization errors result from both the numerical order of accuracy of the discretization scheme, and from grid spacing. It is well known that second, or higher, order discretization schemes are potentially able to produce high-quality solutions. In addition, when either the flow is not aligned with the grid, or is complex, it is recommended that the first order discretization scheme not be used for the convection term, if possible. However, the higher-order scheme can also result in convergence difficulties and instabilities at certain flow conditions.

In this study, to examine the effect of the numerical order of accuracy of the discretization scheme on the prediction accuracy for the turbulent flow structure inside fuel assembly with the split-type mixing vanes, simulations were conducted with the commercial CFD (Computational Fluid Dynamics) software, ANSYS CFX R.14. Two different types of the discretization scheme for the convection-terms-of-momentum and -turbulence equations, i.e. 1st order upwind scheme and a high resolution scheme, were used. The predicted results were compared with the measured data from MATiS-H (Measurement and Analysis of Turbulent Mixing in Subchannles-Horizontal) facility, installed in the KAERI (Korea Atomic Energy Research Institute).
Numerical Simulation of Three-Dimensional Supercritical Water Flows in Hydrothermal Synthesis Reactors With Arbitrary Geometry
Authors: Furusawa Takashi , Qi Shibo , Yamamoto Satoru
Published: July 2018

Numerical simulations of mixing flows of supercritical (SC) water and water liquid in a 3-D T-shaped circular pipe and a 3-D cross pipe are conducted using the numerical method developed by our group. The 3-D geometry is generated by Building-Cube Method (BCM) with the stepwise wall treatment. Numerical results of mixing flows in the two pipes are compared and the effect of the inlet temperature is evaluated. In the T-shaped circular reactor, the mixing is periodic and a vortex is observed at the mixing point. The mixing form certainly depends on the SC water temperature. In the counter flow reactor, the SC water flow becomes unsteady and is mixed with water liquid asymmetrically due to the rapid change of thermophysical properties and the buoyancy effect.
U-RANS Simulation of Single Elbow Pipe Flow Experiments Simulating JSFR Hot-Leg Piping
Authors: Yamano Hidemasa , Tanaka Masaaki , Iwamoto Yukiharu
Published: July 2018

This paper is intended to validate the numerical simulation tool, which is Unsteady Reynolds Averaged Navier-Stokes equation (U-RANS) approach with the Reynolds Stress Model using a commercial computational fluid dynamics code, by applying to the flow through a single short-elbow in the 1/10 and 1/3 scale water experiments simulating the Japan Sodium-Cooled Fast Reactor (JSFR) hot-leg piping. An additional objective of this paper is to investigate the effect of outlet condition at which the coolant overflows a partition wall in the upper part of an intermediate heat exchanger in the JSFR design.

The numerical results were in good agreement with the 1/10 and 1/3 scale experimental data indicating time-averaged velocity distributions, flow field visualization, and power spectral densities of pressure fluctuation. These comparisons can conclude that the U-RANS numerical simulation tool was validated with its applicability to a single short elbow flow. The numerical simulation has also shown that the unsteady flow fields in the short elbow flow, which was characterized by a cyclic secondary flow and the subsequent horseshoe vortex.

In this study, the effect of the outlet condition was also examined through the numerical simulation. At the outlet of the pipe, the simulation modeled the partition wall in the upper part of the intermediate heat exchanger, which has never been simulated in the experiments. The numerical simulation results were compared between with and without the intermediate heat exchanger at the pipe outlet in terms of the time-averaged velocity distribution, pressure fluctuation power spectral density, and so on. In the result, no significant difference between them was observed, so that it can be said that the effect of the outlet condition is negligibly small.
Accuracy Verification of the Turbulent Flame LES Model by a Methane/Air Burner Flame
Authors: Kagenobu Murase , Nobuyuki Oshima , Yusuke Takahashi
Published: July 2018

This paper focuses on the numerical simulation of Sandia National Laboratories “the piloted methane/air burner flame D.” Large Eddy Simulation and 2-scalar flamelet approach are applied for the turbulent and partially premixed combustion field, which is expressed by the LES filtered equations of scalar G for tracking the flame surfaces and mixture fraction of a fuel and an oxidizer. The flamelet data consists of temperature, specific volume and laminar flame speed are calculated by the detail chemical reaction with GRI-Mech 3.0. Two kinds of flamelet data are validated; one is “equilibrium flamelet data” calculated by 0-dimensional equilibrium solution based on equilibrium model; the other is “diffusion flamelet data” calculated by 1-dimensional counter flow solution based on laminar flamelet model. Consequently, the “diffusion flamelet data” gives better result in this type of combustion field.
Turbulent Heat Transfer Enhancement in Round Tubes by Inserting Triple Twisted-Tapes
Authors: Eiamsa-ard S. , Promthaisong P. , Chuwattanakul V.
Published: July 2018

Turbulent flow characteristics and heat transfer performances in a round tube equipped with triple twisted tapes are investigated numerically. Effects of the triple twisted tapes at different twist ratios on the heat transfer and thermal performance characteristics are reported. The results of velocity and temperature fields, and the local heat transfer coefficients as well as the flow structure in tube with tape inserts are also given. A round tube wall is subjected to a constant wall temperature condition. Thermal field, heat transfer and fluid flow characteristics are studied using computational fluid dynamics (CFD) analysis. Computations, based on a finite volume method, are carried out by utilizing the Renormalized Group (RNG) k-ε turbulence model. The investigation is carried out for triple twisted tapes with y/W = 2.0, 3.0 and 4.0 in round tubes for laminar air flow with Reynolds numbers between 500 and 2000. It is found that the use of triple twisted tapes with smallest twist ratio of y/W = 2.0 results in the highest heat transfer and friction factor while the use of the tapes with the largest twist ratio (y/W = 4.0) results in the highest thermal performance. The highest thermal performances based on the constant pumping power criterion of the tubes equipped triple twisted tapes with y/W = 2.0, 3.0 and 4.0 are 2.43, 2.63 and 2.73, respectively.
Thermal-Fluidic Numerical Analysis for the Development of Heat Exchanger in the Propellant Tank Pressurization System of KSLV-II Upper Stage
Authors: Lee Sun-Kyung , Han Sang Yeop , Shin Dong-Soon , Taghavi R. Ray
Published: July 2018

KSLV-II (Korea Space Launch Vehicle - II) launch vehicle is a three staged satellite launch vehicle using a liquid propellant propulsion system in all three stages. It will deliver 1,500 kg satellite to Sun Synchronous Orbit (SSO, 700 km, 98.2°) or 2,600 kg satellite to Low Earth Orbit (LEO, 300 km, 80.3°). Propellants for KSLV-II are kerosene as a fuel and liquid oxygen as an oxidizer for propelling.

Those fuel and oxidizer are stored in on-board tanks separately. To run a liquid propellant rocket engine on ground or in flight, those propellants should be supplied to LRE’s using so-called Propellant Pressurizing Sub-system, which makes propellants be pressurized in tanks using pressurant. A pressurant for PPSS of KSLV-II is helium, which is stored in tanks located in an oxidizer tank. The stored He is under cryogenic condition (50 K) as gaseous state. Such He is heated and expanded through heat exchanger, which is using a combustion gas coming out from gas generator for turbo-pump as an energy source, to be used as pressurant. This paper contains the results of performance analysis and thermal-fluidic numerical analysis to develop the above-mentioned heat exchanger for KSLV-II upper stage (the 2nd stage). The technical requirements for such heat exchanger are as follows: pressurant mass flow rate for oxidizer tank - 0.127 kg/sec; and for fuel tank - 0.043 kg/sec. The outlet temperature of He from heat exchanger is 550±10 K.
Experimental Study on the Forward Flight of the Hawkmoth Using the Dynamically Scaled-Up Robotic Model
Authors: Han Jong-seob , Han Jae-Hung , Chang Jo Won
Published: July 2018

DARPA’s MAV project has accelerated a lot of studies on insect flights to gain insights for flapping MAV development [1]. In particular, the insects adept at hovering have become major subjects of these investigations [2–3]. Due to the great contributions by pioneers, we are now able to well explain how the insects produce the enhanced aerodynamic forces in the hovering flight at intricate flow regime [4].
Pressure and Shock Waves in Bubbly Liquids
Authors: Mahmood Shahid , Yoo Yungpil , Kwak Ho-Young
Published: July 2018

It is well known that sound propagation in liquid media is strongly affected by the presence of gas bubbles that interact with sound and in turn affect the medium. An explicit form of a wave equation in a bubbly liquid medium was obtained in this study. Using the linearized wave equation and the Keller-Miksis equation for bubble wall motion, a dispersion relation for the linear pressure wave propagation in bubbly liquids was obtained. It was found that attenuation of the waves in bubbly liquid occurs due to the viscosity and the heat transfer from/to the bubble. In particular, at the lower frequency region, the thermal diffusion has a considerable affect on the frequency-dependent attenuation coefficients. The phase velocity and the attenuation coefficient obtained from the dispersion relation are in good agreement with the observed values in all sound frequency ranges from kHz to MHz. Shock wave propagation in bubbly mixtures was also considered with the solution of the wave equation, whose particular solution represents the interaction between bubbles. The calculated pressure profiles are in close agreement with those obtained in shock tube experiments for a uniform bubbly flow. Heat exchange between the gas bubbles and the liquid and the interaction between bubbles were found to be very important factor to affect the relaxation oscillation behind the the shock front.
An Efficient Shock-Capturing Scheme for Simulating Compressible Homogeneous Mixture Flow
Authors: Dang Son-Tung , Ha Cong-Tu , Park Warn Gyu , Jung Chul-Min
Published: July 2018

In this paper, we focus on using high-resolution implicit upwind shock-capturing scheme to avoid the formation of non-linear instabilities and numerical oscillations across shock waves or discontinuities. The governing equation is the compressible Reynolds Averaged Navier-Stokes equation based on the homogeneous mixture model. A preconditioned method is applied for enhancing efficient and accurate computations over a wide range of Mach numbers. For evaluation, the results from the present study have been compared with experiments and other numerical results. A fairly good agreement with the experimental data and other numerical results have been obtained. Finally, the simulation of ventilated supercavitating flows over a torpedo with a hot propulsive jet was conducted to verify the efficiency of numerical scheme.
Numerical Simulation of Heat Transfer in Shear Flow of Liquid-Solid Two-Phase Media by Immersed Solid Approach
Authors: Kajishima Takeo , Kondo Katsuya , Takeuchi Shintaro
Published: July 2018

We developed a direct numerical simulation (DNS) method of solid-fluid two-phase flows to study the effects of heat conductivity within a solid particle and the particle motion on the heat transfer. Heat transfer and particle behaviors were studied for different ratios of heat conductivity (solid to liquid) and solid volume fractions. The simulation results emphasize the effect of temperature distributions within the particles, and the heat transfer through each particle plays an important role for the motion of the particulate flow. The particle-laden flow in a two-dimensional channel of instable thermal stratification, namely hot wall at the bottom and cold wall at the top, is simulated. In the two-dimensional computation, the heat transfer attenuates by increasing the neutral conductive particles because of the resistance to the thermal convection. In case of highly conductive particles, the thermal convection and conductions are enhanced to some extent of addition but the overload of particles suddenly reduces the intensity of convection, resulting in the lower heat transfer. The inverse gradient of mean temperature is observed particularly in case of moderate loading of neutral conductive particles. It is due to the modulation of the profile of convection cells. Most of the above-mentioned findings are reproduced by the fully three-dimensional simulation.
Direct Numerical Simulation of Turbulent Channel Flow With Streamwise System-Rotation
Authors: Okamoto Masayoshi
Published: July 2018

The direct numerical simulation (DNS) of the fully developed turbulent channel flows rotating along the streamwise direction with several rotation parameters and two Reynolds numbers is performed. The bulk mean velocity decreases with increasing the rotation parameter, but the decrement is weakened in the high Reynolds number case. Applying the second-kind Chebyshev polynomial expansion into the mean spanwise velocity, the second mode coefficient, which becomes large in the strong rotation, is greatly influenced by the Reynolds number effect. Due to the streamwise rotation, the derivative and integral length scales obtained from the streamwise two-point correlation are extended. From viewpoints of the quadrant analysis, spectral one and instantaneous visualization, the high correlation among three fluctuating velocity components appears and the low-speed streaks are accumulated in the strong rotation and high Reynolds number flow.
Design Optimization for the Hydraulic Efficiency Improvement of a Mixed-Flow Pump Diffuser
Authors: Kim Sung , Lee Kyoung-Yong , Kim Ji-Hyuk , Choi Young-Seok
Published: July 2018

In this paper, design optimization for mixed-flow pump diffusers was carried out using a commercial computational fluid dynamics (CFD) code and design-of-experiments (DOE). The design variables of meridional plane and vane plane development were defined for the diffuser design. The blade shape of the diffuser was designed using the traditional method, in which the inlet and exit angles are connected smoothly. First, the design optimization of the defined design variables for vane plane development was achieved. Next, design optimization of the defined design variables for the meridional plane was performed. The objective functions were defined as the total head and total efficiency of the diffusers. The importance of the geometric design variables was analyzed using 2k factorial designs, and the design optimization of the geometric variables was determined using the response surface method (RSM). The numerical results for reference and optimum models in this work were compared and discussed.
Prediction of the Pressure Pulsation in a Draft Tube for a Part Load Condition Using the LES Approach
Authors: Pacot Olivier , Kato Chisachi , Guo Yang , Yamade Yoshinobu
Published: July 2018

The present paper focuses on the vortex rope that arises when operating a model Francis turbine at a part load condition: 65% of the Best Efficiency Point (BEP). The investigation is performed numerically using the Large Eddy Simulation (LES) approach with the Dynamic Smagorinsky Model (DSM). Such approach and turbulence model are implemented in the overset finite element open source code, FrontFlow/blue (FFB). Furthermore, a cavitation model is implemented allowing computations for non-cavitating and cavitating conditions. Thanks to the use of the K supercomputer, located at Kobe in Japan, and to the use of large computational mesh (123 million elements), it is shown that the frequency of the precession of the vortex rope as well as the head can be accurately computed. However, the predicted amplitude of the fluctuation did not fully agree with the experiment. Differences in a particular region near the back side of the elbow are about 35%. A comparison between the variation of the size of the vortex rope and the swirl number has been investigated and showed a clear relation. The location of the vortex rope and the minimum of the pressure were also investigated and showed that they do not fully share the same location. Furthermore, in a preliminary study to the computation of the cavitating vortex rope, computations of the flow around a Clark-11.7% hydrofoil under cavitation condition and for angles of attack of 2° and 8° are carried out. The results showed the common issue for this computation, i.e. the sharp change of the lift and drag coefficients could not be accurately predicted. Currently underway are the computation of the cavitating vortex rope. The effect of the cavitation on the vortex rope will be studied and reported at a later stage.
Parameter Optimization and Experimental Research of Small Axial Fans With Splitting Blades
Authors: Wei Chu , Yingzi Jin , Peifeng Lin , Yi Li , Wenjun Wu
Published: July 2018

A kind of small axial fans with splitting blades are designed in this work. The application of numerical simulation enables a detailed description of the effect of installation angle, chord length, circumferential position of splitting blades on the fan performance and internal flow field. With a target of static characteristics and sound pressure level, a multi-objective optimization function is established in combination of orthogonal test and entropy law, so that the installation angle and chord length and circumferential position of splitting blades could be optimized. The results show that: 27.7 degree should be a proper installation angle and the chord length can be not too long or too short and appropriate bias to pressure side is a optimum circumferential position for splitting blades. The results of numerical simulation and experimental research show that the performance of the optimized is obviously better that of the original.
Effects of Flow Loss and Inlet Distortions Caused by Radial Inlet on the Performance of Centrifugal Compressor Stage
Authors: Han Fenghui , Tan Jiajian , Mao Yijun , Qi Datong , Zhang Yiyun
Published: July 2018

Radial inlet is a typical upstream component in centrifugal compressors. Compared to axial inlet, radial inlet generates additional flow loss and introduces inlet distortions to the impeller inlet, which negatively impacts the performance of the whole centrifugal compressor. In this paper, two centrifugal compressor stages with different radial inlets were investigated with numerical simulations. Three computational models, (i) with radial inlet (ii) without flow loss and inlet distortions (iii) with flow loss but no inlet distortions, were built for each compressor stage, and calculations were carried out to analyze the respective effects of flow loss and inlet distortions caused by radial inlet on the performances of the compressor stage and the downstream components. The present study validates that flow loss and inlet distortions caused by radial inlet are the main factors by means of which the radial inlet affects the performance of the centrifugal compressor. What’s more, the results indicate that flow loss in radial inlet only affects the performance of the whole radial inlet stage, but has little effect on the downstream components such as the impeller; while inlet distortions caused by radial inlet not only negatively influence the performance of the whole radial inlet stage, but also have significant effects on the downstream components. This research, as a preliminary work of the improvement study, provides references for the structure modifications of radial inlet in the next stage.
Influence of Different Impeller Diameter on Cavitation Performance in an Engine Cooling Water Pump
Authors: Li Wei , Li Weiqiang , Shi Weidong , Zhou Ling , Pei Bing
Published: July 2018

The engine cooling water pump (ECWP) is an important part in the motor and engine. Using the advanced numerical methods and tools to enhance the ECWP performance, not only could reduce the power consumption and weight, but also can promote the safety and reliability of the vehicle system. The cavitation damage in the ECWP shortens the reliability and life of the motor cooling system, as well as produces vibration and noise. Cavitation in the ECWP has been become an important research topic.

To investigate the cavitation performance of ECWP with different impeller diameter, the three dimensional turbulent flow in the ECWP with different impeller diameter was numerically simulated employing the time averaged N-S equation, the standard k-ε turbulent model and multiphase flow model by ANSYS-CFX software. The structured hexahedral mesh has been generated for improving the accuracy of numerical simulation. Comparing with the experimental pump performance results, the cavitation performance is accurately predicted based on structured mesh and cavitation model. The comparison of fluid static pressure and vapor volume fraction contours, hydraulic and cavitation performance was made among different impeller diameter. The cavitation performance curve and bubble distributions under different impeller diameter were compared and analyzed, we find that absolute pressure at the critical cavitation point becomes higher with the decreasing of the impeller diameter, and the anti-cavitation performance becomes worse caused by the increasing of the volume fraction in the impeller. Therefore, there is an optimum impeller diameter value to guarantee the anti-cavitation performance and hydraulic performance of the investigated pump.
Investigation of Flatback Airfoil Effect in the Wind Turbine Blade
Authors: Jeong Jae-Ho , Kim Soo-Hyun
Published: July 2018

The flatback airfoil effect in the inboard region of large wind turbine blade has been investigated by numerical analysis. Complicated flow phenomena in the wind turbine blade were captured by Reynolds-averaged Navier-Stokes flow simulation (RANS) with SST (Shear Stress Transport) turbulence model.

The inboard region of the blade without the flatback airfoils is dominated by the separated vortex. The separated vortex starts to be formed near the blade mid-chord. The separated vortex core is generated by the large pressure difference in the blade inboard trailing edge region. The separated vortex grows nearly in the outboard direction, which is so-called secondary flow on the blade surface. The flatback airfoils are designed, and applied to the wind turbine inboard region. The scale of the separated vortex can be decreased, and the blade performance enhanced up to nearly 6% in the flatback airfoil region. However, the blade with large wake thickness due to the flatback airfoil has a negative impact on the aerodynamic noise.

Regardless of the flatback airfoils, the tip vortex core of the outboard region is formed on the suction surface leading edge, and strongly rolled-up by the pressure surface boundary layers due to the large pressure difference between the suction surface and the pressure surface in the blade tip region. This remarkably strong tip vortex develops downstream, and rakes up the blade trailing edge boundary layer with low energy.
Flow Visualization of Pipe Flows Obtained by MR Imaginary
Authors: Hosotani Kazunori , Ono Atsushi , Takeuchi Kazuhiro , Hashiguchi Yusuke , Nagahata Tomoya
Published: July 2018

In this study, magnetic resonance imaging (MRI), a noninvasive medical diagnostic imaging technique, was evaluated as a noncontact measurement method for fluid machinery. In this report, various simple flow fields are investigated, and a labeled water mass is tracked and visualized in two-dimensional images by the time–spatial labeling inversion pulse (time-SLIP) method. In this article, steady and pulsating pipe flows in a straight tube and in abruptly contracting and expanding channels were tested and compared with particle image velocimetry measurements or numerical simulations to evaluate their validity. In addition, as feasibility test, a rotating water turbine and a fluidic diode with a strong swirling flow were tested to estimate this method’s applicability to fluid machines. The results indicate that the time-SLIP method of tracking labeled water mass is sufficiently accurate for use in simple fluid machinery with slow flows.
Effect of Parameter on Characteristics of Active Charge Accumulator for Water Hydraulic System
Authors: Yoshida Futoshi , Ito Kenji , Iio Shouichiro , Kitagawa Ato
Published: July 2018

Active Charge Accumulator (ACA) is a new pressure convert technology which does not require any pressure control valve. ACA can be easily reduce or boost the pressure in water hydraulic system by using a multistage piston and on-off valves. This paper was focused on the basic characteristic of ACA especially for decompression process. The both of experimental approach and theoretical one were conducted. As the experimental results, it is revealed that the piston stroke of ACA strongly depends on the output flow rate and switching timing of the on-off valves. Analytical model of ACA was made and validated. As a result, it can be revealed influence of parameters on characteristics of ACA. The pressure change in the system was well estimated by the model.
Aerodynamical Improvement of Delta Wing and Flapping Wing
Authors: Ishide Tadateru , Naganuma Kazuya , Seiji Shinsuke , Ishikawa Hiroyuki , Fujii Ryo , Maeno Kazuo
Published: July 2018

Recently, various studies of Micro Air Vehicle (MAV) and Unmanned Air Vehicle (UAV) have been reported from wide range points of view. The aim of this study are researching the aerodynamic improvement of delta wing and flapping wing in low Reynold’s number region to develop an applicative these air vehicle. Various configurations of Leading Edge Flap (LEF) are used to enhance the aerodynamic characteristics in the delta wing. The six kind of elliptical wings made of stainless steel are used in the flapping wing. The effects of flapping amplitude and wing configuration regarding the aerodynamic characteristics are investigated in detail. The fluid force measurement by six component load cell and PIV analysis are performed as the experimental method. In the flapping wing experiment, the simultaneous measuring of the fluid force measurement and PIV analysis is tried by using the trigger signal from the encoder attached to the flapping model. The relations between the aerodynamic superiority and the vortex behavior around the models are demonstrated.
Numerical Study of Plasma Flow Around a Reentry Vehicle During Atmospheric Reentry With an Unstructured Grid Solver
Authors: Nakasato Reo , Takahashi Yusuke , Oshima Nobuyuki
Published: July 2018

When a reentry vehicle enters the planetary atmosphere, a strong shock wave is generated and the strong aerodynamic heating appears. Gas temperature in front of the vehicle exceeds 10,000K and chemical reactions (ionizations and dissociations) occur behind the shock wave. Because the reentry vehicle is damaged by the aerodynamic heating, accurate evaluation of the aerodynamic heating in the high-enthalpy flow is necessary for the design and the development of the vehicle. The communication blackout phenomenon which prevents the propagation of the electromagnetic waves can occur by the characteristics of electrons in the shock layer to absorb and reflect the electromagnetic waves. To estimate the communicationable time and understand the behavior of the electromagnetic waves around the vehicle, the accurate evaluation of the plasma flow around the vehicle is also necessary.

In this study, the three-dimensional numerical analysis was conducted to consider an angle of attack by using the analysis software for compressible fluid, RG-FaSTAR which has been developed by JAXA. Moreover, unstructured grids were used to make it easier to generate computational grid around the vehicle with complicated shape. Note that RG-FaSTAR is a version of FaSTAR (FaST Aerodynamic Routine) installing the real gas effect. We reproduced the actual flow field around the Atmospheric Reentry Demonstrator (ARD) which was launched by the European Space Agency (ESA) in 1998 and revealed the aerodynamic heating and plasma flow properties during atmospheric reentry.

The computational result showed good agreement with measured pressure coefficient at the stagnation point. In addition, the features of the shock layer and the rear region around ARD were revealed.
Turbulent Annular Pipe Flow in Subcritical Transition Regime: Direct Numerical Simulation of a Large Domain
Authors: Ishida Takahiro , Tsukahara Takahiro
Published: July 2018

We performed direct numerical simulations of annular Poiseuille flow (APF) with a radius ratio of η (= rin/rout) = 0.8, in order to investigate the subcritical transition scenario from the developed turbulent state to the laminar state. In previous studies on annular Poiseuille flow, the flows at high Reynolds numbers were well examined and various turbulence statistics were obtained for several η, because of their dependence on η. Since the transitional APF is still unclear, we investigate annular Poiseuille flows in the transitional regime through the large-domain simulations in a range of the friction Reynolds number from Reτ = 150 down to 56. At a transitional Reynolds number, weak-fluctuation regions occur intermittently and regularly in the flow field, and the localized turbulence appears in the form of banded patterns same as in plane Poiseuille flow (PPF). The flow system of APF with a high radius ratio η ≈ 1 can be regarded as PPF and, hence, the transition regime in high radius-ratio of APF and in PPF should be analogous. However, in APF, the banded structure takes on helical shape around the inner cylinder, since APF is a closed system in the spanwise (azimuthal) direction. In this paper, the (dis-)similarity between APF and PPF is discussed.
Effect of Inlet Nozzle Shape on Performance of Darrieus-Type Hydro-Turbine Operated in Small Open Water Channel
Authors: Nakashima Kazuhiko , Moriyama Ryosuke , Matsusita Daisuke , Watanabe Satoshi , Tsuda Shin-ichi , Furukawa Akinori
Published: July 2018

A Darrieus-type hydro-turbine has been developed for the utilization of extra low head hydraulic energy. In the case of a ducted Darrieus-type hydro-turbine which consists of an intake, a runner, a casing and a draft tube, it has been found that the Darrieus runner with the narrow intake can generate larger torque without deterioration of efficiency than that with the parallel intake with the constant width. In this paper, the effect of the shape of the inlet nozzle on the performance of the Darrieus-type hydro-turbine operated in open channel flow is investigated both experimentally and numerically. Tested nozzles are two types of two-dimensional symmetric inlet nozzle, Half Diameter curved nozzle (HD nozzle) and Straight Line nozzle (SL nozzle). As a result, the Darrieus hydroturbine with SL nozzle generates larger power and yields higher efficiency than that with HD nozzle. In addition, the effects of nozzle converging angle and outlet width of SL nozzle on the turbine performance are investigated. As a result, it is found that the Darrieus hydroturbine with SL nozzle having large converging angle generates larger power with higher efficiency than that with the nozzle having small converging angle. And then, it is found that the generated power increases when SL nozzle with large outlet width is installed.
Relationship Between Velocity Field and Curvature of a Vortex in Two-Dimensional Turbulent Flow
Authors: Murao Ikumi , Hidema Ruri , Suzuki Hiroshi , Komoda Yoshiyuki
Published: July 2018

A flowing soap film is a promising test bed to generate two-dimensional turbulence dominated by an extensional stress field. In this study, the effects of visco-elastic fluid on two-dimensional (2D) turbulent flow have been quantified by the curvature of vortices visualized by a Film Interface Flow Imaging (FIFI) method in the flow. The curvatures of the vortices are related to the direction of velocity vector on the vortices. In order to confirm this idea, the velocity field of 2D turbulent flow was obtained by Particle Image Velocimetry (PIV). As a flexible polymer, polyethyleneoxide (PEO) was also added to the flow in order to observe how polymers vary the curvature histogram and velocity fields. From the results, it was found that the variance of the curvature histogram became lower by adding the polymer. This was also confirmed by the phenomena that the fluctuation of the velocity vectors in the normal direction becomes small by adding the polymer.
A Study on Particle Sedimentation Depression With Poly Vinyl Alcohol and Surfactant
Authors: Sato Hideki , Hidema Ruri , Suzuki Hiroshi , Komoda Yoshiyuki
Published: July 2018

The combination structure size in water of poly(vinyl alcohol) (PVA) and drag reducing surfactants has been performed in order to investigate the sedimentation depression effects on latent heat transportation systems found in the previous study. As surfactants, behenyltrimethylammonium chloride with 1.5 molar ratio of counter-ion suppliers, sodium salicylate, was used at the constant surfactant concentration of 2,000 ppm in water, while the concentration of PVA was changed from 0 to 2,000 ppm. The structure size of the combination was measured by a dynamic light scattering (DLS) system. From the results, DLS analysis indicated a large structure is formed by the interaction between PVA and surfactants. It was found that this structure becomes large with PVA concentration and the occupation volume of the structures expands widely in fluid. Thus, it was concluded that this large structure formation causes effective sedimentation depress on particles in latent heat systems.