This thesis is a study of the swimming locomotion of the polychaete worm, Nereisdiversicolor. Previous research has shown that there are two distinct jet-like flowregions in the wake of a swimming polychaete worm (Hesselberg 2006). In the first section of this thesis, this flow pattern is studied in greater detail using a high resolution particle image velocimetry (PIV) technique. A small region close to the wave crest of the undulating worm is recorded and the fluid velocity vector fields are plotted. The close-up PIV results show how the jet-like fluid pattern is formed due to the action both of a single sweeping parapodium and to the interaction between adjacent parapodia, proving for the first time that Gray’s (1939) explanation of the propulsion mechanics is in fact correct.The second part of this thesis is focused on the pumping action of the polychaeteworm, a behaviour adopted by the worms to create a flow of nutrients through their burrows. Particle image velocimetry (PIV) experiments were performed on tethered polychaete worms, Nereis diversicolor. The tethered worms moved in a gait which was different from that of freely swimming ones. They used a much smaller body wave amplitude, pumping liquid with very high efficiency by cooperative movement of their body and parapodia.In the third part of the thesis, a mechanical model was designed and built. The model consisted of a series of paddle units. Each paddle was driven by a servo motor. Breugem (2008) did a CFD simulation of the paddle model. Similar fluid patterns were generated by the physical model. Reversed flow was found at low Reynolds number (Re) and higher Re situations. The flow direction could be controlled by simply adjusting the beating frequency of paddles. The mechanical model is not sufficient to mimic the pumping locomotion of the worms due to absence of an undulatory movement. The pumping efficiency is low compared to pumping worms.
|Date of Award||10 Oct 2012|
|Supervisor||William Megill (Supervisor) & Julian Vincent (Supervisor)|
- fluid dynamics