COMPUTER MODELING FOR WAVE OSCILLATION PROBLEMS IN HARBORS AND COASTAL REGIONS

Oral Defense byXiuying Xing, PhD CandidateSonny Astani
Department of Civil and Environmental EngineeringABSTRACT:Harbors are built to provide a sheltered environment for the mooring of ships and vessels. For some wave periods the semi-enclosed harbor basin acts as a resonator to amplify the wave motions in the harbor due to the combined effects of wave diffractions, refractions and multiple reflections from the boundaries. This undesirable wave motion could induce significant ship motions, damage ships and dock facilities, and delay loading and unloading activities if the resonant wave periods are close to that of the ship mooring system. Harbor planners and engineers need to study the wave induced oscillations as new harbor layouts are contemplated.
This dissertation study presents a finite element model which could be used for predicting the response characteristics of harbors and bays of arbitrary shape and variable depth. The model incorporates the effects of wave reflection, refraction, diffraction and dissipation losses due to boundary absorption, bottom friction and energy losses due to the flow separation at the entrances. The model has been applied to three harbors (Crescent City Harbor in northern California, Pohang Harbor in Korea, and Hualien Harbor in Taiwan) and two bays (San Pedro Bay in southern California and Bay of Fundy in the east coast of Canada and US). The results from the finite element model have been shown to agree surprisingly well with the field data obtained from events such as earthquake generated tsunamis and hurricane induced wave oscillations, as well as normal day observations. The results reveal the fact that the wave oscillation condition inside a harbor or bay is determined by the local layout and bathymetry. The harbor or bay responds to the incident wave in a predictable manner irrespective to the sources of driving forces such as typhoon, tsunami, winter storms, etc. The study also explains the tremendous tide phenomena at Bay of Fundy.
Modification strategy studies for reducing the seiche problems in Pohang Harbor and Hualien Harbor have also been presented. The model is shown to be an effective engineering tool for harbor planning and design to derive ways of eliminating or altering the harbor response so that the harbor may indeed provide a sheltered environment for moored ships and vessels.

Location: Kaprielian Hall (KAP) - 209

Audiences: Everyone Is Invited

Contact: Evangeline Reyes