Characterization of the Boundary Layers on Full-Scale Bluefin Tuna.

摘要

The physics that enable tuna to cross large expanses of ocean while feeding and avoiding predators is not understood; it is widely held that complex control of turbulent boundary layer transition and drag reduction are involved. Although the typical swimming speeds of bluefin tuna are 1-2 m/s, they can be higher during strong accelerations. The goal of the work documented in this report was to experimentally determine the approximate lateral location at which transition to turbulence occurs on the tuna for various speeds. The question is whether laminar flow or an advanced propulsion mechanism (or both) allows them to swim at high speeds. A full-scale model of a Pacific bluefin tuna was fabricated using a mold made from an actual deceased tuna, preserving the surface features and details of the appendages. The model was instrumented with 32 wall pressure sensors; experiments were performed in a tow tank. Results from flow visualization, drag, and wall pressure measurements over a range of speeds and varying angles of attack are presented.