Meeting Abstract
Pressure fields around the body provide a key avenue for fish to interact with their fluid world. Perhaps the most iconic examples are embodied by the fish’s lateral line sensory system and respiratory buccal pump, but pressure gradients are equally important in locomotion. To swim, fish pass a sinusoidal wave of bending down their bodies, creating localized regions of high and low pressure, and shaping this pressure field to promote favorable generation of locomotor forces and torques. Yet, since the seminal works of Dubois and colleagues in the 1970s, there has been little experimental mapping of pressure fields in studies of fish-like propulsion. This is owing in part to the difficulty in producing an accurate pressure measurement, and further difficulty in producing a map on a fine scale. Here, we use a non-invasive approach to calculate detailed, 2D pressure distributions based on digital particle image velocimetry (DPIV) measurements of velocity vector fields. To evaluate the accuracy of this approach, we apply this technique in the study of a fish-like mechanical model for which true forces and torques could be directly measured. Moreover, we identify limitations of this approach by examining static bodies and 3D flows, conditions under which this analytical approach would not be expected to perform well. In many cases, we were able to predict time-dependent patterns of swimming forces and torques with considerable accuracy. We conclude by providing a preliminary example of the pressure field around a freely-swimming fish and discussing the implications of this new approach for understanding the functional design of fishes.
