In this thesis, a device by applying the oscillating water column in a well-like resonant chamber installed in a floating structural system is studied experimentally. The device was designed to utilize the oscillation motion of the water inside the resonant chamber and then the pressure variation of the air to drive the air-turbine system. When connected to a electric power generation system this device may convert the wave power to electric power. A theory assuming independence between the motion of floating structure and the heave of waves inside the resonant chamber, derived by McCormick (1976 ) is adopted in this study. During the experimental tests four groups of test were carried out depending on the parameters that are to be evaluated for the effectiveness of the power conversion, namely, the rotation speed of the turbine with or without the power generator attached, the relative wave-height variation between the incident wave and waves in the well-like resonance chamber and the actually generated electric potential. For each group of test five sets of wave-height from 6 cm to 10 cm and four sets of period of wave, namely, 0.89, 0.92, 1.06, 1.20-second are applied.

The second-order initial value problem y" = f(x,y), y(x(_0)) = y(_0), y'(x(_0)) = z(_0) which does not contain the first derivative explicitly and where the solution is oscillatory has been of great interest for many years. Our aim is to construct numerical methods which are tuned to act efficiently on strongly oscillating functions. The frequencies involved determine the oscillatory character of the function and as the frequencies approach zero, the classical methods are obtained. The exponential- fitting tool has become increasingly popular as it is specially tailored for oscillating functions. Many classes of methods have been used with exponential-fitting and this will be discussed in more detail in the thesis. Collocation methods are considered for which the basis functions are combinations of polynomial and trigonometric terms. The resulting methods can be regarded as Runge-Kutta-Nyström methods with steplength dependent coefficients. We show how order conditions may be obtained, investigate the stability and other properties of particular methods and present some numerical results.

This thesis reports on the structure of the flow inside a nozzle which produces a naturally oscillating jet flow. The nozzle consists of a short cylindrical chamber with a concentric triangular-inlet orifice at one end and a circular exit lip at the other end. This triangular-jet nozzle was developed from the “fluidic-precessing-jet” (FPJ) nozzle, which has a similar arrangement of components, but has a circular rather than a triangular inlet. For reliably oscillating flow, the FPJ nozzle should have an inlet-to-chamber expansion ratio of at least 5.0, a chamber lengthto- diameter ratio between 2.6 and 2.8, and an exit-lip height of about 0.1 chamber diameters. The triangular-jet nozzle produces a continuously and aperiodically oscillating jet flow which is different from the FPJ flow. The oscillation occurs at smaller inlet-to-chamber expansion ratios (2.1 ≲ D /de₁ ≲ 3.5) and over a wider range of chamber lengths (2.0 ≲ L /D ≲ 2.5). The initial spreading angle of the jet flow is smaller, but is still much larger than that of non-oscillating, axisymmetric turbulent-jet flows. In addition, the external “oscillating-triangular-jet” (OTJ) flow has preferred azimuthal directions which are aligned with the three corners of the orifice. The kinetic-energy-loss coefficient of the OTJ nozzle is much smaller than that of the FPJ nozzle because oscillation occurs at much smaller inlet-to-chamber expansion ratios. For a narrow range of length-to-diameter ratios (1.00 ≲ L/D ≲ 1.25), the triangular-inlet nozzle can also produce a non-oscillating or “stationary deflected triangular jet” (SDTJ) which reattaches asymmetrically to the inside surface of the cylindrical chamber. The SDTJ has a weak tendency to oscillate, which suggests that flow patterns required for self-excited oscillation are already present in the SDTJ flow. Surface-flow visualisation and surface-pressure measurements in the SDTJ nozzle have provided the location of critical points and bifurcation lines on the chamber wall, and from this the topology of the SDTJ flow is deduced. Some details of the flow such as a jet-reattachment node near the chamber exit and a strong swirl adjacent to the inlet orifice are known from previous studies of the FPJ flow, but there are many newly observed features. The most easily identified of these are two sink-focus separation points, one on each side of the reattachment node but closer to the inlet plane. The foci counter rotate and are of unequal size. Reverse flow through the exit plane of the chamber is attracted to the larger focus. The vortex core rising from each focus is entrained by the reattaching-jet (SDTJ) flow and is drawn out of the chamber. A backward-facing pressure probe placed in the OTJ “reattaching-flow” region of chamber wall can be used as a reliable detector of jet-flow oscillation. Cross-correlating the signal from this detector probe with simultaneous static-pressure measurements elsewhere on the chamber wall gives a conditionally-averaged pressure on the wall of the OTJ chamber. The OTJ wall-pressure distribution has the same features as the SDTJ surface-pressure distribution, but it has greater asymmetry about a mirror plane drawn through the chamber axis and the detector probe. An array of three backward-facing pressure probes has been used as an “event detector” for conditionally-sampled (PIV) measurements of non-axial velocity components in cross-sections of the OTJ nozzle. The event-detection scheme responds only to a preselected (counter-clockwise) direction of motion of the oscillating-jet flow. The streamline patterns constructed from the conditionally-sampled measurements confirm the presence of the jet-reattachment node, the swirl and the sink foci identified from the SDTJ surface-flow visualisation. The shear-layer interaction between the jet from the triangular orifice and the swirl (adjacent to the inlet plane) produces strong longitudinal vortices in the ensemble-averaged flow. The jet flow distributes these vortices through the length of the chamber. Vortex cores representing the vortices are reconstructed by tracking streamline foci from one PIV cross-section plane to another. The tracking process includes the connection and termination of vortex cores in a manner which is consistent with the Helmholtz vortex law. In this flow field, the vortex core produced by the swirl and the vortex core rising from the larger sink-focus vortex on the chamber wall are connected to form a loop. The extent to which this vortex loop is contained within the chamber determines whether or not the flow is oscillating. If only a small fraction (e.g. 8%) of the vortex circulation passes through the exit plane of the nozzle, the loop is trapped inside the chamber and the deflected jet oscillates. If the length of the chamber is halved, about 35% of vortex circulation escapes from the nozzle and the oscillation stops. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1353005 / Thesis (Ph.D.) - University of Adelaide, School of Mechanical Engineering, 2009

This thesis reports on the structure of the flow inside a nozzle which produces a naturally oscillating jet flow. The nozzle consists of a short cylindrical chamber with a concentric triangular-inlet orifice at one end and a circular exit lip at the other end. This triangular-jet nozzle was developed from the “fluidic-precessing-jet” (FPJ) nozzle, which has a similar arrangement of components, but has a circular rather than a triangular inlet. For reliably oscillating flow, the FPJ nozzle should have an inlet-to-chamber expansion ratio of at least 5.0, a chamber lengthto- diameter ratio between 2.6 and 2.8, and an exit-lip height of about 0.1 chamber diameters. The triangular-jet nozzle produces a continuously and aperiodically oscillating jet flow which is different from the FPJ flow. The oscillation occurs at smaller inlet-to-chamber expansion ratios (2.1 ≲ D /de₁ ≲ 3.5) and over a wider range of chamber lengths (2.0 ≲ L /D ≲ 2.5). The initial spreading angle of the jet flow is smaller, but is still much larger than that of non-oscillating, axisymmetric turbulent-jet flows. In addition, the external “oscillating-triangular-jet” (OTJ) flow has preferred azimuthal directions which are aligned with the three corners of the orifice. The kinetic-energy-loss coefficient of the OTJ nozzle is much smaller than that of the FPJ nozzle because oscillation occurs at much smaller inlet-to-chamber expansion ratios. For a narrow range of length-to-diameter ratios (1.00 ≲ L/D ≲ 1.25), the triangular-inlet nozzle can also produce a non-oscillating or “stationary deflected triangular jet” (SDTJ) which reattaches asymmetrically to the inside surface of the cylindrical chamber. The SDTJ has a weak tendency to oscillate, which suggests that flow patterns required for self-excited oscillation are already present in the SDTJ flow. Surface-flow visualisation and surface-pressure measurements in the SDTJ nozzle have provided the location of critical points and bifurcation lines on the chamber wall, and from this the topology of the SDTJ flow is deduced. Some details of the flow such as a jet-reattachment node near the chamber exit and a strong swirl adjacent to the inlet orifice are known from previous studies of the FPJ flow, but there are many newly observed features. The most easily identified of these are two sink-focus separation points, one on each side of the reattachment node but closer to the inlet plane. The foci counter rotate and are of unequal size. Reverse flow through the exit plane of the chamber is attracted to the larger focus. The vortex core rising from each focus is entrained by the reattaching-jet (SDTJ) flow and is drawn out of the chamber. A backward-facing pressure probe placed in the OTJ “reattaching-flow” region of chamber wall can be used as a reliable detector of jet-flow oscillation. Cross-correlating the signal from this detector probe with simultaneous static-pressure measurements elsewhere on the chamber wall gives a conditionally-averaged pressure on the wall of the OTJ chamber. The OTJ wall-pressure distribution has the same features as the SDTJ surface-pressure distribution, but it has greater asymmetry about a mirror plane drawn through the chamber axis and the detector probe. An array of three backward-facing pressure probes has been used as an “event detector” for conditionally-sampled (PIV) measurements of non-axial velocity components in cross-sections of the OTJ nozzle. The event-detection scheme responds only to a preselected (counter-clockwise) direction of motion of the oscillating-jet flow. The streamline patterns constructed from the conditionally-sampled measurements confirm the presence of the jet-reattachment node, the swirl and the sink foci identified from the SDTJ surface-flow visualisation. The shear-layer interaction between the jet from the triangular orifice and the swirl (adjacent to the inlet plane) produces strong longitudinal vortices in the ensemble-averaged flow. The jet flow distributes these vortices through the length of the chamber. Vortex cores representing the vortices are reconstructed by tracking streamline foci from one PIV cross-section plane to another. The tracking process includes the connection and termination of vortex cores in a manner which is consistent with the Helmholtz vortex law. In this flow field, the vortex core produced by the swirl and the vortex core rising from the larger sink-focus vortex on the chamber wall are connected to form a loop. The extent to which this vortex loop is contained within the chamber determines whether or not the flow is oscillating. If only a small fraction (e.g. 8%) of the vortex circulation passes through the exit plane of the nozzle, the loop is trapped inside the chamber and the deflected jet oscillates. If the length of the chamber is halved, about 35% of vortex circulation escapes from the nozzle and the oscillation stops. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1353005 / Thesis (Ph.D.) - University of Adelaide, School of Mechanical Engineering, 2009

Thesis (M.S.)--Ohio University, August, 1983. / Title from PDF t.p.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 130-135). Also available via the Internet.

In this research, we quantify the parametric effects (number of turns, inclination angle, and filling ratio) on different designs of closed loop oscillating heat pipes (CLOHPs). Experiments were conducted on a CLOHP, which is made of copper tube with 1.65-mm inner diameter. Tubes are heated and cooled by constant temperature in wind tunnels, and n-pentane was used as the working fluid. The numbers of turns used were 5, 7, and 9. The effects of number of turns were investigated in order to prove the less gravity effect when the number of turns increases. Inclination angles used were 75, 82.5, and 90-degree. Inclination angle effects were investigated to verify that inclination angle decreases the affects of gravitational force. The tubes were charged to 0 and to 70 percent of total volume of tubes with n-pentane to demonstrate optimum heat transfer between condenser and evaporation sections. The importance of this work is in presenting design parameters to obtain lower energy consumption in comparison to previous known designs. Results indicate that 9 turns, 90-degree inclination angle, and charging 70 percent n-pentane of tubes were the most effective design parameters.

Vortex induced vibration of a circular cylinder in an inclined flow is a major subject in this thesis, the interaction and effect between a moving cylinder and fluid is always focused and investigated. We used a finite differences method to get the forces on cylinder, and then combined a Runge-Kutta four order approximate method to get a new position of a cylinder at next time step, repeated above procedure and we will get the solutions of a time series of cylinder response for VIV simulations. Most of papers focus on the peak amplitude and its scale due to the shedding frequency of system is near or at the fs, where fs is the shedding frequency of a uniform flow past a stationary cylinder. Except the ¡§first resonance¡¨, we found the ¡§second resonance¡¨ in the VIV simulations. The ¡§second resonance¡¨ occurs due to the natural shedding frequency of system is near or at the twice of the reduced frequency of the oscillator ¡§fs=2F1¡¨. The natural shedding frequency of a body is a key parameter, it always be discussed its effect and importance, and its value is also presented the frequency of lift force (or displacement on Y direction) of a body. On the contrary, the frequency of in-line force (or displacement on X direction) and its effect is seldom be investigated and discussed. In this study, we will discuss the effect of frequency of in-line force and the scale of ¡§first resonance¡¨ and ¡§second resonance¡¨ for VIV simulations. In order to verify the accuracy of our numerical model, this study simulated four different types for the cases of uniform flow past a circular cylinder with stationary, streamwise, transversal and rotational oscillating, respectively. The simulation results are compared with the study results of other paper by experimental and numerical methods, and the comparison show good agreement and high accuracy in the range of the in-line and lift forces on the cylinder, the main wake size behind the cylinder, the vortex shedding mode and the streamline pattern of the flow field. Furthermore, this study investigates a uniform flow past an inclined oscillating cylinder which is forcing oscillation in a range of 00 ~ 900 for the inclined angle (with respect to the X-direction of the Cartesian coordinates system). The effects of giving the different forced frequencies of a cylinder were investigated and discussed. And the application and restriction of Morison¡¦s equation will also be studied and investigated in different input conditions.

Multiple oscillating heat spreaders (OHS) were fabricated for the purpose of effectively transporting heat fluxes from vehicular electronics. The OHSs possessed modified evaporators for enhanced thermal spreading capabilities; one OHS was designed for pressure shorting, i.e. the ‘Slots OHS’, and the other for thermal shorting, i.e. the ‘Perforated Evaporator OHS’. These OHSs were tested in the axial heating configuration with the evaporator length-wise opposite the condenser, as well as in a centralized heating configuration implemented with the condenser thick-wise opposite the heat source to characterize thermal spreading effectiveness. The condensing location and heat input were varied in the central heating and axial configuration to determine thermal spreading effectiveness dependency to condenser location, heat removal, and heat input. Both OHSs were experimentally compared to an OHS of similar dimensions with no modified evaporator, and the results indicate the modified evaporators improve OHS thermal spreading ability for high heat flux thermal management.

Thesis (M.S. in Operations Research)--Naval Postgraduate School, September 2003. / Thesis advisor(s): Alan Washburn, Paul Sanchez. Includes bibliographical references (p. 79-81). Also available online.