bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Computational Assessment of Free Surface and Mount Effects in Towing Tank Experiments on Flow Over a 6:1 Prolate Spheroid
Authors: Johnson Samuel M. , Chyczewski Tom , Schmitz Sven , Yang Xiang 
Published: September 2024

Abstract
Pre-test simulations were performed of the high Reynolds number 6:1 prolate spheroid towing tank experiments to be carried out by the Office of Naval Research. The two Reynolds numbers of interest in the experiments were investigated, Re = 11.74e6 and Re = 1.47e6, with the prolate spheroid inclined 0°, 10°, 20°, and 45° with respect to the incoming flow. Reynolds-Averaged Navier-Stokes simulations were conducted for three flow configurations. The first included a 6:1 prolate spheroid mounted to a sting and strut under a free surface. The second configuration removed the mounting geometry, and the last configuration omitted the mounting geometry and the free surface. Increments in the forces and moments acting on the prolate spheroid were calculated to quantify the impact of the free surface and mounting geometry on the force measurements in the towing tank experiments. The addition of the free surface resulted in relatively small increments except for the side force at 45° incidence. Increments in the forces and moments due to the addition of the strut were generally larger, particularly at high incidence angles, and reached up to 5% of the total values.
Why to Select Wastewater Pumps in Wastewater Treatment Plants?
Authors: Tripolt Yvonne , Thamsen Paul-Uwe 
Published: September 2024

Abstract
Wastewater is by definition a medium which describes used water, not referring if it is caused by private homes, industries or communes. In its raw condition it is pumped or transported by gravity to the next wastewater treatment plant (WWTP).
The wastewater treatment process is basically divided into a mechanical, biological and optional also into a chemical treatment stage.
The transportation of the media inside of WWTPs is done by different pump types. Most common are wastewater pumps with special impellers and positive displacement pumps, which are mainly used in the sludge line of the treatment process.
Compared with other industries, e.g. the desalination or pulp and paper industry where each process step is defined by a certain pump type, there is no clear strategy available for the pump selection in the wastewater treatment process.
The selection of the pumps is done by experience of planning offices as well as by the experience of the sewage plant operators. There is no standard available, which recommends a certain pump type for a certain application or process step.
Taking this into consideration, pumps are selected, which may not be the best choice for a certain pumping position based on efficiency, wear or reliability.
Based on this, three wastewater treatment plants are analyzed according to the process, different pump positions and the related pumped media.
The analysis shows that different pump types are used for the same media. Some of them have a higher or lower failure potential as well as a different efficiency level. In some pumping positions where the media is already precleaned also the question of selecting wastewater hydraulics can be critically scrutinized.
For one WWTP also a power and energy saving analysis is done. Installed hydraulics are changed theoretically with hydraulics at a higher efficiency level. An energy saving potential of about 2% compared to the whole power consumption of the installed pumps is calculated.
By doing this analysis the requirement of having a standard available for the right pump selection in wastewater treatment plants is figured out. Wastewater hydraulics are in some positions not the best choice related to the energy saving potential.
Investigations of Lift to Lift-To-Drag Ratio of an Optimized Airfoil With a Round Leading Edge and a Scorpion Stinger Trailing Edge
Authors: Torres Leovigildo , Rahai Hamid 
Published: September 2024

Abstract
Steady numerical simulations of an optimized airfoil with and without endplates using a half-cylinder at the leading edge and a scorpion stinger-shaped trailing edge at two different trailing angles have been performed to investigate the effects of these geometrical modifications on its lift-to-drag (L/D) ratio at 0- and 20-degrees angles of attack (AOA). The goal of the investigations was to improve the performance of a high-efficiency vertical-axis wind turbine at higher AOA. The investigations were performed at a freestream mean velocity of 10 m/s corresponding to a Reynolds number based on the airfoil chord length of approximately 2.0 × 105. Four cases of 1. the baseline airfoil, 2. the baseline airfoil with a round leading edge, 3. Case 2 and a tail at 20 degrees counterclockwise (ccw) angle (positive angle), and 4. Case 2 and a tail at 20 degrees clockwise (cw) angle (negative angle) was investigated. Results showed with the round leading edge the L/D decreases slightly at 0 AOA but increases by 28% at 20 degrees AOA for no endplates and no significant change with endplates as compared with the corresponding values for the baseline model. For cases 3 and 4 at 0 AOA, the corresponding L/D decreased and increased by respectively 28% and 11.5% without endplates and 7% and −15% with endplates. However, at 20 degrees AOA, the L/D values for cases 3 and 4 are increased by respectively 31% and 19.5% without endplates when compared with the L/D of the baseline model. Details of the mean velocity and pressure contours around the airfoil show that with a round leading edge, increasing AOA increases flow acceleration and pressure on respectively suction and pressure surfaces resulting in increased L/D. The stinger tail in an upward or downward configuration could be effective in increasing the L/D if it acts as a compliant tail rotating from negative to positive angles with increasing AOA.
A Lattice Boltzmann Model for Low-Temperature Plasma Dynamics
Authors: Chen Leitao 
Published: September 2024

Abstract
Low-temperature plasmas are widely used in propulsion systems, advanced manufacturing, biomedical engineering, and many other applications. Such a problem is extremely difficult to simulate due to its physical complexities in three aspects: multi-physics, multi-scale, and highly non-equilibrium. In order to address these three challenges at the same time, a lattice Boltzmann model is developed for three-species low-temperature plasma in this paper, which is completely different from the conventional models based on magnetohydrodynamic equations. Three different numerical cases are simulated and studied in this paper. The results show that the developed model is highly accurate in the simulation of the fundamental diffusion mechanism. In addition, it can reproduce the correct effects of electrostatics and external electromagnetic field, which are two important factors in low-temperature plasma dynamics.
Aerodynamic Analysis of a Small Scale Powered Autonomous Aircraft Employing a KFm2 Modified NACA 2412 Airfoil
Authors: Loza Nolan-Pascal , Ellerbe Michael , Mahjoob Shadi 
Published: September 2024

Abstract
Powered autonomous aircraft can fly under an automatic control system without intervention from a pilot, which is significant for firefighting applications in today’s world. Small, capable, and cost-effective, they can be used to survey an area in more detail and closer to the ground than traditional aircraft and can even deliver humanitarian or fire-suppression payloads. In this work, a small-scale powered autonomous aircraft employing a KFm2 modified NACA 2412 airfoil is designed and analyzed. The conventional airfoils generally follow a teardrop shape, with the interior structure drastically increasing weight. A flat plate design reduces the weight, however, it drastically increases the parasitic drag from exposed avionics components on the surface and does not produce useful lift. The KFm2 airfoil modification is a hybrid of a flat plate and a conventional airfoil (NACA 2412), reducing the weight while maintaining the lift capability of the original airfoil. The KFm2 modified airfoil has a stepped profile where the step is located at the 50% chord length, and the height of the step is 7% of the chord length. The flow field characteristics and aerodynamic performance of this powered autonomous airplane are investigated numerically at different angles of attack (0°, 3°, 5°, 7°, 9°, and 11°) and velocities (6.1 m/s, 12.2 m/s, and 18.3 m/s). A similar study is performed on a small-scale aircraft with an unmodified NACA2412 airfoil to compare the effect of airfoil design at different velocities and angles of attack. For numerical modeling, ANSYS Fluent is employed and the SST K-Omega turbulence model is used for turbulence modeling. A grid independence study is performed and validation study is conducted against experimental data in literature. The results indicate the advantage of the hybrid geometry of the airfoil by increasing the lift force while reducing weight, making it a prime candidate for small powered autonomous aerial vehicles.
Characterizing Air Entrainment at the Gas-Liquid Interface in Stirred Tank Reactors
Authors: Al-Subaey Mohammed Y. , Passalacqua Alberto , Heindel Theodore J. 
Published: September 2024

Abstract
Air entrainment, or surface aeration, is common when the shear between a gas and liquid region is significant. Air entrainment is found in wind-driven flows at the gas-liquid interface of mixing systems and small and large-scale fermentation tanks. This gas-liquid mixing forms a multiphase flow, either promoting the separation of low-density components in a mixture or increasing oxidation, both of which could disrupt the yield of a fermentation process. This study utilizes a standard stirred tank reactor (STR) equipped with a Rushton-type disc turbine impeller and baffles to examine air entrainment at the gas-liquid interface. High-speed backlit imaging is employed to visualize and characterize the air entrainment. The impeller speed and distance between the impeller and the static liquid height significantly impact the amount of air drawn into the system. Substantial surface deformation is observed as a function of impeller speed and location, leading to different surface aeration mechanisms. An average imaging technique was used to characterize air entrained in the system. The results also show the fluid height and depth of entrained air penetration is affected by the impeller speed and location. Recommendations to quantify air entrainment magnitude due to surface aeration will be outlined and will be the focus of future work.
Developments in Taylor Cone Formation: Operation and Testing of Different Liquids
Authors: Moreira Miguel , Rodrigues Frederico , Páscoa José 
Published: September 2024

Abstract
In recent years, the scientific community has focused on Taylor cone formation, a captivating phenomenon at the intersection of fluid dynamics and electricity. This event, induced by a high electric field on a liquid meniscus, produces charged microjets with applications in electrospray ionization, 3D printing, and biomedical research. This paper explores the intricate dynamics of Taylor cone formation, emphasizing the interplay of liquid properties, surface tension, viscosity, and electrical conductivity. By systematically altering liquid properties, such as viscosity and surface tension, the research aims to understand their impact on Taylor cone formation. Surface tension plays a pivotal role in dictating the cone’s initial shape and stability, with lower tension promoting easier cone formation. Viscosity influences cone morphology, while electrical conductivity affects charge distribution, impacting droplet size and charge density. Balancing electric field strength, liquid characteristics, and electrode configuration is crucial for efficient atomization. Meticulous experiments reveal the profound impact of liquid properties on Taylor cone stability and shape, showcasing the transformative potential of this phenomenon in microscale fluid flow manipulation. Controlling surface tension emerges as a powerful tool, allowing for the regulation of microjet size and uniformity, opening possibilities for diverse applications and advancements in drug delivery, inkjet printing, and microencapsulation.
Interaction Between Capillary Waves and Hydrodynamic Turbulence in a Two-Layer Oil-Water Flow
Authors: Giamagas Georgios , Zonta Francesco , Roccon Alessio , Soldati Alfredo 
Published: September 2024

Abstract
We use pseudo-spectral Direct Numerical Simulation (DNS), coupled with a Phase Field Method (PFM), to investigate the turbulent Poiseuille flow of two immiscible liquid layers inside a channel. The two liquid layers, which have the same thickness (h1 = h2 = h), are characterized by the same density (ρ1 = ρ2 = ρ) but different viscosities (η1 ≠ η2), so to mimick a stratified oil-water flow. This setting gives the possibility to study the interplay between inertial, viscous and surface tension forces to be studied in the absence of gravity. We focus on the role of turbulence in initially deforming the interface and on the subsequent growth of capillary waves. After an initial transient, we observe the emergence of a stationary capillary wave regime. Capillary wave propagation and interaction is studied by means of a spatiotemporal spectral analysis and compared with previous theoretical and experimental results. The computed power spectra of wave elevation are in line with previous experimental findings and can be explained in the frame of the weak wave turbulence theory. At wave scales larger than the turbulent forcing range the observed scaling of the one-dimensional wavenumber spectrum suggests an energy equipartition regime (k−1), which is predicted by theory and has been recently observed in experiments with capillary wave turbulence in microgravity. At wave scales directly forced by hydrodynamic turbulence, an initially milder slope (k−4) of the wavenumber spectrum is followed by a sharper decay (k−6) of wave energy at larger wavenumbers, with the transition taking place near the Kolmogorov-Hinze critical scale, where surface tension forces and turbulent inertial forces are balanced.
Adjoint-Based Topology Optimization for Hydraulic Performance Improvement in Double-Suction Volute Pump
Authors: Chen Szu Yung , Shimizu Shunsuke , Watanabe Hiroyoshi 
Published: September 2024

Abstract
The increasing demand for high-speed and miniaturized pumping solutions, as well as the need for high efficiency performance, has made a crucial aspect of the double-suction volute pumps design in modern industrial systems. To achieve these goals, the most important requirement is to design the suction passage to generate uniform velocity distribution and pre-rotation to ensure the incidence matching to the blade angle of the impeller leading edge. Previous studies proposed the optimization design procedure of a double-suction pump using DOE (Design of Experiment) with limited design parameters to improve the pump hydraulic efficiency. However, due to its three-dimensional curved free surface configuration, defining the hydraulic shape of suction passage in limited design parameters is challenging.
To address this issue, this study introduced the adjoint-based topology optimization method to optimize the suction passage of the double-suction volute pump. This method aims to reduce the computational cost because it is independent from the number of design variables. To control the flow distribution at the outlet of the suction passage, the objective functions such as velocity component and flow angle deviation were implemented, ensuring the flow pattern matching and maximum impeller efficiency. Furthermore, the objectives, such as total pressure loss minimization and flow uniformity were also chosen. A three-dimensional RANS equation was used to solve both flow fields and adjoint dual fields, and the results were validated through numerical simulation and experimental testing.
The results showed that the optimal design by topology optimization improved the flow uniformity and the total pressure loss inside the suction passage was reduced, leading to the improvement of suction performance and a slight increase in pump efficiency by 0.2% at the design flow rate compared with the baseline design.
Overall, this study demonstrates that incorporating velocity components and pre-rotation flow angle objectives in topology optimization could improve the hydraulic performance of double suction pumps and provide valuable insights for designing more effective and reliable flow passage in a range of applications.
Comparison of the Flow Behaviour Around a Wedge-Shaped Bluff Body With and Without Upwind Liquid Spray
Authors: Kellogg Cody , Siddiqui Kamran , Chishty Wajid 
Published: September 2024

Abstract
The current work experimentally examines the airflow behaviour around a wedge-shaped bluff body. It focuses on comparisons between the baseline case of the bluff body in an airflow and four cases where a counterflow water spray is added upstream of the bluff body. The cases are distinguished using momentum flux ratios of 0 (no spray), 13, 26, 51, and 98 by varying the water velocity and maintaining the airflow constant. The experiments are performed in a low disturbance wind tunnel with a spray bar 22.3 cm upstream of the bluff body. The bluff body has a height of 5.5 cm, thus creating a blockage ratio of approximately 20%. Data is acquired using a Particle Image Velocimetry (PIV) system. Image pairs are processed to create two-dimensional velocity fields that are further processed to better understand the flow behaviour. Influence of the spray injection on the mean velocity and turbulent kinetic energy (TKE) is investigated. The presence of the spray causes a decrease in the mean velocity around the leading edge, sides of the bluff body, and the expanding wake region as the momentum flux ratio increases. The TKE decreases in the wake region and creates an asymmetric field with the main recirculation zone of the highest TKE moving higher from the centerline of the bluff body as the momentum flux ratio increases. Velocity and TKE vertical profiles taken at the same locations show the main variations in their fields along the bluff body upper edge and in the wake region. The water droplets have a significant impact towards causing dampening of the mean velocity and the TKE magnitudes throughout the regions near the bluff body and in the wake.
Numerical Investigation of Blocked Microchannel Heat Sink Configurations With Porous Fins
Authors: Rodrigues Frederico , Lopes Rute , Francisco Marcelo , Páscoa José , Abdollahzadehsangroudi Mohammadmahdi 
Published: September 2024

Abstract
The fast evolution of electronic devices and focus on their miniaturization and compactness, is increasing the demand of more efficient cooling technologies. Microchannel Heat Sinks (MCHSs) are a key technology for small size electronics cooling with still a great margin of improvement. Therefore, the current study investigates the implementation of blocked MCHS with porous fins with the aim of improving the crossflow in the porous media and, with that, improve the thermal performance. Test cases with inlet and outlet alternately blockage of 25%, 50% and 100%, are numerically studied and the results are compared with conventional MCHSs with solid and porous fins. The various test cases analyzed in terms of velocity and temperature distribution, pressure drop, thermal resistance, Nusselt number and Performance Evaluation Factor (PEF). The findings of the current work show that the implementation of the blocks along with porous fins effectively decreases the thermal resistance and enhances the Nusselt number. However, the presence of the blocks leads to an undesired increase of the pressure drop which, in turn, increases the friction factor and negatively impacts the combined thermal-hydraulic performance.
Using Brightfield Microscopy to Assess the Balloon Expansion Performance of a Microfluidic Cell Compression Device
Authors: Emeigh Carson , Ryu Sangjin 
Published: September 2024

Abstract
Previously, we used photolithography and soft lithography to make a microfluidic cell compression device with a thin layer of polydimethylsiloxane (PDMS) for use with mechanobiological studies. When the microchannel was pressurized, the thin PDMS layer deformed and inflated like a balloon. Cells embedded within hydrogel scaffolds were placed on the balloons and, when inflated, were compressed between the balloon and a glass plate. The balloon’s inflation height played a key role in the amount of compression cells experienced, and understanding the inflation height of the microfluidic balloons is key to assessing the performance of the cell compression device. The device fabrication was then improved by utilizing 3D printed molds.
In this study, a microfluidic cell compression device fabricated with a 3D printed mold, soft lithography, and spin-coating was investigated. Each balloon’s height and diameter were measured using brightfield microscopy. The device’s fabrication method was slightly altered to improve balloon diameter control, and thus, balloon height control. Hydrostatic pressure was used to improve the control and steadiness of the applied pressure. We found that brightfield microscopy-based height measurements were repeatable and were validated using side-view imaging. The obtained height measurements were then compared with previously obtained data and showed qualitative agreement with confocal laser scanning microscopy. Although there was disagreement between the heights measured with brightfield microscopy and confocal laser scanning microscopy, brightfield microscopy imaging was preferred due to its low cost, time efficiency, and accessibility.
An Evaluation of Hybrid RANS-LES Turbulence Modeling on Vortex Shedding From Complex Turning Vanes
Authors: Hayden Andrew P. , Untaroiu Alexandrina , Gillespie John , Hefner Cole , Lowe Todd 
Published: September 2024

Abstract
Complex turning vanes are commonly implemented within advanced turbomachinery systems used to mitigate or generate secondary velocity distortion for ground testing aircraft engines or fan rigs. The vanes generate large-scale vortex structures at the trailing edge region which shed and convect downstream to the neighboring stages and components. This process, known as trailing edge vortex shedding, can induce unwanted vibrations and performance losses if not accurately characterized during design phases. The current work aims to evaluate a hybrid Reynolds-Averaged Navier-Stokes (RANS) and large eddy simulation (LES) turbulence model in the prediction of trailing edge vortex shedding from StreamVane distortion generators at Reynolds numbers on the order of 105. The results are directly compared to unsteady RANS predictions and time-resolved particle image velocimetry measurements acquired in previous studies. The comparisons reveal significant qualitative differences between the large-scale wake structures due to the resolved integral scales of the hybrid model. For certain vane configurations containing highly unstable wake flows in the spanwise direction, the hybrid model improved the shedding frequency predictions by more than 11%. However, the hybrid model only marginally improved the frequency predictions by 0.4% for more stable, albeit more complex, wake flows.