According to the American Heart Association about 795,000 people suffer a stroke each year. Of those strokes almost 140,000 are fatal; this makes Stroke the third leading cause of death in the United States behind coronary heart disease and cancer. Hemorrhagic strokes are caused when an artery in the brain ruptures, such as a ruptured aneurysm. One possible treatment for cerebral aneurysm is a porous tubular structure, similar to a stent, called a flow diverter. A flow diverter can be placed across the neck of a cerebral aneurysm to induce the cessation of flow and initiate the formation of an intra-aneurysmal thrombosis. This excludes the aneurysm from the parent artery and returns the flow of blood to normal. The process of flow diversion alone has been shown to take months to fully exclude the aneurysm. It is possible however with an adjuvant therapy called photothrombosis to accelerate this process so that the aneurysm is excluded within minutes. Previous flow diverting devices have been analyzed to determine optimal characteristics, such as braiding angle and wire diameter. From this information a new optimized device was designed and is now in the process of being tested. In order to evaluate the effect of the device, a model must be created. One such model is the rabbit elastase induced aneurysm, which was characterized so that elastomer models could be created for in vitro studies. Particle Image Velocimetry (PIV) is a method of analysis that utilizes very small glass spheres (between 8 mu m and 12 mu m in diameter) to determine the velocity vectors of fluid flow in an in vitro model. These velocities can be used to calculate hydrodynamic circulation and kinetic energy inside an elastomer model of the elastase induced aneurysm. By comparing these values inside the aneurysm with values for previously developed diverters and a control without a diverter, it can be shown that despite changes in the braiding angle and individual wire thickness that the behavior of the devices is not significantly different (P > 0.05). Flow diversion is also being used in concert with photothrombosis. A flow diverter is used to exclude the neck remnant from the parent vessel and to provide a scaffold for the remodeling of the neck. This combination of techniques allows for very fast and near complete occlusion of the aneurysm thereby excluding the aneurysm from the parent vessel and eliminating the risk of a rupture.

Cardiovascular disease, mostly atherosclerosis, is responsible for one third of all deaths globally, rising to more than 50% in the Western World. Risk factors include smoking, diet, and familial history. Doppler ultrasound can provide estimates of blood velocity and wall shear rate. Clinically, maximum velocity is used to categorise patients for surgery, although Doppler velocity measurement is prone to errors and in need of validation. Wall shear stress—which can be derived from wall shear rate—plays a role in disease initiation and progression, although its clinical utility is unclear due to difficulties associated with its measurement. This thesis investigates the use of Doppler ultrasound as a tool to estimate blood velocity and wall shear rate. A simplified method for estimation of wall shear rate in healthy arteries is developed that uses spectral Doppler ultrasound. This method is based upon the theory of oscillatory flow in rigid pipes, requiring two measurements that are readily available with clinical ultrasound machines. This method is compared to a similar method based on colour flow imaging. The spectral Doppler method underestimated the theoretic value of wall shear rate by between 7 and 22%, with results varying between phantoms. Errors for the colour method were on average 35% greater. Test measurements from one healthy volunteer demonstrated that this method can be applied in-vivo. In more advanced stages of disease, peak velocity distal to a stenosis is of clinical interest and the simplified method for wall shear rate estimation is invalid. Steady flow in a series of simplified stenosis geometries was studied using a dual-beam Doppler system to obtain velocity vectors. These measurements were compared with data from an equivalent system that used particle image velocimetry (PIV) and was considered the gold standard. For Reynolds numbers at the stenosis throat of less than 800, flow remained laminar over the region studied, although distal flow separation did occur. For higher throat Reynolds numbers—corresponding to more severe stenoses or increased flow rates—asymmetric recirculation regions developed; the transition to turbulence occurred more proximally, with a corresponding reduction in stenotic jet and recirculation length. Qualitative agreement was observed in the velocity profile shapes measured using ultrasound and PIV at throat Reynolds numbers less than 800. Above this threshold the qualitative agreement between the velocity profiles became poorer as both downstream distance and the degree of stenosis increased. Peak axial velocity distal to the stenosis was underestimated, on average, by 15% in the ultrasound system. Estimation of shear rate remained difficult with both experimental techniques. Under a Newtonian approximation, the normalised wall shear stresses agree qualitatively. Under pulsatile flow conditions using an idealised flow waveform, superior qualitative agreement was observed in the velocity profiles at diastole than at systole. Similar to the steady flow behaviour, this agreement deteriorated with stenosis severity. The current generation of clinical ultrasound machines are capable of estimating the wall shear rate in healthy arteries. In the presence of significant arterial disease, errors in the peak velocity may result in mis-selection of patients for surgery, while estimation of the wall shear stress remains extremely problematic; particularly with identifying the wall location and measuring velocities close to the wall.

Abstract An experimental study is conducted to determine the velocity fields, from development to steady state, in a square enclosure due to movement of a constant velocity lid using Particle Image Velocitmetry (PIV). Experiments were conducted with water, seeded with hollow glass sphere particles 10 microns in diameter, at three different lid velocities leading to Reynolds numbers in the high laminar to transitional range. Driven Cavity Flow is a classic fluid dynamics case often used for benchmarking of computational codes. Previous work has primarily focused on improving computational codes, experimental work is lacking and focused on obtaining steady state readings. The test cavity is 1 inch (25.4mm) high by 1 inch (25.4 mm) wide leading to an aspect ratio of 1.0. The depth is taken to be 5 (127mm) inches to reduce the three dimensional effects. Readings are taken from development to steady state allowing for a full spectrum of flow characteristics. PIV technique is successful in capturing the development of driven cavity flow. Circulation is shown to increase strength with time and Reynolds number. PIV capture and processing settings are determined. Keywords: Driven Cavity Flow, Particle Image Velocimeter (PIV)

<div>Gas turbine engines have operated on the Brayton cycle for decades, each decade only gaining approximately one to two percent in thermal efficiency as a result of efforts</div><div>to improve engine performance. Pressure-gain combustion in place of constant-pressure combustion in a Brayton cycle could provide a drastic step-change in the thermal efficiency of these devices, leading to reductions in fuel consumption and emissions production. Rotating Detonation Engines (RDEs) have been widely researched as a viable option for pressure-gain combustion. Due to the extremely high frequencies associated with operation of an RDE, the development and application of high-speed diagnostics techniques for RDEs is necessary to further understand and</div><div>develop these devices.</div><div><br></div><div>An application of high-speed diagnostic techniques in a natural gas-air RDE at conditions relevant to land-based power generation is presented. Diagnostics included high-frequency chamber pressure measurements, chemiluminescence imaging of the annulus, and Particle Image Velocimetry (PIV) measurements at the exit plane of the RDE. Results from a case with two detonation waves rotating clockwise (aft looking forward) in the combustor annulus are presented. Detonation surface plots are created from chemiluminescence images and allow for the extraction of properties such as dominant frequency modes and wave number, speed, and direction. The chamber frequency for the case with two co-rotating waves in the chamber is found to be 3.46 kHz and corresponds to average individual wave speeds of 68% Chapman-Jouguet (CJ) velocity. Dynamic Mode Decomposition (DMD) is applied and indicates the presence of two strong detonation waves rotating clockwise and periodically intersecting with weaker, counter-rotating waves in the annulus at certain times during operation. Singular-Spectrum Analysis (SSA) is used to isolate modes corresponding to the detonation frequency in the signals of velocity components obtained from PIV, maintaining instantaneous phase information. Axial and azimuthal components of velocity are observed to remain nearly 180 degrees out of phase. Lastly, approximate angles for the trailing oblique shocks in the combustion chamber are calculated.</div>

The research focus of this thesis is on modelling techniques for river kinetic turbines, to develop predictive numerical tools to further the design of this emerging hydro technology. The performance benefits of enclosing the turbine in a shroud are quantified numerically and an optimized shroud design is developed. The optimum performing model is then used to study river kinetic turbines, including different anchoring systems to enhance performance. Two different turbine numerical models are studied to simulate the rotor. Four different computational fluid dynamics (CFD) turbulence models are compared against a series of particle image velocimetry (PIV) experiments involving highly-separated diffuser-flow and nozzle-flow conditions. The risk of cavitation is briefly discussed as well as riverbed boundary layer losses. This study is part of an effort to develop this emerging technology for distributed power generation in provinces like Manitoba that have a river system well adapted for this technology. / May 2007

Particle Image Velocimetry (PIV) is an optical technique used to display and evaluate the motion of fine particles in a flow. In this experimental study, velocity profiles are examined by PIV system and basic analysis methods are compared.

A number of clinical, in vitro and computational studies have shown the potential for thromboembolic complications in bileaflet mechanical heart valves (BMHV), primarily due to the complex and unsteady flows in the valve hinges. These studies have focused on quantitative and qualitative parameters such as velocity magnitude, turbulent shear stresses, vortex formation and platelet activation to identify potential for blood damage. However, experimental characterization of the whole flow fields within the valve hinges has not yet been conducted. This information can be utilized to investigate instantaneous damage to blood elements and also to validate numerical studies focusing on the hinge’s complex fluid dynamics. The objective of this study was therefore to develop a high-resolution imaging system to characterize the flow fields and global velocity maps in a BMHV hinge. Subsequently, the present study investigated the effect of hinge gap width on flow fields in a St. Jude Medical BMHV. The results from this study suggest that the BMHV hinge design is a delicate balance between reduction of fluid shear stresses and areas of flow stasis during leakage flow, and needs to be optimized to ensure minimal thromboembolic complications. Overall, the current study demonstrates the ability of high-resolution Micro Particle Image Velocimetry to assess the fluid flow fields within the hinges of bileaflet mechanical heart valves, which can be extended to investigate micro-scale flow domains in critical regions of other cardiovascular devices to assess their blood damage potential.

The research focus of this thesis is on modelling techniques for river kinetic turbines, to develop predictive numerical tools to further the design of this emerging hydro technology. The performance benefits of enclosing the turbine in a shroud are quantified numerically and an optimized shroud design is developed. The optimum performing model is then used to study river kinetic turbines, including different anchoring systems to enhance performance. Two different turbine numerical models are studied to simulate the rotor. Four different computational fluid dynamics (CFD) turbulence models are compared against a series of particle image velocimetry (PIV) experiments involving highly-separated diffuser-flow and nozzle-flow conditions. The risk of cavitation is briefly discussed as well as riverbed boundary layer losses. This study is part of an effort to develop this emerging technology for distributed power generation in provinces like Manitoba that have a river system well adapted for this technology.

The research focus of this thesis is on modelling techniques for river kinetic turbines, to develop predictive numerical tools to further the design of this emerging hydro technology. The performance benefits of enclosing the turbine in a shroud are quantified numerically and an optimized shroud design is developed. The optimum performing model is then used to study river kinetic turbines, including different anchoring systems to enhance performance. Two different turbine numerical models are studied to simulate the rotor. Four different computational fluid dynamics (CFD) turbulence models are compared against a series of particle image velocimetry (PIV) experiments involving highly-separated diffuser-flow and nozzle-flow conditions. The risk of cavitation is briefly discussed as well as riverbed boundary layer losses. This study is part of an effort to develop this emerging technology for distributed power generation in provinces like Manitoba that have a river system well adapted for this technology.

Background: Nowadays, one of the medical problem is rolling cell adhesion. Rolling cell adhesion is a complex process that requires the analysis of the challenging environment such as body fluid and is the process responsible for recruiting the cell to specific organs. In order to explore the rolling cell adhesion, mathematical model is proposed. Different image processing methods are created, such as optical flow - Lucas Kanade algorithm, and other type of methods related to mechanical fluid, namely PIV (Particle Image Velocimetry). Aim: The aim of this master thesis is the identification of challenges while using PIV in live cell images and propose the algorithm, which may analyze the rolling cell adhesion problem. Methods: In order to understand properly the rolling cell adhesion problem from biological site, literature review combined with the expert consultation is performed. According to gather information, mathematical model is proposed. Particle Image Velocimetry is explained according to literature review, where at the beginning the expert recommends some books as a primary research. As a result of this research, PIV challenges are identified and generally PIV idea is explained. Then two experiments are performed. The first experiment evaluates detection algorithms and the second one, analyses track algorithm vs. PIV. In order to evaluate the mentioned algorithms, some evaluation method are selected and some criteria are defined. Unfortunately the found methods are not perfect, therefore a new method related to performance evaluation using time series is proposed. Thesis result: The result of this thesis is a proposition of the algorithm, which can be used in the rolling cell adhesion. The algorithm is formed according to the detailed exploration of the rolling cell adhesion and analysis of the selected algorithms related to the image analysis during the theoretical research and experiments.