• 吳 昀達

Student thesis: Doctoral Thesis


This dissertation presents an investigation on the wave hydrodynamics around coastal structures under tsunami–like long waves by means of solitary waves For each topic of interest numerical simulations are supported by carefully conducted experiments or available data in literature Physical modeling relies on a high-resolution particle image velocimetry to measure velocity properties due to wave-structure interaction By repeating sufficient times of identical experiment meaningful turbulence information can be evaluated through the ensemble-averaged method for the mean velocities and the Reynolds-decomposition method for the velocity fluctuations Numerical simulations are computed by a depth- and phase-resolving wave model based on the Reynolds-averaged Navier-Stokes equations with an appropriate turbulence model to relate the Reynolds–Stress Propagation of solitary waves in a constant water depth is first investigated Both the Dirichlet boundary condition and the internal mass source are utilized to generate desired solitary waves with the implementations of various solitary wave theories in the numerical model The purpose of this attempt is to examine how to generate stable and accurate solitary wave in the first place Accurate solitary waves are examined by means of relative error of the wave height between the input signal and the realistic generated wave while stable solitary waves are examined by means of how much distance is necessary to stabilize the waves Attenuation of solitary waves propagating over a significant traveling distance due to viscous effect is then studied experimentally and numerically Next interactions between solitary waves and submerged permeable/impermeable breakwaters are investigated Maximum magnitude of turbulent intensity is always observed at the leading edge of the obstacle for both obstacle scenarios It is found that the macroscopic approach for porous media flow can predict the overall velocity and turbulence fields but the detailed physics need to be achieved by means of the microscopic description for the flow within the porous structure Thirdly we concern the wave hydrodynamics around an environmental-friendly coastal defense by means of submerged solid/slotted barrier under solitary waves For the solid case strong turbulence has been created by large amplitude of solitary wave and wave breaking occurred during wave–structure interaction It is found that the non-linear eddy viscosity model to approximate the Reynolds-Stress is indeed important for the prediction of turbulent kinetic energy For the slotted case a complicated flow pattern due to flow separation and interactions between induced vortices has been observed by laboratory observation and later confirmed by simulation Last topic focuses on successive solitary wave breaking on a sloping beach By varying the time separation between two neighboring crests of solitary waves significant difference on the run-up and run-down processes has been observed through numerical simulation It should be devoted to experimental effort in order to verify the numerical findings This study mainly contributes to provide reliable measured data in terms of velocity and turbulence due to wave-structure interaction Such data is then used to compare with numerical simulation in order to ensure that the present wave model can provide meaningful physics on coastal engineering related applications
Date of Award2015 Feb 3
Original languageEnglish
SupervisorShih-Chun Hsiao (Supervisor)

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