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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 ...


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 ...


Fast Cfd Simulation Method For Indoor Environment Modeling, Haidong Wang Jan 2013

Fast Cfd Simulation Method For Indoor Environment Modeling, Haidong Wang

Civil Engineering Graduate Theses & Dissertations

Computational Fluid Dynamics (CFD) has been becoming an important tool in building environment and airflow modeling. Well validated CFD model can provide more detailed and informative results than other computer models and physical experiment. However, the significant computational cost of CFD has always been the main factor that restricting its broader application.

This study reviews the various means of reducing the computational cost of CFD in literature. With considering the characteristics and result accuracy requirement in indoor environment quality (IEQ) study, the most important factors that affect the computing cost are identified: grid resolution, turbulence modeling and velocity-pressure decoupling algorithm ...