Mechanical Engineering Commons^™

Analyses For Assessing The Centreline Translation, Asymmetrical Wind-Field, And Velocity Fluctuations Of Tornado Vortices, Niall C. Bannigan

Electronic Thesis and Dissertation Repository

Tornadoes present an ever-increasing threat to communities worldwide, especially those with geographic conditions that place them in the path of several tornadoes annually. These conditions are likely to be exacerbated by ongoing trends in the climate. As such, it is necessary to move towards experimental and numerical tornado-like vortex studies that allow for more advanced simulation methods. Novel techniques for tracking and analysing tornado vortices simulated at high spatial and temporal resolution are presented herein. Significant wandering of the tornado's position and large peaks in the velocity field can be captured, demonstrating tangential gusting at more than 1.5 times the …

Study Of Multi-Dimensional Transfer Effects In Applied Smouldering Systems, Seyed Ziaedin Miry Mr

Electronic Thesis and Dissertation Repository

Smouldering is a flameless form of combustion that is driven by oxygen directly diffusing into the surface of condensed phase fuel (liquid or solid) and involves a complex interplay between heat and mass transfer through porous media, chemical reactions, and multiphase flow. Applied smouldering systems have been gaining popularity for a variety of applications including (i) energy and resource recovery, (ii) waste-to-energy, (iii) pyrolysis and gasification, and (iv) applied smouldering of organic liquids/solids for environmental benefits. In all contexts, smouldering is a complicated oxygen-limited phenomenon where multi-dimensional transfer effects (i.e., non-uniformities in …

Numerical Analysis Of Internal Hydraulic Jump In Complex Topography, Dylan Macriner

Electronic Thesis and Dissertation Repository

Topographic effects on internal hydraulic jumps in stratified flow over complex geometry are studied. The simulations are motivated by flow conditions present in a channel in Hood Canal, Washington with continuous density profiles and constant inlet velocities.

Results show that mixing in the domain is typically increased by topographic variation, where isolated expansions saw an increase in mixing, but the associated velocity decrease in expansions had contrasting effects on mixing. Likewise, a contraction with an increased velocity caused more mixing, seeing geometry change and velocity acting as compounding factors. 2D results including along channel topographic variation modelled after Hood Canal's …

Experimental Simulation Of Tornado-Like Vortices And Their Impact On High-Rise Buildings, Arash Ashrafi

Electronic Thesis and Dissertation Repository

One of the most crucial research areas in wind engineering is tornadoes due to the widespread damages to infrastructure and the environment in North America and other parts of the world. The proper scaling of tornadoes in experimental facilities, generating tornado-like vortices (TLVs) is, therefore, an essential part of evaluating tornado-indued damages on engineered buildings. The capability of producing TLVs of length scales in the range between 1:300 and 1:150 inside the Wind Engineering, Energy and Environment (WindEEE) Dome at Western University has already been demonstrated using only one mode of the full potential of this simulator. A new mode …

Integrated Modelling Of Wastewater Treatment And Sewer Processes - Interactions Of Fluid Flow, Mass Transfer, And Biochemical Reactions, Ahmed Khalil

Electronic Thesis and Dissertation Repository

Numerical modelling of wastewater management systems is crucial for investigating alternative designs and developing strategies for operation and control that improve the performance of the treatment stage (such as improving the aeration systems in activated sludge systems). Modelling can also help operators to mitigate common problems that arise from unwanted biochemical conversions in the sewer networks (such as the production of sulfide and methane). Therefore, this work focuses on two major areas related to modelling wastewater management systems. First, it seeks to develop more accurate models for aeration systems in activated sludge reactors. Second, it seeks to study the mathematical …

Sustainable Smouldering For Waste-To-Energy: Scale, Heat Losses, And Energy Efficiency, Tarek L. Rashwan

Electronic Thesis and Dissertation Repository

Applied smouldering combustion is emerging as a highly energy efficient approach towards waste-to-energy. This thesis aims to better understand this potential by addressing a critical knowledge gap between laboratory scale smouldering research and large-scale applications. Altogether, new understanding in provided on the complex and dynamic interactions between the reaction zone (smouldering front) and the cooling zone (treated inert porous media) by integrating theory, experiments, analytical modelling, and global energy balance calculations. The experiments spanned a range of reactor sizes and smouldering conditions (from weak to robust) with dry (carbon) and wet (sludge) fuels mixed in sand. This work revealed that …

Numerical And Semi-Analytical Estimation Of Convective Heat Transfer Coefficient For Buildings In An Urban-Like Setting, Anwar Demsis Awol

Electronic Thesis and Dissertation Repository

Urban building arrangements such as packing density, orientation and size are known to influence the microclimate surrounding each building. Studies on the impact of urban microclimatic changes on convective heat transfer coefficient (CHTC) from a stock of buildings, however, have been rare in surveyed literature. The present study focuses on numerical and analytical investigation of CHTC from building-like models with homogeneous set of equal and unequal planar and frontal densities. Consequently, the study discusses the CHTC response in relation to broader changes in the urban surface form. Part of the process involves the development of a simplified one-dimensional semi-analytical CHTC …

Transient Analysis Of Full Scale And Experimental Downburst Flows, Junayed Chowdhury

Electronic Thesis and Dissertation Repository

Downbursts are highly transient natural phenomena which produce strong downdrafts evolving from a cumulonimbus cloud They induce an outburst of damaging winds on or near to the ground causing an immense damage to the ground mounted structures and aircrafts. This study investigates the transient nature of downbursts using wind speed records from full scale downburst events employing an objective methodology. This method can detect the abrupt change points in a downburst time series based on statistical parameters such as mean, standard deviation and linear trend. In addition to the analysis of the full scale downburst events, several large scale experimental …

Fundamentals Of Applied Smouldering Combustion, Marco Zanoni

Electronic Thesis and Dissertation Repository

Smouldering combustion is defined as a flameless oxidation reaction occurring on the surface of the condensed phase (i.e., solid or liquid). Traditional research on smouldering was related to economic damages, fire risk, and death, due to the release of toxic gases and slow propagation rates. Recently, smouldering has been applied as an intentional, engineering technology (e.g., waste and contaminant destruction). Smouldering involves the transport of heat, mass, and momentum in the solid and fluid phases along with different chemical reactions. Therefore, numerical models are essential for the fundamental understanding of the process. Smouldering models either neglected heat transfer between phases …

Influence Of Turbulence On The Aerodynamics Of Low-Rise Buildings, Fakhruzzaman Arif

Electronic Thesis and Dissertation Repository

During extreme wind events, roofing failures may lead to damage of the whole structure. In order to alleviate the effect, surface pressure coefficients on the roofs have been extensively investigated. This research aims to determine the roof pressures acting on low-rise buildings with consideration of the effects of turbulence (terrain). Pressure measurements, as well as wind speed data, were taken at the Boundary Layer Wind Tunnel Laboratory (BLWTL) of the University of Western Ontario (UWO) to examine the influence of turbulence level (i.e., terrain condition) on the critical wind directions corresponding to the largest surface roof pressure coefficients for various …

The Development And Numerical Modelling Of A Representative Elemental Volume For Packed Sand, Ashraf Thabet

Electronic Thesis and Dissertation Repository

The motivation of this thesis is the development of simple microscopic-scale model (representative elemental volume; REV) that can be used to conduct flow and heat transfer simulations from which closure coefficients can be established for the volume-averaged transport equations for porous media (packed bed). The thesis provides a brief introduction to the computational technique adopted for the geometric generation of the REV (YADE), followed by a parametric study undertaken to reveal the minimum number of particles inside the REV that are required to mimic the appropriate physics. Additional analysis was conducted with the goal of determining the influence of deviation …

Full-Scale And Wind Tunnel Investigation Of The Flow Field Over A Coastal Escarpment, Julien Lotufo

Electronic Thesis and Dissertation Repository

A multiscale experimental approach, consisting of full-scale measurements and physical modeling in a laboratory environment, was conducted to investigate the flow field over a coastal escarpment on the Wind Energy Institute of Canada’s research and development wind park. The influence of sea breeze inflow conditions, thermal stability and local topographic features on the flow field were examined.

The results of the full-scale study show that the near surface flow field is significantly influenced by the sea breeze circulatory coastal flow regime, creating larger shear layers with a smaller recirculation regions compared to cases of typical boundary layer flow typical boundary …

Effects Of Turbulence On The Separating-Reattaching Flow Above Surface-Mounted, Three-Dimensional Bluff Bodies, Abul Fahad Akon

Electronic Thesis and Dissertation Repository

Investigations of separated and reattaching flows over three-dimensional bluff bodies in turbulent boundary layers are important because of the large aerodynamic loads that these flows cause. For example, roofs of low-rise buildings are vulnerable to this kind of wind loading. Turbulence in the upstream flow affects the pressure distributions and the mean size of separation bubbles formed on bluff body surfaces. Whereas a number of studies have focussed on two-dimensional separation bubbles and surface pressures, a comprehensive understanding of the surface pressures and the separating-reattaching flows in relation to the turbulence in the incident boundary layers for surface-mounted, three-dimensional bluff …

Numerical Studies For Improving Fracture Toughness Resistance Curve Testing Using Single-Edge (Notched) Tension Specimens, Yifan Huang

Electronic Thesis and Dissertation Repository

The fracture toughness resistance curve, i.e. the J-integral resistance curve (J-R curve) or the crack tip opening displacement resistance (CTOD-R) curves, is widely used in the integrity assessment and strain-based design of energy pipelines with respect to planar defects (i.e. cracks). This thesis deals with issues related to the experimental determination of the J(CTOD)-R curves using the newly-developed single-edge (notched) tension (SE(T)) specimens. In the first study, the plastic geometry factor, i.e. the η_pl factor, used to evaluate J in a J-R curve test based on …

Self-Sustaining Smouldering Combustion As A Novel Disposal Destruction Method For Waste Water Biosolids, Tarek L. Rashwan

Electronic Thesis and Dissertation Repository

Managing biosolids, the major by-product from wastewater treatment plants (WWTPs), persists as a major global challenge that often constitutes the majority of WWTP operating costs. Self-sustained smouldering is a new approach for organic waste treatment, in which the waste (i.e., the fuel) is destroyed in an energy efficient manner after mixing it with sand. Smouldering has never been applied to biosolids. Column experiments, using biosolids obtained from a WWTP, were employed to identify if - and under what conditions - smouldering could be used for treating biosolids. The parameter space in which smouldering was self-sustaining was mapped as a function …

Wind And Thermal Effects On Ground Mounted Photovoltaic (Pv) Panels, Chowdhury Mohammad Jubayer

Electronic Thesis and Dissertation Repository

A combination of Computational Fluid Dynamics (CFD) simulations and wind tunnel experiments are carried out to investigate the effects of wind on the aerodynamic loading and heat transfer of a ground mounted stand-alone photovoltaic (PV) panel with tilt angle of 25^o in open country atmospheric boundary layer. Several azimuthal wind directions are considered: Southern 0^o, Southwest 45^o, Northwest 135^o and Northern 180^o. Three dimensional Reynolds-Averaged Navier-Stokes (RANS) approaches with an unsteady solver using Shear Stress Transport (SST) k-ω turbulence closure are employed for the CFD simulations, whereas Particle Image Velocimetry (PIV) and …

Hydrogeological And Thermal Sustainability Of Geothermal Borehole Heat Exchangers, S. Emad Dehkordi

Electronic Thesis and Dissertation Repository

Assessment of the current approach taken by guidelines and design methods of vertical closed loop heat exchangers shows that often groundwater flow is either disregarded or is not methodically incorporated. The state of scientific research in this arena reveals that overlooking the groundwater flow in the design procedure may not always be a correct assumption. The significance of advective heat transport compared to conduction is defined by the groundwater flux or Darcy velocity which heavily depends on the hydraulic conductivity of the ground, followed by the hydraulic gradient which has a relatively limited range. A sensitivity analysis on ground and …

Finite Element Analyses Of Single-Edge Bend Specimens For J-R Curve Development, Yifan Huang

Electronic Thesis and Dissertation Repository

The fracture toughness resistance curve such as the J-integral resistance curve (J-R curve) is widely used in the integrity assessment and strain-based design of energy pipelines with respect to planar defects (i.e. cracks). Two studies about the development of the J-R curve are carried out and reported in this thesis. In the first study, the plastic geometry factor, i.e. the η_pl factor, used to evaluate J in a J-R curve test based on the single-edge bend (SE(B)) specimen is developed based on the three-dimensional (3D) finite element analysis (FEA). The main …

Experimental Investigation Of Wind Effect On Solar Panels, Ayodeji Abiola-Ogedengbe

Electronic Thesis and Dissertation Repository

Photovoltaic Solar Panels for electricity generation are outdoor low-rise structures that are vulnerable to damage by the wind. The existing building codes do not contain information about the impact of the wind on these structures and hence do not provide comprehensive guidelines to mitigate such impact. The present study is a contribution to the ongoing efforts to codify the wind loading on solar panels. In this study, experimental investigations were conducted on the scaled model of a ground-mounted solar panel structure whose surface is geometrically similar to an inclined flat plate and mounted on three-legged support. The panel comprises of …

Consistent Density Scanning And Information Extraction From Point Clouds Of Building Interiors, Kuldeep Kumar Sareen

Electronic Thesis and Dissertation Repository

Over the last decade, 3D range scanning systems have improved considerably enabling the designers to capture large and complex domains such as building interiors. The captured point cloud is processed to extract specific Building Information Models, where the main research challenge is to simultaneously handle huge and cohesive point clouds representing multiple objects, occluded features and vast geometric diversity. These domain characteristics increase the data complexities and thus make it difficult to extract accurate information models from the captured point clouds.

The research work presented in this thesis improves the information extraction pipeline with the development of novel algorithms for …

Vortex Shedding From Elongated Bluff Bodies, Zachary J. Taylor

Electronic Thesis and Dissertation Repository

As the spans of suspension bridges increase, the structures become inherently flexible. The flexibility of these structures, combined with the wind and particular aerodynamics, can lead to significant motions. From the collapse due to flutter of the Tacoma Narrows Bridge to the case of vortex-induced vibrations (VIV) of the Storebælt Bridge, it is evident that a better understanding of the aerodynamics of these geometries is necessary. The work herein is motivated by these two problems and is presented in two parts.

In the first part, the focus is on the physical mechanisms of vortex shedding. It is shown that the …