An analytical method was developed to study the wave diffraction effects on arc-shaped bottom-mounted breakwaters. The breakwater was assumed to be rigid, thin, impermeable and vertically located in water of constant depth. The fluid domain was divided into two regions by imaginary cylindrical interface. The velocity potential in each region was expanded with eigenfunctions. By satisfying continuity of pressure and normal velocity across the imaginary fluid interface, a set of linear algebraic equations could be obtained to determine the unknown coefficients for eigenfunction expansions. The accuracy of the present model was verified by a comparison with existing results for the case of an isolated straight-line breakwater. Numerical results, in the form of contour maps of the non-dimensional wave amplitude around the breakwater and diffracted wave amplitude at three typical sections, were presented for a range of wave parameters. Results show the arc-shaped bottom-mounted breakwater is generally effective in defending against waves. The wave amplitudes at most sheltered areas are commonly 10%-50% of incident wave amplitudes under most wave conditions.
An analytical method was developed to study the wave diffraction on arc-shaped floating breakwaters. The floating breakwater was assumed to be rigid, thin, vertical, immovable and located in water of constant depth. The fluid domain was divided into two regions by imaginary interface. The velocity potential in each region is expanded by eigenfunctions. By satisfying continuity of pressure and normal velocity across the imaginary fluid interface, a set of linear algebraic equations could be obtained to determine the unknown coefficients for eigenfunctions. The accuracy of present model and the computer program were verified by a comparison with existing results for the case of arc-shaped bottom-mounted breakwaters. Numerical results, in the form of contour maps of the non-dimension wave amplitude around the breakwater, were presented for a range of wave and breakwater parameters. Results show the wave diffraction on the arc-shaped floating breakwater is related to the incident wavelength and the draft of the breakwater.
A linear hybrid model of Mild Slope Equation (MSE) and Boundary Element Method (BEM) is developed to study the wave propagation around floating structures in coastal zones. Both the wave refraction under the influence of topography and the wave diffraction by floating structures are considered. Hence, the model provides wave properties around the coastal floating structures of arbitrary shape but also the wave forces on and the hydrodynamic characteristics of the structures. Different approaches are compared to demonstrate the validity of the present hybrid model. Several numerical tests are carried out for the cases of pontoons under different circumstances. The results show that the influence of topography on the hydrodynamic characteristics of floating structures in coastal regions is important and must not be ignored in the most wave period range with practical interests.
There are two types of floating bridge such as discrete-pontoon floating bridges and continuous-pontoon floating bridges. Analytical models of both floating bridges subjected by moving loads are presented to study the dynamic responses with hydrodynamic influence coefficients for different water depths. The beam theory and potential theory are introduced to produce the models. The hydrodynamic coefficients and dynamic responses of bridges are evaluated by the boundary element method and by the Galerkin method of weighted residuals, respectively. Considering causal relationship between the frequencies of the oscillation of floating bridges and the added mass coefficients, an iteration method is introduced to compute hydrodynamic frequencies. The results indicate that water depth has little influence upon the dynamic responses of both types of floating bridges, so that the effect of water depth can be neglected during the course of designing floating bridges.
