bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Simulation and Experiment of the Fire Protecting System of the Manipulator in High Temperature Environment
Authors: Kim Byeong Cheon , Chang Kyoungsik 
Published: November 2019

Abstract
In the present work, the strategy for cooling the manipulator in high temperature environment is studied using both numerical and experimental methods. Since the manipulator is designed to operate in the environment with the maximum 250 °C temperature, fire protection system and the cooling system should be installed for normal operation of the manipulator. The para-aramid-filament with the thickness of 0.5 mm and Graphite felt with the thickness of 5.5mm is considered for fire protection suit and air blowing technique is applied for cooling the electronic circuit and hydraulic pressure cylinders. For numerical simulation, ANSYS Fluent V18.2 is adopted to simulate the convective heat transfer flows and the radiation with the model, S2S (Surface to surface). Two types of blowing techniques are considered, global blowing and local one. Even though the global blowing at the inlet is most effective for cooling system, so much amount of compressed air is required, which means that extra big compression system should be added in the system. The local blowing is applied to the component with small holes of the flexible pipe and the magnitude of the local blowing mass flow rate is 0.0166kg/s. The technique of local blowing is more effective than the global blowing for cooling the system. To validate numerical simulation, the model is tested within the hot temperature chamber whose mean temperature is approximately 250 °C.
Flying Spiders: Effects of the Dragline Length and the Spider Mass in Free-Fall
Authors: Stevens Tessa , Zhao Longhua , Courtney Ryan , Zhang Wei , Miller Laura 
Published: November 2019

Abstract
Many species of spiders move from one location to another using a remarkable aerial dispersal “ballooning”. By ballooning, spiders can reach distances as far as 3200 km and heights of up to 5 km. Though a large number of observations of spider ballooning have been reported, it remains a mysterious phenomenon due to the limited scientific observation of spider ballooning in the field, high uncertainties of the meteorological conditions and insufficient controlled laboratory experiments. Most of the ballooning spiders are spiderlings and spiders under 3 mm in length and 0.2 to 2 mg in mass with a few exceptions of large spiders (over 3 mm in length, over 5 mg in mass). What physical mechanism dominates the three stages of spider ballooning — take-off, flight, and settling? Many factors have been identified to influence the physical mechanism, including a spider’s mass, morphology, posture, the silken dragline properties, and local meteorological conditions (e.g., turbulence level, temperature and humidity). A thorough understanding of the roles of key parameters is not only of ecological significance but also critical to advanced bio-inspired technologies of airborne robotic devices.
This work aims to determine how the dragline length and spider mass affect the interaction of the spider-dragline system in the free-fall scenario. Experiments using a thread of different lengths and a sphere of different masses to mimic the spider-dragline were carried out. The first sets of tests focused on the spider-dragline system, rather than the fluid flow. High-speed images of a spider-dragline falling in a closed container of air were recorded with 1500 frames per second at Reynolds numbers of several thousand, based on the spider dragline and the local relative velocity. Image data allow for tracking the vertical velocities and acceleration of the spider-dragline, as well as the drag force acting on the spider-dragline. Terminal velocities in the settling stage are compared with estimates using various fluid dynamics models in previous work. Such results under controlled laboratory conditions are expected to shed lights on the intriguing flow physics of spider ballooning at the settling stage and to inform future experiments and numerical models.
Effect of Bionic Groove Surface Blade on Cavitation Characteristics of Centrifugal Pump
Authors: Zhang Zicheng , Dai Yun , Gu Yunqing , Shi Zhengzan , Mou Jiegang 
Published: November 2019

Abstract
In order to improve the cavitation resistance of centrifugal pump, bionic groove surface structure was arranged on the suction surface of centrifugal pump blade which is the most prone to cavitation. Numerical simulation method was used to study the influence of different-shape groove blade on cavitation performance of centrifugal pump. The results showed that the head and efficiency of the centrifugal pump with circular grooved surface blades were close to the smooth surface blade centrifugal pump and higher than those with triangular grooved surface blades and rectangular grooved surface blades. The low pressure area of the circular groove blade was the smallest and the cavitation resistance was the best. At the critical cavitation margin point, circular groove blade can effectively reduce the probability of negative incidence, and the cavitation inhibition effect was the most obvious.
Robustness of Turbulent Stripes in Particle-Laden Channel Flows
Authors: Hanabusa Masaki , Tsukahara Takahiro 
Published: November 2019

Abstract
It is known that intermittent localized turbulence, so-called turbulent stripes, sustains in the form of oblique bands in subcritical transitional regime of channel flows. The pattern is formed and accompanied by secondary flows along the localized turbulence. In particle-laden turbulent flows, turbulent intensity can be enhanced or suppressed by particles. However, the effect of the particles on the turbulent stripes in subcritical transitional regime is still unknown. In this paper, we investigated the particle distributions with respect to the turbulent stripes in one-way coupling simulations and studied the effect of particle-fluid interactions on the robustness of the stripes in two-way coupling simulations. In one-way coupling, the turbulent stripe provides a cluster of heavier, or large-Stokes-number, particles in a form of oblique band similar to the stripe, in the wall-parallel direction. Furthermore, heavier particles accumulate near the wall even without gravity. In two-way coupling, the stripes tend to be broken for heavier particles. The stability of the pattern also depends on the particle volume fraction. For higher volume fraction of particle, particles have a significant effect on the sustenance of the stripes. In such a case, the particle-fluid interactions exhibit the force that accelerates the fluid near the wall. The turbulent kinetic energies of large-scale flow and fine-scale eddies are attenuated by heavier particles. Different wave-number scaled structures were generated and disappeared as a laminarization process.
Similarity of the Output Characteristics of the Small Vertical Axis Wind Turbine
Authors: Sekiya Naoki 
Published: November 2019

Abstract
Several models have been proposed to predict the shaft output characteristics of the vertical axis wind turbine from the aerodynamic characteristics of the blade. However, it has not predicted the output characteristics of the small wind turbine, turbine diameter less than 1 m, even the multiple stream tube model included effect of the momentum reduction. A solidity of the small wind turbine become higher than large, i.e. blades interval of small wind turbine becomes short. Therefore, it expects that the wake of preceding blade influence strongly aerodynamic character of following blade. Thus, we have investigated the relation between wake of rotating turbine and its shaft output characteristics. From result obtain, we had cleared the shaft output character agree with variation of momentum loss of the wake of turbine. Moreover, the relevance between the shaft output characteristics and velocity fluctuation in the wake had been found. In the low tip speed ratio region increasing the shaft output, the periodical component synchronized with motion of the blade remarkably appear in velocity fluctuation, and it disappear near the peak of shaft output. Meanwhile, in the high tip speed ratio region decreasing the shaft output, the turbulent component is dominant in velocity fluctuation. It indicates that the blade-wake interference was affected on shaft output of the small wind turbine. Therefore, the purpose of this study was to find out a similarity parameter of the shaft output characteristics based on blade-wake interference. The larger the scale of blade wake or slower the advection velocity of it, the higher the possibility that blade wake generated from previous blade interfere to following blade become. For blade-wake interaction, these two parameters which the scale and the advection velocity of blade wake, are important. Thus, I estimated these parameter in this study using the wind turbine model with single blade. From measurement of the blade wake, I found that the scale of the blade wake depends on the ratio of the rotational speed of the turbine to the free stream velocity, and the advection velocity of blade wake depends on the free stream velocity. From these characteristics of blade wake, I suggest a new parameter based on the blade-wake interaction using tip speed ratio, solidity, number of blade, and turbine diameter. The shaft output characteristics of the small wind turbine indicates good similarity for the new parameter.
Numerical Simulation of Intermittent-Controlled Multiple Jets
Authors: Tsujimoto Koichi , Kitahara Kango , Shakouchi Toshihiko , Ando Toshitake 
Published: November 2019

Abstract
Multiple jets are used in industrial processes such as combustion, ventilation and so on, and their improvement of mixing and diffusion is demanded. Unlike single jet, since the jets issuing from nozzles will coalescence, merge or combine with each other, it is necessary to reduce mixing performance such as entrainment from surroundings and spreading into surroundings. It is well known that the characteristics such as mixing and diffusion of the jet are strongly dependent on the large-scale vortex structures being formed near the nozzles. Therefore, an appropriate inflow condition at a nozzle is capable of controlling the large vortex structures near field around the nozzle and improves the mixing performance. In this study, we examine an intermittent control of jets varying the control frequency and the jet spacing so as to reduce the interaction between each jet. We conduct the DNS (direct numerical simulation) of intermittently-controlled two round jets. In order to quantify the mixing efficiency of the intermittent control, statistical entropy and entrainment are examined. Compared to the uncontrolled jet, it is confirmed that the mixing efficiency is markedly improved, suggesting that the intermittent control can be expected to be useful for the improvement of mixing performance of multiple jets.
Temperature Compensation for Measurement of Low-Speed Internal Flow Fields Using Fast-Response Pressure Sensitive Paint
Authors: Mori Hideo , Imazeki Tomohiro , Moon Kil-Ju 
Published: November 2019

Abstract
Because most fast-response pressure sensitive paints (PSP) suffer from temperature sensitivity, causing large error in pressure measurement when spatial non-uniformity of pressure distribution is large. In this study, the two methods of composite measurement of temperature and pressure by using the segment painting of PSP and TSP, and Dual-layer PSP/TSP (DL-PTSP), are applied to measurement of pressure distribution on inner surface of casing of test axial compressor, by using transparent method. We apply a paintable fast-response PSP composed of PtTFPP and silica nanoparticles and polymer-based TSP composed of Ru-phen and PMMA, with opaque, oxygen permeable overcoat, in order to enhance the luminescence intensity of PSP and TSP and avoid overlaying image of rotors inside the casing. When segmented-painting method of PSP and TSP is applied, pitch-wise symmetry is assumed. Therefore, asymmetric temperature distribution causes error in temperature compensation. On the other hand, DL-PTSP method can be used for asymmetric conditions, but sequential measurement of pressure and temperature may cause error in temperature compensation, when temperature distribution on the surface is nonstationary.
Is Radioactive Tank Waste a Bingham Fluid?
Authors: Pease Leonard F. , Fuher Arich J. , Bamberger Judith A. , Burns Carolyn A. , Daniel Richard C. , Minette Michael J. 
Published: November 2019

Abstract
Slurries and sludges across the United States Department of Energy (DOE) complex rank among the most rheologically interesting. Their composition is heterogeneous, spanning a very broad range of particle sizes, densities, and interparticle forces. All exhibit shear thinning, some have yield stresses, and many are thixotropic. Despite the variety, these complex fluids are often represented using the historic Bingham fluid model, which fits higher shear rate data to a simple straight line. The intercept provides a yield stress, which has been a key design parameter in construction of large-scale waste processing facilities. However, many radioactive wastes are simply not Bingham fluids, and this representation extrapolates poorly across low to intermediate shear rates that are characteristic of typical processing conditions. Indeed, processing shear rates as high as 200 1/s, which has been a typical minimum shear rate used in fitting the Bingham fluid model, are seldom encountered in nuclear waste processing. Therefore, more realistic rheological models are necessary to accurately predict waste processing performance.
Pacific Northwest National Laboratory (PNNL) recently re-evaluated the rheology of reconstituted Hanford REDOX (reduction-oxidation) process sludge waste against a wide variety of rheological models including the Bingham, Cross, Cross with yield stress, Carreau, biviscous, Herschel-Bulkley (which includes a power law dependence), Casson, and Gay models. They found that all of the models provided a closer fit than the Bingham model and that the biviscous model and Cross with yield stress model were convincing. However, reconstituted Hanford REDOX sludge waste is but one type of DOE waste and a direct contrast, and comparison of these three models against undiluted, unmixed tank waste (actual not simulant) has not been performed previously. Therefore, the purpose of this paper is to evaluate the rheology of actual tank waste with these more accurate rheological models.
In this paper, we evaluate select rheological data for slurry samples from Hanford’s AZ-101, AZ-102, and SY-101 waste tanks. In each of these cases, we find that Cross’ model with yield stress and the biviscous model significantly outperform the Bingham fluid model. Furthermore, the AZ-101 data also shows that the shear stress peak at startup significantly exceeds the Bingham yield stress, which is commonly observed in the initial moments of rheological measurements on simulants. Remarkably, Cross’ model may empirically accommodate an initial spike in shear stress at modest shear rates. These are important observations because computational and analytical fluid dynamics simulations rely on rheological constitutive models for accurately and conservatively predicting waste processing performance. These findings suggest the need for better rheological modeling of and validation against radioactive waste.
Contribution of Fluctuating Large-Scale Motions in Turbulent Fluid Flow Through a Channel
Authors: Mito Yoichi 
Published: November 2019

Abstract
The key mechanism that sustains fluid turbulence flowing through a channel is examined using the Lagrangian experiment, done in a direct numerical simulation (DNS) of the turbulent fluid flow and that being damped by addition of a small amount of small particles. The results indicate large contribution of the fluctuations of large-scale fluid motions, which are seen as their multi-directionality and multi-dimensionality, to sustenance of wall turbulence. Small-scale fluid turbulence structures, such as vortices and packets of them, are seen to induce the fluctuations of large-scale fluid motions.
Influence of Nozzle Aspect Ratio and Orientation on Flow Characteristics of Multiple Elliptic Jets
Authors: Teramoto Hiroshi , Kiwata Takahiro , Yajima Kako 
Published: November 2019

Abstract
An experimental study is conducted to investigate the flow characteristics of multiple elliptic jets issuing from a 6 × 6 nozzle array at a relatively low-Reynolds number (Re = 4.3 × 103). Two aspect ratios of the multiple elliptic nozzles (equivalent diameter, de, of a nozzle was 6 mm), namely a/b = 2.25 and 6.25, where a and b are the radii of the major and minor axes of an elliptic nozzle, respectively, and two nozzle azimuthal orientations, namely the same and alternate azimuthal orientation arrangements, were used. The mean and fluctuating velocities were measured using a constant-temperature hot-wire anemometer. The multiple jets located at the side of the ambient fluid were stretched due to interactions between the self-induced flow of an elliptic vortex ring and the secondary flow caused by the entrainment of the ambient fluid. For a/b = 2.25, axis switching occurred only once in the range of 1 &lt; x/de ≤ 3 for both nozzle azimuthal orientations. For a/b = 6.25 and the same azimuthal orientation arrangement, axis switching occurred only once at 3 &lt; x/de ≤ 5; axis switching did not occur for the alternate azimuthal orientation arrangement. Thus, the flow characteristics of multiple elliptic jets are influenced by the azimuthal orientation of adjoining nozzles.
Predictability Study of Viscoelastic Turbulent Channel Flow Using Deep Learning
Authors: Nagamachi Atsushi , Tsukahara Takahiro 
Published: November 2019

Abstract
We tested Artificial Neural Networks (ANNs) to predict a fully-developed turbulent channel flow of a viscoelastic fluid in preparation for elucidating flow phenomenon and solving the difficulty in DNS (Direct Numerical Simulation) due to numerical instability of the viscoelastic fluid. Two kinds of ANNs (multi-layer perceptron (MLP) and U-Net) were trained using DNS data to predict conformation stress from given instantaneous field. The MLP showed accurate predictions and predictions got better with z-score normalization. ANN predicted accurately in near-wall region having coherent structures. In addition, we demonstrated that ANN get the nonlinear relationship between velocity gradient and viscoelastic stress partially.
Void Waves Developing in Gas-Liquid Two-Phase Turbulent Boundary Layers Beneath a Flat Bottom Model Ship
Authors: Tanaka Taiji , Park Hyun Jin , Tasaka Yuji , Murai Yuichi 
Published: November 2019

Abstract
To investigate the development process of a void wave, spatio-temporal fluctuation of void fraction, we examined experimentally a turbulent boundary layer with bubble injections. The experiments performed on a flat bottom of 4-mlong transparent model ship towed in a tank of 100 m length with the speed of up to 3.00 m/s. In bubbles injection with constant air flow rate, void fluctuations with 4 Hz or 8 Hz appeared dependent on the towing speed. With periodically fluctuated air flow rate, artificial void waves were provided into the turbulent boundary layer and their frequency was maintained during the downstream propagation. The attenuation rate of the fluctuation evaluated using Fourier analysis of the wave took the minimum value at specific injection frequency conditions.
Effect of Splitter Configurations on the Performance of a Sludge Pump
Authors: Jin Jeong-Min , Ji Hyo-Geun , Kim Youn-Jea 
Published: November 2019

Abstract
Sludge pump, a type of centrifugal pump, is widely used to transport high-density sludge. The pump uses the impeller to generate a pressure difference for transporting the working fluid. The impeller is a crucial component of the pump. The internal pressure becomes higher with an increasing number of impeller blades, and this in turn results in an increased head. However, the increase in the number of blades interferes with the pump inlet flow, resulting in an efficiency loss due to an increase of surface friction. Therefore, in this study, numerical analysis was performed using ANSYS CFX ver. 17.1 to elucidate the effect of splitter configurations on the performance of sludge pump. The numerical results were compared with the efficiency and head according to the change of the splitter length, as 35%, 60%, and 80% of the reference blade shape.
Direct Numerical Simulation of Supersonic Flow Over a Counter-Rotating Vane-Type Vortex Generator Implemented on Slip Wall
Authors: Nagata T. , Daspit T. , Nonomura T. , Loth E. 
Published: November 2019

Abstract
In this study, flow over a pair of vane-type vortex generator is investigated by solving the Navier–Stokes equation. A pair of the vane-type vortex generator implemented on a slip wall in laminar flow is considered so that the problem setting could be simple. The Reynolds number based on freestream quantities and the height of the vanes is set to be 500. The effect of the arrangement and geometry of vanes on the circulation coefficients, induced flow velocities, and aerodynamic force coefficients of VGs are investigated. In addition, a new non-dimensional circulation coefficient, normalized by freestream velocity and the height of the vortex core was introduced and its effectiveness is examined. This new parameter, CΓ’, include the height of the vortex core, so that appears to be a better measure of VG effectiveness on momentum exchange. From the computational results, the wider arrangement can introduce the effective vortices with small drag. Also, the longer vanes can introduce strong and effective vortices with smaller drag coefficient.
Simultaneous Optimization of Impeller Blade Loading Distribution and Meridional Geometry for Aerodynamic Design of Centrifugal Compressor
Authors: Manabe Kaito , Ito Sasuga , Furukawa Masato , Yamada Kazutoyo , Oka Nobuhito , Tomita Isao , Hayashi Yoshihiro 
Published: November 2019

Abstract
The present optimum design method has been advanced for simultaneous optimization of impeller blade loading distribution and meridional geometry. This is based on an aerodynamic design method and a genetic algorithm. The aerodynamic design method consists of two parts: a meridional viscous flow analysis and a two-dimensional inverse blade design procedure. In the meridional viscous flow analysis, an axisymmetric viscous flow is numerically analyzed on a two-dimensional grid to determine the flow distribution around the impeller and diffuser. Effects of blades onto the axisymmetric flow field are considered by a blade force modeling. In the inverse blade design procedure, 3-D impeller geometry can be obtained from the result of meridional viscous flow analysis and the predetermined blade loading distribution. In the optimization procedure, the total pressure ratio and adiabatic efficiency obtained from the meridional viscous flow analysis are employed as objective functions. As a constraint of the optimization, mass flux distribution at the impeller trailing edge is introduced in the evaluation procedure, in order to suppress the boundary layer development near the shroud, especially under low flow rate condition.
Total performances and three-dimensional flow fields of centrifugal compressors have been analyzed by 3D-RANS simulations to certify effectiveness of the present design method. The 3D-RANS simulations and the flow visualization have been applied to a conventional centrifugal compressor and optimized design cases. From the analysis results, the performance enhancement of optimized designs is confirmed under low flow rate condition including design point. In addition to that, it is revealed that the constraint works effectively on the performance improvement. As a result, construction of the simultaneous optimization using the aerodynamic design method and the genetic algorithm is successfully achieved.