bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of Bubble Size on Flow Response to Transient Pressure Drop Through Converging Nozzle
Authors: Garbaly Aleksey , Shepard Thomas 
Published: October 2020

Abstract
For homogenous two-phase bubbly flows, the theoretical speed of sound is dramatically reduced at moderate void fractions to speeds much lower than the speed of sound for either single phase. This theoretical speed of sound would suggest a propensity for bubbly flows to reach choked conditions when traveling through a convergent nozzle. However, for a bubbly flow to be considered homogenous requires assumptions that may not be realized in practical applications. In this experimental study, a bubbly flow was sent through a convergent nozzle before entering a large chamber. By setting steady flow conditions upstream and then reducing the chamber pressure via a vacuum pump, the transient response in terms of gas and liquid flow rates and upstream channel pressure was determined. The bubble size was carefully varied from ∼0.3–1 mm while holding gas and liquid flow rates constant in order to study how bubble size affects the transient flow characteristics. High-speed imaging was used for measuring the bubbles. Experiments were also conducted at two gas-liquid mass flow ratios. Results are presented to demonstrate the impact of bubble size and gas-liquid ratio on the transient response of upstream gas and liquid flow rates, upstream pressure and exit Mach number to the lowering of pressure downstream of the convergent nozzle. Results are presented both for flows that remained in the bubbly regime and for flows that transitioned to an annular flow regime during a trial.
Capstone Design Sequence in Engineering Education
Authors: Taghavi R. , Farokhi S. 
Published: October 2020

Abstract
The Capstone design requirements have become an integral part of the most engineering curricula in the United States. They all share the goal of developing multidisciplinary designs for real-world problems/applications, often with industry sponsorship. In this paper, the three-capstone design options required by the aerospace engineering department at the University of Kansas are discussed. The aerospace engineering seniors have three design options based on their career interests. These are aircraft design, propulsion system design, and spacecraft system design options. In the aircraft design, our students may select individual or team design for their competitions. In the latter two, the propulsion and spacecraft system designs, the students are grouped in a number of teams, based on the class and team size requirements. The individuals and teams participate and compete in the respective American Institute of Aeronautics and Astronautics (AIAA) Design Competitions at the end of their senior year. Participation in the AIAA Design Competition is one of the course requirements. Written and oral communication is assessed throughout the semester. In this paper, the methodology used in the aerospace engineering propulsion system capstone design is presented.
Experimental and Numerical Analysis of Fluid Flow Through a Micromixer With the Presence of Electric Field
Authors: Rubby Md Fazlay , Parvez Mohammad Salman , Biswas Prosanto , Huq Hasina , Islam Nazmul 
Published: October 2020

Abstract
Fluid flows in a microchannel with highly ordered laminar fashion. For this reason, two different fluid streams cannot mix easily, or it takes a very long time. The problem becomes intense for large molecules such as peptides, proteins, and nucleic acids during rapid mixing for biochemical applications in a microfluidic device. Many researchers tried to solve this problem by applying an electric potential. In this work, a numerical simulation was performed on a 2D micromixer. Four symmetric electrodes were placed on the wall of a straight microchannel of width 19 μm. The electroosmotic slip velocity boundary condition was used to create the turbulence on the laminar fluid stream. It was found that this model creates a well-mixed flow at the channel outlet. Then the input parameters were changed to compare the mixing performance in terms of concentration distribution at the channel outlet. Channel width, inter-electrodes gap, the magnitude of electric potential, frequency of the electric potential and asymmetricity of the electrodes were changed and results were compared. An experimental micromixer like the numerical model was fabricated by dc magnetron sputtering machine. Four gold electrodes (thickness, 120 nm) were sputtered on top of a silicon substrate. The value of the input parameters was chosen based on the results obtained from the numerical simulation. To test the mixing functionality of our device the movement of tracer particles was tracked down on the zone surrounded by four electrodes. The micro-PIV (Particulate Image Velocimetry) system was used to analyze the movement of the tracer particles and visualize the flow field in the mixing zone. The magnitude of the AC electric potential and frequency was changed to find out the optimum input parameters for the micromixer. These results could play an important role to design and improve a micromixer design using an AC electric field. A micromixer has many potential applications in biology (DNA analysis, enzyme Screening), chemistry (synthesis, polymerization) and detection (drug discovery, diagnosis).
Comparison of Turbulent Boundary Layer Profiles Modified With Injection or Uniform Concentration of Drag-Reducing Polymer Solution
Authors: Elbing Brian R. 
Published: October 2020

Abstract
The current study explores the influence of polymer drag reduction on the near-wall velocity distribution in a turbulent boundary layer. The classical view is that the polymers modify the intercept constant within the log-region without impacting the von Kármán coefficient, which results in the log-region being unaltered though shifted outward from the wall. However, it has been recently shown that this is not accurate, especially at high drag reduction (&gt; 40%). Past work examining the von Kármán coefficient and intercept constant has shown that polymer properties must impact the deviations, but without any quantification of the dependence. This work reviews the literature to make estimates of the local polymer properties and then demonstrates that the scatter at HDR can be attributed to variations in the Weissenberg number. In addition, new polymer ocean results are incorporated and shown to be quite consistent with polymer injection results using the maximum polymer concentration to define the polymer properties.
Erosion Testing and Modeling of a Triangular Elbow As Compared to a Circular Elbow
Authors: Kolla Srinivas S. , Asgharpour Alireza , Shirazi Siamack A. , Silva Gabriel 
Published: October 2020

Abstract
The erosion patterns in elbows with circular cross-sections have been investigated extensively experimentally and computationally in the past. However, in a bid to reduce erosion in elbows, a new triangular (in cross-section) elbow has been designed and investigated comprehensively during this study. The goal of this work was to examine experimentally and predict computationally using existing erosion models, the erosion patterns in a triangular elbow geometry and compare it to circular elbows for stainless steel materials. Initially, computational fluid dynamics erosion modeling was used to compare erosion in a triangular in-cross-section elbow to a circular elbow. Computational fluid dynamics were then followed by an experimental investigation using flow visualization with a paint removal study to determine the location where particles impinge and lead to erosion. Erosion measurement experiments are also conducted in a flow loop containing liquid and 300 microns sand particles. Within the experimental rig, to avoid abrupt changes of the triangular elbow with the circular pipe, a smooth transition region is designed and utilized. Various transition geometries such as transition length, eccentricity have been investigated with CFD to ensure smooth flow and reduced erosion from the circular pipe to the triangular elbow. CFD simulation results showed that erosion also occurred on the side of the triangular elbow and have been concurred by the paint study as well. It is observed that the erosion in the triangular elbow is approximately 68% lower than that in the circular elbow for the tested conditions. Thus, it is advantageous to use these elbows for practical applications such as fracturing to reduce replacement time of elbows.
Adaptive Simulation Based on URANS and Ensemble Kalman Filter for Resolving Turbulent Flow on LES
Authors: Ito Sasuga , Furukawa Masato , Kazutoyo Yamada , Manabe Kaito 
Published: October 2020

Abstract
Turbulence is one of the most important phenomena in fluid dynamics. In general, turbulent phenomena can be resolved more clearly with Large Eddy Simulation (LES) compared with Unsteady Reynolds Averaged Navier-Stokes (URANS), and the numerical solution shows good agreements with that based on Direct Numerical Simulation (DNS). However, more time and computational power are needed on LES than those on URANS. If possible, the ideal simulation method is that the method is able to resolve the turbulent phenomena same quality as the results based on DNS and LES with less time and less computational power same as that on URANS. This paper shows an adaptive simulation method based on URANS and Ensemble Kalman Filter (Enkf) to reproduce the flow fields based on LES. In this study, a two-dimensional turbine cascade flow has been solved with URANS and LES. The adaptive simulation method has been also applied to the cascade flow. As the results, in the flow field of URANS with the assimilated turbulence model’s parameters, the separation phenomenon and the boundary layer thickness was close to that of the time averaged LES.
A Computational Fluid Dynamic Study of a Momentum and Energy Method on Rough Surfaces
Authors: Urcia Jose , Kinzel Michael 
Published: October 2020

Abstract
The Discrete Element Roughness Method (DERM) has been used to improve convective heat transfer predictions on surface roughness. This work aims to validate the core momentum-correlation of DERM through evaluating Computational fluid dynamics (CFD)-based solution of the flow around individual roughness elements with the goal of improving the correlations. More specifically, the matrix of scenarios evaluated using includes three different roughness elements at three different pressure drops (or flow rates). Results from these studies are to be used to validate and improve correlations used to approximate roughness in DERM. For further comparison, a fourth roughness element analyzed in previous work will also be compared. For each element, a steady and unsteady case are conducted and analyzed. The momentum loss results obtained from the CFD are then compared to the DERM-based predictions from the same roughness elements in search of any discrepancies. It is observed the momentum-correlation deviates from the CFD prediction with increasing element height.
Effect of Neutrally Buoyant Particles on Horizontal Turbulent Flow Through a Tee-Junction
Authors: Bluestein Andrew M. , Bohl Douglas 
Published: October 2020

Abstract
Turbulent particle-laden flows are of high interest due to their presence in many industrial applications. High Reynolds number flows containing solid particles, create complex flows and erosive environments. The effect that the particles have on the turbulence of the surrounding fluid is referred to in the literature as turbulence modulation. This is an area of research in which there is still much to learn to enable a deeper understanding of the physics behind these complex flows. Data that would be of particular usefulness are at higher Reynolds numbers (Re ≥ 100,000), and dense loadings (ΦV ≥ 1%). In this work, turbulent particle-laden flow through a simplified industrial geometry was studied at an upper Reynolds number of 115,000 and particle loadings up to 5% by weight/volume (specific gravity = 1) to address these needs. The flow within a tee junction with the 90-degree branch closed-off downstream was studied. This is analogous to a duct flow but with an exposed region of fluid at the location of the closed-off branch. Super absorbent particles were used as the solid phase, which became index-matched and neutrally buoyant upon saturation with water. Data were acquired using 2-D planar particle image velocimetry (PIV) along the center span of the tunnel. Mean and root-mean-square (rms) velocities were calculated for the fluid phase. Particle loadings studied were 0%, 1%, 3%, and 5 at flow Reynolds numbers of 11,500 and 115,000. Velocity contour plots are presented to provide a macro description of the flow. Three horizontal positions within the shear layer region were selected for profile comparison (x* = −0.45, 0, 0.45). Prior literature suggested that the particles would attenuate the turbulence, however, the result showed no single trend in the current data. The mean velocities were nominally unaffected by loading for a respective Reynolds number case. Turbulence modulation of the flow was found to be sensitive to the Reynolds number, as at x* = −0.45 weakening of the rms was observed in the low Reynolds number case and strengthening in the high Reynolds number case for the same particle loading in the same region of the geometry.
A Numerical Study of Oblique Water Entry Problems
Authors: Chang Yanni , Tong Albert Y. 
Published: October 2020

Abstract
A series of numerical experiments have been carried out on the water entry problem of three-dimensional multi-degree-freedom cylinders. The circular cylinder was released above the water with a specified inclined angle and velocity at entry. The hydrodynamics of the water entry problem have been investigated numerically. The Piecewise Linear Interface Calculation (PLIC) schemes have been applied in conjunction with the Volume of Fluid (VOF) method to capture the interface. Overset meshes have been adopted to handle the moving object. The numerical model is built on the framework of OpenFOAM which is an open-source C++ toolbox. Numerical results have been obtained. Transient flow and pressure distributions have been generated. The presence of air entrapment which has been reported experimentally has also been confirmed in the numerical solution. The fluid physics of the oblique water entry problem such as the formation and development of the air entrapment has been explored. The transient positions and inclined angles of the moving circular cylinder have been found to be in good agreement with the experimental results. Parametric studies have been performed with major findings reported.
Evaluation of a Statistically Targeted Forcing Method for Synthetic Turbulence Generation in Large-Eddy Simulations and Hybrid RANS-LES Simulations
Authors: Shobayo Olalekan O. , Walters D. Keith 
Published: October 2020

Abstract
Computational fluid dynamics (CFD) results are presented for synthetic turbulence generation by a proposed statistically targeted forcing (STF) method. The new method seeks to introduce a fluctuating velocity field with a distribution of first and second moments that match a user-specified target mean velocity and Reynolds stress tensor, by incorporating deterministic time-dependent forcing terms into the momentum equation for the resolved flow. The STF method is formulated to extend the applicability of previously documented methods and provide flexibility in regions where synthetic turbulence needs to be generated or damped, for use in engineering level large-eddy and hybrid large-eddy/Reynolds-averaged Navier-Stokes CFD simulations. The objective of this study is to evaluate the performance of the proposed STF method in LES simulations of isotropic and anisotropic homogeneous turbulent flow test cases. Results are interrogated and compared to target statistical velocity and turbulent stress distributions and evaluated in terms of energy spectra. Analysis of the influence of STF model parameters, mesh resolution, and LES subgrid stress model on the results is investigated. Results show that the new method can successfully reproduce desired statistical distributions in a homogeneous turbulent flow.
Development of Ball-Enabled Miniaturized Valves for Sample Preparation and Microheaters for Pathogen Detection
Authors: Manzanas Carlos , Jiang Xiao , Lednicky John A. , Fan Z. Hugh 
Published: October 2020

Abstract
There have been numerous Zika virus (ZIKV) outbreaks in the past few years, representing a public health problem. The recommended tests for the diagnosis of Zika infections are performed in a laboratory setting. However, diagnostics platforms at the point-of-care (POC) are highly desirable for understanding and preventing ZIKV transmission. To address this need, we have developed a testing platform that (1) can be operated in the field for pathogen detection, (2) is rapid, cost-effective, and reliable, and (3) does not require a power supply.
To realize the platform, we have developed (1) a series of ball-based valves for the storage and sequential delivery of reagents and (2) microheater-enabled RNA amplification, both of which are integral components of this POC device. The multiple reagents are needed for virus lysis, RNA enrichment and purification. These ball-based are employed for fluid-control and they are actuated manually by sliding the unit and a pole under it, which can lift the balls. Nucleic acid amplification is then performed by a smart coffee mug that provides a constant temperature for reverse transcription loop mediated isothermal amplification (RT-LAMP), followed by colorimetric detection. We have demonstrated the detection of Zika virus in human urine and saliva samples using this testing platform.
Particle Tracking Velocimetry in Noisy Environment
Authors: Mousavisani Seyedmohammad , Kelly Scott D. , Kafashi Sajad , Smith Stuart T. 
Published: October 2020

Abstract
The encoded Particle Tracking Velocimetry (ePTV) is introduce in this paper as a specific approach of Particle Tracking Velocimetry (PTV). This method is applied to track particles obtained from flow images that contain significant background noise and relatively low particle density. Encoding is achieved by illuminating the flow with a series of light pulses within individual image exposures. Dependent upon the velocity, each particle will be illuminated multiple times in each image frame with spacing determined by both the pulse train timing and the particle velocity. A search algorithm is used that identifies each particle and seeks the encoded pattern with other particles in the image, repeating this until all encoded particles are found.
Based on probability analysis and finite image size an analytic model is developed to determine the ratio of true particles, false particles and those that are ‘lost’ by exiting the image frame.
This ePTV technique has been experimentally implemented to track spherical particles suspended in stationary vortices.
By using a suspension of micro-particles, subsequent imaging with encoded pulse trains provided snap-shots of the complex flow patterns. Typically, even after filtering, the images show around 100 to 200 particles from which encoded trajectories have been extracted and typically account for about 30% of the objects identified in the image.
Estimation of the Risk Zones Affected by Repeated Floods by Numerical Modeling
Authors: Radulescu Victorita 
Published: October 2020

Abstract
In Romania, in the last decades, was not realized any complex plan of management concerning the environmental rehabilitation of the natural riverbeds, even if there are even in present many places confronted with repeated floods. After the floods from 2004, 2005 and 2014 have been recorded in some places large deposits of sediments or contrary, in other zones with erosion and uncontrolled coastal slides. As an immediate effect, zones with risk for the local population and not only, have appeared. The present paper estimates the capacity of transport for a riverbed in natural conditions, based on the local measurements registered before and after a flood. The model is tested for a tributary of the Bistrita River, the Cracau River, near the Siret basin, an area well-known for such repeated floods sometimes even two or three recorded in the same year, as it was in 2005 and 2008. Three of these floods were confronted with human losses, many dead animals, and agricultural flooded areas. Near the analyzed watercourse there are many localities, with a high density of population. The realized numerical model for the flow with free surface was taking into account the possibility of the permanent changing of the lateral surfaces (riverbeds) during the floods. A continuous balance of the entered and transported sediments is realized, due to the erosion and sediment transportation. The time variation of the discharged liquid and the solid phases are directly connected with the sediment transport. In these conditions, the fine fractions of sediments from the bed’s structure are removed from its surface. In some places, the sediments become “armored” with the coarser part of the bed sediment. It is proposed a mathematical model to simulate the effect of both types of deposits into a fluid flow in open channels, with a movable bed. The entire alluvial stream, until the base rock, is considered with a small thickness so the non-uniformity of the grain size in the vertical distribution in riverbed could be neglected. The boundary conditions in the flood analysis consist of the upstream hydrograph and the stationary level of the downstream watercourse. Knowing the flow rate and the water levels by direct measurements, there is possible to establish the risk zones, far away from the river borders. The primary purpose of this study is to minimize the effects of such uncontrolled floods by determining the risk zones and to present a solution for increasing population safety which lives near the riverbed. Finally, some conclusions and references are mentioned.