The flow field behavior in the vicinity of a perforated breakwater and the efficiency of the breakwater under regular waves were studied. To examine the efficiency of the structure thirteen types of regular wave conditions with wave periods T = 1, 1.2, 1.6, 2, 2.5 sec and wave heights Hi = 2, 4, 6, 8, 10 cm in an intermediate water depth of 50 cm were tested. The incoming, reflected and transmitted wave heights were measured using resistance type wave gauges positioned at the required locations. The efficiency of the structure was calculated considering the energy balance for the system. The efficiency of the structure for different wave conditions and with different parameters are shown and compared. Seven types of regular waves with wave periods T = 1, 1.6, 2, 2.5 sec and wave heights Hi = 4, 6, 8, 10 cm in an intermediate water depth of 50 cm were tested for the flow behavior study. In order to study the flow field variation with phase, ten phases were considered per one wave. The Particle Image Velocimetry (PIV) technique was employed to measure the two dimensional instantaneous velocity field distribution and MPIV (Matlab toolbox for PIV) and DaVis (a commercial software) were used to calculate the velocity vectors. By repeating the experiments and taking an average, the mean velocity field, mean vorticity field, mean turbulent intensity and mean turbulent kinetic energy field were calculated for each phase and for each wave condition. The phase average fields for each wave condition for each of the above mentioned parameters were calculated taking the average of ten phases. The phase averaged velocity, vorticity and turbulent kinetic energy fields are presented and compared. The energy dissipation based on both elevation data and the velocity data are presented and compared. It was found that for more than 75% of the tested wave conditions, the energy dissipation was above 69%. Thus the structure is very effective in energy dissipation. Further it was found that for all the tested wave conditions most of the turbulent kinetic energy form near the free surface and near the front wall, where as behind the back wall of the structure the turbulent kinetic energy was very small.

The flow field behavior in the vicinity of a perforated breakwater and the efficiency of the breakwater under regular waves were studied. To examine the efficiency of the structure thirteen types of regular wave conditions with wave periods T = 1, 1.2, 1.6, 2, 2.5 sec and wave heights Hi = 2, 4, 6, 8, 10 cm in an intermediate water depth of 50 cm were tested. The incoming, reflected and transmitted wave heights were measured using resistance type wave gauges positioned at the required locations. The efficiency of the structure was calculated considering the energy balance for the system. The efficiency of the structure for different wave conditions and with different parameters are shown and compared. Seven types of regular waves with wave periods T = 1, 1.6, 2, 2.5 sec and wave heights Hi = 4, 6, 8, 10 cm in an intermediate water depth of 50 cm were tested for the flow behavior study. In order to study the flow field variation with phase, ten phases were considered per one wave. The Particle Image Velocimetry (PIV) technique was employed to measure the two dimensional instantaneous velocity field distribution and MPIV (Matlab toolbox for PIV) and DaVis (a commercial software) were used to calculate the velocity vectors. By repeating the experiments and taking an average, the mean velocity field, mean vorticity field, mean turbulent intensity and mean turbulent kinetic energy field were calculated for each phase and for each wave condition. The phase average fields for each wave condition for each of the above mentioned parameters were calculated taking the average of ten phases. The phase averaged velocity, vorticity and turbulent kinetic energy fields are presented and compared. The energy dissipation based on both elevation data and the velocity data are presented and compared. It was found that for more than 75% of the tested wave conditions, the energy dissipation was above 69%. Thus the structure is very effective in energy dissipation. Further it was found that for all the tested wave conditions most of the turbulent kinetic energy form near the free surface and near the front wall, where as behind the back wall of the structure the turbulent kinetic energy was very small.

Thesis (Ph. D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1992. / Includes bibliographical references (leaves 231-241).

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains xii, 140 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical references (p. 137-139).

Xu, Xiaoqi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 91-92). / Abstracts in English and Chinese. / Xu, Xiaoqi. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Experimental measurements --- p.10 / Chapter 3 --- Review of earlier work --- p.13 / Chapter 3.1 --- Moments of {xP fT) --- p.13 / Chapter 3.2 --- Earlier results of Xr --- p.18 / Chapter 4 --- Probability Density Functions --- p.24 / Chapter 5 --- Scaling behavior of the moments --- p.43 / Chapter 5.1 --- Longest time scale in the problem --- p.43 / Chapter 5.2 --- The maximum order of the moment that can be calculated from a given set of data --- p.47 / Chapter 5.3 --- Moments of the surrogate XT --- p.50 / Chapter 5.4 --- The surrogate XT using water measurements and helium measurements --- p.59 / Chapter 5.4.1 --- PDFs comparison --- p.59 / Chapter 5.4.2 --- Scaling behavior of moments --- p.61 / Chapter 5.5 --- Investigation --- p.64 / Chapter 5.5.1 --- Helium measurements and water measurements --- p.64 / Chapter 5.5.2 --- Xr and Xfr using water measurements --- p.69 / Chapter 5.6 --- Conclusion --- p.73 / Chapter 6 --- Conditional statistics of temperature fluctuations --- p.74 / Chapter 6.1 --- Estimating the maximum order of moment --- p.74 / Chapter 6.2 --- Conditional temperature structure functions using Xfr and Xr --- p.78 / Chapter 6.3 --- Conditional temperature structure functions using x/r and XT at various r in the temperature derivatives --- p.83 / Chapter 7 --- Conclusion --- p.89 / Bibliography --- p.91

In this thesis,I discuss the wave pass on submerged bweakwater,and theheight of submerged breakwater,different slope of submerged breakwater with breaking wave relations.I do experiment to find the regular between breaking wave and the design of submerged breakwater.I use different submerged breakwater,there are two slope.There are 1/2 and 1/5.The height of submerged breakwater is 45 cm,the wide of submerged breakwater is 75 cm.the water deep is from 50cm to 90 cm,Wave cyclical is from 1.2 sec to 2.7 sec,I use H L to choose wave height,and save the data of incident wave.and then I analysis the data to get t K and energy.I also memorize the site of breaking wave and breaking type. From the experiment ,we know that wave do not be broken, be broken, and the regular of breaking wave and breaking type ,so we can use the regular to design the height of submerged breakwater, the slope of submerged breakwater. So we can use the least costs to protect the seacoast. When we know local wave condition, we can design the height of submerged breakwater to break wave that is dangerous for seacoast ,or we want to break wave when the wave height at 1 m or 2 m or others design the height of submerged breakwater. When £m^2h/g is between 0.3 and 2.5,we can find that when R/H0¡¦ is smaller than 1,the wave will break¡CWhen wave break bysubmerged breakwater ,we can find the slope of 1/5 is better than the slope of 1/2 to reduce the wave.Both slope of 1/2 and slope of 1/5 are effective to reduce wave energy at Hi/R=2.

Bibliography : leaves 231-241 / ix, 241 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1992

Aircraft designed for naval aircraft carriers experience great airframe stress during landing due to the high vertical velocities that they must maintain as a consequence of the extremely short runway and shallow landing angle of attack. This creates a need for structural rigidity to counteract the forces that land-based aircraft never experience. This is not ideal if it otherwise limits the performance and flying capabilities of the aircraft that are otherwise necessary for the environments they might find themselves in. As such, a new approach to protecting the aircraft from the immense loads they experience during landing could be to add flexibility to the airframe and landing gear, promoting deflection instead of failure. This thesis aims to investigate this idea, starting with an elementary set of tests, looking into material flexibility, and then moving on to adding this concept to progressively more advanced structural systems. Using balls of varying material, preliminary drop tests indicated that material flexibility could assist the dissipation of landing energies, showing that the coefficient of restitution increases with the stiffness. Drop tests involving mass-spring-damper systems as well as cantilever plates and transverse beams also indicated that the strain energy a body can absorb from a set load case can be increased if its flexibility also grows. This finding led to the important conclusion and finding that a flexible body can transfer and store at least 10 times its initial contribution of energy to a system in the form of strain energy. Through these tests, it was shown that flexible structures can be a beneficial design feature in combatting and dissipating vertical landing energies. / Master of Science / Historically, airplanes landing on naval aircraft carriers are subject to high impact loads when they land because the plane is traveling at a high velocity downward and has a short runway to stop on. This impact on the runway is so severe that it requires the structure of the airplane to be reinforced, which in turn makes the plane heavier and less capable in flight. This reinforcement also implies that the plane is quite stiff in all of its components. One solution to this issue is to reverse the design logic historically taken, and impose flexible structures into the main body of the plane, which can bend and absorb some of the vertical energy that the plane possesses. This theory was investigated using a series of drop tests, starting with ball drop tests of varying materials. These tests showed that the material of a ball can affect the energy that it absorbs and how much is kept by the ball after it collides with the ground. Next, more complex structures were tested, using shock absorbers, metal plates, and metal beams. These components were combined to form drop systems, which were dropped to measure the bending in the plates and beams, as well as the shock absorbers. The conclusion made from these tests is that a more flexible structure can absorb a higher percentage of energy compared to its initial contribution, than its stiffer and heavier counterpart. This important conclusion shows that the application of flexible structures could be a vital step in improving the design of airplane wing and body structures to promote the longevity of the structure of the aircraft.

In this dissertation, first, the theoretical and experimental viewpoints of instability and bifurcation in mechanics are reviewed and discussed. The onset of instability of bifurcation depends on the constitutive assumptions, and is marked by the loss of ellipticity, singularity of the stiffness matrix, and negative or complex eigenvalues. Non-traditional regularization is necessary to obtain useful post-instability solutions. Based on dissipated energy and elastic potential, energy based instability criterion is considered and developed. The global instability criterion is concerned with global non-uniform deformation while the surface degradation instability criterion deals with near surface non-uniformities. In addition, the connection between surface degradation and size, shape effects for brittle materials is examined. The energy based stability theory is applied for some typical problems through analytical and numerical implementations. It is shown that the onset of both surface instability and global degradation instability occurs in the strain hardening stage, that is, before and close to the peak strength. The theoretical results are compared with experimental observations. Both strain gage tests and ultrasonic scanning tests are processed to study the degradation mechanisms of a brittle material. The surface effects are highlighted by the experiments. Ultrasonically dissipated energy shows a random distribution and it follows, in general, the initial non-homogeneity pattern. The relationship between the ultrasonically dissipated energy and mechanically dissipated energy is dependent on deformation and can be approximated by a power function of the factor of load level. The theory for surface degradation consideration involves a few material constants, and these constants are identified against experimental observations. The degradation mechanism and damage growth patterning of simulated rock under uniaxial load are modeled numerically by implementing the theory for damage and surface degradation with initial state consideration. The theoretical results are compared with experimental observations obtained through ultrasonic scanning tests. To extend the study to post-instability modelling by using various constitutive models, three alternative considerations are proposed to achieve so-called regularization of the problem.