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Full-Text Articles in Mechanical Engineering

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 ...


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 ...


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 ...


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 ...


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 ...


A Reduced Order Model For Efficient Physiological Flow Analysis In Aneurysms By Proper Orthogonal Decomposition, Gary Han Chang, Yahya Modarres-Sadeghi May 2016

A Reduced Order Model For Efficient Physiological Flow Analysis In Aneurysms By Proper Orthogonal Decomposition, Gary Han Chang, Yahya Modarres-Sadeghi

UMass Center for Clinical and Translational Science Research Retreat

Simulating physiological flows using computational fluid dynamics (CFD) remains to be computationally expensive and difficult for clinical usage because of the physiological flow and geometrical complexity involved in patient specific situations. We use the reduced order modeling (ROM) of such systems with high nonlinearity and geometrical non-uniformity to replace the full, nonlinear model with a low-degrees of freedom ROM model. We construct ROM models by the proper orthogonal decomposition (POD) method to estimate the flow-induced wall shear stress (WSS) and pressure loading of a simplified abdominal aortic aneurysm and a bifurcation cerebral aneurysm. This method allows us to investigate a ...


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 ...


Large Eddy Simulation Of Dispersed Multiphase Flow, Yejun Gong Jan 2012

Large Eddy Simulation Of Dispersed Multiphase Flow, Yejun Gong

Dissertations, Master's Theses and Master's Reports - Open

This thesis covers two main topics. The first is the comparison between the Reynoldsaveraged Navier-Stokes (RANS) simulation and the Large Eddy Simulation (LES) of high injection pressure diesel sprays under non-evaporating or evaporating conditions. The second topic is the comparison of the fuel behavior in the spray process between the hydrotreated vegetable oil (HVO) and the conventional EN 590, diesel #2 and n-heptane fuels.

To validate the RANS and LES spray simulations, comparisons were made with experimental data. The LES turbulence model, the initial drop size distribution (IDSD), the Levich jet breakup model and the CAB drop breakup model are ...


Cavitation From A Butterfly Valve: Comparing 3d Simulations To 3d X-Ray Computed Tomography Flow Visualization, Graham Brett, Marc Riveland, Terrence C. Jensen, Theodore J. Heindel Jul 2011

Cavitation From A Butterfly Valve: Comparing 3d Simulations To 3d X-Ray Computed Tomography Flow Visualization, Graham Brett, Marc Riveland, Terrence C. Jensen, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Flow control valves may experience localized cavitation when the local static pressure drops to the liquid vapor pressure. Localized damage to the valve and surrounding area can occur when the vapor cavity collapses. Valve designs that reduce cavitation are based on empirical evidence and accumulated experience, but there are still considerable cavitation problems in industry. Valve designers may use computational fluid dynamics (CFD) to simulate cavitation in flow control valves, but model validation is challenging because there are limited data of local cavitation from the valve surface. Typically, the intensity of cavitation in a control valve is inferred from measurements ...


Modeling A Biomass Fluidizing Bed With Side Port Air Injection, Mirka Deza, Francine Battaglia, Theodore J. Heindel Aug 2009

Modeling A Biomass Fluidizing Bed With Side Port Air Injection, Mirka Deza, Francine Battaglia, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Fluidized beds are used to gasify materials such as coal or biomass in the production of producer gas. Modeling these reactors using computational fluid dynamics is advantageous when performing parametric studies for design and scale-up. While two-dimensional simulations are easier to perform than three-dimensional simulations, they may not capture the proper physics. This paper compares two- and three-dimensional simulations with experiments for a reactor geometry with side port air injection. The side port is located within the bed region so that the injected air can help promote mixing. Of interest in this study is validating the hydrodynamics of fluidizing biomass ...


Modeling Of Dispersed Phase By Lagrangian Approach In Fluent - 2d Exercise, Kari Myöhänen Jan 2008

Modeling Of Dispersed Phase By Lagrangian Approach In Fluent - 2d Exercise, Kari Myöhänen

Kari Myöhänen

This shows an example calculation applying DPM model in Fluent. This is related to the other DPM presentation and was prepared for the course 'Theory and simulation of dispersed-phase multiphase flows" by Dr. Payman Jalali, Lappeenranta University of Technology.


Modeling Of Dispersed Phase By Lagrangian Approach In Fluent, Kari Myöhänen Jan 2008

Modeling Of Dispersed Phase By Lagrangian Approach In Fluent, Kari Myöhänen

Kari Myöhänen

This is a seminar work prepared for a course 'Theory and simulation of dispersed-phase multiphase flows' by Dr. Payman Jalali, Lappeenranta University of Technology


Lectures In Computational Fluid Dynamics Of Incompressible Flow: Mathematics, Algorithms And Implementations, James M. Mcdonough Jan 2007

Lectures In Computational Fluid Dynamics Of Incompressible Flow: Mathematics, Algorithms And Implementations, James M. Mcdonough

Mechanical Engineering Textbook Gallery

From Prologue:

The present lecture notes are written to emphasize the mathematics of the Navier–Stokes (N.–S.) equations of incompressible flow and the algorithms that have been developed over the past 30 years for solving them.


The Microchannel Flow Of A Micropolar Fluid, Guohua Liu Oct 1999

The Microchannel Flow Of A Micropolar Fluid, Guohua Liu

Doctoral Dissertations

Micro-channel flows have been computed to investigate the influence of Navier-Stokes formulation for the slip-flow boundary condition, and a micro-polar fluid model, respectively.

The results of the slip boundary condition show that the current methodology is valid for slip-flow regime (i.e., for values of Knudsen number less than approximately 0.1). Drag reduction phenomena apparent in some micro-channels can be explained by slip-flow theory. These results are in agreement with some computations and experiments.

An ad hoc micro-polar fluid model is developed to investigate the influence of micro effects, such as micro-gyration, in micro-scale flows. The foundation of the ...


Three-Dimensional Aerodynamic Design Optimization Using Discrete Sensitivity Analysis And Parallel Computing, Amidu Olawale Oloso Apr 1997

Three-Dimensional Aerodynamic Design Optimization Using Discrete Sensitivity Analysis And Parallel Computing, Amidu Olawale Oloso

Mechanical & Aerospace Engineering Theses & Dissertations

A hybrid automatic differentiation/incremental iterative method was implemented in the general purpose advanced computational fluid dynamics code (CFL3D Version 4.1) to yield a new code (CFL3D.ADII) that is capable of computing consistently discrete first order sensitivity derivatives for complex geometries. With the exception of unsteady problems, the new code retains all the useful features and capabilities of the original CFL3D flow analysis code. The superiority of the new code over a carefully applied method of finite-differences is demonstrated.

A coarse grain, scalable, distributed-memory, parallel version of CFL3D.ADII was developed based on "derivative stripmining". In this data-parallel ...