Digital particle image velocimetry is employed to investigate acoustically-coupled flow past a coaxial deep cavity (side branch) resonator mounted in a duct. The emphasis is on the effect of the separation between the coaxial side branches on the interaction between separated shear layers that form across the side branch openings. Various resonator geometries are characterized in terms of patterns of instantaneous and time-averaged flow velocity, vorticity. and streamline topology at several phases of the acoustic cycle. In addition. phase-averaged images of the flow in conjunction with unsteady pressure measurements are evaluated in order to provide insight into the mechanisms of acoustic power generation. Generally, the acoustic source undergoes a significant transformation as the distance between the coaxial side branches changes. When the side branches are located relatively far away from each other. each of them forms an independent acoustic source. As the distance between the side branches decreases. interaction between the associated oscillating shear layers results in formation of a single acoustic source of complex spatial structure.

There is a demand for a whole field velocimetry technique which offers the capability of rapid characterisation of complex engineering flow fields. This thesis describes a research programme aimed at the development of a reliable Doppler global velocimeter, suited to the measurement of such flows. The programme of work undertaken is discussed with reference both to research undertaken elsewhere and to previous work on the system at Oxford. While much of the underlying technology required for the construction of an accurate and reliable velocimeter has already been studied in Oxford and elsewhere, little attention has been paid by previous workers to the examination of the impact of data processing techniques on attainable flow measurement accuracy. In the present work, a number of image processing methods have been utilised for Doppler global velocimetry data processing. Those methods are described here, together with a theoretical analysis of their expected performance when applied to Doppler global velocimetry data. The expected error resulting from image processing considerations and also from the physical characteristics of the Doppler global velocimetry hardware are quantified in such a way that error estimates may be computed for real measured data frames. The results of the application of the velocimeter to the simple test case of measuring a velocity component of a rotating disc are presented. The velocimeter was subsequently applied to the measurement of a free jet flow and to a transonic flow field in a convergent-divergent nozzle. Correlations with accepted velocity field values were undertaken, and compared to the expected error previously determined. The choice of image processing algorithms was found to be of great importance in terms of Doppler global velocimetry measurement accuracy.

Since the discovery of the drag reduction effects of even small amount of macromolecules in solutions in turbulent pipe flows, there have been many experimental and theoretical studies in order to understand mechanisms behind this phenomenon. Theories have been proposed based on the observations on the change in the characteristics of the turbulent flow near the pipe wall where friction of the momentum transfer between the flow and the conduit takes place. In this study drag reduction in fully developed turbulent pipe flow with four concentrations (200 to 500 wppm) of low molecular weight Sodium Carboxymethylcellulose (CMC) in aqueous solutions was investigated experimentally. Drag reduction was determined by pressure drop measurements. In order to observe the impact of the presence of CMC on the flow, Ultrasound Doppler Velocimetry (UDV) was employed to monitor the instantaneous velocity distributions. UDV is a non-invasive technique allowing one to obtain quick velocity profiles. Experimental measurements were used to calculate Fanning friction factor and radial distributions of the axial time-averaged velocity, velocity fluctuation (turbulent intensity) and eddy viscosity. The drag reduction level was determined through the Fanning friction factor versus Reynolds number data. Velocity data could be obtained as close as 3 mm to the wall by UDV. Two impacts of increasing CMC concentration on the flow field, hence pressure drop, were observed. The first effect was the decrease of the mean velocity gradient especially near the wall with increasing polymer amount which in turn gave rise to lower friction factor or pressure drop. In addition smaller eddy viscosities were obtained in the flow. The second impact of the polymer addition was on the velocity fluctuation or turbulent intensity variation along the radial distribution. An increasing trend in turbulence intensity in the turbulent core with polymer addition was observed. This was in agreement with the earlier studies in which similar turbulence behavior was observed in addition to the suppression of the turbulent intensities near the wall

Effervescent atomization has been a topic of considerable investigation in the literature due to its important advantages over other atomization mechanisms. This work contributes to the development of both effervescent atomizers and also laser-based techniques for spray investigation In order to develop non-intrusive measurement techniques for spray applications, a procedure is suggested to characterize the shape of droplets using image-based droplet analyzers. Image discretization which is a major source of error in droplet shape measurement is evaluated using a simulation. The accuracy of StereoPIV system in conducting droplet velocity measurement in a spray field is also investigated. To assist in the design of effervescent atomizers, bubble formation during gas injection from a micro-tube into liquid cross-flow is investigated using a Shadow-PIV/PTV system. The generated spray fields of two effervescent atomizers which operate using a porous and a typical multi-hole air injector are compared using qualitative images and Shadow-PTV measurement.

Concern for the nonphysiologic energy required to actuate medical devices utilizing “smart material” properties of shape memory polymer (SMP) compels a rigorous investigation into the flow and temperature fields surrounding a thermally activated catheter device. Multiple analyses include the theoretical approaches of exact analytical solutions and finite difference modeling combined with the experimental techniques of particle image velocimetry (PIV) and laser-induced fluorescence (LIF). The attained velocities and temperatures related to the convective heat transfer impact the potential for blood or tissue damage caused by intravascular heating. The clinical scenario involving a catheter device receiving heat within an artery is modeled in its simplest form as a cylindrical metal cap on the tip of a hollow glass rod placed inside of a long straight tube of constant cross-sectional area. Using a working fluid with properties comparable to blood, flow rates and energy input is then varied to determine their effects on velocity fields and temperature gradients. Analytical solutions for both the straight tube and concentric annulus demonstrate the two velocity distributions involved, as flow moves past the gap between the catheter and artery wall and then converges downstream to the Poiseuille solution for steady pipe flow of an incompressible fluid. To solve for the transition between the velocity profiles, computational fluid dynamics software simulates a finite volume model identical to the experimental setup used for intravascular heating experiments. PIV and LIF, both experimental techniques making use of similar hardware, determine velocity fields and temperature distributions, respectively, by imaging fluid seeding agents and their particular interaction with the light sheet. The velocity and temperature fields obtained experimentally are matched with the analytical and finite volume analysis through fluid properties, flow rates, and heating rates. Velocities determined during device heating show a small increase in local velocity, due to temperature dependent viscosity effects. When the device is centered in the model, flow patterns constrain the heat flow near the center axis and away from the channel walls. Increasing flow rate consequently decreases temperature rise, as the heat is carried more quickly downstream and away from the heat source. Using multiple analyses, fluid velocity and temperature distributions are first theorized with analytical and finite element methods and then validated through experimental imaging in a physical model.

Zugl.: Aachen, Techn. Hochsch., Diss., 2007.

Thesis (Ph.D.) - Carleton University, 2007. / Includes bibliographical references (p. 251-264). Also available in electronic format on the Internet.

Thesis (M.Oc.E.)--Oregon State University, 2011. / Printout. Includes bibliographical references (leaf 70). Also available on the World Wide Web.

Techn. Universiẗat, Diss., 2002--Berlin.

Thesis (Ph. D.)--University of Rhode Island, 2006. / Typescript. Includes bibliographical references (leaves 97-99).