Jack Mao Chen

Interaction between Tsunami Waves and Isolated Conical Islands

Abstract Chen, J.M.; Liang, D., and Tang, H., 2012. Interaction between tsunami waves and isolated conical islands. A newly developed computer model, which solves the horizontal two-dimensional Boussinesq equations using a total variation diminishing Lax-Wendroff scheme, has been used to study the runup of solitary waves, with various heights, on idealized conical islands consisting of side slopes of different angles. This numerical model has first been validated against high-quality laboratory measurements of solitary wave runups on a uniform plane slope and on an isoliated conical island, with satisfactory agreement being achieved. An extensive parametric study concerning the effects of the wave height and island slope on the solitary wave runup has subsequently been carried out. Strong wave shoaling and diffraction effects have been observed for all the cases investigated. The relationship between the runup height and wave height has been obtained and compared with that for the case on uniform plane slopes. It has been found that the runup on a conical island is generally lower than that on a uniform plane slope, as a result of the two-dimensional effect. The correlation between the runup with the side slope of an island has also been identified, with higher runups on milder slopes. This comprehensive study on the soliton runup on islands is relevant to the protection of coastal and inland regions from extreme wave attacks.

Experimental study of water and dissolved pollutant runoffs on impervious surfaces

The water and dissolved pollutant runoffs on impervious surfaces are the essential factor to be considered in design methods to minimize the impacts of the diffuse water pollution. In this paper, experiments are conducted to study the water and dissolved pollutant runoffs on impervious surfaces for different rainfall intensities and surface roughnesses. It is shown that a larger rainfall intensity and a smaller surface roughness reduce the time of concentration and increase the pollutant transport rate. Most of the pollutant runoffs take place at the initial stage of the rainfall. The pollutant transport rate rapidly reaches a peak and then gradually drops to zero.

Nonlinear Effect on Wave-Structure Interaction

Accurate prediction on the behaviour of the nonlinear waves in a coastal environment is vital to the safe design and performance of coastal defence. This paper is concerned with the description of tsunami wave-island interaction, and includes both linear and nonlinear modelling of the maximum free surface motion arising within distorted flow field. A deterministic nonlinear effect on the predicted maximum runup is examined using a Boussinesq-type model. Statistics of the predicted maximum leading-crest motion are obtained and discussed in light of linear diffraction theory. The results show that the predicted maximum runup and free surface motion by the quaternary-islands is affected by nonlinear wave transformation. The numerical simulations suggest that the present model describes the wave field very accurately even for extreme events. The present study provides a critical insight into the free surface elevation maxima at surf zone, thus safeguarding the structure design. Copyright

N-Wave Runup Statistics at Surf Zone Using Boussinesq-Type Model

A TVD Lax-Wendroff scheme solves the Boussinesq-type equations is presented, extensively validated, and clearly demonstrated to be a robust and efficient engineering tool to simulate the physical processes involved in the tsunami wave runup and interaction of the propagating solitary waves with the idealized coastal beaches. To better understand the physical processes of the tsunami wave runup at surf zone, a parametric study concerning N-wave runup is carried out. For all cases investigated, the qualitative features of the propagating Nwaves remain unaltered, even for the large wave events. The relative maximum runup height and wave steepness are found to be strongly correlated and appeared to be linearly asymptotic in form. Also, the severity of extreme wave attack is found to be a function of beach slope for a given extreme event. The numerical simulations reveal the significance of the nonlinear wave effects on the predicted maximum N-wave runup heights, which provide guidance in selecting the design height of coastal defence structures and specifying the clearance distance between the shoreline and infrastructure. Copyright