bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance of Kaplan Turbine Operating at Design Condition
Authors: Altimemy Muhannad , Watheq Saif , Caspar Justin , Oztekin Alparslan 
Published: October 2021

Abstract
Design and optimization using computational fluid dynamics to enhance the hydro turbine’s performance are becoming gradually more common because of its flexibility, minor detailed flow description, and cost-effectiveness. These features are not easily achievable in model testing. k–ω simulations conducted in OpenFOAM 7 characterize the flow structure inside an industrial-sized Kaplan turbine module operating at the peak design flowrate. The power signal, velocity, vorticity, and pressure field are presented over the blades and throughout the draft tube. Additionally, pressure fluctuations were probed along the draft tube wall. The simulation shows a tip vortex rope in the narrow gap between the blade tip and turbine casing. The strong influence of the swirl leaving the runner had a negative impact on the flow pressure fluctuation. Also, high vortical activity was presented near the draft tube wall, leading to turbine instability. It was demonstrated that the turbine generates 14.923 MW of average power. The power signal showed minor fluctuations induced by the vortical activity close to the runner region and the corresponding pressure fluctuations. The Fast Fourier Transform showed the system is dominated by low frequency, high amplitude fluctuations.
Pressure Drop Mechanisms Generated in a Cooling System Enclosure of Construction Machinery
Authors: Kawano Takashi , Fuchiwaki Masaki 
Published: October 2021

Abstract
A potential way to reduce cooling system noises generated by heavy construction machines is to generate the required cooling airflow with a low fan speed, and one way to accomplish this is to optimize the ventilation path through which the airflow generated by the cooling fan must travel. However, while the computational fluid dynamics (CFD) approach would be effective for modeling the three-dimensional (3D) pressure drop characteristic of such systems, there have been few reports aimed at clarifying the loss generation mechanisms or suggesting minimization methods based on flow field viewpoints. Accordingly, in this study, we visualize the 3D flow field characteristics of an electric cooling fan system installed within the cooling enclosure of a heavy construction machine and investigate the details of the system’s pressure drop mechanisms.
Our results confirm that airflow pressure declines in areas other than the radiator account for more than half of the reduced pressure experienced by the whole system. Additionally, we found that, in the exhaust side enclosure, pressure drops increased because the exhaust port outlet shapes were not optimized to the annular airflow of the cooling fan. Most notably, we found that in the region before reaching the exhaust port outlets, the airflow from the fan repeatedly collides with obstacles within the enclosure, thus producing stagnation and turbulence that exacerbates pressure drops before being expelled into the outside environment.
Multiphase Flow Simulation of Subsea Pipeline Leakage Detected by Acoustic Emission Method
Authors: Shama Ahmed M. , Swidan Ahmed , Young John 
Published: October 2021

Abstract
Subsea pipelines are the heart of the oil transportation system. Oil leakages from subsea pipelines is one of the principal risks associated with oil transportation. An experimental test rig was designed to identify a range of scenarios that could cause leakage, and consequently marine pollution. The Acoustic Emission (AE) technique was employed to sense the flow behaviour inside the pipeline through quantifying and analysing key parameters, such as; energy, amplitude, and the counts number. Although, the size and location of the oil leakage were acquired experimentally utilising highly sensitive acoustic sensors. Two series of numerical simulations utilising Computational Fluid Dynamics (CFD) – Reynolds-Averaged Navier-Stokes (RANS) model, were performed to accurately predict the rate of the oil spill and the corresponding trajectory to the free-surface at Reynolds number Re range from 0.3702 × 103 to Re 9.775 × 103 for flow inside pipeline. The computed results showed good agreement with the experimental data. The results demonstrated that the current experimental measurements analysis could determine the leakage location and the leakage hole capacity, then the numerical calculations could predict the leaked oil volume and the leaked oil route to prevent oil diffusion and mitigate its harmful impact. The findings of this work is a step forward for preventing and controlling oil pollution to protect the marine environment.
Experimental Characterization of Two-Phase Swirl Flow Interacting With a Circular Bluff Body
Authors: Gonzalez Hernandez Rafael , Goharzadeh Afshin , Meribout Mahmoud , Khezzar Lyes 
Published: October 2021

Abstract
This study presents an experimental investigation of two-phase swirl flow interacting with a circular bluff body. A horizontal and transparent multiphase flow loop is employed to investigate the dynamic of swirl flow close to the circular bluff body. Using high-speed photography, air-core development during the transition period is characterized. Analysis of both instantaneous and averaged images provides key information on air-core length and diameter for steady state conditions. The distance from air-core tip to the disk depends on a critical gas-liquid ratio (GLRc). The presence of air pocket behind the circular bluff body depends on a critical distance to the disk.
Influence of the Blade Design Parameters on Hydraulic Noise Generation by a Low Specific Speed Radial Pump With Narrow Channel Flow
Authors: Gangipamula Rajavamsi , Ranjan Pritanshu , Patil Ranjit S. 
Published: October 2021

Abstract
Present work aims to investigate the hydro acoustic behavior of a typical low specific speed radial type centrifugal pump with narrow channel impeller passage. The blade design parameters play an important role in hydraulic noise generation by a low specific speed radial pump with narrow impeller channels. Though, these pumps are hydraulically efficient for a given design point, the hydraulic noise production may be higher at duty point. The blade passage length along with the outlet width of the impeller are the two main design parameters of a radial impeller with narrow channels, which can impact the flow quality along the impeller blade passage. To understand the effect of the narrow channel, initially steady state simulation is conducted to predict and validate the hydraulic performance. Then transient simulations were conducted using Detached Eddy Simulation (DES) using STAR-CCM+ to predict the hydro acoustic behavior of the pump in terms of pressure fluctuations and far field noise spectra of the pump at specific points. The velocity profiles along the impeller channels, shows the formation of wake region, which strongly affects the jet wake flow phenomenon near impeller trailing edge. This results in high pressure fluctuations near impeller outlet.
An Improved Hybrid Alternative WENO Scheme for High Mach Number Flows
Authors: Rajput Uttam Singh , Singh Krishna Mohan 
Published: October 2021

Abstract
This study presents the development of a fifth-order hybrid alternative mapped weighted essentially non-oscillatory scheme (HAW-M) for high-speed compressible flows. A new, improved smoothness indicator has been developed to design the HAW-M scheme. The performance of the present scheme has been evaluated through different one and two-dimensional test cases. The developed scheme shows higher accuracy and low dissipation. Further, it captures the fine-scale structures smoothly than the existing high-resolution method.
Comparative Evaluation of Dielectric Materials for Plasma Actuators Active Flow Control and Heat Transfer Applications
Authors: Rodrigues F. F. , Nunes-Pereira J. , Abdollahzadeh M. , Pascoa J. , Lanceros-Mendez S. 
Published: October 2021

Abstract
Dielectric Barrier Discharge (DBD) plasma actuators are simple devices with great potential for active flow control applications. Further, it has been recently proven their ability for applications in the area of heat transfer, such as film cooling of turbine blades or ice removal. The dielectric material used in the fabrication of these devices is essential in determining the device performance. However, the variety of dielectric materials studied in the literature is very limited and the majority of the authors only use Kapton, Teflon, Macor ceramic or poly(methyl methacrylate) (PMMA). Furthermore, several authors reported difficulties in the durability of the dielectric layer when the actuators operate at high voltage and frequency. Also, it has been reported that, after long operation time, the dielectric layer suffers degradation due to its exposure to plasma discharge, degradation that may lead to the failure of the device. Considering the need of durable and robust actuators, as well as the need of higher flow control efficiencies, it is highly important to develop new dielectric materials which may be used for plasma actuator fabrication. In this context, the present study reports on the experimental testing of dielectric materials which can be used for DBD plasma actuators fabrication. Plasma actuators fabricated of poly(vinylidene fluoride) (PVDF) and polystyrene (PS) have been fabricated and evaluated. Although these dielectric materials are not commonly used as dielectric layer of plasma actuators, their interesting electrical and dielectric properties and the possibility of being used as sensors, indicate their suitability as potential alternatives to the standard used materials. The plasma actuators produced with these nonstandard dielectric materials were analyzed in terms of electrical characteristics, generated flow velocity and mechanical efficiency, and the obtained results were compared with a standard actuator made of Kapton. An innovative calorimetric method was implemented in order to estimate the thermal power transferred by these devices to an adjacent flow. These results allowed to discuss the ability of these new dielectric materials not only for flow control applications but also for heat transfer applications.
Investigating the Potential Drag Reduction and Thermal Transport Improvement in Textured Microchannels
Authors: Rabiei Nastaran , McDonough Grace , Hidrovo Carlos H. 
Published: October 2021

Abstract
Over the past few decades, microscale duct flow has been the key element for many applications, such as drug delivery and microelectronics cooling. To enhance the performance of such systems and to save more energy, looking for new ways to control the hydrodynamic and thermal characteristics of the microchannel flow has been of great interest lately. The aim of this research is to gain a better understanding of the flow physics within microchannels with microtextured walls. Therefore, a set of numerical study has been conducted on the combined effect of flow and heat transfer for spanwise rectangular trenches. The surface microstructures increase the wetting surface area, which is supposed to increase friction (skin drag). Recirculation produced inside the grooves, on the other hand, aids in increasing main flow slippage and lowering pressure drop along the microchannel. It is also worth noting that recirculation creates a negative pressure difference in the opposite direction of the flow (pressure drag). The geometrical parameters of the trenches have a significant impact on the trade-off between the drag reducing and drag increasing factors in textured microchannel flow, which is addressed in this research. Furthermore, the textures disrupt the thermal boundary layer, which can boost thermal transport through recirculation mixing. However, the stagnant fluid trapped within the grooves has weak convective heat transfer. So far, the results have been promising and a drag reduction of about 25% has been reported for wide trenches at low Reynolds numbers. Thermal transport enhancement is also possible for some tested geometries when the flow has not achieved the thermally fully development.
A CNN With Deep Learning for Non-Equilibrium Characterization of Al-Sm Melt Infusion Into a B4C Packed Bed
Authors: Aguilar Julio , Sandoval Laura , Rodriguez Arturo , Kumar Sanjay Shantha , Terrazas Jose , Adansi Richard , Kumar Vinod , Bronson Arturo 
Published: October 2021

Abstract
In seeking predictability of characterizing materials for ultra-high temperature materials for hypersonic vehicles, the use of the convolutional neural network for characterizing the behavior of liquid Al-Sm-X (Hf, Zr, Ti) alloys within a B4C packed to determine the reaction products for which they are usually done with the scanning electron microscope (SEM) or X-ray diffraction (XRD) at ultra-high temperatures (&gt; 1600°C). Our goal is to predict ultimately the products as liquid Al-Sm-X (Hf, Zr, Ti) alloys infiltrate into a B4C packed bed. Material characterization determines the processing path and final species from the reacting infusion consisting of fluid flow through porous channels, consumption of elemental components, and reaction forming boride and carbide precipitates. Since characterization is time-consuming, an expert in this field is required; our approach is to characterize and track these species using a Convolutional Neural Network (CNN) to facilitate and automate analysis of images. Although Deep Learning seems to provide an automated prediction approach, some of these challenges faced under this research are difficult to overcome. These challenges include data required, accuracy, training time, and computational cost requirements for a CNN. Our approach was to perform experiments on high-temperature metal infusion under B4C Packed Bed infiltration in a parametric matrix of cases. We characterized images using SEM and XRD images and run/optimize our CNN, which yields an innovative method for characterization via Deep Learning compared to traditional practices.
An Investigation of the Effects of Volume Fraction on Drag Coefficient of Non-Spherical Particles Using PR-DNS
Authors: Mahyawansi Pratik , Lin Cheng-Xian 
Published: October 2021

Abstract
Prediction of the drag coefficient is required in gas-particle multiphase flow modeling and simulation. Experimental data and correlations on the fixed-bed system of spherical particles with high volume fractions for various possible arrangements are available in the literature. However, the effect of volume fraction on the drag coefficient of non-spherical particles is not well studied. In solving the momentum equation, the volume fraction plays a vital role in determining the flow resistances. In this paper, we study the impact of volume fraction in the range of 0.069 to 0.65 on the drag coefficient using the computational fluid dynamics (CFD) simulation of air for Reynold number in the range of 10 to 10000 using particle resolved direct numerical solution (PR-DNS). Regular non-spherical particles such as a cube, tetrahedron, and spheroids are used in this study since their single particle’s drag coefficient data are available in the literature for comparison. For this work, the simulations are carried out in the Ansys Fluent using polyhedral mesh, which consumes significantly less computational time and power. The study showed the sphericity and volume fraction have significant impact on the bed pressure drop and average drag coefficient of the particles in the bed especially in high Reynolds number regime. The bed of the spheroid experiences the lowest drag being the most streamlined particle, and the particles with the edges result in a large drag coefficient due to flow separation at the discontinuity. The vector plots verify this behavior where large wake regions are observed behind the tetrahedron particle.
Design of Gust Wind Tunnel With Unsteady and Shear Main-Flows
Authors: Nishio Yu , Miyazaki Ryotaro , Ogawa Takanobu 
Published: October 2021

Abstract
Micro air vehicles (MAVs) have been developed for many fields. The MAVs usually receive strong impact from a velocity change in time or space, and facilities for aerodynamic experiments of MAVs under a gusty environment have been required. The present study has developed a gust wind tunnel to generate unsteady and non-uniform flows. We developed a small wind tunnel with eight multi-fans and a shutter mechanism at the upstream of the test section. We controlled the outputs of the fans independently and obtained a linear shear layer with an error of 5 percent. The velocity gradient of the shear layer was from 5 to 8 s−1. The shutter mechanisms provided a longitudinal gust with the velocity change from 2 m/s to 10 m/s within 0.3 seconds.
Uncertainty Estimation in CFD Simulations of Erosion for Elbows
Authors: Fallah Shojaie Elham , Sedrez Thiana A. , Darihaki Farzin , Shirazi Siamack A. 
Published: October 2021

Abstract
Computational Fluid Dynamics (CFD) is used extensively in the industry and academia for analyzing the motion of solid particles and the associated solid particle erosion that may occur in various pipe components. However, CFD simulations always carry levels of inherent uncertainties due to the numerical approximations of governing equations, generated grid, and turbulence models. Also, because of the complex nature of solid particle erosion, additional uncertainties are added to erosion prediction simulations. Aspects such as particle size, number of impacts, particles’ initial condition, near-wall mesh effects, forces considered in particle tracking procedures, particle-particle interaction, and near-wall particle-fluid interactions are all possible sources of uncertainties associated with erosion prediction in CFD. Furthermore, unique problems that accompany discrete phase handling and erosion calculation needed for the industrial applications magnify the importance of uncertainty estimation in erosion calculations. Commercially available CFD codes are used with user-developed subroutines to investigate particle erosion prediction uncertainties, numerically in elbows, by considering gas and liquid flow for several pipe sizes. Moreover, different particle sizes, inlet flow velocities, turbulence models, wall functions, and erosion models are examined. According to the ASME’s Verification and Validation (V&V) standard, uncertainties are divided into 3 categories; input, numeric, and modeling. Thus, it is possible to utilize the ASME’s standard as guidance to predict uncertainty for erosion simulations. Furthermore, an extra parameter was considered for uncertainties to account for the uncertainties induced by different simulation procedures and erosion models. The current investigations resulted in developing a framework for estimating uncertainties of erosion simulation. For each simulation result, two bounds (upper and lower) were predicted for erosion. The results show that the Reynolds Stress turbulence model (RSM) and Arabnejad’s erosion model usually predict results corresponding to the lowest uncertainties.
Aerodynamic Performance Evaluation of a Skydio UAV via CFD As a Platform for Bridge Girder Inspection: Phase 1 Study
Authors: Hewlin Rodward L. , Smith Elizabeth , Cavalline Tara , Karimoddini Ali 
Published: October 2021

Abstract
The goal of the proposed work was to analyze the aerodynamic performance of a Skydio 6 unmanned aerial vehicle (UAV) as a supplementary tool for bridge girder inspections. The use of UAVs has become more attractive due to their ability to gather critical information in less time and at a lower cost when compared to traditional bridge girder inspection techniques. In pursuit of this goal, the present work presents aerodynamic performance evaluation results via computational fluid dynamics (CFD) of a Skydio 2 UAV for bridge girder inspection. The study is implemented using the commercially available CFD solver, ANSYS FLUENT (v. 19). The evaluation study utilized an unstructured tetrahedron meshing technique throughout the numerical analysis, with a standard k-epsilon turbulence model. The Multiple Reference Frame (MRF) model was also used to model the rotation of the propellers toward their local reference frame at 6000 revolutions per minute (RPM). This paper presents the numerical modeling methodology as well as a discussion of parametric results. The parametric results presented show reliable moment coefficient and thrust making the Skydio 2 UAV suitable for bridge inspection.
Numerical Analysis of Oil/water Dispersion Interface Prediction in Horizontal Pipe Separators
Authors: Kolla Srinivas Swaroop , Mohan Ram S. , Shoham Ovadia 
Published: October 2021

Abstract
This paper presents the comparative study of experimental, modeling, and simulation results that are performed using commercially available ANSYS Fluent software to analyze the separation kinetics of oil and water in a horizontal separator at various velocities and watercuts. The horizontal pipe separator used in this study has an internal diameter of 0.0762 m and a length of 10.3 m separating oil and water with specific gravities of 1.0 and 0.857 and watercuts ranging from 20 to 90%. The mixture velocities studied are 0.08, 0.13, and 0.20 m/s. Numerical simulations are done using the hybrid Eulerian-Eulerian multifluid VOF model to study the effect of watercut on the creaming of the oil layer and sedimentation of the water layer respectively. As the mixture velocities increased, the initial length of separation increased like experimental results. As the watercut increased, the separation of water enhanced, while the oil creaming improved with the lowering of the watercut as expected. Numerical results showed good agreement for water/dispersion interface predictions for all the conditions studied. The CFD results are compared against experimental results obtained by Othman in 2010 and agree with the trend of separation. The numerical simulations gave insights into the velocity profiles in each of the layers such as creamed oil, sedimented water, and the layer of emulsion that is not separated. Also, the numerical results are validated against the extended Gassies (2008) model incorporating correlation for turbulent time decay and oil volume fraction proposed by Dabirian et al in 2018.
Prediction of Combustion Performance of Biodiesel in Gas Turbine Combustor
Authors: Yadav Priyanka , Yadav Nagendra P. 
Published: October 2021

Abstract
This paper focuses the computational fluid dynamics analysis inside the gas turbine combustor for the combustion of biodiesel and air mixture. The biodiesel (methyl soyate) is made from the vegetable oil (soybean oil). ANSYS fluent is used for Numerical simulation and model adapted Eddy dissipation concept for turbulence, discrete model, k-epsilon (standard), and the species transport. The model was validated and the combustion performance of biodiesel is predicted with an air-assist injector. The fuel spray is created by commercially available airblast atomizer in this study. The strength of recirculation increases with increased in equivalence ratio. The strong corner recirculation was observed at 0.75 equivalence ratio. The higher turbulence kinetic energy is found at the middle of the combustor. The temperature increases with the increase in the equivalence ratio in the flame stable region while it decreases with increases in the equivalence ratio. It was observed that an increase in the equivalence ratio, flame length increases. The profiles of carbon monoxide (CO) and nitric oxides (NOx) emissions can be obtained at 15% atomizing airflow rates, while the total airflow rate kept constant. The NOx and CO emissions are effected mainly by the fuel-air mixing process that the fuel-air mixing process and atomization have the great impact on CO and NOx emissions.