Abstract:
The lateral line is a critical component of the fish sensory system, found to affect numerous
aspects of behavior including maneuvering in complex fluid environments, schooling, prey
tracking, and environment mapping. This sensory organ has no analog in modern ocean
vehicles, despite its utility and ubiquity in nature, and could fill the gap left by sonar and
vision systems in turbid cluttered environments. Yet, while the biological sensory system
suggests the broad possibilities associated with such a sensor array, nearly nothing is known
of the input processing and what information is available via the real lateral line. This thesis
demonstrates and characterizes the ability of lateral-line-inspired linear pressure sensor
arrays to perform two sensory tasks of relevance to biological and man-made underwater
navigation systems, namely shape identification and vortex tracking.
The ability of pressure sensor arrays to emulate the ”touch at a distance” feature of
the lateral line, corresponding to the latter’s capability of identifying the shape of objects
remotely, is examined with respect to moving cylinders of different cross sections. Using
the pressure distribution on a small linear array, the position and size of a cylinder is tracked
at various distances. The classification of cylinder shape is considered separately, using a
large database of trials to identify two classification approaches: One based on differences
in the mean flow, and one trained on a subset which utilizes information from the wake.
The results indicate that it is in general possible to extract specific shape information from
measurements on a linear pressure sensor array, and characterize the classes of shapes
which are not distinguishable via this method.
Identifying the vortices in a flow makes it possible to predict and optimize the performance
of flapping foils, and to identify imminent stall in a control surface. Vortices in
wakes also provide information about the object that generated the wake at distances much
larger than the near-field pressure perturbations. Experimental studies in tracking a vortex
pair and an individual vortex interacting with a flat plate demonstrate the ability to track
vortices with a linear pressure sensor array from both small streamlined bodies and large
flat bodies. Based on a theoretical analysis, the relationship between the necessary array
parameters and the range of vortices of interest is established.
