Thrust generation during steady swimming and acceleration from rest in anguilliform swimmers

Abstract

Escape swimming is a crucial behavior by which undulatory swimmers evade potential threats. The hydrodynamics of escape swimming have not been well studied, particularly for anguilliform swimmers, such as the sea lamprey Petromyzon marinus. For this study, we compared the kinematics and hydrodynamics of larval sea lampreys with those of lampreys accelerating from rest during escape swimming. We used experimentally derived velocity fields to calculate pressure fields and distributions of thrust and drag along the body. Lampreys initiated acceleration from rest with the formation of a highamplitude body bend at approximately one-quarter body length posterior to the head. This deep body bend produced two highpressure regions from which the majority of thrust for acceleration was derived. In contrast, steady swimming was characterized by shallower body bends and negative-pressure-derived thrust, which was strongest near the tail. The distinct mechanisms used for steady swimming and acceleration from rest may reflect the differing demands of the two behaviors. High-pressure-based mechanisms, such as the one used for acceleration from rest, could also be important for low-speed maneuvering during which drag-based turning mechanisms are less effective. The design of swimming robots may benefit from the incorporation of such insights from unsteady swimming.

Tuna robotics: hydrodynamics of rapid linear accelerations

“…In another study, incorporating 51 anguilliform and carangiform swimming fish species, it was shown that undulating fishes show increased tail beat amplitudes during linear accelerations compared to steady swimming [5]. This finding was corroborated by detailed analyses of bluegill sunfish showing increased head and tail amplitudes [7] and lamprey showing higher amplitudes along the entire body [6] during linear acceleration. Wise et al [7] also found indications of larger force production rather than the reorientation of axial forces during acceleration compared to steady swimming patterns, which differs slightly from the conclusions of [5] who documented vortex wake reorientation during acceleration.…”

“…Coordinated body and tail movements linearly accelerate the fish forward rapidly. Nearly all previous analyses of linear fish acceleration consider accelerations while transitioning between steady swimming speeds and accelerations from rest have rarely been studied [6]. Fish typically alter their tail beat frequency and amplitude to accelerate between different steady swimming speeds, generating a vortex wake with geometry and orientation that differ from those of steady swimming [1,5,7].…”

“…Fish typically alter their tail beat frequency and amplitude to accelerate between different steady swimming speeds, generating a vortex wake with geometry and orientation that differ from those of steady swimming [1,5,7]. However, the dynamics of fish accelerating from rest are far less understood and have only been studied in lamprey [6]. Using the Tunabot Flex platform, we are able to generate linear accelerations of variable magnitude and analyse the resulting wake flow patterns of fish-like propulsion.…”

“…Fish also accelerate when shifting between different steady swimming speeds while maintaining their average heading, a behaviour termed as linear acceleration. The most common type of linear acceleration occurs when fish start swimming [6], as starting with zero velocity necessarily means that acceleration is required to reach a steady swimming speed.…”

Swimming kinematics and performance of spinal transected lampreys with different levels of axon regeneration

“…To compare the kinematics and swimming of the lamprey, each animal was video recorded during steady state swimming according to Gemmell et al (2016) and (Du Clos et al, 2019)Du Clos et al (2020). Accordingly, lampreys were placed at one end of long (1.5 meter) tanks where swimming was initiated by touching the individual gently at the tail.…”