Body dynamics and hydrodynamics of swimming fish larvae: a computational study

The fluid forces that govern propulsion determine the speed and energetic cost of swimming. These hydrodynamics are scale dependent and it is unclear what forces matter to the tremendous diversity of aquatic animals that are between a millimeter and a centimeter in length. Animals at this scale generally operate within the regime of intermediate Reynolds numbers, where both viscous and inertial fluid forces have the potential to play a role in propulsion. The present study aimed to resolve which forces create thrust and drag in the paddling of the water boatman (Corixidae), an animal that spans much of the intermediate regime (10

Section: The Energetics Of Swimmingcontrasting

confidence: 63%

The hydrodynamics of swimming at intermediate Reynolds numbers in the water boatman (Corixidae).

Ngo¹,

McHenry²

2014

“…high circulation and 'jets'). Both vortices and accelerated velocities are hydrodynamic features associated with and directly related to zones of negative pressure in the fluid (Batchelor, 1973;Li et al, 2012), and, for the control lampreys, the gradual development of these hydrodynamic features gradually developed large negative pressure zones in the troughs of the traveling waves ( Fig. 9F; Gemmell et al, 2015).…”

Section: Pressure and Thrust Resulting From Different Hydrodynamic Comentioning

confidence: 99%

“…However, we have much less of an understanding of the mechanisms through which bending kinematics interact with adjacent fluids to enhance thrust. One effect of bending is that it enhances negative pressure regions of the fluid adjacent to the inflexion point of the bending appendage (Colin et al, 2012;Li et al, 2012;Nakata and Liu, 2012). This serves to accelerate more fluid than fluid around rigid propulsors, which enhances the momentum of the surrounding fluid.…”

Section: Introductionmentioning

confidence: 99%

How the bending kinematics of swimming lampreys build negative pressure fields for suction thrust

Gemmell

Fogerson

Costello

et al. 2016

Swimming animals commonly bend their bodies to generate thrust. For undulating animals such as eels and lampreys, their bodies bend in the form of waves that travel from head to tail. These kinematics accelerate the flow of adjacent fluids, which alters the pressure field in a manner that generates thrust. We used a comparative approach to evaluate the cause-and-effect relationships in this process by quantifying the hydrodynamic effects of body kinematics at the body-fluid interface of the lamprey, Petromyzon marinus, during steady-state swimming. We compared the kinematics and hydrodynamics of healthy control lampreys to lampreys whose spinal cord had been transected midbody, resulting in passive kinematics along the posterior half of their body. Using high-speed particle image velocimetry (PIV) and a method for quantifying pressure fields, we detail how the active bending kinematics of the control lampreys were crucial for setting up strong negative pressure fields (relative to ambient fields) that generated highthrust regions at the bends as they traveled all along the body. The passive kinematics of the transected lamprey were only able to generate significant thrust at the tail, relying on positive pressure fields. These different pressure and thrust scenarios are due to differences in how active versus passive body waves generated and controlled vorticity. This demonstrates why it is more effective for undulating lampreys to pull, rather than push, themselves through the fluid.

“…Jiang and Kiørboe, 2011;Li et al, 2012;Liu et al, 1996;Van Wassenbergh et al, 2015a). CFD analyses can consider the fluid forces generated by complex geometries with fully resolved volumetric flow fields.…”

Section: Introductionmentioning

confidence: 99%

The comparative hydrodynamics of rapid rotation by predatory appendages

McHenry

Anderson

Wassenbergh

et al. 2016

Countless aquatic animals rotate appendages through the water, yet fluid forces are typically modeled with translational motion. To elucidate the hydrodynamics of rotation, we analyzed the raptorial appendages of mantis shrimp (Stomatopoda) using a combination of flume experiments, mathematical modeling and phylogenetic comparative analyses. We found that computationally efficient blade-element models offered an accurate first-order approximation of drag, when compared with a more elaborate computational fluid-dynamic model. Taking advantage of this efficiency, we compared the hydrodynamics of the raptorial appendage in different species, including a newly measured spearing species, Coronis scolopendra. The ultrafast appendages of a smasher species (Odontodactylus scyllarus) were an order of magnitude smaller, yet experienced values of drag-induced torque similar to those of a spearing species (Lysiosquillina maculata). The dactyl, a stabbing segment that can be opened at the distal end of the appendage, generated substantial additional drag in the smasher, but not in the spearer, which uses the segment to capture evasive prey. Phylogenetic comparative analyses revealed that larger mantis shrimp species strike more slowly, regardless of whether they smash or spear their prey. In summary, drag was minimally affected by shape, whereas size, speed and dactyl orientation dominated and differentiated the hydrodynamic forces across species and sizes. This study demonstrates the utility of simple mathematical modeling for comparative analyses and illustrates the multi-faceted consequences of drag during the evolutionary diversification of rotating appendages.