Experimental Study of Solitary Wave Interaction With Vertical Structures

Li, Lei (University of Strathclyde) | Zhang, Jingxin (Shanghai Jiao Tong University) | Chen, Jack M. (University of Cambridge) | Zhao, Xuanyu (University of Cambridge)

OnePetro 

ABSTRACT

Laboratory experiments have been carried out in a piston-driven wave flume to investigate the solitary wave impact on three types of vertical cylindrical objects, including the vertical cylinder, cone and bell-shaped lighthouse structure. First, the quality of the generated waves is examined by comparing their profiles with the theoretical solutions. The range of piston movements that generates good-quality solitary waves is determined. The scattering of solitary waves around geometrically different vertical structures is then focused on. The wave heights around the structures are measured in detail, from which the wave impact force is derived. The results regarding vertical cylinders agree well with the past research outcomes. It shows that the vertical cone structure experiences the largest impact force. Although the bellshaped lighthouse structure incurs slightly larger impact force than the vertical cylinder, it has a much larger and thus more stable base to resist the overturning moment. The findings confirm the good mechanical performance of some of the old lighthouse structures, which have existed for around 200 years.

INTRODUCTION

A solitary wave is described by Goring (1978) as a single “hump” of water that is entirely above still water level with an infinite wavelength. Solitary waves were first identified by Russell (1845) and have been the subject of considerable research ever since. Theoretical and experimental work by Hammack and Segur (1974) showed that from any water displacement above still water level at least one solitary wave shall emerge followed by a number of dispersive waves.

The Boxing Day tsunami of 2004 will go down in history as being one of the worst natural disasters ever recorded as it claimed the lives of more than 150,000 people, left millions homeless and caused billions of dollars’ worth of damage (Briggs et al. 2005). Although the Boxing Day tsunami shall be remembered for the devastating amount of damage it caused, it is important that it is not classed as being a “freak event of nature”. The tsunami itself was fairly typical of other tsunamis that have occurred in the past and are likely to strike again as shown recently by the tsunami that struck the north-east coast of Japan on the 11th March 2011. Solitary waves are not only used to model tsunamis but are also used to model large storm surges that commonly occur as a result of hurricanes.