Surfactant effects on the interaction of a three dimensional vortex pair with a free surface; and,

In part I of the thesis, a canonical problem of three dimensional surfactant hydrody namics, the three-dimensional laminar interaction between a clean or contaminated free surface and a vortical flow underneath is considered. Initially, the vortical flow is in the form of two modulated finite-core vortex tubes parallel to the free surface. The vortex tubes break down via instability and helical vorticity is generated. The most prominent feature at the surface is that associated with the connection of helical vorticity to the free surface. For clean surface, the helical vorticity would interact fully with the free surface and reconnects to it under the influence of the primary vorticity. The presence of surfactant leads to substantial increase in the generation of free-surface secondary vorticity which results from large gradients in the surface surfactant distribution created by induced velocities at the free surface due to the primary vortex tubes. The secondary structure in the bulk interacts with the he lical vorticity, which totally alters the vortex pattern and connection process. The presence of contamination considerably weakens the connection in terms of strength, location and duration. The degree of secondary vorticity generation by the surfac tant is limited by a closed-loop interaction between the flow field (primary flow and secondary flow) and surfactant transport.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Ocean Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2001

Author dc:creator

• Zhang, Xiang, 1969-

Advisor dc:contributor.advisor

• Dick K.P. Yue.

• Ocean Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/8234

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8234