Experiments of interactions between an inflexible inverted flag and K?rm?n vortex streets
Date Issued
2016
Date
2016
Author(s)
Kung, Yen-Hui
Abstract
There are lots of vortex energy in the nature, for example, the known tornadoes and the whirlpool scaring swimmer. I want to explore new method of vortex energy harvesting. According to Inverted-flag experiments and the experiment of flapping fish model behind semicircular cylinder, I produce the Karman vortex street by triangular prism and put an inflexible inverted flag which is free-rotating. Change free stream velocity, length of flags and the distance between inverted flag and triangular prism. Then observe and record the results and use numerical analysis to know the reason of the flapping results more. Some of researches are the Karman vortex street of different shapes of column and their Drag coefficient. Some are flapping of the inverted flags. I put inverted flag behind triangular prism and use laser, Polyamide Seeding Particles and camera to get the pictures of flow field. Then figure out the reason of the results by numerical analysis. At different length of flags and velocity, there are several flapping conditions of inverted flag. There is reverse double-side flapping when the length of inverted flag is three and a half times of characteristic length. By observing the flow field of experiment, we know that the flags behind column will affect the Karman vortex street and more seriously when the length of flags is longer. Flow over different shapes of cylinder will occur different forms of Karman vortex street. I think the wing-form cylinder is the best instrument of harvesting vortex energy of four cylinders in this experiment.
Subjects
K?rm?n vortex street
triangular prism
inverted flag
Type
thesis
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