Engineering Commons^™

Modeling Target Disinfection By-Product Dynamics In Indoor Swimming Pools, Barnard S. Mondal, Cary Troy, Mehrnaz Afifi, Shih-Chi Weng, Ernest R. Blatchley Iii

The Summer Undergraduate Research Fellowship (SURF) Symposium

Chlorination is the primary disinfection method for swimming pools in the United States; however, chlorine also reacts with pollutants (e.g., sweat, urine and anthropogenic compounds) to form disinfection by-products (DBPs). Some DBPs are asthma causing (e.g. nitrogen-trichloride) and even carcinogens (e.g., trihalomethanes and nitrosamines). Consequently, exposure to DBPs poses health risks to patrons and staff in pool environments. Furthermore, volatilization of DBPs is enhanced by bather activity, but the relationship between activity and volatilization has yet been quantified such that the dynamic behavior of DBPs can be predicted. Therefore, the objective of this research is to …

Deep-Water Near-Bottom Turbulence In Lake Michigan: An Underwater Investigation, David J. Cannon, Cary Troy

The Summer Undergraduate Research Fellowship (SURF) Symposium

Motivated by a need to characterize near-bottom deep-water turbulence for an understanding of the filtration capabilities of invasive quagga mussels, an instrument tripod was deployed in Lake Michigan for six months in 60m of water to measure current velocities, with specific interest being paid to near-bottom (0.10 to 0.95 meters above bottom) velocities during the deployment. The deployment period (September 2012-April 2013) was characterized by very little stratification and a median temperature of about throughout the water column. A mean horizontal velocity of 3.6 cm/s with a standard deviation of 2 cm/s was also measured at 1 meter above the …

Small Wind Turbines In Turbulent (Urban) Environments: A Consideration Of Normal And Weibull Distributions For Power Prediction, Keith Sunderland, Thomas Woolmington, Jonathan Blackledge, Michael Conlon

Articles

The urban terrain and the associated morphological complexities therein, present significant challenges for the deployment of small wind turbines. In particular, a considerable amount of uncertainty is attributable to the lack of understanding concerning how turbulence within urban environments affects turbine productivity. Current wind turbine power output measurements (particularly for small/micro wind turbines) are based on an average wind speed over an observation period; with limited accountability of the variability of wind speed within the observation time frame. This paper however, presents two models that can instead accurately consider such wind speed variation and how it affects the turbine, based …

Channel Flow Behaviour During Mixed Convection At Low Reynolds Numbers, Ahmed Elatar

Electronic Thesis and Dissertation Repository

The effect of mixed convection on low Reynolds numbers flow inside a horizontal square channel heated from below have been investigated experimentally. The channel flow rate ranged from 0.0210 kg/s to 0.0525 kg/s which correspond to Reynolds numbers between 300 and 750 in the absence of heating. The channel bottom surface temperature was controlled and varied from 30 ºC to 55 ºC (Grashof number ranged between 6.37×10⁶ and 3.86×10⁷). Planer Particle Image Velocimetry (PIV) technique was used to measure two-dimensional velocity fields in the channel mid-vertical plane and two horizontal planes close to the bottom heated wall. …

Urban Deployment Of Small Wind Turbines: Power, Performance And Turbulence, Keith Sunderland, Thomas Woolmington, Michael Conlon, Jonathan Blackledge

Conference papers

The urban terrain and the associated topographical complexities therein, present significant challenges to the deployment of small wind turbines. In particular, a considerable amount of uncertainty is attributable to the lack of understanding concerning how turbulence within urban environments affects turbine productivity. This paper considers how the industry standard metric, turbulence intensity (TI), in conjunction with the power characteristic of a 2.5kW wind turbine, can be employed to estimate turbine power performance. The research presented here considers the potential productivity of a wind turbine installation at two sites in (urban and suburban) Dublin, Ireland where the prevalent turbulence at both …

Piv-Based Investigation Of Hemodynamic Factors In Diseased Carotid Artery Bifurcations With Varying Plaque Geometries, Sarah Kefayati

Electronic Thesis and Dissertation Repository

Ischemic stroke is often a consequence of complications due to clot formation (i.e. thrombosis) at the site of an atherosclerotic plaque developed in the internal carotid artery. Hemodynamic factors, such as shear-stress forces and flow disturbances, can facilitate the key mechanisms of thrombosis. Atherosclerotic plaques can differ in the severity of stenosis (narrowing), in eccentricity (symmetry), as well as inclusion of ulceration (wall roughness). Therefore, in terms of clinical significance, it is important to investigate how the local hemodynamics of the carotid artery is mediated by the geometry of plaque. Knowledge of thrombosis-associated hemodynamics may provide a basis to introduce …

Experimental Investigation Of Blowing Effects On Turbulent Flow Over A Rough Surface, Mark A. Miller, Alexandre Martin, Sean C. C. Bailey

Mechanical Engineering Faculty Publications

A high Reynolds number turbulent channel flow facility was used to study the combined effects of roughness and flow injection on the mean flow and turbulence characteristics. It was found that the additional momentum injection through the surface enhanced the roughness effects and for the mean flow the effect of blowing was indistinguishable from that of increased roughness. However, for the turbulence statistics, this analogy broke down in that the addition of blowing resulted in behavior which did not follow that predicted by Townsend’s hypothesis. This was observed as a reduction of outer-scaled Reynolds stress well into the outer layer. …

Advances In The Quantification Of Turbulence: A Wind Resource Characteristic, Thomas Woolmington, Keith Sunderland, Jonathan Blackledge, Michael Conlon

Conference papers

Wind resource assessment is a critical parameter in a diverse range of considerations within the built environment. Engineers and scientists, engaging in building design, energy conservation/application and air-quality/air-pollution control measures, need to be cognisant of how the associated wind resource imposes increased complexities in their design and modelling processes. In this regard, the topographical heterogeneities within these environments, present significant challenges to quantifying the resource and its turbulent characteristics. Indeed, from the perspective of assessing the wind resource within the built environment, topographical heterogeneity is the primary proponent of turbulence and the main inhibitor to acquiring meaningful measurements.

This paper …

Microphone-Based Pressure Diagnostics For Boundary Layer Transition, Spencer Everett Lillywhite

Master's Theses

An experimental investigation of the use low-cost microphones for unsteady total pressure measurement to detect transition from laminar to turbulent boundary layer flow has been conducted. Two small electret condenser microphones, the Knowles FG-23629 and the FG-23742, were used to measure the pressure fluctuations and considered for possible integration with an autonomous boundary layer measurement system. Procedures to determine the microphones’ maximum sound pressure levels and frequency response using an acoustic source provided by a speaker and a reference microphone. These studies showed that both microphones possess a very flat frequency response and that the max SPL of the FG-23629 …

Application Of One Dimensional Turbulence (Odt) To Model Fire Spread Through Biomass Fuel Bed, Abinash Paudel

Theses and Dissertations

Each year fires destroy millions of acres of woodland, lives, and property, and significantly contribute to air pollution. Increased knowledge of the physics and properties of the flame propagation is necessary to broaden the fundamental understanding and modeling capabilities of fires. Modeling flame propagation in fires is challenging because of the various modes of heat transfer with diverse fuels, multi-scale turbulence, and complex chemical kinetics. Standard physical models of turbulence like RANS and LES have been used to understand the flame behavior, but these models are limited by computational cost and their inability to resolve sub-grid scales. Application of several …

The Quantification Of Wind Turbulence By Means Of The Fourier Dimension, Thomas Woolmington, Keith Sunderland, Jonathan Blackledge, Michael Conlon

Conference papers

Signal Processing within the frequency domain has long been associated with electrical engineering as a means to quantify the characteristics of voltage/current waveforms. Historically, wind speed data (speed/direction) have been captured and stored as statistical markers within a time series description. This form of storage, while cumbersome, is applicable in wind regimes that are relatively laminar. In urban environments, where the associated topographies and building morphologies are heterogeneous, wind speeds are highly turbulent and chaotic. In such environments and with particular reference to wind energy, time series statistics are of limited use, unless the generic probability distribution function (PDF) is …

Verification And Validation Of The Spalart-Allmaras Turbulence Model For Strand Grids, Oisin Tong

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The strand-Cartesian grid approach is a unique method of generating and computing fluid dynamic simulations. The strand-Cartesian approach provides highly desirable qualities of fully-automatic grid generation and high-order accuracy. This thesis focuses on the implementation of the Spalart-Allmaras turbulence model to the strand-Cartesian grid framework. Verification and validation is required to ensure correct implementation of the turbulence model.

Mathematical code verification is used to ensure correct implementation of new algorithms within the code framework. The Spalart-Allmaras model is verified with the Method of Manufactured Solutions (MMS). MMS shows second-order convergence, which implies that the new algorithms are correctly implemented.

Validation …

Turbulence Modeling For Subsonic Separated Flows Over 2-D Airfoils And 3-D Wings, Aaron Michael Rosen

Open Access Theses

Accurate predictions of turbulent boundary layers and flow separation through computational fluid dynamics (CFD) are becoming more and more essential for the prediction of loads in the design of aerodynamic flight components. Standard eddy viscosity models used in many commercial codes today do not capture the nonequilibrium effects seen in a separated flow and thus do not generally make accurate separation predictions. Part of the reason for this is that under nonequilibrium conditions such as a strong adverse pressure gradient, the history effects of the flow play an important role in the growth and decay of turbulence. More recent turbulence …

Discrete Phase Simulations Of Drilled Cuttings Transport Process In Highly Deviated Wells, Doguhan Yilmaz

LSU Master's Theses

Transporting drilled cuttings from the bottomhole to the surface becomes more difficult and problematic in highly deviated wells than in vertical wells. Cuttings tend to settle down on the low side of the annulus typically in the form of a bed which can cause further problems. The height of this bed depends on many parameters such as annular domain geometry, drilling fluid density and rheology, annular flow rate, drill pipe rotation speed, cuttings size, shape, and their density. Prediction of the stationary cuttings bed height with respect to these aforementioned parameters is thus necessary to optimize the range of the …

The Determination Of Drag And Lift Forces Of A Rigid Beam Located Within A Turbulent Boindary Layer By Means Of Large Eddy Simulation Modeling, Santiago Helman

Dissertations and Theses

"Recent studies such as those conducted by Akaydin, Elvin and Andreopoulos in [1] have described and quantified the electrical power that can be extracted from a moving flow by the implementation of energy harvesters. In such study, a flexible cantilevered beam was fitted with a cylindrical prism at the free end and placed within a uniform flow field. Due to the vortex shedding generated by the prism (e.g. Von Karman vortices) the beam was found to oscillate about the undisturbed position. The beam in question was then outfitted with a piezoelectric material in order to translate the transient strain energy …

Experimental Characterization Of Roughness And Flow Injection Effects In A High Reynolds Number Turbulent Channel, Mark A. Miller

Theses and Dissertations--Mechanical Engineering

A turbulent channel flow was used to study the scaling of the combined effects of roughness and flow injection on the mean flow and turbulence statistics of turbulent plane Poiseuille flow. It was found that the additional momentum injected through the rough surface acted primarily to enhance the roughness effects and, with respect to the mean flow, blowing produced similar mean flow effects as increasing the roughness height. This was not found to hold for the turbulence statistics, as a departure from Townsend’s hypothesis was seen. Instead, the resulting outer-scaled streamwise Reynolds stress for cases with roughness and blowing deviated …

Electrokinetic Mixing And Separation In Microfluidic Systems, Fang Yang

Theses and Dissertations

Electrokinetics involves the study of liquid or particle motion under the action of an electric field; it includes electroosmosis, electrophoresis, dielectrophoresis, and electrowetting, etc. The applications of electrokinetics in the development of microfluidic devices have been widely attractive in the past decade. Electrokinetic devices generally require no external mechanical moving parts and can be made portable by replacing the power supply by small battery. Therefore, electrokinetic based microfluidic systems can serve as a viable tool in creating a lab-on-a-chip (LOC) for use in biological and chemical assays. Here we present our works of electrokenitic based mixing and separation in microfluidics …

Modeling And Design Of Photocatalytic Reactors For Air Purification, Yangyang Zhang

USF Tampa Graduate Theses and Dissertations

Photocatalysis is a promising technique for the remediation of indoor air pollution. Photocatalysis utilizes semiconductor photocatalysts (such as TiO₂ or ZnO) and appropriate light to produce strong oxidizing agents (OH*) that are able to break down organic compounds and inactivate bacteria and viruses. The overall goal of the research is to develop an efficient photocatalytic reactor based on mass transfer for indoor air purification. This study has focused on the enhancement of the effectiveness of the photocatalytic process by the introduction of artificial roughness on the reactor catalyst surface. The major effect of artificial roughness elements on the catalytic …

Large Eddy Simulation And Analysis Of Shear Flows In Complex Geometries, Prasad Mohanrao Kalghatgi

LSU Doctoral Dissertations

In the present work, large eddy simulation is used to numerically investigate two types of shear flows in complex geometries, (i) a novel momentum driven countercurrent shear flow in dump geometry and (ii) a film cooling flow (inclined jet in crossflow). Verification of subgrid scale model is done through comparisons with measurements for a turbulent flow over back step, present cases of counter current shear and film cooling flow. In the first part, a three dimensional stability analysis is conducted for countercurrent shear flow using Dynamic mode decomposition and spectral analysis. Kelvin-Helmholtz is identified as primary instability mechanism and observed …