bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mitigation of Flow-Induced Pressure Fluctuations in a Francis Turbine Using Water Injection
Authors: Altimemy Muhannad , Attiya Bashar , Daskiran Cosan , Liu I-Han , Oztekin Alparslan 
Published: November 2019

Abstract
Computational fluid dynamics simulations are conducted to characterize the spatial and temporal characteristics of the turbulent flow fields inside Francis turbine operating at the design and partial load regimes. High-fidelity large eddy simulations turbulence model is applied to investigate the flow-induced vibrations in the draft tube of the unit. The water injection at 4% rate from the runner cone is implemented to control the flow-induced pressure fluctuations. The simulations are conducted at the turbine design point and two partial load operations with and without water injection. It has been demonstrated that the water injection has a profound influence in the turbulent flow structure and the pressure field inside the draft tube at the partial load operating conditions. To evaluate the effectiveness of the water injection techniques in mitigating flow-induced fluctuations, the probes at various locations along the wall of the draft tube are used to monitor the pressure signals. It appears to be a reduction in the level of pressure fluctuations by the water injection at both partial load operating regimes. However, we could not draw a firm conclusion about the level of mitigation of flow-induced vibrations. Simulations should be carried out for much longer flow time. Water injection hardly influenced the unit power generation. Hence water injection can be employed effectively without a major liability on the power generation.
Plasma Driven Shock Tube for Dynamic Characterization of Sensors
Authors: Bivolaru Daniel , Papadopoulos George 
Published: November 2019

Abstract
The development and evaluation of a small scale plasma driven shock tube is described in the current paper, as a new option to sensor characterization for dynamic flow measurements. The initiation of a high energy plasma discharge at one end of a quartz tube generates a shock wave that travels the length of the tube. The rate of shock generation is governed by the discharge energy and can easily be several tens of pulses per minute, instead of several pulses per day as with traditional diaphragm-based shock tubes. There is no contamination with solid particles at the test location, and rise times of the order of microseconds can be achieved. The energy release is controllable resulting in robust and repeatable operation. Lastly, the overall footprint of the plasma driven shock tube is small and ideal for frequent laboratory bench top operation.
Can Naturally Pulsating Prefilming Slurry Atomization Be Enhanced by Artificial External Modulation?
Authors: Strasser Wayne 
Published: November 2019

Abstract
Under certain conditions in preferred three-stream geometries, a non-Newtonian airblast atomization flowfield violently pulses (axially and radially) by self-generating and self-sustaining interfacial instability mechanisms. The pulsing is severe enough to send acoustic waves throughout feed piping networks. The most recent work on this system instructed that exothermic chemical reactions enhance this moderate Mach number atomization. Explored herein is the potential to further enhance reaction-assisted disintegration by independently superimposing both sinusoidal and randomized mass flow fluctuations of +/− 50% of the mean onto otherwise constant gas feed streams. Two nozzle geometries (low versus high prefilming distance) and multiple superimposed feed frequencies (ranging from below to above the naturally dominant tone) are considered for each gas stream, making twenty-one total long-running unsteady PLIC-VOF CFD models. Droplet size, plus nine other temporal measures, were considered for assessing atomizer performance in our energy production process. Results indicate that superimposed frequencies have potential to enhance chaotic atomization in a statistically significant manner. Depending on the geometry, the largest effect was about a 10% reduction in droplet size; however, some combinations experienced a droplet size increase. Only marginal differences were seen in the nine other measures, such as injector face heat exposure. In addition to the immediate industrial benefit from modulation, dramatic changes in acoustics were produced by imposed feed perturbations at frequencies lower than the natural tone. A detailed study of start-up flow reveals new mechanisms which explain performance differences.
Numerical Investigation of Pressure Pulsation in Vaneless Region of a High Speed Centrifugal Pump
Authors: Zeng Yongshun , Yang Min , Zhai Yuqing , Yao Zhifeng , Wang Fujun , Xiao Ruofu 
Published: November 2019

Abstract
The pressure pulsation due to rotor-stator interaction (RSI) is unavoidable for high-speed centrifugal pump when operating under different conditions. The frequency components of pressure pulsation in the vaneless region are the most complex, and the pressure pulsation characteristic plays an important role in pump structural stress analysis. A numerical simulation method is used to obtain the hydraulic performances of a high-speed centrifugal pump with 9857 r/min at the range of flow rates between 48.1 to 155.0 m3/h. The head and efficiency under different operating conditions have good agreement with experimental results, with maximum deviations in 3.82% and 5.37%, respectively. The results show that the level of the pressure pulsation from the inlet to the outlet of the impeller increased gradually, and the pressure pulsations between the short blades are greater than that between the long and short blades. In the diffuser, the pressure pulsation is the highest near the tongue, whereas it is lower in the region between the two tongues, and this region is defined as the vaneless region. The pressure contours in the vaneless region almost have no change, while they near the tongue are densely distributed, revealing the mechanism of uneven pressure pulsation distribution. Moreover, there is a high radial velocity distribution near the tongue in the vaneless region, indicating that there may be a jet-wake pattern occured in this region.
Hydrodynamic Performance and Appendage Considerations of Wave-Piercing Planing Craft Overlapping Waves and Porpoising
Authors: Kim Sang-Won , Lee Sang-Eui , Lee Gyoung-Woo , Seo Kwang-Cheol , Oshima Nobuyuki 
Published: November 2019

Abstract
This work addresses the numerical study of wave-piercing planing hull and related hydrodynamic performance as the appendages. From the half century ago, the interest in high-speed planing crafts has been advanced toward maintaining performance stably. The main reasons to make it hard are instability motion occurring from porpoising and wave condition. Porpoising is mainly due to overlap the heaving and pitching motion with certain period, which is caused by instable pressure distribution and changing longitudinal location of center of gravity. In addition, in wave condition, encountering wave disturbs going into planing mode. This paper presents numerical results of wave-piercing planing hull in porpoising and wave condition. Numerical simulation is conducted via Reynolds Averaged Navier-stokes (RANS) with moving mesh techniques (overset grid), performed at different wave condition. The results for the behaviors of wave-piercing hull form are practically presented and investigated in this study. The understanding of these phenomena is important for design of appendages of wave-piercing hull-form.
Suppression of the Surging Phenomenon by Modifying Tongue Shape of Air Conditioner Mounted With Cross-Flow Fan
Authors: Nukaga Haruki , Maita Hiroshi , Daisaka Hisashi 
Published: November 2019

Abstract
Energy saving of room air-conditioner (RAC) is strongly required due to growing environmental concern. It is difficult to work a cross flow fan (CFF) at the most efficient operating point (OP) because a surging phenomenon occurs near this efficient OP. The conventional method for suppressing the surging phenomenon by increasing a rotation speed is unfavorable because a fluidic noise and a fan power consumption increase. Therefore, we investigated the new method for suppressing the surging phenomenon focusing on a structure of a fan casing.
It is known that the surging phenomenon is likely to occur from both right and left ends of the CFF. However, an area where surging occurs and a flow pattern in this area have not been revealed in detail. In this study, we experimentally investigated the area where surging occurs by measuring the outlet air velocity distribution across the CFF. In addition, the flow pattern in this area was compared with that of the center area using simulation. Simulation results showed that an area ratio of a vortex flow inside the CFF is high at both ends of the CFF, and a part of the mainstream flows back to the upstream side through a gap between the tongue and the CFF. Therefore, we thought that the function of the tongue, which divide inflow and outflow, is not sufficient.
The influence of modifying the tongue shape was experimentally evaluated. The test results showed that the surging limit shifted to the low flow rate and high static pressure side, and the noise at the condition of the surging limit decreased. The surging phenomenon was suppressed by modifying the tongue shape at both ends of the CFF compared to the center area. This technique makes it possible to work the CFF in a more efficient OP.
An Optimization Study on Cavitation Flow in a Steam Trap Valve
Authors: Qiu Chang , Zhang Han , Yang Chen , Hou Cong-wei , Jin Zhi-jiang , Qian Jin-yuan 
Published: November 2019

Abstract
Steam trap valves are mainly used in thermal power systems to pour out condensate water and keep steam inside. While during the condensate water flowing through steam trap valves, the condensate water is easy to reaching cavitation, which may cause serious damage to the piping system. In order to reducing the cavitation occupation in steam trap valves, this paper mainly deals with an optimization study. With Computational Fluid Dynamics codes, numerical model of a typical steam trap valve is established with Mixture model. The inner pressure field, flow field and steam volume fraction are all achieved under both maximum flow rate working condition and regular working condition. Based on the cavitation results, the throttling stages of the steam trap valve are optimized. And the results show that cavitation range inside the steam trap valve is reduced.
Effects of Mass Eccentricity on the Motion of Spherical Particles in Shear Flows
Authors: Tanaka Mitsuru , Matsuura Akira , Tajiri Kyohei , Nishida Hidetoshi , Yamakawa Masashi 
Published: November 2019

Abstract
A particle-resolved simulation is performed on the motion of spherical particles with an eccentric internal mass distribution in laminar and turbulent vertical flows subjected to horizontal shear in order to examine the effects of mass eccentricity on the motion of particles in shear flows. A spherical shell/hollow particles with an inner spherical core is focused on as a typical example of mass eccentric particles. The Navier-Stokes equations and the Newton-Euler equations are solved for the fluid phase and the particles, respectively. An immersed boundary method is adopted to represent the shell particle. The Newton-Euler equations are solved using the body-fixed coordinate system and four quaternion parameters, considering the deviation of the mass center from the center of the spherical shell particle. Numerical results show that a particle tends to stop its rotation when the torque acting on the particle due to the gravity exceeds that due to the shear. It is found that the transverse migration of mass-eccentric particles becomes less vigorous in both laminar and turbulent flows since the effect of the Magnus force is also weakened for mass-eccentric particles. It is also found that the evolution of fluid kinetic energy is significantly affected by the mass-eccentricity of particles in laminar flows.
Investigations on Energy Shares and Flow Structures of the Mixing Flow Using 3D-POD Analyses
Authors: Kong Daekyeong , Cho Gyeongrae , Kim Myoung-Jin , Doh Deog Hee , Kang Sangmo , Suh Yong Kweon , Ninomiya Nao , Kang Sunghee 
Published: November 2019

Abstract
The objective of this report is investigate the influences of the mixing state to the productions of the vaterite crystal of CaCO3. In order to quantify the three-dimensional flow structures and their physical contribution to the mixing properties, a stereoscopic PIV (SPIV) has been adopted.
The SPIV systems consists of two high speed cameras and an optical encoder which is used for trigging the SPIV system to capture the instantaneous flow images. A continuous laser (550nm) has been used. For mixing, an agitator having four blades has been used. The mixing tank has been filled with water up to 85% level of the tank height. The agitator has been rotated with 200rpm, 250rpm and 300rpm, and the 3D flow structures have been captured by the constructed SPIV system.
Using measured instantaneous 3D vectors, POD (proper orthogonal decomposition) analyses has been adopted to investigate the energy distributions of the major vortical structures, and to evaluate the flow features regarding on the production of the vaterite crystal of CaCO3.
Analysis of Characteristics of Bubble on Electrode Surface of Forced Convective Electrolyte Using Image Processing
Authors: Lee Jaewon , Sohn Dong Kee , Ko Han Seo 
Published: November 2019

Abstract
‘Electrolysis’ is a technology about the transport of electrons caused by placing electrodes in an electrolyte using the difference of electric potential. It has been applied to various industrial fields, e.g., energy storage systems (ESS), fuel cells, and water treatment. Despite the outwardly simple phenomenon of this technology, it has been investigated because of the complex electro-physical process inside the electrolysis system, which can be designed in various ways. Two plate electrodes placed on a bulk of electrolyte is the most common electrolysis system. The electrolysis systems can be identified by the electrolyte flow, such as Forced convection configuration (FCC), Forced convection-induced circulation configuration (FCICC), and No net flow configuration (NNFC). The purpose of the study about the bubbles around the electrodes was to characterize the potential drop induced by the existence of the bubbles in the electric field. The dispersed bubbles, which have less electrical conductivity than does the bulk of the electrolyte, can reduce the efficiency of electrolysis. Therefore, in order to study the relationship between the electrical properties in the channel and the gas layer, the equation was derived with the void fraction and other electrical variables.
Fabrication and Testing of a Magnetophoretic Bioseparation Chip for Isolation and Detection of Circulating Tumor Cells From Peripheral Blood
Authors: Jackson Seth , Darabi Jeff , Schober Joseph 
Published: November 2019

Abstract
Significant research involving the isolation and detection of circulating tumor cells (CTCs) has become prevalent in the field of biomedicine. It plays a crucial role in the diagnosis and treatment of cancer and has made substantial strides in recent years. A major event in the timeline of cancer is metastasis, a set of occurrences where cells are shed from a cancerous site, then flow through the circulatory system and seed themselves throughout the body, forming secondary tumors. There are few observable symptoms in the early stages of metastasis and this fact severely limits clinical treatment. The fabrication and preliminary testing of a magnetophoretic bioseparation chip capable of isolating and detecting CTCs from peripheral blood, which can aid in early detection of metastases, is presented in this work. MCF7 breast cancer cells along with superparamagnetic microparticles, which are specifically coated with anti-EpCAM to bind to the cancer cells, are spiked into a blood sample. After the spiked blood sample is introduced into the biochip, a locally engineered magnetic field gradient captures the magnetically labeled cancer cells while the non-target cells are allowed to pass by. Once the target cells are isolated from the blood sample, flow cytometry is used to determine the recovery rate of the magnetophoretic device. The proposed device can operate at continuous flow rates magnitudes higher than other CTC isolation devices and is fabricated using much simpler methods which make it quite unique. These properties combined with greater than 80% recovery rates make the device quite favorable for economic point of care use in clinical applications.
A Finite Element Based Partitioned Coupling Method for the Simulation of Flow-Induced Fiber Motion
Authors: Zhang Diwei , Peng Xiaobo , Zhang Dongdong 
Published: November 2019

Abstract
A finite element based partitioned coupling method is presented for the simulation of flow-induced fiber motion in this paper. Quasi-static Stokes equation is used as the governing equation of the fluid domain. Mixed finite element is used to solve it. Fiber motion is modeled as a nonlinear geometric dynamic problem. Total-Lagrangian incremental finite element method is used to address the nonlinear geometry. Bathe method is applied to discretize the time domain. Then, two domains are coupled by a loosely partitioned coupling strategy. The derived method can be applied to the simulations of fiber motion in the low Reynolds number fluid, e.g. an injection molding process for manufacturing short fiber reinforced composite materials. In this paper, the effects of fiber shape, axis ratio of fiber, and boundary effect on the fiber’s motion are discussed. A phenomenon of repulsion is found in a simulation of the double-particle motion immersed in the double Couette flow.
An Evaluation of Open Source CFD for Study of Aerodynamics of Vehicle Platooning
Authors: Farid T. , Shakeel A. , Sajid M. 
Published: November 2019

Abstract
The ever-growing road congestion and safety hazards induced by conventional highways has inspired the development of automated highways which provides four key benefits: fuel economy, environmental protection, road safety and smooth traffic flow. Vehicle platooning is a vital component of automated highways which contributes directly to these four benefits with its sequence of closely spaced leader-follower vehicle configuration by taking advantage of the ‘slip-stream’ effect to minimize the aerodynamic drag. Exploratory studies into platooning parameters, vehicle spacing, speeds and number of vehicles, have proven to be prohibitive expensive both computationally and experimentally due to the complexity of tests and the large number of test cases. In recent years, OpenFOAM® an independently developed, supported and documented open-source toolbox has gained popularity by offering a lower cost alternative to leading commercial CFD products. This paper summarizes the results from a computational study of autonomous vehicle platoons and the capability of OpenFOAM® to substitute leading commercial CFD solutions currently used to support vehicle aerodynamic development. This study investigates the aerodynamic characteristics of a 4-SUV platoon at inter-vehicle distances ranging from 0.25 to 1 SUV length at a constant speed of 23 m/s. Trends of the predicted aerodynamic drag coefficients (Cd) are then compared against experimental data from published literature as well as the results obtained from a leading commercial CFD package.
A Numerical Study on Improvement of Coating Uniformity by Controlling the Pressure at the Exit of the Slot Die Nozzle
Authors: Oh Sang Hyun , Kim Sung Il , Park Ki Ho , Yu Byeong Hyeok 
Published: November 2019

Abstract
In this study, numerical analysis was carried out to investigate the effects of slot die nozzle exit rear pressure on coating uniformity improvement in coating nozzles which are widely used in industry. Coating uniformity in coatings of viscosity materials such as inks and surface coating solutions is closely related to the quality of the product. Especially, coating uniformity is an important performance indicator for slot die coatings, which are used primarily in the production of optical or chemical products such as displays, touch screens, solar panels, and batteries. In general, the average thickness of a thin film in a slot die coating is determined by the supply flow rate and the moving speed of the plate. However, due to various parameters, thickness irregularities and coating defects due to pores occur locally. Therefore, many studies have recently been performed to solve the local defect of the slot die coating. In order to improve the coating uniformity, this study applied the vacuum pressure condition to the slot die nozzle rear end and numerical study on the coating uniformity according to the vacuum pressure was carried out. The numerical analysis proceeded to 2-D, unsteady condition and the VOF method. A commercial numerical simulation software (STAR-CCM+ V.12.06) was used. It was simulated that the coating liquid was supplied onto the moving plate surface. The moving plate speed was fixed 0.01m/s. The nozzle geometry simulates a slot die nozzle. And the coating raw material supply flow rate was considered for two conditions (0.005, 0.006m/s). Two vacuum pressure conditions (−3, −300Pa) were applied to the rear end of the nozzle. The viscosity of the viscous material was fixed at 2 Pa.s. The analysis results were analyzed through the uniformity of the material supplied to the surface. As a result of analysis, uniformity of coating was lowered regardless of the velocity when the vacuum pressure condition was −3.0 Pa, and uniformity was lowered as the velocity increased. However, it was confirmed that uniformity of the coating was increased at all velocity condition when the vacuum pressure condition was −300 Pa. This is because as the flat plate moves, the reverse pressure is applied to the downstream of the coating solution, thereby improving the uniformity of the coating liquid flowing through the flat plate and preventing the inflow of air or the like. Through this study, it was confirmed that the coating uniformity can be improved by controlling the vacuum pressure at the rear end of the nozzle.
Ionic Wind Application to Vortex Ring Generator and its Transportation Efficiency
Authors: Fukunaga Kengo , Satake Masayoshi , Maeda Noboru , Shikata Kazushi , Ezaka Tomohisa 
Published: November 2019

Abstract
In this study, ionic wind generated in corona discharge is focused for producing an air flow without having mechanical actuators. First, the kinetic energy conversion efficiency to ionic wind from electric power is experimentally estimated to be 0.32%. Then, it is confirmed that intermittent blows of ionic wind enable to produce vortex rings without using mechanical system. We adopt novel sub-chamber structure to avoid the concentration of the substance in a vortex ring low, so that the substance concentration transported to the target distance of 200 mm increases by 9%. As an application, the efficiency for moisture transportation is evaluated through experimental measurements. As a result, it is shown that the substance (moisture) can be transported at an efficiency of about 85% to target distance of 200 mm under conditions where the influence of external turbulence is small.