Validity ranges of interfacial wave theories in a two-layer fluid system

In the present paper, we endeavor to accomplish a diagram, which demarcates the validity ranges for interfacial wave theories in a two-layer system, to meet the needs of design in ocean engineering. On the basis of the available solutions of periodic and solitary waves, we propose a guideline as principle to identify the validity regions of the interfacial wave theories in terms of wave period T, wave height H, upper layer thickness d(1), and lower layer thickness d(2), instead of only one parameter-water depth d as in the water surface wave circumstance. The diagram proposed here happens to be Le Mehautes plot for free surface waves if water depth ratio r = d(1)/d(2) approaches to infinity and the upper layer water density rho(1) to zero. On the contrary, the diagram for water surface waves can be used for two-layer interfacial waves if gravity acceleration g in it is replaced by the reduced gravity defined in this study under the condition of sigma = (rho(2) - rho(1))/rho(2) -> 1.0 and r > 1.0. In the end, several figures of the validity ranges for various interfacial wave theories in the two-layer fluid are given and compared with the results for surface waves

分层海洋中典型内波流场及其对小尺度杆件的作用

In early 20th century Canada, middle-class social reformers campaigned for urban parks and supervised playgrounds to provide children with appropriate places for leisure activities. Drawing on adult memories of participating in playgrounds in London, Ontario, this study explores the issues and complexities of establishing the playground program in London and, more specifically, the opportunities provided for girls and young women to learn and play sport. I consider the implications of social and moral reform initiatives on leisure spaces, and the impact of the delivery of social welfare at the municipal level on the lives of female participants.Au début du XXe siècle, des campagnes furent menées pour l’établissement de lieux destinés plus particulièrement aux loisirs des enfants, parcs urbains et aires de jeux surveillés. À partir des souvenirs recueillis auprès d’adultes ayant utilisés autrefois ces aires de jeux, cet article étudie les problèmes posés par leur établissement, et notamment leur utilisation par les jeunes filles et jeunes femmes, ces lieux leur offrant l’opportunité d’apprendre et de pratiquer différents sports. Les implications aussi bien sociales que morales de ces initiatives menées en vue du développement d’aires de loisirs, et les conséquences de l’aide sociale municipale sur la vie de ces jeunes filles et femmes, sont également étudiées dans cet article

海洋内波与海洋工程

简介海洋内波的研究历史;概述海洋的密度分层结构;根据观测,分析地球上和我国海域内波分布,认识海洋内波发生、传播和耗散的机理;概述海洋内波、内波流场理论研究进展.最后,以深海石油开采为背景,提出若干同海洋内波相关的科学问题

The induced flow field by internal solitary wave and its action on cylindrical piles in the stratified ocean

The induced flow fields by internal solitary waves and its actions on cylindrical piles in density stratified ocean with a basic density profile and a basic velocity profile are investigated. Some results, such as the time evolution of flow fields and hydrodynamic forces on the piles are yielded both by theoretical analysis and numerical calculation for general and specific cases. Several kinds of ambient sea conditions of the South China Sea are specified for numerical simulation. Moreover, the effects of relative density difference, depth ratio and wave steepness on maximal total force and total torque are analyzed