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2019

CFD

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Full-Text Articles in Engineering

Numerical Investigation Of Laser-Induced Ignition Phenomena, Deshawn Coombs Dec 2019

Numerical Investigation Of Laser-Induced Ignition Phenomena, Deshawn Coombs

Dissertations - ALL

This thesis investigates various aspects of laser-ignition. Laser ignition is a form of combustion initiation by means of a focused laser pulse in a combustible mixture. The ignition process consists of a chain of processes with varying degrees of importance to the prediction of a successful flame propagation. Some of these processes include plasma formation, induced shock wave, emergence of a flame kernel, and successful transition to a self-sustained flame or flame quenching. This thesis will explore various aspects of this process using computational fluid dynamics and model analysis with the aim of identifying the controlling processes and simplified ways ...


On The Fuel Spray Applications Of Multi-Phase Eulerian Cfd Techniques, Gabriel Lev Jacobsohn Oct 2019

On The Fuel Spray Applications Of Multi-Phase Eulerian Cfd Techniques, Gabriel Lev Jacobsohn

Masters Theses

Eulerian-Eulerian Computational Fluid Dynamics (CFD) techniques continue to show promise for characterizing the internal flow and near-field spray for various fuel injection systems. These regions are difficult to observe experimentally, and simulations of such regions are limited by computational expense or reliance on empiricism using other methods. The physics governing spray atomization are first introduced. Impinging jet sprays and Gasoline Direct Injection (GDI) are selected as applications, and modern computational/experimental approaches to their study are reviewed. Two in-house CFD solvers are described and subsequently applied in several case studies. Accurate prediction of the liquid distribution in a like-doublet impinging ...


Investigating Inducer Performance Over A Wide Range Of Operating Conditions, David Tate Fanning Sep 2019

Investigating Inducer Performance Over A Wide Range Of Operating Conditions, David Tate Fanning

Theses and Dissertations

Inducer performance is investigated for a variety of inducer geometries operating at multiple flow conditions using computational fluid dynamics. Inducers are used as a first stage in turbopumps to minimize cavitation and allow the pump to operate at lower inlet head conditions. The formation of inlet flow recirculation or backflow in the inducer occurs at low flow conditions and can lead to instabilities and cavitation-induced head breakdown. Backflow formation is often attributed to tip leakage flow. The performance of an inducer with and without tip clearance is examined. Removing the tip clearance eliminates tip leakage flow; however, backflow is still ...


Modeling And Simulation Of High-Density Spray Combustion, Chenwei Zheng Aug 2019

Modeling And Simulation Of High-Density Spray Combustion, Chenwei Zheng

Dissertations - ALL

High-efficiencies and low-emissions can be realized in combustion engines that operate at high-pressures and low-temperatures conditions (high densities). The design of such engines relies on accurate models of the physical processes involved. Three areas of concern are multi-phase phenomena, the equation of state for the gas phase and cost-effective chemical kinetic modeling. Fuel injected as liquid must break up into droplets, evaporate, and mix with air before combusting. Models for these processes have been developed and need to be tested against experiments. As for the gas phases, the ideal gas model fails to capture thermodynamic relations at high-density combustion. A ...


Unsupervised-Learning Assisted Artificial Neural Network For Optimization, Varun Kote Jul 2019

Unsupervised-Learning Assisted Artificial Neural Network For Optimization, Varun Kote

Mechanical & Aerospace Engineering Theses & Dissertations

Innovations in computer technology made way for Computational Fluid Dynamics (CFD) into engineering, which supported the development of new designs by reducing the cost and time by lowering the dependency on experimentation. There is a further need to make the process of development more efficient. One such technology is Artificial Intelligence. In this thesis, we explore the application of Artificial Intelligence (AI) in CFD and how it can improve the process of development.

AI is used as a buzz word for the mechanism which can learn by itself and make the decision accordingly. Machine learning (ML) is a subset of ...


Composite Experimental And Numerical Modeling Of Arced Labyrinth Weirs, Seth Thompson, Blake Tullis Jun 2019

Composite Experimental And Numerical Modeling Of Arced Labyrinth Weirs, Seth Thompson, Blake Tullis

International Junior Researcher and Engineer Workshop on Hydraulic Structures

Arced labyrinth weirs are a viable option for existing spillway retrofit due to their increased flow capacity. This study supplies additional arced labyrinth weir hydraulic design empirical data and uses this data to validate a numerical model (utilized Flow-3D) of the same experimental setup. The dimensionless discharge coefficient relationship is presented for the physical model, potential errors due to physical model crest referencing are discussed, and the relative and absolute errors along with a grid convergence study are given for the numerical model.


Comparison Of Modelling Approaches For Development Of Discharge Rating Curves For Spillway/Bridge Combinations, Nathan Young Jun 2019

Comparison Of Modelling Approaches For Development Of Discharge Rating Curves For Spillway/Bridge Combinations, Nathan Young

International Junior Researcher and Engineer Workshop on Hydraulic Structures

When estimating spillway discharge rating curves, engineers can use a variety of methods such as empirical equations, one- (1D) or two-dimensional (2D) hydraulic computer models, or a combination thereof; however, conservative assumptions are often applied to such methods. The use of three-dimensional (3D) computational fluid dynamics (CFD) models is an alternative modelling approach that can often better estimate spillway discharge rating curves, especially for complex flow situations. In this study, the results of 3D CFD models are compared to estimates of spillway discharge rating curves developed with a combination of empirical equations and other hydraulic computer models for spillway/bridge ...


Large-Eddy Simulations Of T-Shaped Open-Channel Confluences With Different Downstream Channel Widths, Pedro Xavier Ramos, Laurent Schindfessel, João Pedro Pêgo, Tom De Mulder Jun 2019

Large-Eddy Simulations Of T-Shaped Open-Channel Confluences With Different Downstream Channel Widths, Pedro Xavier Ramos, Laurent Schindfessel, João Pedro Pêgo, Tom De Mulder

International Junior Researcher and Engineer Workshop on Hydraulic Structures

Confluences of open-channel flows are common in nature as well as in urban drainage networks and in hydraulic structures. The complex hydrodynamics is often studied in schematized, right-angled confluences. In this paper, the influence of the downstream channel width onto time-averaged and turbulent flow features will be investigated numerically, based on Large-Eddy Simulations. For one flow situation, i.e. flow ratio and downstream Froude number, two geometries will be compared: a discordant width case, which was studied experimentally by Yuan et al. (2016) in a flume with a wider downstream channel than the upstream mean and tributary channels, and the ...


Transient Flow Analysis Of A Closing Blowout Preventer Using Computational Fluid Dynamics (Cfd), Daniel Barreca Jun 2019

Transient Flow Analysis Of A Closing Blowout Preventer Using Computational Fluid Dynamics (Cfd), Daniel Barreca

LSU Master's Theses

Reliability of blowout preventers (BOPs) is crucial for drilling and production operations. Erosion of BOP components and hydrodynamic forces on rams may cause failure of BOP elements to seal the well. Transient computational fluid dynamics (CFD) simulations of fluids within the wellbore and BOP offer quantitative and qualitative data related to this reliability during the closure of various BOP components. Since limited research has been published in transient CFD simulations of closing BOPs, this thesis discusses challenges and solutions to simulating closing blowout preventers. Single component fluids are simulated through several BOP geometries such as annular preventers, pipe rams, and ...


A Homegrown Dsmc-Pic Model For Electric Propulsion, Dominic Charles Lunde Jun 2019

A Homegrown Dsmc-Pic Model For Electric Propulsion, Dominic Charles Lunde

Master's Theses

Powering spacecraft with electric propulsion is becoming more common, especially in CubeSat-class satellites. On account of the risk of spacecraft interactions, it is important to have robust analysis and modeling tools of electric propulsion engines, particularly of the plasma plume. The Navier-Stokes equations used in classic continuum computational fluid dynamics do not apply to the rarefied plasma, and therefore another method must be used to model the flow. A good solution is to use the DSMC method, which uses a combination of particle modeling and statistical methods for modeling the simulated molecules. A DSMC simulation known as SINATRA has been ...


Optimization Of Window Confirguration In Buildings For Sustainable Thermal And Lighting Performance, Meseret Tesfay Kahsay May 2019

Optimization Of Window Confirguration In Buildings For Sustainable Thermal And Lighting Performance, Meseret Tesfay Kahsay

Electronic Thesis and Dissertation Repository

In recent years, there is an urban architectural evolution towards significant use of glazing in high-rise buildings. Windows play a critical role in moderating the elements of the climate. Although good for outdoor viewing and daylighting, glazing has very little ability to control heat flow and solar heat gain. As a result, about 20 - 40% of the energy in a building is wasted through windows. Finding an optimal configuration of windows is a complex task due to its conflicting objectives, such as outdoor view, daylighting, and thermal comfort demands. Further buildings interact with the microclimate in a complex manner, the ...


Numerical Investigation Of Coalescence-Induced Self-Propelled Behavior Of Droplets On Non-Wetting Surfaces And Wedged Surfaces., Yan Chen May 2019

Numerical Investigation Of Coalescence-Induced Self-Propelled Behavior Of Droplets On Non-Wetting Surfaces And Wedged Surfaces., Yan Chen

Electronic Theses and Dissertations

When small drops coalesce on a superhydrophobic surface, the merged drop can jump away from the surface due to the surface energy released during the coalescence. This self-propelled behavior has been observed on various superhydrophobic surfaces and has potential applications in areas related to the heat and mass transfer, such as heat exchangers, anti-icing and anti-frost devices, thermal management and water harvesting. The jumping velocity model was obtained based on published experimental data and the balance of various energy terms described in previous studies. However, the self-propelled mechanism is still not fully understood. In this study, the self-propelled droplet phenomenon ...


Cavitation Number As A Function Of Disk Cavitator Radius: A Numerical Analysis Of Natural Supercavitation, Reid Prichard Apr 2019

Cavitation Number As A Function Of Disk Cavitator Radius: A Numerical Analysis Of Natural Supercavitation, Reid Prichard

Senior Honors Theses

Due to the greater viscosity and density of water compared to air, the maximum speed of underwater travel is severely limited compared to other methods of transportation. However, a technology called supercavitation – which uses a disk-shaped cavitator to envelop a vehicle in a bubble of steam – promises to greatly decrease skin friction drag. While a large cavitator enables the occurrence of supercavitation at low velocities, it adds substantial unnecessary drag at higher speeds. Based on CFD results, a relationship between cavitator diameter and cavitation number is developed, and it is substituted into an existing equation relating drag coefficient to cavitation ...


Horizontal Flow Loop Design For The Study Of Drill String Rotation Effects On Cuttings Transport, David C. Rathgeber Apr 2019

Horizontal Flow Loop Design For The Study Of Drill String Rotation Effects On Cuttings Transport, David C. Rathgeber

Graduate Theses & Non-Theses

Exploration and Production companies are continually focusing more time, energy and resources into Extended Reach Drilling in order to maximize reservoir production while minimizing both environmental impact and development costs. These long laterals (2:1 Measured Depth: True Vertical Depth) are often more difficult to drill and can be severely impacted by inadequate drilling practices. Cuttings transport efficiency is a critical parameter of Extended Reach Drilling operations, and poor wellbore cleaning can lead to excessive torque, drag, and several other serious downhole problems.

Although many studies have been performed that identify the importance of drill string rotation on cuttings movement ...


The Characterization Of Char Particle Morphology And Its Effects On Combustion, Scott Jorgensen Apr 2019

The Characterization Of Char Particle Morphology And Its Effects On Combustion, Scott Jorgensen

Master's Theses (2009 -)

Char particle combustion typically occurs under internal diffusion control, which results in inter-particle reactant gradients. Reactant concentrations throughout the char’s carbon structure must be known in order to predict overall particle reaction rates. These concentrations can be predicted by analytical models; however, effects of char morphology are typically ignored within these simplified models. In order to incorporate these effects, the morphology of Illinois coal #6 was studied by visualizing their structure in three-dimensions through the use of micro-computed tomography. Morphological characteristics of macro-porosity, macro-porosity location, and wall thickness were then measured for the sampled char particles. The sampled char ...


Sweep And Taper Analysis Of Surfboard Fins Using Computational Fluid Dynamics, Brandon James Baldovin Mar 2019

Sweep And Taper Analysis Of Surfboard Fins Using Computational Fluid Dynamics, Brandon James Baldovin

Master's Theses

The research presented here provides a basis for understanding the hydrodynamics of surfboard fin geometries. While there have been select studies on fins there has been little correlation to the shape of the fin and its corresponding hydrodynamic performance. This research analyzes how changing the planform shape of a surfboard fin effects its performance and flow field. This was done by isolating the taper and sweep distribution of a baseline geometry and varying each parameter individually whilst maintaining a constant span and surface area. The baseline surfboard fin was used as a template in Matlab to generate a set of ...


A Higher-Order Method Implemented In An Unstructured Panel Code To Model Linearized Supersonic Flows, Jake Daniel Davis Feb 2019

A Higher-Order Method Implemented In An Unstructured Panel Code To Model Linearized Supersonic Flows, Jake Daniel Davis

Master's Theses

Since their conception in the 1960s, panel codes have remained a critical tool in the design and development of air vehicles. With continued advancement in computational technologies, today's codes are able to solve flow fields around arbitrary bodies more quickly and with higher fidelity than those that preceded them. Panel codes prove most useful during the conceptual design phase of an air vehicle, allowing engineers to iterate designs, and generate full solutions of the flow field around a vehicle in a matter of seconds to minutes instead of hours to days using traditional CFD methods. There have been relatively ...


Adding Semi-Structured Automated Grid Generation And The Menter-Shear Stress Turbulence Transport Model For Internal Combustion Engine Simulations To Novel Fem Lanl Combustion Codes, Brad Montgomery Philipbar Jan 2019

Adding Semi-Structured Automated Grid Generation And The Menter-Shear Stress Turbulence Transport Model For Internal Combustion Engine Simulations To Novel Fem Lanl Combustion Codes, Brad Montgomery Philipbar

Mechanical Engineering ETDs

The addition of GridPro semi-structured, automated generation of grids for complex moving boundaries for combustion engine applications and the Menter Shear Stress Turbulent Transfer (SST) model are being developed by Los Alamos National Laboratory. The software is called Fast, Easy, Accurate, and Robust Continuum Engineering (FEARCE). In addition to improving the time and effort required to build complex grid geometry for turbulent reactive multi-phase flow in internal combustion engines, the SST turbulence model has been programmed into the Predictor Corrector Fractional-Step (PCS) Finite Element Method (FEM) for reactive flow and turbulent incompressible flow regime validation is performed. The Reynolds-Averaged Navier-Stokes ...


Ignition And Extinction Behavior Of Fuels In A Microcombustor, Pawan Sharma Jan 2019

Ignition And Extinction Behavior Of Fuels In A Microcombustor, Pawan Sharma

LSU Doctoral Dissertations

Conventional fuel testing device-CFR engine requires large quantities of fuels, which makes it unsuitable for research of small samples of fuels. This current study seeks to address this limitation by using an externally heated microcombustor as an alternative fuel testing device. Mainly three combustion behaviors have been observed inside a microcombustor: strong flames at higher flow rates, Flames with Repetitive Extinction and Ignition (FREI) at intermediate flow rates, and weak flames at marginal flow rates. In previous studies, weak combustion behavior has been proven suitable to study fuel properties from small samples of fuels. Microcombustor experiments typically rely on flame ...


Magneto-Active Slosh Control System Using Free Floating Membrane For Cylinderical Propellant Tanks Read More: Https://Arc.Aiaa.Org/Doi/Abs/10.2514/6.2019-2177, Pedro Llanos Jan 2019

Magneto-Active Slosh Control System Using Free Floating Membrane For Cylinderical Propellant Tanks Read More: Https://Arc.Aiaa.Org/Doi/Abs/10.2514/6.2019-2177, Pedro Llanos

Pedro J. Llanos (www.AstronauticsLlanos.com)

The phenomenon of sloshing is a substantial challenge in propellant management, particularly in reduced gravity where surface tension-driven flows result in large slosh amplitudes and relatively long decay time scales. Propellant Management Devices (PMDs) such as the rigid baffles and elastomeric membranes are often employed to counteract motion of the free surface. In the present study, we investigate an active PMD that utilizes a free-floating membrane that, under an applied static magnetic field, becomes rigid and suppresses slosh. This semi-rigid structural layer can thereby replace bulky baffle structures and reduce the overall weight of the tank. In this paper, the ...


Numerical Simulation For The Hydrodynamic Performance Of Hydropower Turbine Near Free Surface, Zeda Yin Jan 2019

Numerical Simulation For The Hydrodynamic Performance Of Hydropower Turbine Near Free Surface, Zeda Yin

Theses, Dissertations and Capstones

The performance of hydropower turbine in shallow water can be affected by the presence of free surface. Therefore, it is of great interest to investigate the influence of free surface on hydropower turbine performance through computational simulations. For a better understanding of flow field around hydropower turbine operating in shallow water, it is important to analyze the flow over a single hydrofoil beneath free surface first. Therefore, as the first part of this thesis, the Computational Fluid Dynamics (CFD) methodology was used for numerical simulation of 2D unsteady incompressible viscous flow over a hydrofoil under the free surface. The computation ...


Mixing In Bi-Dispersed Granular Flows, Venkata Satya Pavan Kotrike Jan 2019

Mixing In Bi-Dispersed Granular Flows, Venkata Satya Pavan Kotrike

Graduate Theses and Dissertations

Autothermal pyrolysis is the process of converting biomass into biofuels and other chemical products where the energy for the pyrolysis process is obtained by partial oxidation of products. The sand acts as the fluidizing medium and heat carrier inside the fluidized bed reactor. Perfect mixing of biomass with sand particles enables better heat transfer, which further facilitates the devolatilization process to produce higher yields. The objective of this study is to use a multi-fluid Euler-Euler methodology to predict mixing and segregation phenomena in bi-dispersed flows. The method was extended to simulate the hydrodynamics of biomass and sand particles inside a ...


Computational Study Of Water Desalination Using Forward Osmosis, Ahmed Mohammed Alshwairekh Jan 2019

Computational Study Of Water Desalination Using Forward Osmosis, Ahmed Mohammed Alshwairekh

Theses and Dissertations

Forward Osmosis is a natural phenomenon that takes places across a semi-permeable membrane when there is a concentration difference across the membrane. Pure water permeates to the highly concentrated channel until the concentration across the membrane equilibrates. In water desalination applications, the same principle is applied. Spiral-wound membrane, flat sheet, or hollow fiber module are typical configurations in forward osmosis desalination modules. The application of water desalination using forward osmosis requires the existence of two channels separated by a suitable forward osmosis membrane. Sea or Brackish water is introduced in one side while the other side has a suitable draw ...


The Effects Of Low Aspect Ratio And Heat Exchanging Internals On The Bubble Properties And Flow Regime In A Pilot-Plant Bubble/Slurry Bubble Column For Fischer-Tropsch Synthesis, Hayder Al-Naseri Jan 2019

The Effects Of Low Aspect Ratio And Heat Exchanging Internals On The Bubble Properties And Flow Regime In A Pilot-Plant Bubble/Slurry Bubble Column For Fischer-Tropsch Synthesis, Hayder Al-Naseri

Doctoral Dissertations

"Fischer-Tropsch synthesis (F-T) is a process utilized to convert the syngas mixture of CO and H2 to synthetic fuel and chemicals that executed commercially by using the bubble/slurry bubble column reactor. The experimental results reveal that the investigated parameters, in terms the presence of internals, and reducing the aspect ratio and the solids loading, increase the local gas holdup, interfacial area, bubble passage frequency, and decrease the bubble rise velocity, bubble chord length. Meanwhile, the aspect ratio H/D = 4, and 5 provide enough height to established the fully developed flow regime. As a result of the variation ...


Aerodynamics Of Fan Blade Blending, Clint J. Knape Jan 2019

Aerodynamics Of Fan Blade Blending, Clint J. Knape

Browse all Theses and Dissertations

Blending is a method of fan and compressor blade repair. The goal of the blending process is to remove stress concentration points such as cracks and nicks along the leading, trailing, or tip edges of the blade. The stressed areas are typically removed by grinding or cropping away the surrounding material. For integrally bladed rotor (IBR) disks, repairing a damaged blade is much more economical than replacing the entire disk. However, the change in shape of the blade will change the local aerodynamics and result in mistuning, both structurally and aerodynamically. In a worst case scenario, the change in the ...


Using Cfd To Improve Off-Design Throughflow Analysis, Troy J. Lanchman Jan 2019

Using Cfd To Improve Off-Design Throughflow Analysis, Troy J. Lanchman

Browse all Theses and Dissertations

In turbomachinery design, complex internal flows give rise to significant losses and blockage whose effects are difficult to properly analyze without detailed computational fluid dynamics (CFD) methods or experiments. In a typical design method, CFD is used in conjunction with simpler throughflow or cascade codes to hasten the process. However, the lesser physical accuracy of the design codes demands the inclusion of models to improve the accuracy of the throughflow codes. This thesis aims to use CFD data to generate improved loss and blockage models for a 2D compressor throughflow code by matching throughflow data to CFD data using optimizations ...


Computational Study Of Flow Interactions Over A Close Coupled Canard-Wing On Fighter, Setyawan Bekti Wibowo, Sutrisno Sutrisno, Tri Agung Rohmat Jan 2019

Computational Study Of Flow Interactions Over A Close Coupled Canard-Wing On Fighter, Setyawan Bekti Wibowo, Sutrisno Sutrisno, Tri Agung Rohmat

International Journal of Aviation, Aeronautics, and Aerospace

There have been many attempts to improve the flying performance of a fighter. By modifying the flow that occurs along the fuselage is expected to improve the performance of the aircraft. One of the indicators of combat aircraft performance is the ability to perform maneuver movement. Adding a canard as forewing on the fighter wing configuration is considered capable of raising the ability in maneuver movement. The use of canard-delta pairs will affect the performance and aerodynamic characteristics of the plane. Wings and canards with delta configuration will make the rolled-up vortex as a lifting force producer on the aircraft ...


Employing 2-D Cfd & Lrb Model Around Trees To Improve Vawt Placement, David Chukwuebuka Bassey Jan 2019

Employing 2-D Cfd & Lrb Model Around Trees To Improve Vawt Placement, David Chukwuebuka Bassey

All Graduate Theses, Dissertations, and Other Capstone Projects

In the placement of vertical axis wind turbines, trees are a constant presence in the vicinity. They are found to grow at different height and shape configurations. And in areas such as the Minnesota State University, Mankato (MNSU) campus, they serve as blockage to airflow; limiting the efficiency of installed turbines. This work sets the precedent for the validation of vegetative numerical models created for the Xcel Energy Research Development Fund (RDF) project.

Using two-dimensional (2-D) numerical simulations of porous cylinders placed in a rectangular medium of air, insight into the flow profile and distribution in the leeward side of ...