bluuebunny/crossref_metadata_2025_split huggingface dataset:
A CFD Study on the Effects of Sand Particle Size on Erosion of an Elbow
Authors: Haider Ghulam , Sedrez Thiana , Shirazi Siamack A. 
Published: September 2022

Abstract
During production operations from oil and gas condensate wells, sand particles also travel with the raw petroleum products. These sand particles impact the walls of transportation infrastructure and erode the wall thickness. This continuous degradation of wall thickness can result in leakages which has severe implications for production and safety. These sand particles can be of various sizes such as 300, 75, and 25 microns. Most of the studies on this phenomenon of solid-particle erosion focus on bigger particles such as 300-microns. Similarly, sand management techniques such as sand screens and gravel packs are used to control sand are specifically designed for bigger particles. However, recently the aging reservoirs are shedding small particles. These small particles can pass through these controls. Furthermore, small particles can block a portion of the sand screen, causing high velocities in other sections which can cause erosion of the sand screen openings allowing larger particles to pass through which in turn cause more erosion. Furthermore, these small particles are highly susceptible to turbulent regions of flow and can cause severe erosion in these regions. Hence, it is critically important to understand the effect of particle size on erosion behavior such as the location of maximum erosion, particle trajectories followed by various sized particles, and locations of maximum erosion. This study investigates the effect of particle size on erosion. Small particle erosion is more severe in gas-dominated multiphase flows such as annular and mist flows than liquid-dominated bubbly and slug flows. A 90-degree standard elbow is used in the analysis because of its high erosion vulnerability and its importance in pipeline applications. This is because the flow changes direction in this kind of geometry which has complex implications for erosion. Furthermore, the effects of particle size on erosion ratio and its distribution in pipe bends are discussed. The CFD results of larger particles agree better with experimental data than for smaller particles utilizing existing erosion models.
A Study of Second Moment Closure Modeling for Stratified Wakes Using DNS Ensembles
Authors: Jain Naman , Huang Xinyi , Yang Xiang , Kunz Robert 
Published: September 2022

Abstract
Buoyant wakes are widely encountered in ocean environment and undersea vehicle flows. These are typically characterized by high Reynolds (Re) and Froude (Fr) numbers, so turbulence resolving CFD models of such flows, i.e., Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES), require significant computational resources. Therefore, Reynolds-Averaged Navier-Stokes (RANS) based models are attractive for these configurations, but their performance hinges on numerous modeling assumptions. The inherently complex dynamics of stratified systems render eddy-viscosity-based modeling inappropriate. RANS Second-Moment Closure (SMC) based modeling is more suitable for such complex systems because they account for flow anisotropy by solving the transport equations of important second-moment terms. For stratified flows, turbulent density fluctuations and their auto- and velocity cross-correlations are dynamically important. Accordingly, at the SMC level of modeling, eleven transport equations are solved, and a range of sub-models are implemented for diffusion, pressure strain and scrambling, and dissipation, in the Reynolds stress, density flux, variance, and dissipation transport equations.
In this work, we study the stratified wakes of axisymmetric towed bodies using SMC and DNS. Sub-models in the SMC are evaluated in terms of how well their exact Reynolds averaged form impact the accuracy of the full RANS closure. An ensemble average of 100 DNS realizations is conducted to obtain converged higher-order statistics for direct comparison. For a stratified towed wake at Re = 10000 and Fr = 2, RANS successfully captures the peak mean defect velocity and wake width evolution when accurate initial conditions are provided from DNS. However, RANS over-predicts the wake height, and turbulent kinetic and potential energies, and exhibits larger amplitude oscillations and slower decay rates. Also, RANS predicts a near isotropic decay of normal Reynolds stresses in contrast to the anisotropic decay returned by DNS. The DNS data also provide important physics and modeling insights related to the inaccuracy of the dissipation rate isotropy assumption, and the non-negligible size of pressure-diffusion terms. These results lead to several important recommendations for SMC modeling improvement.
Clogging Behavior of Different Impeller Types of Sewage Pumps at Speed Variation
Authors: Müller Enrico , Pensler Thomas , Thamsen Paul Uwe 
Published: September 2022

Abstract
Nonwoven wet wipes are the most hazardous substances that cause clogging of sewage pumps, due to the increasing amount of wet wipes in sewer systems. The clogging of sewage pumps causes a considerable additional economic expense every year, which can be avoided by well-functioning sewage pumps. An additional problem to be considered is the reduced water consumption, which increases the concentration with the increased use of wet wipes in the wastewater. With demand-driven pumping of wastewater due to large diurnal fluctuations, pumps are speed-controlled as the price of frequency converters decreases.
The current advice when speed variation in wastewater pumps are used, affects the minimum velocity in the pipes. The study investigates how speed influences the clogging phenomena of wastewater pumps. The pumps have been approved at a test stand in a laboratory that is designed for functional tests on wastewater pumps. During the test the operating behavior is logged and indicates how clogging influences the pumping performance. Those tests have been done for a long-time performance test, in which the wastewater is pumped in a loop for 60 Minutes.
During the test procedure the clogging is observed with a high speed camera, so that the clogging on the impeller can be visualized. This helps to understand the clogging and self-cleaning ability of impellers better. The behavior of the susceptibility to clogging of the wastewater pumps was very different. The type of impeller as well the speed are the most influencing characteristics that influence clogging.
CFD Simulation of Hurricane Force Wind and Its Impacts on Residential Buildings
Authors: Siaka Ghalib , Zhang Ning 
Published: September 2022

Abstract
The landfall of hurricane Laura and Delta during the 2020 hurricane season cost the Southwest Louisiana Area (SWLA) $19 billion and $2.9 billion in damage respectively. Since then, the need to use computational fluid dynamics to study hurricane effects on buildings to reduce damage costs is more alarming. In this research, common residential building designs will be put under different levels of hurricane size winds and barometric pressure conditions from different directions through CFD simulations. The effect of the roof shape, size, and placement on the pressure, shear stress, and eddies acting on the roof will be studied since they are the major causes of roof damage on a building during a hurricane. The objective of this research is to identify the areas of a building’s roof most vulnerable to damage during a hurricane, to ensure reinforcements to prevent future damage. Higher category hurricanes are more likely to cause roof damage due to the lower barometric pressure and higher Reynold’s number characteristics the possess. In the CFD simulation, a Steady and Unsteady Reynolds Averaged Navier-Stokes (RANS) turbulence model will be used. Also, a Large Eddy Simulation (LES) turbulence model will be used to study the flow structure in the domain.
Effect of Microfiber Length on Microfiber Motion in Human Nasal Airways
Authors: Li J. , Ma J. , Tu J. Y. , Tian L. , Ahmadi G. 
Published: September 2022

Abstract
Respiratory inhalation of elongated mineral particles has been a significant concern for humans due to the adverse health consequences. In recent years, the increased usage of carbon nanofiber and carbon nanotubes in high-performance engineered materials has raised renewed concerns. However, studies on this subject are still limited, and many aspects of the respiratory deposition of elongated microfibers are not fully understood. In this study, simulations of the transport and deposition of elongated microfibers in a realistic human nasal cavity model were performed. A constant breathing rate of 15 L/min under laminar flow conditions was assumed, and the airflow field was evaluated using the ANSYS FLUENT™ 19.2. Motions of the elongated ellipsoid were simulated using the coupled translational and rotational governing equations, accounting for the hydrodynamic drag and torque, shear-induced lift, and gravitational sedimentation utilizing an in-house microfiber code incorporated in the ANSYS FLUENT™ UDF (user Defined Function). Sample single microfiber trajectories were presented and analyzed to provide insight into their motions. In addition, the microfiber deposition due to microfiber lengths, rotation, and interaction with the local flow stream, were investigated.
Fluid Velocity Sensing at Extreme Altitude or Low Density Environments
Authors: Papadopoulos George , Bivolaru Daniel , Murphy Andrew , Siu Spencer 
Published: September 2022

Abstract
Methods to measure wind speed and direction range from simple hot-wire / hot-film anemometers to sophisticated sonic and laser/image-based instrumentation. While these can work well on the ground and to low altitudes, there are challenges in implementation for high altitude measurements at the 20 km and above range, where a near space environment exists. The low pressure, low density environment does not support the conditions needed for all known measurement methods to generate an engineering value for the full velocity vector at the cm/s accuracy and resolution needed to allow for high altitude balloon or platform trajectory correction. The National Oceanic and Atmospheric Administration (NOAA) regularly reports relative wind conditions to the 60 kft (18 km) level. Above this level operators are left to modeling and simulation of the stratified air to determine prevailing wind conditions that can be used to provide trajectory control via altitude changes. An in-situ, on-board sensor that can measure all three components of velocity with resolution and accuracy in the cm/s range can take out the uncertainty that is involved in the software-based approach, and together with other navigation aids, complete a trajectory solution for high altitude platforms and science balloons that will help them extend their mission envelope to greatly benefit operational effectiveness. The development of a novel wind speed sensor solution that can operate at the high altitudes of interest and meet resolution requirements is described. The sensor solution can also be applied in other low density environments to measure flow velocity, as well as, harsh environments that may be challenging for other velocity measurement methods. The paper also includes discussion on the design and fabrication of a special high altitude closed vessel with an integrated wind tunnel, capable of generating wind at altitudes more than 45 km, used in the current project for experimental validation, but could also support future sensor calibration efforts.
A Micro-Scale Computational Investigation on the Effects of Leaf Hair on PM2.5 Deposition
Authors: Boontanom Jedhathai (Vicky) , Tafti Danesh K. 
Published: September 2022

Abstract
According to the United Nations, 55% of the world’s population currently lives in urban areas and which is projected to increase to 67% by 2050. Trees and green spaces are effective strategies for mitigating urban pollution. This study develops a framework to investigate the impact of trichome morphology and wind speed on the deposition of 0.3 μm and 1.0 μm particles at the micro-scale. Representative trichome diameters, D = 5 and 20 μm are investigated by varying their height, H, between 100 to 600 μm with packing density of 5 and 15 mm−2. The results show that trichome diameter, density, and wind speed have a favorable impact on deposition velocity. Compared to a smooth leaf, the presence of the thicker 20 μm hairs increases the deposition velocity by 1.5–4 times, whereas, the presence of short 5 μm trichomes reduces the deposition by 15–45%. Increasing trichome height to diameter ratio from H/D = 20 to 30 shows benefits for the thinner trichomes but lowers the deposition for the densely packed thicker trichomes. Less aerosol deposition is also observed when the particle diameter increases from 0.3 μm to 1.0 μm. Within the scope of this study, the complex interplay between these various traits, is captured via a non-dimensional ratio Rhp to model the aerosol deposition on the leaf surface. The results offer valuable insight into the effects of trichome morphology on pollutant deposition in isolation from other environmental and macro-factors.
Is it Turbulent or Laminar? Convolutional Neural Network Predictions
Authors: Dudu Nicholas , Rodriguez Arturo , Kotteda V. M. Krushnarao , Terrazas Jose , Villanueva Daniel , Chijioke Clinton , Baez Rafael , Paez Brandon , Kumar Vinod 
Published: September 2022

Abstract
Laminar flow has been characterized for its smooth and linear behavior concerning its flow. When a non-linearity is introduced, the flow becomes turbulent. Visually it is possible to distinguish between laminar and turbulent flow by identifying areas in the flow that become chaotic or non-smooth. We used a Convolutional Neural Network (CNN) trained on labeled laminar and turbulent images to automate the process. This form of machine learning is called supervised machine learning. The training data set is labeled for the neural network to identify distinguishing parameters that make them different. In this study, we take simulated contours from a flow past cylinder simulation, train it, and test it to see how effective the CNN is at distinguishing between the laminar and turbulent flow.
Shock System Dynamics of a Morphing Bump Over a Flat Plate
Authors: Hamada Ahmed A. , Margha Lubna , AbdelRahman Mohamed M. , Guaily Amr 
Published: September 2022

Abstract
The shock wave boundary layer interaction (SW-BLI) phenomenon over transonic and supersonic airfoils captured the attention of aerospace engineers, due to its disastrous effect on the aerodynamic performance of these vehicles. Thus, the scientific community numerically and experimentally investigated several active and passive flow control elements to reduce the effect of the phenomenon, such as vortex generator, cavity, and bump. They focused on designing and optimizing the shape and location of the bump control element. However, the transit movement of the bump from the state of a clean airfoil to the state of an airfoil with a bump needs more investigation, especially the dynamics of the shock system. Thus, it is preferred to start with simple geometry, such as a flat plate, to fully understand the flow behavior with a morphing bump. In this paper, the shock dynamics due to the movement of a bump over a flat plate flying at supersonic speed are numerically investigated. The bump is located at the impingement position of the shock wave and is moved at different speeds. This study determines the suitable speed that achieves the minimum entropy change, which is the representation parameter of the transition period. The two-dimensional unsteady Navier-Stokes equations are solved using OpenFOAM to simulate the flow field variables, while the motion of the bump is tracked using the Arbitrary Lagrangian-Eulerian (ALE) technique. The results show that a spatial lag on the shock system from the steady-state solution occurs due to the movement of the bump. Further, the spatial lag increases with the increase in the bump’s speed. This causes a high increase in the flow parameters and consequently the total entropy changes on the bump surface. Generally, it is common to move the bump over the longest possible time to approximate a quasi-steady flow during the motion. However, this causes a deviation in the flow parameters between the final time of transition and the steady-state case of bump existence. Thus, it is concluded that the optimal non-dimensional time for a morphing bump in a supersonic flow of Mach number of 2.9 is 2, which is different than the longest time of 10.
Study of Couette-Taylor-Poiseuille Flow With a Wavy Internal Cylinder Surface at Low Taylor and Axial Reynolds Numbers
Authors: Gaied Lamia , Berrich Emna , Aloui Fethi 
Published: September 2022

Abstract
The flow models of a Taylor-Couette-Poiseuille flow with a wavy interior surface have been studied at low axial Reynolds numbers (Reax less than or equal to 32) and Taylor numbers (Ta less than or equal to 606). Two types of surfaces were operated; smooth and wavy. The surface of the wavy cylinder has 18 identical axial waves, which are arranged periodically. The Taylor-Couette system is characterized by an average inner and outer cylinder radius ratio of 0.9, an average gap between the two concentric cylinders of 10mm and an aspect ratio equal to 45, corresponding to the dimensionless height of these cylinders.
The spatiotemporal flow representation was provided quantitatively and qualitatively by exploiting flow visualizations and simultaneous measurements of the components of the wall shear rate. An axial flow imposed on the base flow not only modifies the conditions for the appearance of instabilities, but also the vortex structure of vortices. It can have a stabilizing effect for a regime flow and a destabilizing effect for another, i.e., the transition to Taylor vortices occurred at higher or lower Taylor numbers. In such destabilizing cases, the vortices are either folded or stretched or overlapped or completely destructed.
As a function of the axial Reynolds and Taylor numbers, helices appear, develop and wind in the same direction as the base flow or in the opposite direction. It has been observed that the shear stress of the wall strongly depends on the nature of the surface in contact with the flow, on Ta and Re.
Phototactic Behavior of Micro-Swimmers: Light Effects on Cell Swimming in Oscillating Flow
Authors: Pashmi Elnaz , Peerhossaini Hassan , Jarrahi Mojtaba 
Published: September 2022

Abstract
In this investigation, the phototactic behavior of the swimmer alga Chlamydomonas reinhardtii was studied in oscillatory flows. Two light-emitting diodes (LED) were placed next to one of the lateral walls of a long PDMS microchannel of rectangular cross-section (width = 500 μm, height = 85 μm) which was enclosed in a dark box. Oscillating flow of algal suspension was generated using a pressure-driven control system. Both low and high concentrations of the cells were considered. The short- and long-term effects of light exposure on the cells swimming, and the influence of amplitude and frequency of flow oscillation in the presence of light stimulus were determined.
It was shown that if the period of flow oscillation is shorter than the response time of the cells to a light stimulus (about 1 second), the cells cannot react immediately to the light and thus, the increase in the percentage of cells population showing a negative phototaxis (Nup) occurs later compared to the cases where the oscillation period is long enough (low frequencies). Moreover, it was shown that a smaller oscillation amplitude results in a sharper and earlier increase in Nup since the cells are less affected by the flow advection and respond more efficiently to the light stimulus.
Regarding the long-term effects of light exposure, it was shown that the phototactic behavior of the cells is a function of time, in both low and high concentrated suspensions; however, this evolution with time depends on the concentration. Over a cycle of light exposure on the dilute suspensions, Nup increases in the beginning of the cycle until reaching a peak; then it decreases to the initial value indicating that the effect of light is no longer perceptible by the cells.
Numerical Simulation on Application of Airfoil Cross-Section Rod of Pantograph
Authors: Zhang Mohan , Yin Bo , Yang Guowei 
Published: September 2022

Abstract
Pantograph is a kind of structure composed of many rods parts. Due to its complex structure, the drag of pantograph is relatively high in the drag of the whole high speed train. In order to reduce the aerodynamic drag, many scholars put forward methods such as adding a deflector and installing a baffle plate on the roof of the train, but these methods have little effect on improving the lift force of the pantograph. Regarding this situation, this paper applies airfoil section (naca0012) to the panhead section of the pantograph strips. Knuckle-downstream and knuckle-upstream operating conditions with three running speeds (300km/h, 350km/h and 400km/h) are considered. The drag and lift forces are compared with those of regular pantograph strip in order to confirm the improvement of aerodynamic performance. It indicated that the optimized panhead pantograph has a better performance in drag and lift forces under all the conditions except the lift force rises 14 percent at knuckle-upstream.
Fabrication of a Microfluidic Cell Compressor Using a 3D-Printed Mold
Authors: Emeigh Carson , Zhang Haipeng , Ryu Sangjin 
Published: September 2022

Abstract
Microfluidic devices are used to apply mechanical stimuli, such as compressive force and flow shear force, to cells for mechanobiology studies. Previously, we developed a microfluidic cell compressor in which cells embedded in hydrogel scaffolds were compressed by polydimethylsiloxane (PDMS) balloons, which were expanded pneumatically, in proportion to the balloon diameter. The device consisted of two PDMS layers. The bottom layer contained channels connected to circular wells and was fabricated using SU-8 photoresist molds. The top layer was a thin PDMS membrane separately prepared by spin coating PDMS on a plastic film. The two layers were bonded together using plasma bonding to form PDMS balloons and pneumatic channels. Therefore, fabrication of the device involved multiple steps of photolithography and soft lithography.
In this study, we have improved the fabrication method of the microfluidic cell compressor by printing a master mold using a commercial microfluidic 3D printer for more efficient and cost-effective fabrication with higher design flexibility. The new method is more efficient because it does not require separate preparation of PDMS layers, the mold fabrication can be completed quicker, and a photomask is not necessary. We found that proper printing, UV light exposure, cleaning, baking, and temperature control of the mold affected the ability of the 3D printed mold to cure PDMS.
Also, multiple maintenance requirements of the 3D printer were found for curing PDMS on the printed mold. For example, the resin within the 3D printer must be free of debris, the resin in the printer must be stirred before printing to ensure homogeneity, and the light filtering elements of the printer must be clean. With proper methodology and maintenance, the printer can be used to fabricate the microfluidic cell compressor and similar high-quality microfluidic devices capable of performing laboratory experiments efficiently. Further developing a methodology of creating 3D printed microfluidic device molds would expand access to microfluidics.