bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fuzzy Method Applied at Energetic and Economic Rehabilitation of Pumping Station
Authors: Radulescu Victorita 
Published: October 2021

Abstract
Many pumping stations require an urgent rehabilitation from hydraulic, energetic, and economic point of view, being older than 30 years. Some urban stations for the water supply are nowadays under-dimensioned compared with the necessary consumption. Such an example is the pumping station of the Buzau City, realized in 1986. Its population has grown in the last decades by about 30% due to industrial development and its water pumping station from the treatment plant is currently totally insufficient. The hydraulic losses through the control discharge valve have become too high. This pumping station ensures the water supply for the south and east part of the city. Firstly, some characteristics of the pumping station equipped with pumps 12NDS- Normal-Double spiral casing-Single-layer of 160kW and 18NDS of 400kW and 500 kW, all from domestic production, are presented. Modernization of the pumping station has started few years ago and being realized in steps, so as not interrupt the city’s water supply. To establish the optimal operating point some algorithms are presented, developed based on the experimental data and using functions with one or two independent variables. Firstly, the interpolation function is determined, followed by its numerical calculation. To establish the characteristics’ equations H = f(Q), P = f(Q), and η = f(Q) starting from experimental results obtained by direct measurements, a polynomial approximation was chosen by the method of the least squares, using the polynomials Lagrange and Bezier. For optimization, the fuzzy technique is adopted regarding the flow fusing, intervals between start and stop following some policies concerning the aggregates’ starting. For a year, the energy saved between these intervals was calculated. Finally, the obtained yields of about 90% proved that the pumps modernization adopting new functioning techniques is more advantageous in some situations than the purchase of new equipment.
Transient Rayleigh-Bénard Thermal Convection With Radiation Heat Transfer in Participating Media Using the Control Volume Finite Element Method (CVFEM) and Lattice Boltzmann Method
Authors: Chaabane Raoudha , Jemni Abdelmajid , Aloui Fethi 
Published: October 2021

Abstract
In this paper, a gas-kinetic Bhatnagar-Gross-Krook (BGK) model is constructed for the Rayleigh-Benard thermal convection transfer in a two-dimensional cavity containing an absorbing, emitting, and scattering medium, where the flow field and temperature field are described by two coupled Lattice Boltzmann Method (LBM) BGK models. Heat radiation is solved using the Control Volume Finite Element Method (CVFEM). The two-dimensional Rayleigh-Benard thermal convection with radiation is studied and numerical results are compared with some available benchmark solutions and a good agreement has been observed.
Performance Analysis of Multi-Sectional Cycloidal Hydrokinetic Turbines
Authors: Li Ang , Wang Yijie , Chen Jun , Jensen Greg , Zhang Haiyan 
Published: October 2021

Abstract
Hydrokinetic power is the most efficient and reliable source of renewable energy and it has been utilized to produce power for centuries. The cycloidal water turbine is a subset of the H-bar type Darrieus turbines that are designed to actively controls the pitch angle of blades to improve turbine efficiency. However, the traditional cycloidal turbine has some shortcomings. For example, the torque and power coefficient vary significantly as the turbine rotates, which means the produced power is not uniform in one revolution. The associated hydrodynamic load will lead to fatigue of the turbine structure that will shorten the turbine lifespan. To solve this problem, a concept of the multi-sectional cycloidal water turbine is proposed. In the present study, computational fluid dynamic (CFD) simulations are applied to investigate the performance of the multi-sectional cycloidal turbine. A cycloidal turbine with three identical sections is designed. Each section consists of three blades and NACA0021 is chosen as the hydrofoil. Structured mesh with sliding interfaces is generated and arbitrary Mesh Interface (AMI) technique is employed. Unsteady RANS simulations with SST k–ω model are conducted to compute the flow field and torque generated by the turbine, and then power coefficient is computed. The results demonstrates that the three-section turbine has uniform performance in one revolution. At the design condition, the power coefficients of the one-section turbine and the three-section turbine are similar; when the TSR is much larger or less than the desired value, the three-section turbine has better performance.
Wake Structures and Effect of Hydrofoil Shapes in Efficient Flapping Propulsion
Authors: Kelly John , Han Pan , Dong Haibo , Van Buren Tyler 
Published: October 2021

Abstract
In this work, direct numerical simulation (DNS) is used to investigate how airfoil shape affects wake structure and performance during a pitching-heaving motion. First, a class-shape transformation (CST) method is used to generate airfoil shapes. CST coefficients are then varied in a parametric study to create geometries that are simulated in a pitching and heaving motion via an immersed boundary method-based numerical solver. The results show that most coefficients have little effect on the propulsive efficiency, but the second coefficient does have a very large effect. Looking at the CST basis functions shows that the effect of this coefficient is concentrated near the 25% mark of the foils chord length. By observing the thrust force and hydrodynamic power through a period of motion it is shown that the effect of the foil shape change is realized near the middle of each flapping motion. Through further inspection of the wake structures, we conclude that this is due to the leading-edge vortex attaching better to the foil shapes with a larger thickness around 25% of the chord length. This is verified by the pressure contours, which show a lower pressure along the leading edge of the better performing foils. The more favorable pressure gradient generated allows for higher efficiency motion.
Effect of Non-Planar Tungsten V-Electrode Pattern in a 3D Printed Microfluidic System
Authors: Parvez Mohammad Salman , Rubby Md Fazlay , Kabir Shanzida , Zulkarnain Meah Imtiaz , Islam Nazmul 
Published: October 2021

Abstract
Manipulation, guiding, and focusing of particles is an important phenomenon in the area of biomedical research. In most cases, particles are suspended in a microfluidic environment. These microfluidic environments can be high or low conductive. Most importantly these flows seeded with the micro-particles are manipulated and guided in microfluidic channels. Microfluidic channels have very low dimensions and considering the flow rate the characteristic of the flow in a microfluidic channel is laminar in nature. There are many micromachining methods available for fabricating microfluidic channels such as soft-lithography, wet etching, electroforming, PDMS molding, laser ablation followed by wet etching but in most of these cases, a microfabrication facility is required which is very costly in nature. Now a days 3D printing process is widely used to design microfluidic channels as a cheap process for conducting laboratory experiments. In this work, a 3D printed microfluidic channel fabrication process was presented along with a CAD drawing with microstructural dimension analysis. Previously V-electrode pattern was used in the static fluid system. In this work, a V-elect rode pattern was inserted in the microfluidic system for the first time to analyze the behavior of the flowing fluid of different conductivity under the application of AC current. The flow characteristics were presented and analyzed with the Reynolds number and the flow region of maximum velocity before and after the implementation of the AC electric field. The direction of the flow was also observed in the V-shaped microfluidics environment.
Effects of Valve Disc on Flow Characteristics Inside a Swing Check Valve During Opening and Closing Processes
Authors: Xu Yi-xiang , Ru Qiang , Yao Huai-yu , Jin Zhi-jiang , Qian Jin-yuan 
Published: October 2021

Abstract
The check valve is one of the most important devices for safety protection of the piping system in thermal and nuclear power plants. As the key component of the check valve, the valve disc accounts for a major effect on the flow characteristics especially during the opening and closing processes. In this paper, a typical swing check valve is taken as the research object. In order to make a comparative study, three working conditions of 30% THA (Turbine Heat Acceptance), 50% THA and 100% THA are selected. Focusing on the effects of valve disc, how does the valve disc motion interact with the flow field around the valve disc is analyzed with the help of the dynamic mesh technology. The results show that under the combined action of fluid force and gravity, the check valve can be opened and closed quickly. During the opening process, the maximum total moment of the disc appears between 45° ∼ 50° opening angle, and during the closing process the maximum total moment occurs when the disc fully closed. The flow field near the valve disc has similar variation rules with the rotation of the valve disc in the three working conditions, and the pressure near the valve disc reaches the maximum value at the moment of opening and closing. This study can provide some suggestions for the further optimal design of similar swing check valve.
Application of OpenFOAM in Numerical Simulations of High-Speed Trains Aerodynamics
Authors: Lu Panpan , Yin Bo , Yang Guowei , Ji Zhanling 
Published: October 2021

Abstract
The present study uses openFOAM package to simulate and investigate the aerodynamic performance and characteristics of high-speed trains (velocity beyond 250 km/h) under typical and critical conditions, which include flow passing a high-speed train, and two trains meeting towards each other at the same velocity in the open air. In terms of different operation conditions, separate openFOAM solvers are adopted. For flow passing a high-speed train at a constant velocity, a steady solver for incompressible, viscous and turbulent flow is employed on a fixed mesh and the results are compared with commercial software Star CCM+. For trains meeting towards each other, overset mesh method is used in which inverse distance interpolation is taken to couple background and inner overset mesh. The built-in mesh generation tool SnappyHexMesh is utilized to generate background and inner overset mesh. In all simulations, k-ω SST two equations RANS model is used to simulate the turbulent flow.
An Investigation on the Bubble Breakup Characteristics by Recirculation Flow in a Venturi Channel
Authors: Ding Guodong , Chen Jiaqing , Li Zhenlin 
Published: October 2021

Abstract
Discrete bubbles can be effectively cracked and dispersed in a Venturi channel with its unique structural characteristics, and the general Venturi channel has been widely used in the practical engineering. Bubble breakup mechanisms based on Venturi channels have been extensively studied, but most of them are based on single bubble or bubble flow pattern. In this paper, the transport process of slug flow in a Venturi channel was explored through visualization experiments, and the characteristics of recirculation flow were indicated by numerical simulation method. The liquid velocity sensitively affects the bubble generation process. With the increase of the liquid velocity, the initial bubble is no longer detached from the gas injector hole, and the gas-liquid flow pattern changes from bubbly flow to slug flow. The slug bubble extends to the diverging section and experiences the process of interface instability, sub-bubble detachment and bubble collapse. The average Sauter bubble diameter decreases with the increase of liquid velocity, and the fitting function is Log Normal. There is a recirculation flow in the side wall region of the diverging section, and the area of the recirculation flow increases with the increase of the liquid velocity at the inlet. The numerical simulation results indicated that there is a large velocity gradient in the boundary region of the recirculation flow under slug flow pattern, which contribute to the bubble collapse.
Impact of Skew Vane Cut on Alternating Stress in a Low Specific Speed Radial Pump Impeller Vane Using Fluid-Structure Interaction (FSI) Simulations
Authors: Gangipamula Rajavamsi , Prajapati Ashish , Birajdar Ravindra , Shukla Shyam 
Published: October 2021

Abstract
Numerical studies are presented on the pressure pulsations, hydraulic excitation forces and alternative stresses produced in a radial volute pump with high head application. The effect of excitation forces due to Rotor-Stator Interaction (RSI) are evaluated using One-way fluid structure Interaction in terms of alternative stresses on impeller pressure side and suction side. Initially, the pump performance parameters are predicted using steady state Computational Fluid Dynamics (CFD) simulations and compared with the available test data. Due to the transient behavior of pressure pulsations, a transient CFD simulation has been conducted using RANS models to predict the pressure pulsations and its behavior with time on impeller vane outlet and tongue locations. These unsteady pressure distributions are further coupled with the Finite element (FE) model of the impeller to solve and monitor for the stresses induced due to the transient hydraulic loading. To attenuate the alternating stresses produced due to RSI, the geometry of the vane is modified by providing a skew cut with 30° at vane outlet. The pressure pulsation amplitude and stresses are reduced by 10% and 10% respectively for a skew cut of 30° at vane trailing edge.
Performance Optimization for Cycloidal Hydrokinetic Turbine With Augmentation Duct for Harvesting Riverine Energy
Authors: Wang Yijie , Li Ang , Jensen Greg , Chen Jun , Zhang Haiyan 
Published: October 2021

Abstract
With the increased demand for developing renewable energy, hydro energy has attracted more attention since it is reliable and easy to acquire. In this area, the cycloidal turbine has been recently studied and applied to ocean energy for its stable and efficient output. Compared to the ordinary vertical/horizontal axis turbine with fixed pitch angle blades (e.g., Darrieus turbine), the cycloidal turbine can maximize the extracted power efficiency by keeping the optimized angle of attack for the blades. Meanwhile, the cycloidal turbine provides a potential solution to solve the problems of self-starting and seasonal flow variations. Introducing an augmentation duct is considered as a method to further increase the incoming flow velocity of the turbine. Inspired by the design of the wind tunnel, a convergent-divergent design of the augmentation duct is developed. One is noted that the dimensions of the augmentation duct are essential to the performance of the duct. In this study, a convergent-divergent augmentation duct is developed based on a 3-blade cycloidal hydro-turbine, operated at a 2 m/s river. Computational fluid dynamic (CFD) analysis with sliding unstructured mesh is applied to investigate the extent how the dimensions of the duct affect the flow velocity to the turbine as well as the extracted power efficiency.
Time Resolved PIV Measurements of a Slot Lobed Jet Issuing Into a Crossflow
Authors: Lewandowski Michael , Kristo Paul , Weiss Abdullah , Kimber Mark 
Published: October 2021

Abstract
The near field mixing phenomenon created by a round jet with three slot lobes exhausting into a crossflow are investigated at a velocity ratio of 0.5. Time-resolved particle image velocimetry measurements provide instantaneous velocity fields of the slotted jet in crossflow, allowing for evaluation of the first and second order turbulent statistics in two perpendicular planes of interest. The independently controlled jet exit and crossflow inlet are first characterized extensively to confirm the velocity ratio and anticipated momentum exchanges. Spanwise and transverse mean velocity profiles reveal that the interaction of the three slot lobes and the center round jet primarily occur in the immediate jet exit region, though residual effects are also found in the wake. Evaluation of the Reynold stresses aims to quantify the near region mixing between the jets collated geometric features and their interaction with the crossflow. Frequency analysis reveals that low-frequency harmonics in the wake region provide greater energy contributions than that of the higher-frequency harmonics found along the leading edge shear layer. This behavior is attributed to the low velocity ratio, where the freestream velocity is twice as large as the jet exit velocity. The experimental data and observations herein serve analogous computational modeling efforts for the slotted jet in crossflow at low velocity ratios, with ample information to inform necessary boundary conditions, fluid properties, and flow fields for validation.
Computational Investigation of Thrust Production of a Dolphin at Various Swimming Speeds
Authors: Wang Junshi , Pavlov Vadim , Lou Zhipeng , Dong Haibo 
Published: October 2021

Abstract
Dolphins are known for their outstanding swimming performance. However, the difference in flow physics at different speeds remains elusive. In this work, the underlying mechanisms of dolphin swimming at three speeds, 2 m/s, 5 m/s, and 8 m/s, are explored using a combined experimental and numerical approach. Using the scanned CAD model of the Atlantic white-sided dolphin (Lagenorhynchus acutus) and virtual skeleton-based surface reconstruction method, a three-dimensional high-fidelity computational model is obtained with time-varying kinematics. A sharp-interface immersed-boundary-method (IBM) based direct numerical simulation (DNS) solver is employed to calculate the corresponding thrust production, wake structure, and surface pressure at different swimming speeds. It is found that the fluke keeps its effective angle of attack at high values for about 60% of each stroke. The total pressure force coefficient along the x-axis converges as the speed increase. The flow and surface pressure analysis both show considerable differences between lower (2 m/s) and higher (5 m/s and 8 m/s) speeds. The results from this work help to bring new insight into understanding the force generation mechanisms of the highly efficient dolphin swimming and offer potential suggestions to the future designs of unmanned underwater vehicles.
Numerical Simulation of a Canadian Well With Several Circumferential Rows of Internal Vortex Generators
Authors: Kharoua Nabil , Semmari Hamza , Korichi Houssem , Haroun Mehdi 
Published: October 2021

Abstract
Canadian Wells exploit the quasi-stable underground temperature throughout the year for cooling and heating applications. This type of heat exchangers is used in residential buildings, agriculture and industry. Implementing Vortex Generators (VGs) is intended to disturb the thermal and dynamic boundary layers developing in the near-wall regions leading to the increase of the heat transfer coefficient.
The present work investigates the positive effects of a sequence of several rows of VGs. The commercial code ANSYS FLUENT was used to perform numerical simulations mimicking the variation of the seasonal operational conditions occurring within one year. The ambient conditions were considered for the city of Constantine located in the east of Algeria at an altitude of 600m over the sea level. Sinusoidal functions of time and depth, were used for the yearly variations of the ground and air temperatures. Parallelepiped VGs were considered in this study. The Reynolds number was in the range Re = 14975–42789.
The results illustrated a contrasting effect of the Reynolds number on the heat transfer coefficient and the temperature difference between the inlet and outlet of the Canadian Well. In terms of number of VGs rows, the beneficial heat transfer effects were observed till the fifth row only.
Flow Characterization in the Upper Cavity of a Rotary Compressor
Authors: Wu Puyuan , Li Ang , Chen Jun , Sojka Paul E. , Li Yang , Cao Hongjun 
Published: October 2021

Abstract
As hundreds of millions of Air conditioning (AC) systems are produced each year, and many of them use rotary compressors as the heat pump, optimizing the flow inside the rotary compressor to improve its reliability and efficiency becomes a key issue of the manufactures. Since the invention of the rotary compressor, its internal flow has been studied numerically with real models. However, a rotary compressor’s internal flow can be extremely complicated due to the complex internal structures’ geometry and high-speed moving parts, making it difficult to interpret the result by CFD simulation and repeat the simulation in different models. In our experiments for observing lubricant oil droplets above the rotor/stator in a rotary compressor, droplets’ movement reveals that two major effects control the gas flow in the compressor’s upper cavity. One is the swirling jet produced by the high-speed rotating rotor with no-slip condition on its sidewall. The other one is the rotating disk effect induced by the top of the high-speed rotating rotor. Either of them has been studied individually in different areas. For example, the swirling jet is often used in combustors while the rotating disk is applied in the viscous pump. However, the coupling of these two effects in the rotary compressor with different velocity ranges, size scales, and fluid properties has not been studied according to our best knowledge. In our simulation, a model that only consists of a simplified rotor, simplified stator, sidewall, and discharge tube (outlet) is built. Thus, the effect by small parts, such as the balance block and coils, is excluded. The rotor is set to rotate at 30, 60, and 90 Hz. Uniform velocity calculated with the theoretical flow rate and ambient pressure conditions are given at the inlet (rotor/stator clearance) and outlet, respectively. No-slip conditions are defined at other walls. Steady-state K-ω SST turbulence models are applied, and the cases are computed with OpenFoam. The CFD results show an inner recirculation zone above the rotor that creates a downward velocity component above the rotor and an outer circulation zone above the stator. The CFD result meets the observation of the droplets’ movement above the rotor/stator. With the CFD results and the experiment’s observations, we propose the model of the oil droplet’s path in the rotary compressor’s upper cavity, which can help reduce the exhausted lubricant oil droplets from the compressor.
CFD Simulation of COVID Aerosol Dispersion in Indoor Environments
Authors: Abushamleh Mohammed , Zhang Ning 
Published: October 2021

Abstract
Computational Fluid Dynamics simulations for the droplet’s dispersion generated by a cough in an indoor background, droplets trajectory, and evaporation time are predicted to be related to the droplet’s diameter and relative humidity. In general, medium-size droplets have higher axial penetration potential, and large droplets tend to settle on the ground due to gravity. Also, larger droplets take a longer time to evaporate. Smaller droplets tend to be suspended in the flow field with small penetration potential and tend to fade faster; smaller droplets &lt; 20 μm evaporate completely before the simulation time reaches 0.75 sec. To study the effect of Relative Humidity (RH) on the evaporation rate, in particular, the present study offers three simulations, all with the same standard room conditions, only differ in relative humidity s 40%, 60%, and 90%. Another source of variability is the cough-expired volume. This study adopts existent experimental work to establish two cough flow rate profiles. The Lagrangian discrete phase model is adopted along with the species model to track and investigate the cough droplet dispersion and evaporation.