Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 141-148). Also available in print.

A technique for measuring fluid velocities by means of neutrally-buoyant, phophorescent particles was investigated in a small-scale water jet facility. A nitrogen laser briefly illuminated the flow, exciting only those particles resident within the pulsed beam. The particles luminesce for a short while following excitation, during which time they also move with the flow. This creates a visible particle streak, the intensity of which decays along the direction of motion. A strobe illuminates the particles again a known time following the laser pulse. The magnitude and direction of a particle's velocity in the plane of view are deduced from an image of it streak captured by a video camera and recorded by a digital image processing system.

published_or_final_version / Mechanical Engineering / Master / Master of Science in Engineering

No description available.

Thesis--M. Sc., University of Hong Kong, 1982.

A scroll vortex intake is a hydraulic structure that transfers water stably from one elevation to a lower one by generating a swirling vortex flow down a vertical drop- shaft. Scroll vortex intakes are applied widely in water supply, stormwater drainage and sewerage systems. For a good engineering design, a sufficiently large and stable air core needs to be maintained within the dropshaft. Although a number of the- oretical and experimental investigations have been conducted, the understanding and predictions of the vortex flow is still far from complete due to a lack of de- tailed velocity field and air core measurements. This study aims to achieve a better understanding of the scroll vortex intake flow. The hydraulic theory of scroll vortex intake is revisited and detailed measurements of air core and velocity field of the vortex flow is conducted. A 1:15 physical model of a scroll vortex intake has been designed according to dynamic Froude similitude and constructed. Experiments have been conducted to measure the head-discharge relation. Piezometric head and air core size are measured at the throat of the vortex flow. Velocity fields are measured using Laser Doppler Anemometry (LDA). The measurements show that the vortex flow in the chamber resembles a free vortex and the circulation is approximately equal to that at the inlet to chamber. The chamber flow is not affected by the bottom boundary effect at bottom above a depth of the order of the dropshaft diameter. The throat section of the vor- tex flow is located slightly below the chamber bottom and within the bellmouth at the entrance to dropshaft. For the vortex flow in and downstream of the bell- mouth, the tangential velocity distribution can be described by a Rankine vortex (combination of forced and free vortex); the transition from forced to free vortex occurs at around the middle of the vortex flow layer. The pressure is positive for all locations and all discharges. Due to viscous effect, the maximum circulation is found to be lower than the inlet circulation. Consistent with the free vortex theory, the vertical velocity in the dropshaft is approximately constant. By accounting for the loss of circulation between chamber inlet and the dropshaft, a new 1D theory is proposed. Unlike previous models, the new theory gives good predictions of head-discharge relation and minimum air core size without the need of physically unrealistic assumptions. This study has revealed the structure of a scroll vortex intake flow for the first time. Characteristic flow features of the scroll vortex intake have been elucidated. The findings have helped to explain and resolve the long-standing discrepancies between the theoretical predictions of three representative 1D hydraulic theories. The vortex flow measurements also provide a basis for the development of a new theory and the validation of 3D numerical models. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

published_or_final_version / Civil Engineering / Master / Master of Philosophy

No description available.

Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1963. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed July 1, 2008) Includes bibliographical references (p. 32).

This thesis presents the numerical solution for two-dimensional incompressible viscous flow over a rigid bluff body which is elastically supported or alternately undergoing a specified harmonic oscillations. Solutions for the related associate flow in which the body is at rest in a two-dimensional incompressible time-dependent viscous flow have also been -obtained. This work is an extension of the work by Pattani [19] to include the effect of a steady far field flow on an oscillating body. The numerical model utilizes the finite element method based on a velocity-pressure primitive variable representation of the complete Navier-Stokes equations. Curved isoparametric elements with quadratic interpolation for velocities and bilinear interpolation for pressure are used. Nonlinear boundary conditions on the moving body are represented to the first order in the body amplitude parameter. The method of averaging is used to obtain the resulting periodic motion of the fluid. Three non-dimensional parameters are used to completely characterise the flow problem: the frequency Reynolds number Rω , the Reynolds number of steady flow Rℯ₁ and the Reynolds number for time-dependent flow Rℯ₂. Numerical results are obtained for a circular body, a square body and an equilateral triangular body. A parametric study is conducted for different values of the Reynolds numbers in the viscous flow regime. In all cases, results are obtained for streamlines, streaklines, added mass, added damping, added force and the drag coefficients. The limiting cases of steady flow over a fixed body and an oscillating body in a stationary fluid are checked with known results. Results for the associated flow are also obtained. The transformations derived, between the two associated flows are checked. Good agreement is obtained between the present results and other known results. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate