Narrow Results

In the present paper, the bounds on fractal dimension of Coalescence Hidden-variable Fractal Interpolation Surface (CHFIS) in ℝ³ on a equispaced mesh are found. These bounds determine the conditions on the free parameters for fractal dimension of the constructed CHFIS to become close to 3. The results derived here are tested on a tsunami wave surface by computing the lower and upper bounds of the fractal dimension of its CHFIS simulation.

Hundreds of bridges were washed away or heavily damaged by tsunami waves during the two tragic tsunamis that devastated the west coast of Sumatra Island, Indonesia, in 2004 and North East Japan in 2011. This vast damage was a clear warning for scientists to pay more attention and investigate, assess and mitigate the effect of tsunami loads on various structures including bridges. This multidisciplinary research presents a review of the literature and comprehensive evaluation on previous research concerning the effect of tsunamis on bridges. It begins with the basic evaluation of tsunami loads on bridges through to the current tsunamis. The experimental, numerical and survey reports on tsunami loads on bridges are reviewed and discussed. Tsunami mitigation systems on bridges are examined and classified in this paper. In addition, the open issues and challenges are outlined for future studies to help evaluate new research concerning the assessment, design and mitigation of tsunami loads on bridges.

Seawall is a most commonly used structure in coastal areas to protect the landscape and coastal facilities. The studies of interactions between the tsunami-like solitary waves and the seawalls are relatively rare in the literature. In this study, a three-dimensional numerical model based on OpenFOAM® was developed to investigate the tsunami-like solitary waves propagating over a rectangular seawall. The Navier–Stokes equations for two-phase incompressible flow, combining with methods of $k-\epsilon$ for turbulence closure and Volume of Fluid (VOF) for tracking the free surface, were solved. Laboratory experiments were performed to measure some of the hydrodynamic feature associated with solitary waves. The model was then validated by the laboratory data, and good agreements were found for free surface, velocity and dynamic pressure around the seawall. Finally, a series of numerical experiments were conducted to analyze the evolution of both wave and flow fields, the overtopping discharge as well as wave pressure (force) around the seawall, special attention is given to the effects of seawall crest width. Our findings will help to improve the understanding in the occurrences of tsunami-induced damages in the vicinity of seawall such as wave impact and local scouring.

Tsunami wave profile is one of the important inputs for evaluating impacts of the tsunami on coastal and offshore structures. To understand the tsunami wave patterns along the northern coastal regions of South China Sea, we simulate the tsunami propagation in the South China Sea generated by a hypothetical earthquake of magnitude $Mw9.3$ in Manila trench. The Boussinesq equations are adopted to account for the nonlinear and dispersive effects on the propagation and deformation of tsunami wave propagating over the continental shelf. Focusing on several locations in the northern region of South China Sea, the nested grids with gradually higher spatial resolution are used to ensure computational accuracy. Numerical results reveal that undular bores and several soliton-like waves may develop in shallow water in regions where water depth is less than 100m. The shallow continental shelf length and the steepness of wavefront are the two dominant variables that determine the development of undulation.

The purpose of this experimental study was to investigate the effects of a rectangular canal on the hydrodynamics of turbulent surges before and after the canal by implementing a series of physical experiments. A dam-break wave model was used to simulate the tsunami-like turbulent waves passing over a smooth and horizontal surface, in the presence and absence of a canal. Three canal depths of $d=0.05$, 0.10 and 0.15m were used to model shallow, moderate and deep conditions and three canal widths of $w=0.60$, 1.60 and 3.0m were selected to model narrow to wide canals. The front velocity of the dam-break induced surges were controlled by rapidly releasing upstream impounded set volumes of water with depths of $d_o=0.20$, 0.30 and 0.40m. The dam-break wave propagation over a horizontal, dry and smooth bed revealed four regimes describing the variations of surge height with time. The arrival time to reach the maximum surge height and the quasi steady-state regime was correlated with each impoundment depth and an empirical formulation was proposed to estimate the onset of the quasi steady-state flow. The maximum surge heights measured before and after the mitigation canal location were compared with those recorded in the corresponding tests without the presence of the canal. It was found that the peak surge height upstream of the canal could increase up to 40% compared to the test without the presence of the canal in relatively small impoundment depth and in presence of a narrow canal due to momentum dissipation. The wave height downstream of the canal increased between 10% and 50% of the wave height without the presence of the canal and the minimum change in the wave height occurred for the canal width to depth ratio of 20. The time-history of surge velocity after the mitigation canal indicated a significant decay of between 40% and 60% in the presence of a canal due to the bed friction changes and momentum dissipation.