Underwater exploration is an important area of research, whether to expand our knowledge base of underwater environments, or to monitor and preserve structures both natural and man-made. Biomimetic fish-like robots are being developed to incorporate some of the aspects of live fish in the hope that more efficient machines can be produced by exploiting the energy available within flow phenomena such as vortices. However, in order for a fully autonomous robot to be able to swim in natural environments, a navigational strategy is needed that distinguishes between steady and unsteady flows. To develop an effective strategy, the link between the local flow fields measured by sensors on the robot and the global flow phenomena needs to be determined. Therefore, the objective of this study was to link the local and global flow fields around a fish-like robot with an on-board pressure sensor array in both steady and unsteady flows. Two hypotheses were put forward: that the signal from pressure sensors towards the front of a fusiform-shape robot could be used to detect the relative position of vortices; and that the changing aspects of the Karman vortex street could be identified by changing aspects of the pressure signals detected. These hypotheses were tested by placing the fish-like robot in steady flows and in Karman vortex streets, both whilst held stationary and whilst moving. The global flow field was measured using DPIV and the local flow field was measured using the pressure sensor array on-board the robot.The results showed characteristic patterns within the pressure signals when the robot was within the Karman vortex street. By combining different characteristics of the pressure signals, detection of the Karman vortex street was possible, with the relative position and characteristics of the vortices able to be determined.It is hoped that the results of this study could be used within navigational strategies for fish-like robots in order that they can identify and successfully navigate unsteady flows such as the Karman vortex street, with the potential for this to reduce the energy usage of the robot in these flows.
|Date of Award||24 Feb 2015|
|Supervisor||Michael Carley (Supervisor) & William Megill (Supervisor)|