| With the rapid development of China’s economy,more and more sea-crossing bridges have been built in coastal areas to stimulate the greater traffic demand.The sea area of the bridge site may be threatened by extreme waves caused by storm surge,tsunami,typhoon,etc.The huge wave force impact on the bridge structure may play a major role in its design and construction.And because sea-crossing bridges are often built on islands and reefs,the variable topography of the sea floor will affect the propagation of extreme waves and the wave force on the bridge infrastructure.Therefore,it is necessary to consider the influence of variable topography on the extreme wave forces of bridge structures.Based on wave flume experiment and FLOW-3D numerical wave flume model,the paper takes the dumbbell-shaped structure of the sea-crossing bridge as the research object,and studies the influence of slope,semi-parabolic and parabolic on the hydrodynamic characteristics of two extreme waves,solitary wave and focused wave(non-breaking waves),during the propagation process of them.On this basis,the influence of the variable topography on the wave force of the dumbbellshaped structure of the sea-crossing bridge is discussed.And the action mechanism is analyzed from the flow field characteristics such as wave surface change around the structure,hydrodynamic pressure and velocity distribution.Contents of this thesis are as follows:(1)Based on the Navier-Stokes equation,the renormalized RNG k-ε turbulence model and the TruVOF calculation method,a three-dimensional numerical wave flume model is established,and the target wave is generated by the wave-generation method of defining inlet boundary conditions.The numerical wave flume model is verified based on the wave flume experiment,including the extreme wave formation on flat topography,the extreme wave force of the dumbbell-shaped structure on the flat topography and the wave propagation on the slope.The parameters of pure waves and wave forces for solitary and focused waves are analyzed based on the numerical wave flume,including wave height of solitary waves,peak frequency of focused waves,etc.(2)Based on the numerical wave flume,the effects of type of variable topography,slope of topography and relative position on the hydrodynamic properties of solitary waves without structure,and the solitary wave force on dumbbell-shaped structures are discussed.The results show that the variable topography changes the solitary wave surface,thereby affecting the solitary wave hydrodynamic pressure when there is no structure.When there is a structure,the variable topography can significantly affect the distribution of the free surface elevation around the structure,thereby affecting the hydrodynamic pressure on the structure,eventually lead to a change in the solitary wave force.Although the reflection of wave and the decrease of flow area lead to the change of the velocity distribution of solitary wave,since the structure studied in this paper is mainly controlled by the inertial wave force,the velocity change does not have a significant effect on the solitary wave force of the structure.(3)Based on the numerical wave flume,the effects of type of variable topography,slope of topography and relative position on the hydrodynamic properties of focused waves without structure,and the focused wave force on dumbbell-shaped structures are discussed.The results show that the changes of the focused wave water depth and wave surface caused by the variable topography will affect the focused wave hydrodynamic pressure when there is no structure.When there is a structure,the water depth around the dumbbell structure and the surface of the focused wave caused by the variable topography will affect the hydrodynamic pressure on the dumbbell structure,eventually lead to a change in the focused wave force.The focusing position,wave reflection and the reduction of the flow area lead to the change of the focused wave velocity field,and the original direction and magnitude of the velocity will also affect the velocity change.(4)Based on the above research,the effects of variable topography on the solitary wave force and the focused wave force of dumbbell-shaped structure are compared.Most of the components of the focused wave have small amplitudes and wavelengths,located near the judgment region of deep-water wave.The velocity and energy are mainly concentrated near the crest,so the variable topography has little influence on the focused wave force;The solitary wave is in the shallow water wave determination area.The velocity and energy are distributed evenly along the vertical direction,so it has a great influence on the solitary wave force. |
