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Full-Text Articles in Engineering

Effects Of Grooves On Drag In Laminar Channel Flow, Yanbei Wang Jul 2018

Effects Of Grooves On Drag In Laminar Channel Flow, Yanbei Wang

Electronic Thesis and Dissertation Repository

This thesis presents the analysis of the effects of three-dimensional grooves on the flow responses in laminar channel flows. The wall topographies were expressed using the two-dimensional Fourier expansions. A spectrally accurate algorithm based on the Immersed Boundary Conditions (IBC) was used to determine the solution for the field equations and extract information about the velocity and pressure fields. The effects of grooves on the pressure losses were assessed by determining the additional pressure gradient required to maintain the same flow rate through the grooved channel as through the reference smooth channel. Effects of groove wave numbers, groove amplitudes, the ...


Optimization Of Superhydrophobic Surface Production Using Ambient-Dried Silica-Based Aerogels, Elizabeth Donlon Jun 2018

Optimization Of Superhydrophobic Surface Production Using Ambient-Dried Silica-Based Aerogels, Elizabeth Donlon

Honors Theses

Superhydrophobic surfaces exhibit particular properties that make them functional in various anti-sticking, anti-contamination, self-cleaning and drag reduction applications. Though such surfaces are found in nature - most notably the lotus leaf - they are difficult to produce. There are numerous methods and techniques for fabricating superhydrophobic surfaces. One such method is the sol-gel method, in which aerogel, a highly porous and lightweight material that can be made hydrophobic or superhydrophobic, is coated onto a surface. The purpose of this project is to devise a simple and repeatable procedure for making hydrophobic silica aerogel coatings that can be used for drag reduction. Hydrophobic ...


On The Reduction Of The Driving Force In Shear-Driven Flows, Sakib Shadman Apr 2018

On The Reduction Of The Driving Force In Shear-Driven Flows, Sakib Shadman

Electronic Thesis and Dissertation Repository

In shear-driven flows, an external driving force is needed to maintain the relative movement of horizontal plates. This thesis presents a systematic analysis on using spatially periodic heating and grooved surfaces to control this force. It is found that the use of periodic heating creates a buoyancy-driven effect that always reduces this force. The use of proper heating may even lead to the complete elimination of this force. It is further found that the use of isothermal grooved surfaces always enhances flow resistance, resulting in an increase of this force. When grooves and heating are applied together, their interaction induces ...


Hydrodynamic And Thermal Effects Of Sub-Critical Heating On Superhydrophobic Surfaces And Microchannels, Adam M. Cowley Nov 2017

Hydrodynamic And Thermal Effects Of Sub-Critical Heating On Superhydrophobic Surfaces And Microchannels, Adam M. Cowley

Theses and Dissertations

This dissertation focuses on the effects of heating on superhydrophobic (SHPo) surfaces. The work is divided into two main categories: heat transfer without mass transfer and heat transfer in conjunction with mass transfer. Numerical methods are used to explore the prior while experimental methods are utilized for the latter. The numerical work explores convective heat transfer in SHPo parallel plate microchannels and is separated into two stand-alone chapters that have been published archivally. The first considers surfaces with a rib/cavity structure and the second considers surfaces patterned with a square lattice of square posts. Laminar, fully developed, steady flow ...


An Experimental Study On Drag Reduction Of Aftermarket Additions On An Suv, Christiana L. Katsoulos May 2017

An Experimental Study On Drag Reduction Of Aftermarket Additions On An Suv, Christiana L. Katsoulos

Senior Honors Projects, 2010-2019

Over recent years, the awareness of climate change has become more prevalent worldwide and one major contributor to global warming has been the use of transportation. Vehicles contribute to global warming by releasing petroleum based emissions such as significant amounts of carbon dioxide and numerous other harmful environmental pollutants. SUVs contribute to the emissions problem more so than sedans, since they have lower gas mileage and need more gasoline regularly. The main functionality of sport utility vehicles, or SUVs, includes hauling or off-roading and fuel efficiency is not always the focus in the design process. However, aerodynamic enhancements could improve ...


Aerodynamic Improvement Of The Byu Supermileage Vehicle, Sayan Dobronsky Nov 2015

Aerodynamic Improvement Of The Byu Supermileage Vehicle, Sayan Dobronsky

Theses and Dissertations

The purpose of this thesis work was to design a new shape for the BYU Supermileage vehicle in order to improve its fuel efficiency. Computational Fluid Dynamics (CFD) was used to obtain the coefficient of drag (CD) and drag area of the current baseline vehicle at a Reynolds number of 1.6x10^6 and 8.7x10^5. Then a new shape was developed using mesh morphing software. The new shape was imported into the CFD program and the drag figures and airflow plots from the modified design were compared with the baseline vehicle. Scale models of the vehicles were also ...


Flows In Vibrating Channels, Sahab Zandi Sep 2015

Flows In Vibrating Channels, Sahab Zandi

Electronic Thesis and Dissertation Repository

A spectral algorithm based on the immersed boundary conditions (IBC) concept has been developed for the analysis of flows in channels bounded by vibrating walls. The vibrations take the form of travelling waves of arbitrary profile. The algorithm uses a fixed computational domain with the flow domain immersed in its interior. Boundary conditions enter the algorithm in the form of constraints. The spatial discretization uses a Fourier expansion in the stream-wise direction and a Chebyshev expansion in the wall-normal direction. Use of the Galileo transformation converts the unsteady problem into a steady one. An efficient solver which takes advantage of ...


Piv Measurements Of Turbulent Flow In A Rectangular Channel Over Superhydrophobic Surfaces With Riblets, Richard Mark Perkins Sep 2014

Piv Measurements Of Turbulent Flow In A Rectangular Channel Over Superhydrophobic Surfaces With Riblets, Richard Mark Perkins

Theses and Dissertations

In this thesis I investigate characteristics of turbulent flow in a channel where one of the walls has riblets, superhydrophobic microribs, or a hybrid surface with traditional riblets built on a superhydrophobic microrib surface. PIV measurements are used to find the velocity profile, the turbulent statistics, and shear stress profile in the rectangular channel with one wall having a structured test surface. Both riblets and superhydrophobic surfaces can each provide a reduction in the wall shear stress in a turbulent channel flow. Characterizing the features of the flow using particle image velocimetry (PIV) is the focus of this research. Superhydrophobicity ...


Effects Of Surface Topographies On Heat And Fluid Flows, Hadi Vafadar Moradi Jan 2014

Effects Of Surface Topographies On Heat And Fluid Flows, Hadi Vafadar Moradi

Electronic Thesis and Dissertation Repository

Responses of annular and planar flows to the introduction of grooves on the bounding surfaces have been analyzed. The required spectral algorithms based on the Fourier and Chebyshev expansions have been developed. The difficulties associated with the irregularities of the physical domain have been overcome using either the immersed boundary conditions (IBC) concept or the domain transformation method (DT).

Steady flows in annuli bounded by walls with longitudinal grooves have been studied. Analysis of pressure losses showed that the groove-induced changes can be represented as a superposition of a pressure drop due to a change in the average position of ...


Flows In Grooved Channels, Alireza Mohammadi Sep 2013

Flows In Grooved Channels, Alireza Mohammadi

Electronic Thesis and Dissertation Repository

This dissertation presents the analysis of effects of two-dimensional grooves on flow responses in laminar channel flows. Straight grooves have been considered which may have an arbitrary cross-section and an arbitrary orientation with respect to the flow direction. It has been shown that the grooves effects can be split into two parts; one due to the change in the mean positions of the walls and the other due to the flow modulations created by the groove geometry. The former effect can be determined analytically, while the latter effect requires numerical modelling. Projection of groove shape onto a Fourier space creates ...


Numerical Study Of Fully Developed Laminar And Turbulent Flow Through Microchannels With Longitudinal Microstructures, Kevin B. Jeffs Nov 2007

Numerical Study Of Fully Developed Laminar And Turbulent Flow Through Microchannels With Longitudinal Microstructures, Kevin B. Jeffs

Theses and Dissertations

Due to the increase of application in a number of emerging technologies, a growing amount of research has focused on the reduction of drag in microfluidic transport. A novel approach reported in the recent literature is to fabricate micro-ribs and cavities in the channel wall that are then treated with a hydrophobic coating. Such surfaces have been termed super- or ultrahydrophobic and the contact area between the flowing liquid and the solid wall is greatly reduced. Further, due to the scale of the micropatterned structures, the liquid is unable to wet the cavity and a liquid meniscus is formed between ...


Analysis Of Viscous Drag Reduction And Thermal Transport Effects For Microengineered Ultrahydrophobic Surfaces, Jason W. Davies Mar 2006

Analysis Of Viscous Drag Reduction And Thermal Transport Effects For Microengineered Ultrahydrophobic Surfaces, Jason W. Davies

Theses and Dissertations

One approach recently proposed for reducing the frictional resistance to liquid flow in microchannels is the patterning of micro-ribs and cavities on the channel walls. When treated with a hydrophobic coating, the liquid flowing in the microchannel wets only the top surfaces of the ribs, and does not penetrate into the cavities, provided the pressure is not too high. The net result is a reduction in the surface contact area between channel walls and the flowing liquid. For micro-ribs and cavities that are aligned normal to the channel axis (principal flow direction), these micropatterns form a repeating, periodic structure. This ...