3-D MULTI-PHASE NUMERICAL MODELLING OF TSUNAMI-INDUCED HYDRODYNAMIC LOADING ON NEARSHORE STRUCTURES

摘要

In recent years, the world has witnessed several major tsunamis that became unprecedented natural catastrophes in terms of human casualties and economic losses. Reconnaissance missions in the aftermath of the 2004 Indian Ocean Tsunami and the 2011 Tohoku Tsunami, carried out by researchers from the University of Ottawa, Canada, have revealed that many structures previously thought to be capable of withstanding tsunami-induced forces were heavily damaged and, in some cases, even completely destroyed. In response to these findings, an ongoing comprehensive interdisciplinary (hydraulic-structural engineering) research effort was initiated at the University of Ottawa, Canada, with the intent of advancing the current understanding of tsunami wave-structure interaction and to review and improve existing design codes accordingly. In the current study, a multi-phase three-dimensional numerical model was developed using OpenFOAM. This model was further applied to investigate hydrodynamic loading on a three-dimensional structural model caused by the inland intrusion of a broken tsunami wave. For model validation, a qualitative and quantitative comparison of numerical and physical measurements was performed using results from extensive laboratory experiments conducted at the National Research Council's Ocean, Coastal and River Engineering facilities (NRC-OCRE) in Ottawa. A recent analytical solution derived from the shallow-water wave theory was used to predict the bore profile and its results shows excellent agreement with the numerical ones. An analysis of key moments during the bore-structure interaction was also performed to better understand how water surface profiles and flow velocities are correlated to the forces exerted on surface-piercing structures. Of particular interest, the effect of entrained and entrapped air during the initial impact is captured by the model, augmenting the current understanding of its role in the loading process. In addition, results of a single-phase three-dimensional weakly compressible smoothed particle hydrodynamics (WCSPH) model, previously developed within the aforementioned research program, were further analyzed and compared to the OpenFOAM results. Finally, results obtained using a method proposed by a recent design guideline which provides guidance for estimating tsunami loading, FEMA P646 (2012), were compared to the numerical results to provide additional support in establishing updated design practices for tsunami-resistant structures.