This thesis presents a study on the applicability of common roughness parameterization guidelines in determining values of the surface roughness length (z0). These guidelines are often used for vertical extrapolation of wind speeds in the renewable energy industry. The specific goal of this thesis is to determine whether these guidelines (most notably the Davenport roughness classification system) can provide a quality estimate of the roughness length for wind resource assessment purposes. To test this hypothesis, empirical relationships between calculated values of z0 derived from logarithmic profile fitting and those estimated from subjective terrain analyses guidelines are compared at two prospective wind farm locations in Southern Ontario. The results suggest that the use of roughness parameterization guidelines for extrapolating wind speeds can cause serious underestimation of the local wind resources, especially at locations where local topographic challenges exist. Their use in energy assessments should be avoided if possible through on-site measurements of the wind profile.

Wetting behavior of fluid/fluid/solid systems, largely influenced by surface properties and interactions between the three phases, plays a big role in nature and in industrial applications Traditionally, wetting studies have focused on liquid/vapor systems, especially the study of a sessile liquid droplet in air. Liquid/vapor systems can only probe the effects of surface properties and interactions between the solid and the wetting liquid. This type of characterization is inadequate for liquid/liquid systems, where surface wettability is additionally influenced by interactions between the two wetting liquids. The present study is the first to examine the effects of nanoscale roughness on wetting behavior in liquid/liquid systems and the modulation of roughness effects by fluid properties and the wetting order. This study examines both equilibrium and dynamic wetting behavior in liquid/liquid systems using well characterized substrates. Rough substrates were fabricated by coating glass substrates with nanometer sized polymer particles. Partial dissolution of the particles and molecular de-deposition of the polymer allowed for tuning of substrate roughness while retaining the original surface chemistry. The effectiveness of this fabrication technique was verified using electron microscopy and electrokinetic analysis. We examined the wetting behavior in three fluid/fluid systems: an air/water system, a decane/water system, and an octanol/water system. The oils were chosen based on their different polarities. Equilibrium wetting behavior was determined using contact angle measurements. Results indicate that for all systems where the primary wetting fluid was a liquid, an increase of the surface roughness resulted in Cassie-Baxter wetting. How hydrophilic a surface appears with regard to a water/fluid interface depended on the polarity of that fluid. The octanol/water system provided the strongest evidence regarding the effect of wetting order: a transition from Wenzel to Cassie-Baxter wetting was only observed when water was the primary wetting liquid. The observed transition was confirmed using a modified Wenzel/Cassie-Baxter model. The kinetics of droplet spreading was measured using high speed optical microscopy. After a droplet was placed on a solid surface, the motion of the contact line was imaged at a rate of 1000 fps. The wetted area was then extracted using custom Matlab® scripts. The spreading kinetics underwent a transition between two regimes: a visco-inertial regime and a slower spreading regime. Results indicated that surface roughness influenced spreading kinetics in both regimes. The overall spreading rate was always slower for rough surfaces than for smoother surfaces. In liquid/liquid systems, the duration of visco-inertial regime was dependent on the surface roughness as well; in general, it was shorter for smooth substrates compared to rough substrates. Increasing the viscosity of the non-aqueous fluid significantly increased the duration of the visco-inertial regime and decreased the overall spreading rate. This study provides insight into the competitive wetting of solid surfaces relevant in many industrial applications such as oil recovery or inkjet printing, and may guide the development of improved wetting models in an area that currently lacks an adequate theoretical description.

Hydraulic fracture conductivity in ultra-low permeability shale reservoirs is directly related to well productivity. The main goal of hydraulic fracturing in shale formations is to create a network of conductive pathways in the rock which increase the surface area of the formation that is connected to the wellbore. These highly conductive fractures significantly increase the production rates of petroleum fluids. During the process of hydraulic fracturing proppant is pumped and distributed in the fractures to keep them open after closure. Economic considerations have driven the industry to find ways to determine the optimal type, size and concentration of proppant that would enhance fracture conductivity and improve well performance. Therefore, direct laboratory conductivity measurements using real shale samples under realistic experimental conditions are needed for reliable hydraulic fracturing design optimization. A series of laboratory experiments was conducted to measure the conductivity of propped and unpropped fractures of Barnett shale using a modified API conductivity cell at room temperature for both natural fractures and induced fractures. The induced fractures were artificially created along the bedding plane to account for the effect of fracture face roughness on conductivity. The cementing material present on the surface of the natural fractures was preserved only for the initial unpropped conductivity tests. Natural proppants of difference sizes were manually placed and evenly distributed along the fracture face. The effect of proppant monolayer was also studied.

The characteristics of the subcritical, critical and supercritical flows at the rectangular free overfall were studied experimentally to obtain a relation between the brink depth and the flow rate. A series of experiments were conducted in a tilting flume with wide range of flow rate and two bed roughness in order to find the relationship between the brink depth, normal depth, channel bed slope and bed roughnesses. An equation was proposed to calculate the flow rate if only the brink depth, roughness, and channel bed slope are known. An alternate iterative solution was offered to calculate discharges if the brink depth and uniform flow depth are known.

Discontinuity surfaces generally consist of undulations termed as roughness. It is well known that surface roughness plays an important role on the shear strength and shear behavior of discontinuities. However, the effect of roughness will not be the same when the direction of shearing changes. This effect causes variation of shear strength with shearing direction or in other words anisotropy on shear strength. In this thesis, an experimental study was performed to investigate the effect of roughness and anisotropy on shear strength. For this purpose, joint samples were prepared using a model material and direct shear tests were conducted at different normal stress levels and shearing directions.

The objective of this study is to determine the effect of different roughness types and arrangements on hydraulic jump characteristics in a rectangular channel. Three different types of roughness were used along experiments. All of them had rectangular prism shapes and that were placed normal to the flow direction. To avoid cavitation, height of roughness elements were arranged according to level of the channel inlet, so that the crests of roughness elements would not be protruding into the flow. The effects of roughness type and arrangement on hydraulic jump properties, i.e. energy dissipation, length of the jump and tail water depth were investigated. These properties were compared with the available data in literature and with the properties of hydraulic jump occurred on smooth bed.

No description available.

Biomaterial surface properties such as microtopography and energy can change cellular responses at the cell-implant interface. Phospholipase D (PLD) is required for differentiation of osteoblast-like MG63 cells on machined and grit-blasted titanium surfaces. Here, we determined if PLD is also required on microstructured/high-energy substrates and the mechanism involved. shRNAs for human PLD1 and PLD2 were used to silence MG63 cells. Wild-type and PLD1 or PLD1/2 silenced cells were cultured on smooth-pretreatment surfaces (PT); grit-blasted, acid-etched surfaces (SLA); and SLA surfaces modified to have higher surface energy (modSLA). PLD was inhibited with ethanol or activated with 24,25-dihydroxyvitamin-D₃ [24R,25(OH)₂D₃]. As surface roughness/energy increased, PLD mRNA and activity increased, cell number decreased, osteocalcin and osteoprotegerin increased, and protein kinase C (PKC) and alkaline phosphatase specific activities increased. Ethanol inhibited PLD and reduced surface effects on these parameters. There was no effect on these parameters after knockdown of PLD1, but PLD1/2 double knockdown had effects comparable to PLD inhibition. 24R,25(OH)₂D₃increased PLD activity and production of osteocalcin and osteoprotegerin, but decreased cell number on the rough/high-energy surfaces. These results confirm that surface roughness/energy-induced PLD activity is required for osteoblast differentiation and that PLD2 is the main isoform involved in this pathway. Here we showed that PLD is activated by 24R,25(OH)₂D₃ in a surface-dependent manner and inhibition of PLD reduced the effects of surface microstructure/energy on PKC, suggesting that PLD mediates the stimulatory effect of microstructured/high-energy surfaces via PKC-dependent signaling.

Additive friction stir deposition (AFSD) of AZ31B magnesium alloy was conducted to examine evolution of grain structure, phases, and crystallographic texture. AFSD was carried out using a hollow tool made from tool steel at a constant rotational velocity of 400 rpm on the AZ31B base plate. Bar stock of AZ31B was utilized as a feed material. The linear velocity of the tool was varied in the range of 4.2-6.3 mm/s. The feed rate of the material had to be maintained at a half value compared to the corresponding linear velocity for the successful deposition. The layer thickness and length of the deposits were kept constant at 1 mm and 50 mm respectively. The tool torque and actuator force values were recorded during the process and for calculation of the average input energy for each processing condition. Temperature during the AFSD experiments was monitored using a type k thermocouple located 4 mm beneath the deposition surface at the center of the deposition track. The average input energy values showed a decreasing trend with increasing tool linear velocity. The temperature values during deposition were ∼0.7 times the liquidus of the alloy. The deposited material then was examined by laser microscope and profilometer, X-ray diffraction, scanning electron microscopy, electron back scatter diffraction (EBSC), contact angle measurement and micro hardness tests. The AFSD AZ31B samples showed reduction in areal surface roughness with an increase in the tool linear velocity. The X-ray spectra revealed increase in the intensity of prismatic planes of α-Mg phase with increase in tool linear velocity. AFSD of AZ31B Mg alloy resulted in shifting of the grain size from a broader and courser distribution within the feed material to a tighter distribution. Moreover, EBSD observations confirmed the refinement in grain size distribution as well as the presence of predominantly prismatic texture for the AFSD samples when compared to the feed material. There was a marginal improvement in the hardness for the AFSD samples compared to the feed material. However, there was no significant change in the contact angle measurements in simulated body fluid for the AFSD samples compared to the feed material. The current work demonstrated ability of AFSD technique for the additive fabrication of magnesium-based alloys and provided a methodology for examining various process attributes influencing the processing-structure-property relationship.

To survive in today's manufacturing environments companies must push the standards of accuracy and speed to the highest levels possible. Electro Discharge Machining (EDM) has been used for over 50 years and recent developments have seen the use of EDM become much more viable. The goal of this research is to produce and evaluate electrodes produced by different manufacturing methods. The use of electroforming and spray-metal deposition has only recently become viable methods of producing usable rapid tooling components. The speed and accuracy as well as the cost of manufacture play a vital role in the tool and mould manufacturing process. Electroforming and spray-metal deposition offer an alternate option to traditional machining of electrodes. Electroforming is one method of producing electrodes for EDM. The fact that electroforming can be used to produce multiple electrodes simultaneously gives it the advantage of saving on costs when multiple electrodes are needed. Spray-metal deposition offers another alternative that is much cheaper and relatively faster to manufacture. The used of these non-traditional manufacturing methods in this research are compared to the performance of traditional solid electrodes in terms of machining time, material removal rate, tool wear rates and surface roughness at several standard machining settings. The results of this research are presented in this thesis along with conclusions and comments on the performance of the different methods of electrode manufacture. The major findings of the research include the solid electrodes performed better than the electroformed electrodes in Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (Ra) at all machine settings. However it was found that the production cost of the solid electrodes was six times that of the electroformed electrodes. The production of spray metal electrodes was unsuccessful. The electrode shell walls were not an even thickness and the backing material broke through the shell making them unusable. It is concluded that with further refinements and research, electroforming and spray metal processes will become an extremely competitive method in electrode manufacture and other rapid tooling processes.