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Computational fluid dynamics

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Full-Text Articles in Mechanical Engineering

Computational Analysis And Design Optimization Of Convective Pcr Devices, Jung Il Shu Jul 2019

Computational Analysis And Design Optimization Of Convective Pcr Devices, Jung Il Shu

Mechanical & Aerospace Engineering Theses & Dissertations

Polymerase Chain Reaction (PCR) is a relatively novel technique to amplify a few copies of DNA to a detectable level. PCR has already become common in biomedical research, criminal forensics, molecular archaeology, and so on. Many have attempted to develop PCR devices in numerous types for the purpose of the lab-on-chip (LOC) or point-of-care (POC). To use PCR devices for POC lab testing, the price must be lower, and the performance should be comparable to the lab devices. For current practices with the existing methods, the price is pushed up higher partially due to too much dependence on numerous developmental ...


Direct Numerical Simulations Of The Compressible Low Atwood Rayleigh-Taylor Instability, Scott A. Wieland Jan 2019

Direct Numerical Simulations Of The Compressible Low Atwood Rayleigh-Taylor Instability, Scott A. Wieland

Mechanical Engineering Graduate Theses & Dissertations

Two fluids are considered Rayleigh-Taylor unstable when the more dense fluid is suspended above the less dense fluid in the presence of a gravitational like accelerative force. When a pertur- bation is applied to the interface between the two, they begin mixing as the light fluid rises and the heavy fluid drops. The extension of this to the compressible regime leads to the densities of the fluids to not be constant, but instead the molar mass is used to define the weights. At the interface, a density jump still occurs, but away from the interface the densities can vary in ...


Flow Fields Past Grain Bins As It Relates To Vertical Axis Wind Turbine Placement Optimization, Jon Richter Jan 2019

Flow Fields Past Grain Bins As It Relates To Vertical Axis Wind Turbine Placement Optimization, Jon Richter

All Theses, Dissertations, and Other Capstone Projects

This thesis studies the 3D flow field of grain bins as it relates to Vertical Axis Wind Turbine (VAWT) placement. Numerical CFD simulations using ANSYS FLUENT were created and validated with the Minnesota State University, Mankato water channel. It was found that the best speed-up regions were on the outer most sides of the models, closest to the walls of the water channel. The model that is furthest upwind in the group has the best speed-up velocity. As the models become closer together, an asymmetric flow field develops. VAWT placement between the models for any case researched is not recommended ...


Computational Study Of Desalination By Membranes, Mustafa Usta Aug 2018

Computational Study Of Desalination By Membranes, Mustafa Usta

Theses and Dissertations

Water desalination by membranes constitutes the majority of the low-quality water purication systems that extends across many different techniques. This study considers transport phenomena in reverse osmosis (RO) and vacuum membrane distillation (VMD) modules using computational techniques. Reverse osmosis is a pressure-driven separation method using semi-permeable membranes featuring nanoporous structures. Vacuum membrane distillation is another emerging separation method relying on the temperature difference across the microporous hydrophobic membranes.The membrane separation process intrinsically gives rise to temperature polarization (TP) and concentration polarization (CP) which could be severe limitations in these systems. To eliminate these polarizations and increase the module performance ...


High-Fidelity Multidisciplinary Design Optimization Of A 3d Composite Material Hydrofoil, Silvia Volpi May 2018

High-Fidelity Multidisciplinary Design Optimization Of A 3d Composite Material Hydrofoil, Silvia Volpi

Theses and Dissertations

Multidisciplinary design optimization (MDO) refers to the process of designing systems characterized by the interaction of multiple interconnected disciplines. High-fidelity MDO usually requires large computational resources due to the computational cost of achieving multidisciplinary consistent solutions by coupling high-fidelity physics-based solvers. Gradient-based minimization algorithms are generally applied to find local minima, due to their efficiency in solving problems with a large number of design variables. This represents a limitation to performing global MDO and integrating black-box type analysis tools, usually not providing gradient information. The latter issues generally inhibit a wide use of MDO in complex industrial applications.

An architecture ...


Simplified, Alternative Formulation Of Numerical Simulation Of Proton Exchange Membrane Fuel Cell, Russell L. Edwards Apr 2018

Simplified, Alternative Formulation Of Numerical Simulation Of Proton Exchange Membrane Fuel Cell, Russell L. Edwards

Mechanical & Aerospace Engineering Theses & Dissertations

Three-Dimensional proton exchange fuel cell (PEMFC) operation in steady-state is simulated with computational fluid dynamics / multiphysics software that is based upon the finite-element method. PEMFC operation involves the simultaneous simulation of multiple, interconnected physics involving fluid flows, heat transport, electrochemical reactions, and both protonic and electronic conduction. Modeling efforts have varied by how they treat the physics occurring within and adjacent to the membrane-electrode assembly (MEA). Several approaches treat the MEA as part of the computational domain, solving multiple, and coupled conservation equations via the CFD approach within the 3 regions of the MEA. The thickness dimensions of the 3 ...


Computational Investigation Using Bleed As A Method Of Shock Stabilization, Dayle L. Chang Mar 2018

Computational Investigation Using Bleed As A Method Of Shock Stabilization, Dayle L. Chang

Theses and Dissertations

Shock-wave/boundary layer interactions (SWBLI) produce undesirable dynamic loads and separated unsteady flows, adversely impacting the performance and structural integrity of supersonic vehicles. Computational fluid dynamics (CFD) is a successful tool in experimental planning and shows promise as a critical tool in understanding and mitigating negative effects of SWBLI. The goal of this research is to demonstrate the effect of bleed holes on shock stability using the OVERFLOW CFD solver to inform the planning of an Air Force Research Laboratory (AFRL) SWBLI wind tunnel experiment. First, a two-dimensional, flat plate, single-hole configuration was developed. Massflow discrepancies of 14.8% were ...


Uncertainty In Combustion Reaction Rates And Its Effects On Combustion Simulations, Joshua Piehl Jan 2018

Uncertainty In Combustion Reaction Rates And Its Effects On Combustion Simulations, Joshua Piehl

Wayne State University Theses

This work investigates the uncertainties in reaction rates of an n-dodecane model on turbulent spray combustion simulations. Six major reactions were found to significantly impact the ignition delay of the mechanism in a 0-D batch reactor model. These reactions’ rates were independently modified and placed into individual mechanisms. These newly developed mechanisms were simulated in a 3-D turbulent spray simulation and a 0-D batch reactor at a pressure of 60 bar and temperatures from 900 to 1100 K. The combustion characteristics (e.g. ignition delays, flame lift-off length, liquid and vapor penetration) of the modified mechanisms were compared to those ...


Electric-Field Assisted Manipulation And Self-Assembly Of Particle Suspensions, Edison Chijioke Amah Jan 2018

Electric-Field Assisted Manipulation And Self-Assembly Of Particle Suspensions, Edison Chijioke Amah

Dissertations

No abstract provided.


Design Of A Novel Tissue Culture System To Subject Aortic Tissue To Multidirectional Bicuspid Aortic Valve Wall Shear Stress, Janet Liu Jan 2018

Design Of A Novel Tissue Culture System To Subject Aortic Tissue To Multidirectional Bicuspid Aortic Valve Wall Shear Stress, Janet Liu

Browse all Theses and Dissertations

Blood vessels experience complex hemodynamics marked by three-dimensionality and pulsatility. Arterial endothelial cells interact with the characteristics of the fluid wall shear stress (WSS) to maintain homeostasis or promote disease states. In particular, the bicuspid aortic valve (BAV), a congenital heart valve anatomy consisting of two leaflets instead of three, is associated with aortic complications presumably promoted by hemodynamic abnormalities. While devices have been used to test this hypothesis, their capabilities are limited to the generation of time-varying WSS magnitude in one direction. However, the increased flow helicity generated by BAVs in the aorta is expected to result in increased ...


Dust Control Examination Using Computational Fluid Dynamics Modeling And Laboratory Testing Of Vortecone And Impingement Screen Filters, Ashish R. Kumar Jan 2018

Dust Control Examination Using Computational Fluid Dynamics Modeling And Laboratory Testing Of Vortecone And Impingement Screen Filters, Ashish R. Kumar

Theses and Dissertations--Mining Engineering

Heavy industries, such as mining, generate dust in quantities that present an occupational health hazard. Prolonged exposure to the respirable dust has been found to result in many irreversible occupational ailments in thousands of miners. In underground mining applications, a variety of scrubbing systems are used to remove dust near the zones of generation. However, the wire-mesh type fibrous screens in the flooded-bed dust scrubbers used on continuous miners, are prone to clogging due to the accumulation of dust particles. This clogging results in a reduced capture efficiency and a higher exposure to the personnel. This research establishes the Vortecone ...


Optimization Of Microfluidic Particle Separator Geometry Using Computational Fluid Dynamics, Joseph Petersen Jan 2018

Optimization Of Microfluidic Particle Separator Geometry Using Computational Fluid Dynamics, Joseph Petersen

Electronic Theses and Dissertations

Computational fluid dynamics software was used to simulate the motion of circulating tumor cells in a variety of microfluidic cell isolation devices. Design of several novel microfluidic cell isolation devices was aided by viewing streamlines of fluid in devices in simulation. Devices that performed best in simulation used 5-micrometer wide guiding channels to guide cells to the capture location in the device. While these devices performed better than other devices in simulation and captured all particles regardless of position along inlet, experimental results differ from simulation.


Evaluation And Enhancement Of Clean Energy Systems: Analytical, Computational And Experimental Study Of Solar And Nuclear Cycles, Nima Fathi Jul 2017

Evaluation And Enhancement Of Clean Energy Systems: Analytical, Computational And Experimental Study Of Solar And Nuclear Cycles, Nima Fathi

Mechanical Engineering ETDs

Clean (and specifically renewable) energy is steadily improving its global share. However, finite availability of fossil fuels and the growing effects of climate change make it an urgent priority to convince the industry and governments to incentivize investment in the renewable energy field and to make it more attractive by decreasing the capital cost. Until recently, uncertainties in funding limited renewable energy development, especially in the US. That limitation has been one of the barriers to progress. Another limitation of many renewable energy systems is the variability in their output, which makes them unsuitable for baseline power production. Therefore, fossil ...


A Ship Advancing In A Stratified Fluid: The Dead Water Effect Revisited, Mehdi Esmaeilpour May 2017

A Ship Advancing In A Stratified Fluid: The Dead Water Effect Revisited, Mehdi Esmaeilpour

Theses and Dissertations

A computational fluid dynamics (CFD) methodology is presented to predict density stratified flows in the near-field of ships and submarines. The density is solved using a higher-order transport equation coupled with mass and momentum conservation. Turbulence is implemented with a k-ε/k-ω based Delayed Detached Eddy Simulation (DDES) approach, enabling explicit solution of larger energy-containing vortices in the wake. Validation tests are performed for a two-dimensional square cavity and the three-dimensional stratified flow past a sphere, showing good agreement with available data. The near-field flow of the self-propelled Research Vessel Athena advancing in a stably stratified fluid is studied, as ...


The Development Of A Vertical-Axis Wind Turbine Wake Model For Use In Wind Farm Layout Optimization With Noise Level Constraints, Eric Blaine Tingey Mar 2017

The Development Of A Vertical-Axis Wind Turbine Wake Model For Use In Wind Farm Layout Optimization With Noise Level Constraints, Eric Blaine Tingey

Theses and Dissertations

This thesis focuses on providing the means to use vertical-axis wind turbines (VAWTs) in wind farms as an alternative form of harnessing wind energy in offshore and urban environments where both wake and acoustic effects of turbines are important considerations. In order for VAWTs to be used in wind farm layout analysis and optimization, a reduced-order wake model is needed to calculate velocities around a turbine quickly and accurately. However, a VAWT wake model has not been available to accomplish this task. Using vorticity data from computational fluid dynamic (CFD) simulations of VAWTs and cross-validated Gaussian distribution and polynomial surface ...


Design Of A Novel Microreactor To Study Short Residence Time Combustion, Tianzhu Fan Jan 2017

Design Of A Novel Microreactor To Study Short Residence Time Combustion, Tianzhu Fan

Mechanical Engineering Graduate Theses & Dissertations

Microreactors are useful tools for understanding the short residence time reactions of biomass polymers and fuel molecules. When coupled with sensitive detection methods, microreactors have the ability to detect all molecules produced in the reactor, including stable, meta-stable, and radical species, making microreactors one of the few experiments where nearly all chemical species may be detected. At the University of Colorado Boulder, our microreactor studies have involved very small (~1 mm internal diameter, ~28 mm long) silicon carbide (SiC) tubes to study short residence time pyrolysis reactions in conjunction with photoionization mass spectrometry (PIMS) and Fourier transform infrared spectroscopy (FTIR ...


Stabilized Conservative Level Set Method With Adaptive Wavelet-Based Mesh Refinement, Navid Shervani-Tabar Jan 2017

Stabilized Conservative Level Set Method With Adaptive Wavelet-Based Mesh Refinement, Navid Shervani-Tabar

Mechanical Engineering Graduate Theses & Dissertations

This study investigates one of the well-known shortcomings of the conservative level set method, namely the ill-defined normal vector. A stabilized formulation is proposed which does not rely on the unit normal vector anymore. Instead, the proposed stabilized conservative level set, SCLS, utilizes a modified normal vector, magnitude of which is unit in the interfacial region of width ε and approaches zero in the far field from the interface. Respective adjustments have been applied on the reinitialization equation to comply with the proposed normal vector. This methodology is general and robust and it is not topology dependent. Since the information ...


Immersed Boundary Methods For Optimization Of Strongly Coupled Fluid-Structure Systems, Nicholas J. Jenkins Jan 2017

Immersed Boundary Methods For Optimization Of Strongly Coupled Fluid-Structure Systems, Nicholas J. Jenkins

Aerospace Engineering Sciences Graduate Theses & Dissertations

Conventional methods for design of tightly coupled multidisciplinary systems, such as fluid-structure interaction (FSI) problems, traditionally rely on manual revisions informed by a loosely coupled linearized analysis. These approaches are both inaccurate for a multitude of applications, and they require an intimate understanding of the assumptions and limitations of the procedure in order to soundly optimize the design. Computational optimization, in particular topology optimization, has been shown to yield remarkable results for problems in solid mechanics using density interpolations schemes. In the context of FSI, however, well defined boundaries play a key role in both the design problem and the ...


Cfd Analysis Methods For Systems Driven By Natural Convection, Aaron Propst Jan 2017

Cfd Analysis Methods For Systems Driven By Natural Convection, Aaron Propst

Electronic Theses and Dissertations

Natural convection driven flows are present in many engineering applications such as HVAC, electronics cooling, and cryogenic systems. Predicting the flow behavior of such systems requires experimentation or numerical simulation through Computational Fluid Dynamics due to the complex interactions of natural convection. Recent advances in computing resources have made CFD increasingly popular for engineering analysis of fluid dynamics and heat transfer. CFD simulation has several advantages over experimentation including: 1) cost, 2) ease of changing design parameters, and 3) time required to obtain results. These advantages lead to an increased likelihood of discovering an optimal design. However, systems with complex ...


Assessment Of Varying Model Representations In Cfd Simulations, Caitlin R. Gerdes Jan 2017

Assessment Of Varying Model Representations In Cfd Simulations, Caitlin R. Gerdes

Electronic Theses and Dissertations

This thesis investigates the effects of varying model refinement and representation of computational fluid dynamics (CFD) simulations in two case studies. Product and process realization in engineering design requires substantial resources (time and money) in order to test novel designs for effectiveness. In recent decades, engineering has been relying more heavily on simulation-based analysis in the design process with computer models to help reduce the demands for real-life testing. The first case study analyzed in this thesis is a photobioreactor, which is used to grow microalgae for biofuel and require a balance of nutrients, light, and mixing for growth. The ...


Hydrodynamics Of Swimming Microorganisms In Complex Fluids, Gaojin Li Dec 2016

Hydrodynamics Of Swimming Microorganisms In Complex Fluids, Gaojin Li

Open Access Dissertations

Swimming motion of microorganisms, such as spermatozoa, plankton, algae and bacteria, etc., ubiquitously occurs in nature. It affects many biological processes, including reproduction, infection and the marine life ecosystem. The hydrodynamic effects are important in microorganism swimming, their nutrient uptake, fertilization, collective motions and formation of colonies. In nature, microorganisms have evolved to use various fascinating ways for locomotion and transport. Different designs are also developed for the locomotion of artificial nano- and microswimmers. In this study, we use several different computational models to investigate the behavior of microswimmers.

Microorganisms typically swim in the low Reynolds number regime, where inertia ...


Implementations Of Fourier Methods In Cfd To Analyze Distortion Transfer And Generation Through A Transonic Fan, Marshall Warren Peterson Jun 2016

Implementations Of Fourier Methods In Cfd To Analyze Distortion Transfer And Generation Through A Transonic Fan, Marshall Warren Peterson

Theses and Dissertations

Inlet flow distortion is a non-uniform total pressure, total temperature, or swirl (flow angularity) condition at an aircraft engine inlet. Inlet distortion is a critical consideration in modern fan and compressor design. This is especially true as the industry continues to increase the efficiency and operating range of air breathing gas turbine engines. The focus of this paper is to evaluate the Computational Fluid Dynamics (CFD) Harmonic Balance (HB) solver in STAR-CCM+ as a reduced order method for capturing inlet distortion as well as the associated distortion transfer and generation. New methods for quantitatively describing and analyzing distortion transfer and ...


Cfd Model For Ventilation In Broiler Holding Sheds, Christian Heymsfield May 2016

Cfd Model For Ventilation In Broiler Holding Sheds, Christian Heymsfield

Biological and Agricultural Engineering Undergraduate Honors Theses

Broiler production in Arkansas was valued at over $3.6 billion in 2013 (University of Arkansas Extension of Agriculture). Consequently, improvement in any phase of the production process can have significant economic impact and animal welfare implications. From the time poultry leave the farm and until they are slaughtered, they can be exposed to harsh environmental conditions, both in winter and in summer. After road transportation, birds are left to wait in holding sheds once they arrive at the processing plant, for periods of approximately 30 minutes to two hours. This project was interested in this holding shed waiting time ...


Improving Ventricular Catheter Design Through Computational Fluid Dynamics, Sofy Hefets Weisenberg May 2016

Improving Ventricular Catheter Design Through Computational Fluid Dynamics, Sofy Hefets Weisenberg

Masters Theses

Cerebrospinal fluid (CSF) shunts are fully implantable medical devices that are used to treat patients suffering from conditions characterized by elevated intracranial pressure, such as hydrocephalus. In cases of shunt failure or malfunction, patients are often required to endure one or more revision surgeries to replace all or part of the shunt. One of the primary causes of CSF shunt failure is obstruction of the ventricular catheter, a component of the shunt system implanted directly into the brain's ventricular system. This work aims to improve the design of ventricular catheters in order to reduce the incidence of catheter obstruction ...


Analysis Of High Fidelity Turbomachinery Cfd Using Proper Orthogonal Decomposition, Ronald Alex Spencer Mar 2016

Analysis Of High Fidelity Turbomachinery Cfd Using Proper Orthogonal Decomposition, Ronald Alex Spencer

Theses and Dissertations

Assessing the impact of inlet flow distortion in turbomachinery is desired early in the design cycle. This thesis introduces and validates the use of methods based on the Proper Orthogonal Decomposition (POD) to analyze clean and 1/rev static pressure distortion simulation results at design and near stall operating condition. The value of POD comes in its ability to efficiently extract both quantitative and qualitative information about dominant spatial flow structures as well as information about temporal fluctuations in flow properties. Observation of the modes allowed qualitative identification of shock waves as well as quantification of their location and range ...


A Novel Approach To Evaluating Compact Finite Differences And Similar Tridiagonal Schemes On Gpu-Accelerated Clusters, Ashwin Trikuta Srinath Dec 2015

A Novel Approach To Evaluating Compact Finite Differences And Similar Tridiagonal Schemes On Gpu-Accelerated Clusters, Ashwin Trikuta Srinath

All Theses

Compact finite difference schemes are widely used in the direct numerical simulation of fluid flows for their ability to better resolve the small scales of turbulence. However, they can be expensive to evaluate and difficult to parallelize. In this work, we present an approach for the computation of compact finite differences and similar tridiagonal schemes on graphics processing units (GPUs). We present a variant of the cyclic reduction algorithm for solving the tridiagonal linear systems that arise in such numerical schemes. We study the impact of the matrix structure on the cyclic reduction algorithm and show that precomputing forward reduction ...


Using Star-Ccm+ To Evaluate Multi-User Collaboration In Cfd, Kasey Johnson Webster Oct 2015

Using Star-Ccm+ To Evaluate Multi-User Collaboration In Cfd, Kasey Johnson Webster

Theses and Dissertations

The client-server architecture of STAR-CCM+ allows multiple users to collaborate on a simulation set-up. The effectiveness of collaboration with this architecture is tested and evaluated on five models. The testing of these models is a start to finish set-up of an entire simulation excluding computational time for generating mesh and solving the solution. The different models have distinct differences which test every operation that would be used in a general CFD simulation. These tests focus on reducing the time spent preparing the geometry to be meshed, including setting up for a conformal mesh between multiple regions in conjugate heat transfer ...


A Numerical Study Of Periciliary Liquid Depth In Mdct-Based Human Airway Models, Dan Wu May 2015

A Numerical Study Of Periciliary Liquid Depth In Mdct-Based Human Airway Models, Dan Wu

Theses and Dissertations

Periciliary liquid (PCL) is a critical component of the respiratory system for maintaining mucus clearance. As PCL homeostasis is affected by evaporation and mechanical forces, which are in turn affected by various breathing conditions, lung morphology and ventilation distribution, the complex process of PCL depth regulation in vivo is not fully understood. We propose an integrative approach to couple a thermo-fluid computational fluid dynamics (CFD) model with an epithelial cell model to study the dynamics of PCL depth using subject-specific human airway models based on multi-detector row computed-tomography (MDCT) volumetric lung images.

The thermo-fluid CFD model solves three-dimensional (3D) incompressible ...


Three Dimensional Simulations Of Tornado Sheltering Effect Of Man-Made Structures, Piotr Gorecki May 2015

Three Dimensional Simulations Of Tornado Sheltering Effect Of Man-Made Structures, Piotr Gorecki

Theses and Dissertations

A three dimensional computational fluid dynamics (CFD) model was utilized to investigate tornado-like vortex interactions with wide man-made structures. The tornado-like wind profile was approximated using Rankine vortex model. By utilizing the CFD model, it was explained why tornadoes exhibit less damage on leeward side of large structures. During the preliminary stage of this study, a perpendicular vortex-prism interaction was analyzed. The prism height and the length were equal to the vortex core radius. The prism was also 12 times wider than the vortex core radius. During the vortex-prism interaction, the near-ground portion of the vortex was blocked by the ...


Analytical And Numerical Validation Of Nozzle Spray Measurement Data Obtained From A Newly Developed Production System, Iddrisu Seidu Jan 2015

Analytical And Numerical Validation Of Nozzle Spray Measurement Data Obtained From A Newly Developed Production System, Iddrisu Seidu

ETD Archive

A newly developed production test stand for measuring the spray angle of a pressure swirl atomizer was constructed and used to measure a product line of these pressure swirl atomizers -- the macrospray atomizer. This new test stand, utilizing constant temperature hot wire anemometers, captures the spray angle data based on the voltage drop the hot wire probes see as they traverse the spray cone of the atomizer and as fluid droplets impinge upon the wire. Datasets acquired from the experiments are compared and correlated with computational fluid dynamics (CFD) simulation data. In addition, angles obtained from another type of spray ...