bluuebunny/crossref_metadata_2025 huggingface dataset:
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

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

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

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

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

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

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

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

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

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

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

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.
Physics-Informed Data Augmentation of Experimental Erosion Data Through Generative Adversarial Networks
Authors: Zhang Jun , Li Jamie (Yijie) , Pei Weiping , Shirazi Siamack
Published: September 2024

Erosion is a phenomenon of material removal by particles impinging the walls of materials. Experiment is an important approach to investigate erosion severity and the influences of different physical parameters. However, conducting experiments is expensive and time-consuming. It’s also challenging to collect high quality data due to the scales of the material removal and its sensitivity to the change of external environments. Over the years, research has been conducted at the Erosion/Corrosion Research Center at the University of Tulsa to investigate solid particle erosion in pipelines and fittings. The experiments are conducted with a large-scale boom tower flow loop and erosion data is collected with high accuracy temperature compensated ultrasonic transducers. The efforts have resulted in more than 200 sets of high-quality experimental data under various pipe diameters, particle diameters, sand concentrations and flow velocities. Mining the inherent pattern and/or laws within the data is of great value to guide future process condition selections and experimental tests. More importantly, with the existing data that has covered a wide range of flow, particle, pipe size and sand concentration conditions, machine learning methods can be utilized to augment the data itself so that the new generated data obeys the physical laws and have similar distributions. Generative Adversarial Networks (GANs) is a class of machine learning models designed for generating data. It has a broad application. Data augmentation is an area where it can be applied to generate additional training data when data is limited for later machine learning or deep learning. The feature is of significance to expand erosion databank based on a relatively small high-quality database for subsequent mechanistic modeling. This present work shows how to apply GANs to achieve the goal and the newly generated data are validated with both original data and the data obtained through Computational Fluid Dynamics of which physics of unseen conditions are fully simulated and SPPS which is a semi-mechanistic model developed at E/CRC. The work provides engineers and researchers with a new approach to expand databases and build mechanistic models upon it.
Assessing Particle Concentration in the Breathing Zone of a Receptor Mannequin in an Indoor Environment
Authors: Anvari Amirmasoud , Ahmadi Goodarz
Published: September 2024

This study examined the distribution and dispersion of respiratory droplets in a ventilated office space containing two mannequins with a partition between them. It was assumed that one of the mannequins was speaking and emitting respiratory droplets., The transition k-kl-ω turbulence model was employed to analyze the airflow pattern and the dispersion of droplets in the presence of the partition. The ANSYS-Fluent code was used to simulate the airflow conditions in the room. The Lagrangian particle tracking method was used to evaluate the droplet velocity and trajectories in the room. The Discrete Random Walk (DRW) model was used to simulate the effects of turbulence fluctuations on particle dispersion. The airflow conditions for different ventilation flow rates and dispersion of droplets of different sizes emitted by the speaking mannequin were evaluated. In addition, the concentration of droplets of different sizes near the receptor mannequin was evaluated. Furthermore, the distribution of droplets of varying sizes close to the receptor mannequin was evaluated. The droplet concentrations were evaluated using the two-way coupling technique implemented through ANSYS-Fluent code and a MATLAB Code using the Lagrangian particle tracking approach. The concentration results obtained from the Lagrangian approach are compared with those predicted by the enhanced diffusion model.
Fluid Flow Characteristics of Twin and Gerotor Screw Compressors
Authors: Hsieh Chiu-Fan , Cao Yu-Ji , Lin Yi-Hao , Wang Sheng-Yao
Published: September 2024

The study explores variations in fluid flow characteristics between two types of screw compressors: the twin-screw compressor (TSC) and the gerotor screw compressor (GSC). After generating rotor profiles using mathematical models, 3D fluid analysis models for both screw compressors are constructed using computational fluid dynamics (CFD). To facilitate comparison, the cross-sectional areas in the TSC chamber and the outer rotor of the GSC are designed to be the same, with identical area efficiency and screw rotor helix angles. Under consistent design conditions, the study examines three different rotor lengths (120mm, 180mm, and 240mm) for both GSC and TSC to assess the impact of screw compressor design on output performance and compare their flow characteristics. The evaluation includes output mass flow rate, pressure, temperature, and their fluctuation properties to discern the advantages and disadvantages of the two screw compressor designs. Simulation results indicate that increasing the length of the screw compressor enhances the mass flow rate. However, higher lengths lead to power losses and increased leakage, potentially negatively affecting compressor efficiency. Furthermore, the GSC exhibits a higher outlet average pressure compared to the TSC for the same length, with relatively smaller pressure fluctuations in a suitable rotor length. Additionally, the GSC design achieves a lower stable temperature through a smoother compression process. This smoother compression process ensures a steady fluid flow, resulting in reduced friction and stable temperatures. Overall, the GSC demonstrates several advantages, including a higher flow rate, greater operating stability, lower leakage, reduced power loss, and improved efficiency compared to the TSC across all three rotor lengths.
Using Japanese Animation for Fluid Mechanics Education: Examples From “One Punch Man”
Authors: Ryu Sangjin
Published: September 2024

Visual popular culture provides various engaging examples for teaching STEM (science, technology, engineering, and mathematics). As one genre of visual pop culture, Japanese animation, or anime, has steadily gained popularity in the United States. Since anime is not constrained by reality, this separation from reality offers unique opportunities to use anime to teach the key principles of fluid mechanics. I have been using fluid-mechanics-related examples found in anime not only for formal fluid mechanics education but also for informal STEM outreach activities. In this paper, I present examples found in “One Punch Man.” In this anime, Saitama is a superhero who can defeat any monsters and supervillains with a single punch. However, he cannot kill an irritating mosquito although he swats the insect with his hands. I use this scene as an example to explain the flow caused by a moving object due to the no-slip boundary condition and the stagnation point of the caused flow. Then, I recommend Saitama to use a fly swatter based on the aerodynamics of the fly swatter. The aerodynamics of the swatter head is related to the boundary layer and extended toward the olfactory antenna motion of lobsters. Since Japanese animation is widely enjoyed by people around the world, it has rich potential as a source of novel fluid mechanics examples that connect with students’ interests and thus capture their attention.
An Experimental Study on the Sublimation-Induced Porous Structure Formation in a Freezing-Based Inkjet 3D Printing Method
Authors: Zhang Haipeng , Zhang Xiaoxiao , Liu Yang
Published: September 2024

A colloidal solution is a mixture of small insoluble solid particles with a fluid, widely used as ink solutions in inkjet-based 3-dimensional (3D) printing technology. During the printing process, the liquid solvent is removed via subsequent drying processes, such as evaporation, with only solid particles deposited on the substrate. The printed products’ quality and mechanical properties can be harmed when the particle distribution is non-uniform due to the internal flows occurring in a droplet during evaporation. To address this issue, a freezing sublimation-based printing method was developed in recent year to minimize internal flow-related particle motions during the drying process, which can improve the quality of printing. While the colloidal particles were found to be distributed much more uniformly on substrates using the novel freezing sublimation-based method, it was found that colloidal particles could form 3D porous structures on substrates after the solvent was sublimated. In this paper, an experimental study was conducted to evaluate the particle deposition patterns of 15% (w/v) Pearlitol 100 SD Mannitol water solution droplets under different sublimation conditions. The porous structures formed on substrates after sublimation were visualized using microscopy imaging technology. The results obtained from this study showed that pores formed in printed structures are directly related to the escaping gaseous phase from frozen droplets during sublimation. Smaller and fewer pores are formed when the heating rate during sublimation is slower. Therefore, a slow sublimation process is recommended for the freezing sublimation-based inkjet 3D printing method for producing better quality and higher resolution 3D products.
Development of a Novel Stewart Motion Platform for Wind Tunnel Testing of Floating Wind Turbines
Authors: Laisee Laiba , Aguayza Carlos , Carter Shawn , Liu Yang
Published: September 2024

The utilization of offshore floating wind turbines is anticipated as one of the most sustainable sources of renewable energy. The research on these floating wind turbines requires highly sophisticated and established testing facilities that can produce simultaneous aerodynamic and hydrodynamic loadings on the floating turbines. However, due to the scaling mismatch of the airflow, water-flow, and wave profiles in most of the current test facilities, the laboratory testing of floating wind turbines has been very challenging. The primary focus of the present study is to develop a novel method of testing floating wind turbines in regular wind tunnel facilities. In this paper, we aim to develop a new experimental approach of simulating the floating turbine motions induced by ocean waves using Stewart motion platforms. These motion platforms can generate six degrees of freedom and mimic the motions of linear translations and axial rotations found in a multitude of floating devices. In designing the Stewart motion platform, kinematics was used with rotational actuators in translating the platform and developing a wave generation program for general motion displacement. In addition, multiple types of wave formations and their displacements are generated based on a systematic calculation and coordinate conversions of each individual actuator. The motion platform is capable of translating to nearly 5 cm linearly and reaching a maximum rotation of 15 degrees in both directions individually and simultaneously. The prototype platform model in this paper is used for turbine models about 30 cm in height for testing in a large-scale atmospheric wind tunnel facility. This work can be further developed by harnessing machine learning capabilities of data collection from research performed in wave tanks or field testing. Subsequently, in considering the effects of a floater, further research implementations of a floater’s response are dependent on the properties and behavior of a buoyant structure which leads to a closer accurate model of a floating wind turbine in the ocean.
Asymmetric Wind Turbine Blades: Numerical Investigation of Wake Interactions for Rotors With Non-Identical Blade Loadings
Authors: Sarlak Hamid
Published: September 2024

The inner and outer regions of a wind turbine blade, known as the root and tip, produce powerful vortex structures in the helical vortex system that form the near wake region. Over time and space, these large vortex structures break down to smaller-scale turbulence, which characterizes the far-wake region. The presence of perturbation is one of the means to trigger a faster breakdown of the vortex structures. A faster breakdown of the vortices is considered favorable due to the so-called momentum entrainment from the boundary layer that in turn energizes the flow for the downstream turbines to extract more energy. In this research, we will demonstrate the effects of introducing rotor asymmetries in wake development and dynamics of tip vortex interactions in a cluster of two wind in-line turbines. Simulations are performed by representing wind turbine blades using the blade element method (BEM) based actuator line modeling and large eddy simulation (LES) technique is employed to solve the governing Navier-Stokes equations of motion. Our preliminary investigations suggest that introducing an asymmetry in the rotor can alter wake structures and their downstream development, causing a faster transition into the far wake leading to a higher power density.
Passive Suppression of Diffuser Rotating Stall in a Centrifugal Pump by the Non-Symmetry Diffuser Vane
Authors: Takahashi Mikio , Iwasaki Dai , Konno Shinichi , Ejiri Shinichiro , Miyabe Masahiro
Published: September 2024

Diffuser Rotating Stall (DRS), a fluid instability, often restricts the operational range of diffuser-type centrifugal pumps, requiring countermeasures in industry. Despite various proposed methods for DRS suppression, the optimal approach minimizing pump efficiency reduction remains nonexistent.

In this study, we explored a new DRS suppression method by investigating the mechanism when combining long and short vanes in the vaned diffuser of an industrial pump.

The original vaned diffuser has eight long vanes, with short vanes created by removing the leading edge alternately. Varying short vanes from one to three, we studied the phenomena through experiments and Computational Fluid Dynamics (CFD). Experiments used a closed-loop piping system with a centrifugal pump (specific speed Ns = 138 m3/min, m, rpm = 920 USgpm, ft, rpm). Four pressure sensors in the diffuser passage captured DRS behavior. Incremental valve adjustments from high to low flow (minimum ϕ = 0.002) explored pump performance and DRS occurrence.

Results showed DRS at ϕ = 0.048 for the original diffuser shape, absent at higher flow rates and present at lower ones. With a single short vane, DRS occurred at ϕ = 0.058 without circumferential propagation. Increasing short vanes to two or three prevented DRS until ϕ = 0.010, demonstrating non-symmetric vane effectiveness.

Internal flow analysis using CFD software (Unsteady RANS calculation = URANS) explored time evolution within the diffuser and detailed short vane influences on DRS.
Hydrodynamic Interactions in Fish-Like Robotic Swarms With Flexible Propulsors
Authors: Menzer Alec , Lengkong Theodore , Ni Di , Nagpal Radhika , Dong Haibo
Published: September 2024

In this work computational models of Bluebots, bio-inspired swimming robots that demonstrate 3D maneuverability and collective behaviors, are developed. Flexibility is prescribed to the caudal fins (CF) using a virtual skeleton. The hydrodynamic interactions occurring within in-line arrangements of these Bluebots is investigated by altering the flexion angle of the leader Bluebot caudal fin and a balance between optimizing leader Bluebot (LB) performance and follower Bluebot (FB) wake interaction is identified. Compared to the rigid CF baseline, optimal CF flexion for the thrust of LB leads to higher negative pressure within generated vortex structures and narrowing of the thrust jet which impinges along the entire body of the FB. Further increase of the LB flexion creates even stronger negative pressure regions while widening the thrust jet behind the leader. These flow conditions are more favorable for the FB as the accelerated flow only interacts with the anterior of the robot body and the stronger negative pressure supplies stronger anterior suction. The ability of the FB to sense these flow changes is also important, and the pressure sensor data on the FB exhibits differences between the cases. Near the anterior surface, the sensor pressure data provides insight to the varying vortex ring strengths for higher LB CF flexion, meanwhile, such differences are not as obvious when examining probe data further downstream on the FB.
Surface Roughness Effects on the Hypersonic Flow Over Double-Wedge Bodies With a Blunt Leading Edge at Different Aft-Wedge Angles
Authors: Kumar Piyush , Rodriguez Arturo , Adansi Richard O. , Kumar Vinod , Moreno Esperanza , Alonzo Eric M.
Published: September 2024

Recently, blunt bodies have been studied numerically through computational fluid dynamics due to their ability to maintain higher heating loads at hypersonic speeds due to their heat distribution on a larger volume than their counterparts: sharp bodies. For this study, we have simulated a blunt double-wedge geometry using different fluid flow models, such as turbulence models: k-omega and laminar, to be compared against varying levels of surface roughness. Additionally, we compare the sharp cone with the aforementioned leading-blunt edge bodies, both with double wedges, at varying degrees of surface roughness. We then find that a leading blunt edge can alter the shock interaction pattern compared to its sharp geometrical counterpart. We aim to study aerothermal heating under different conditions without incorporating the ablation effects during hypersonic flight for extended periods that depend on the Mach Number. This study approximates the aero-thermal heating the double-cone wedge geometry will experience under different hypersonic speeds on turbulent fluid flow regimes and surface roughness values. We know that turbulent fluid flow will create higher aero-thermal heating and drag than laminar fluid flow. We estimate transition effects on the double wedge blunt geometry by comparing the laminar and turbulent fluid flow regimes. This paper will explicitly provide those values from computational fluid dynamics studies. We have performed benchmark studies and have compared our studies against literature values against other geometries.
Sustainable Building Energy Modeling: the Synergistic Interplay of Urban Heat Island, Heat Waves, and Climate Zones
Authors: Najian Maede , Goudarzi Navid
Published: September 2024

This study explores the impact of climate phenomena and their interactions on evaluating building energy analysis. The Urban Heat Island (UHI) is highlighted as a key parameter affecting the microclimate around buildings, influencing energy consumption, and thermal comfort. This study also examines other relevant factors such as Heat Waves (HWs) and their interaction with UHI and climate zones. Employing the Weather Research Forecasting (WRF) model and statistical analyses, the research focuses on Singapore and Australia to investigate the relationships between UHI, HW, and climate zones. Our findings indicated that climate zones and the frequency of climate phenomena play a pivotal role in determining the impact of HW on UHI. Although HWs had a limited effect on UHI in Singapore, data from Sydney showed varied UHI responses to HWs. Understanding these complex interactions is crucial for designing high-performance buildings and improving building energy modeling tools.
Experimental Investigation of Water Droplet Erosion on Metallic and Non-Metallic Materials
Authors: Anderson Keldon , Azimy Noushin , Lichty Emmelia , Karimi Soroor
Published: September 2024

Water droplet erosion (WDE) is a complex phenomenon that has been investigated for nearly a century. This form of erosion affects a wide range of energy industries from steam turbines and natural gas pipelines to wind turbine blades. The moving droplets impacting at a high relative speed create a high surge in surface pressure on the impacted material and damage the surface. The damage removes materials and can compromise strength for steam turbines and pipelines or affect the lift and drag forces on wind turbine blades. Research on WDE has been ongoing for decades with a majority of the reported results focused on metallic material testing and qualitative analysis comparing methodologies or surface conditions. The ongoing research at The University of Tulsa is conducting experiments with a variety of materials while exposed to an environment where water droplet erosion occurs. Impact velocity and droplet sizes are controlled within the facility and ongoing research with particle image velocimetry (PIV) is in use to characterize the falling droplets. Stainless steel 316, Aluminum 6061, and a variety of non-metallic materials are tested for a variety of conditions. The mass of each specimen is tracked and recorded at set intervals to determine the erosion ratio and erosion rate. Various other factors such as flowrate and rotational velocity are determined before testing as well as the percentage of droplets which impact the surface is determined with the use of a highspeed camera. Scanning electron microscopy (SEM) is also utilized to examine the material’s surfaces before and after testing to investigate the severity of erosion by water droplets. One impact velocity and one impact angle are set for all tested materials. These data points will be the starting point for future tests and modeling work to predict water droplet erosion based on simple factors.
Spin Coating on Freeform Surfaces: A Numerical Study
Authors: Shan Yujie , Mao Huachao
Published: September 2024

Spin coating on flat substrates is a well-understood fluid phenomenon, creating uniform thin films with microscale and nanoscale thicknesses. It is widely used in the microscale and nanoscale fabrication of functional devices. Beyond flat substrates, there is an increasing manufacturing demand for fabricating micro/nanoscale thin films on non-flat substrates, such as spherical and freefrom surfaces. However, it is still challenging to model spin coating on a non-flat substrate. This paper numerically models the spin coating on a freeform substrate as a laminar flow. The centrifugal force from spinning was modeled as a volume force proportional to the spin coating speed square and radius. Various initial thicknesses were simulated and compared. A two-way sinusoidal surface was used as the freeform surface. The simulation results showed that the coating thickness converged to an asymptotic solution, regardless of the initial coating conditions. Also, similar to the spin coating on a flat surface, we found the thickness of the spin coating on a non-flat surface was halved when the spin coating time was increased to four times. These surprising results produce a predictable thin film coating on the freeform surfaces, which enables microfabrication on the freeform substrate.
Signal flow in the NMDA receptor–dependent phosphoproteome regulates postsynaptic plasticity for aversive learning
Authors: Funahashi Yasuhiro , Ahammad Rijwan Uddin , Zhang Xinjian , Hossen Emran , Kawatani Masahiro , Nakamuta Shinichi , Yoshimi Akira , Wu Minhua , Wang Huanhuan , Wu Mengya , Li Xu , Faruk Md Omar , Shohag Md Hasanuzzaman , Lin You-Hsin , Tsuboi Daisuke , Nishioka Tomoki , Kuroda Keisuke , Amano Mutsuki , Noda Yukihiko , Yamada Kiyofumi , Sakimura Kenji , Nagai Taku , Yamashita Takayuki , Uchino Shigeo , Kaibuchi Kozo
Published: September 2024

Structural plasticity of dendritic spines in the nucleus accumbens (NAc) is crucial for learning from aversive experiences. Activation of NMDA receptors (NMDARs) stimulates Ca
2+
-dependent signaling that leads to changes in the actin cytoskeleton, mediated by the Rho family of GTPases, resulting in postsynaptic remodeling essential for learning. We investigated how phosphorylation events downstream of NMDAR activation drive the changes in synaptic morphology that underlie aversive learning. Large-scale phosphoproteomic analyses of protein kinase targets in mouse striatal/accumbal slices revealed that NMDAR activation resulted in the phosphorylation of 194 proteins, including RhoA regulators such as ARHGEF2 and ARHGAP21. Phosphorylation of ARHGEF2 by the Ca
2+
-dependent protein kinase CaMKII enhanced its RhoGEF activity, thereby activating RhoA and its downstream effector Rho-associated kinase (ROCK/Rho-kinase). Further phosphoproteomic analysis identified 221 ROCK targets, including the postsynaptic scaffolding protein SHANK3, which is crucial for its interaction with NMDARs and other postsynaptic scaffolding proteins. ROCK-mediated phosphorylation of SHANK3 in the NAc was essential for spine growth and aversive learning. These findings demonstrate that NMDAR activation initiates a phosphorylation cascade crucial for learning and memory.
Influence of Simulation Box Sizes on the Stability of Lysozyme Dimers and Hexamers in a Crystallization Solution
Authors: Kordonskaya Yu. V. , Garipov I. F. , Timofeev V. I. , Marchenkova M. A. , Dyakova Yu. A. , Pisarevsky Yu. V. , Kovalchuk M. V.
Published: September 2024

The effect of the simulation box size on the stability of lysozyme dimers and hexamers formed in its solution before crystallization is studied by molecular dynamics. The behavior of these oligomers in boxes of different sizes is simulated, and their stability is assessed. It is shown that increasing the simulation box does not lead to refinement of the simulation results. The dimer stability weakly depends on the box sizes, while hexamers dissociated in all boxes considered, which is consistent with small-angle scattering data. The minimum distance between the protein and the box edge, at which the results of modeling oligomer behavior in crystallization solutions are reliable, is determined (1 nm).
The 2023 wildfires in British Columbia, Canada: impacts, drivers, and transformations to coexist with wildfire
Authors: Daniels Lori D. , Dickson-Hoyle Sarah , Baron Jennifer N. , Copes-Gerbitz Kelsey , Flannigan Mike D. , Castellanos-Acuna Dante , Hoffman Kira M. , Bourbonnais Mathieu , Wilkinson Sophie L. , Roeser Dominik , Harvey Jill E. , Laflamme Jocelyne , Tiribelli Florencia , Whitehead James , Leverkus Sonja E.R. , Gray Robert W.
Published: September 2024

In 2023, all regions of British Columbia (BC) experienced record-breaking fire weather and wildfires, with extreme behavior and social-ecological effects. In total, 2245 wildfires burned 2840 545 hectares. Contemporary wildfires are the culmination of a century of altered human–forest–wildfire relationships, exacerbated by climate change. Transformative change is urgently needed for the ecosystems and communities to be resilient to wildfire. We present six interrelated strategies needed to amplify the pace and scale of change in response to recent wildfire extremes: (1) Immediately diversify wildfire response strategies and restore the ecological and cultural role of fire in BC’s ecosystems. (2) Invest in suppression capacity at local and national scales. (3) Support innovations to overcome the economic barriers for mitigating risk and building resilience within communities and the wildland-urban interface. (4) Apply landscape fire management to drive a paradigm shift in forest management to increase ecological resilience to wildfire. (5) Transform wildfire governance to support collaborative and community-based solutions. (6) Strengthen expertise and capacity to uplift diverse ways of knowing, managing, and coexisting with fire. These strategies, combined with bold policy and governance changes and supported by sustained funding programs, provide a holistic approach to transform management and coexist with wildfire.
Generating Synthetic Data for Medical Imaging
Authors: Koetzier Lennart R. , Wu Jie , Mastrodicasa Domenico , Lutz Aline , Chung Matthew , Koszek W. Adam , Pratap Jayanth , Chaudhari Akshay S. , Rajpurkar Pranav , Lungren Matthew P. , Willemink Martin J.
Published: September 2024

Synthetic data can address data scarcity and privacy issues, but generating realistic, identity-free medical images remains a challenge; adequate legislation with clinician involvement is necessary to ensure responsible use and clinical relevance and trust.
Development and Validation of a Contrast-Enhanced US VI-RADS for Evaluating Muscle Invasion in Bladder Cancer
Authors: Han Jing , Lin Min , Lin Qingguang , Guo Ruohan , Liao Ying , Wu Zhiming , Ye Yunlin , Guo Zhixing , Yao Kai , Li Lingling , Zhou Jianhua
Published: September 2024

A Vesical Imaging Reporting and Data System developed based on features on contrast-enhanced US images acquired via transabdominal and intracavity approaches showed good performance and interreader agreement for the assessment of muscle invasion in patients with bladder cancer.