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Student Number : 9804064R - MSc research report - School of Mechanical, Industrial and Aeronautical Engineering - Faculty of Engineering and the Built Environment / A qualitative and quantitative study of the hydraulic analogy; that is the analogy between flow with a free surface and two dimensional compressible gas flow, is described. The experimentation was done using a water table, and results are compared with Computational Fluid Dynamic (CFD) results for actual free surface flow models, and a fictitious gas model. Different test cases are considered (i) a wedge moving at steady supersonic/supercritical speeds of Froude or Mach number equal to 2.38, 3.12 and 4.31 (ii)unsteady motion of a wedge accelerating to supersonic speeds and then decelerating. Quantitative results for the experimental case are achieved by using a colour encoding slope detection technique. Qualitatively, with respect to wave angles, the fictitious gas case shows the best agreement to the experimental case, but at higher Froude/Mach numbers the free surface models also show good agreement. Quantitatively, with respect to wave location and depth profile, the free surface models show better agreement to the experimental case. For the unsteady case the resulting flow patterns are quite similar for the two cases considered, namely the experimental and free surface CFD cases.

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MMORPG game as the a representative product of video game from its birth to the present more than several decades, have been developing at an astonishing speed and MMORPG player groups have expanded. Nevertheless, there are questions being raised of the relatively new and successful field of sense of immersion of MMORPG game design. In the previous studies, the theory of flow had been testified to be the tremendously significant to explore sense of immersion while performing the activities and it had been applied to many different domains. Based on three conditions of that are necessary to achieve the flow state, the paper addresses the predicaments by analyzing the research results in relation to previous design report on the sense of immersion of MMORPG game design. The paper also provides the constrictive thoughts and productive sketches on how to promote the sense of immersion of MMORPG game using the design artifacts in an early design process.

This thesis investigates a horizontal water turbine blade designed to suit the periodical ocean current in Penghu sea region. Blade element momentum theory is exploited to design blade profiles. Then, CFD software, Fluent, is used to obtain such simulation result for torque, power, and efficiency. Firstly, performance of turbines with various cross-sectional profiles is discussed. Then, we use quasi-steady method to simulate power output of turbines from periodical ocean current and estimate how much ocean current energy we can obtain per day. Further, the performance of a turbine installed for different immersed depth from the surface is investigated. Our studies show that airfoil profile NACA6409 can outperform others in terms of high lift/drag ratio under low Reynolds number, and better hydrodynamic properties help the water turbine obtain higher torque and power output. A water turbine designed by using NACA6409, at R=1 m, at uniform velocity=2 m/s is estimated to generate 5KW output power. On condition of periodical current flow, the ebb tidal current can rotate water turbine, but power output is only 0.54 times of flood tidal current. The water turbine can generate more power when it is sited in deeper water, and less torque when it is sited near the water surface.

Abstract The experiment was performed to measure the flow-induced vibration of tubes in cross flow and to study the effect of different experimental parameters, natural frequency, tube patterns and positions of the missing tube, on the tube vibration. The vibration mode of structures was investigated by root-mean-square values of tube displacements, dominant response frequencies, power spectral densities and orbits. The vibration signals in various velocities were used to analyze the mode and mechanism of the tube vibration by examining the interrelations between power spectral densities and orbits of the tube vibration. It was found that the stability thresholds were higher at the higher natural frequencies of the tubes and approach angles of the flow. Missing tube would affect the stability of local flow field, so that the surrounding tubes became more unstable. For each array pattern, the dominant response frequency of tube was changed with the flow velocity. It should be associated with the flow field, the mode and mechanism of vibration. As the tube frequency jumped, it should be the change of vibrating mode and mechanism. From the spectra and orbits of the tube vibrations, it can be found that the dominant frequencies are more complex at the high flow velocity.

Flow induced vibration of flow around a flexible tube array in cross flow are investigated experimentally. The different parameter including velocity, turbulent intensity, and nature frequency of tube. The flow structure and stability between flow and tube are analyzed by flow visualization and flow measurement. Further more, missing tube to find the change of the flow and the influenced of nearby tube, to get the way decreasing the vibration of tube.

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ABSTRACT The flow-induced vibrations of tubes in a rotated triangular array subject to cross flow are investigated numerically and experimentally. The parameters are inlet velocity of cross flow, number of tube, and tube natural frequency. In the study, the instantaneous fluid forces on tube surfaces are computed numerically, the instantaneous displacement of the tubes due to the fluid forces is calculated, and thus the motions of the tubes in cross flow are described. Experiments are also conducted to compare the numerical results. The tube vibrations in a water tunnel are measured by two accelerometers. The amplitudes, spectra, and trace of tube motion are presented. The critical velocities of tube vibrations are then determined. Experimental results show that some tubes vibrate seriously when the flow velocity increases up to a critical value, and hysteresis of the tube vibrations is observed. In case of the seven-tube array, the tubes in the fourth row exhibit the most serious vibration. When the flow velocity is above the critical value, only one dominant frequency of the tube vibrations is detected, comparing to multiple dominant frequencies in subcritical condition. Furthermore, the tube in supercritical condition behaves like a limit cycle, especially when the natural frequency is equal to or near the vortex shedding frequency from the upstream tubes. It is also shown that the critical velocity decreases with more surrounding tubes in the upstream and does not change as more adjacent tubes are added in the downstream. However, the tube number seems to have no effect on the critical velocity when the tube natural frequency is far from the vortex shedding frequency.