Meeting Abstract
Recent work by us and our collaborators has demonstrated that the performance (speed, cost of transport, and thrust) of swimming plastic panels is a function of length and stiffness for any given actuation of the leading edge. More interestingly, we found by experiment and modelling that there are multiple performance maxima and minima as panel length is varied, and that swimming panels exhibit kinematic differences that correlate with performance. The work suggests the existence of resonance in the fluid-body interaction of undulatory swimming. To investigate whether this phenomenon plays a role in the behavior and morphology of fishes in vivo, we tracked the trailing edge of the tail of swimming striped bass (n = 3, FL = 37.3 – 48cm) in live digital video as fish swam in a recirculating temperature controlled flume. What distinguishes these data from past studies of tail beat frequency and amplitude is that we took data in very small increments of swimming speed from very slow up to speeds where the fish began to exhibit burst-and-coast behavior, and we processed 5500 – 7400 tail beats per fish to generate a very high-resolution data set. Swimming speed versus body length at fixed tail beat frequencies, and tail beat frequency versus swimming speed show evidence of deviations from gradual increase. This is suggestive of the sort of resonance seen in the swimming performance of plastic panels. If swimming performance in fish is characterized by significant peaks and troughs that are a function of body stiffness and length, then fluid-body resonance could be important in understanding how and why fish control changes in swimming speed, especially through development from fry to adult.
