Abstract:

Of the few analytical approaches available for solving linear problems, one is the singularity method. By the superposition principle for linear systems, a body of arbitrary shape can be simulated, at least theoretically, by a discrete or continuous distribution of fundamental singularities while the flow field can be represented by the corresponding distribution of fundamental solutions. The type and distribution of fundamental singularities to be used depend both on the geometry of the moving body and on the nature of the flow. Therefore, the mathematical formulation for a body-induced flow may be characterized by a fundamental singularity, and it is essential to seek the corresponding fundamental solution as the first step to solve the full problem.

As is well known, the fundamental singularity for an inviscid flow is a simple source, which physically represents a point mass source in the fluid while the fundamental singularity for a viscous Stokes/Oseen flow is a Stokeslet/Oseenlet, which physically represents a point force acting on the fluid. In the present study, the steady interfacial waves due to fundamental singularities in a system of two semi-infinite fluids, the transient waves due to impulsive disturbances in an inviscid fluid with an ice-cover, and the unsteady free-surface waves due to suddenly starting and oscillating Stokeslet/Oseenlet in a single fluid of infinite depth are analytically investigated in detail by the means of integral transforms and large-time/distance asymptotic approximation. The results obtained show the effects of density ratio, viscosity, unsteadiness, submergence, and the presence of an ice cover on the gravity waves generated.

Biography:

Dr Dongqiang Lu obtained his BSc degree in Mechanics in 1995 from Fudan University and his MSc degree in Fluid Mechanics in 1998 from Shanghai University. From Mar. 1998 to Feb. 1999, he worked as an assistant lecturer in Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University. In 1999, he went on pursuing a Ph.D. degree in Marine and Offshore Engineering at the Department of Mechanical Engineering, The University of Hong Kong. After obtaining his PhD degree in 2003, he returned to Shanghai University and was promoted to Associate Professor in June 2005. He is currently a research associate at the Department of Mechanical Engineering, The University of Hong Kong. From 1998 to 2005, Dr Lu has published 14 Journal papers, 7 international conference papers and 5 national conference papers. His current research interests include (i) the generation of waves due to submerged bodies, and (ii) the interaction between waves and maritime structures.