Back of the class: Capturing vortices from those ahead helps fish swim more efficiently in schools
Back of the class: Capturing vortices from those ahead helps fish swim more efficiently in schools lead image
Swimming collectively in a school confers several advantages to fish, such as protection from predators and easier access to food. Schooling has also been theorized to confer hydrodynamic advantages to individual fish, but the specific mechanisms remain incompletely understood. Investigating these dynamics could lead to better understanding of fish social structures as well as better designed underwater drone swarms.
Pan and Dong employed a numerical simulation to characterize how the beating of one fish’s tail affects the hydrodynamic performance of those behind it. Using supercomputing to tackle computational fluid dynamics algorithms, the duo modeled tail-beat differences between fish in a two-dimensional high-density school.
The results help explain how fish swimming at the back of a school can save energy by changing their swimming kinematics to be in harmony with the flow from other fish.
“It surprised us when we found that we can build a relationship between the performance of the school and the wake by changing the phase,” said author Yu Pan. “To our knowledge, it is the first work summarizing the wake pattern of multiple moving objects and building the relationship between the performance and vortex wake.”
The pair found that trailing fish can improve their swimming efficiency by 58 percent, and overall thrust by 108 percent, if they adjust the tail-beating phase of their swimming movement while traveling in a diamond-shaped school. This allows the trailing fish to capture the vortices generated by preceding fish and takes advantage of a suction type effect that stems from fish on the sides of the school.
The group hopes to examine other parameters, such as frequency and locomotion mode, in the future.
Source: “Effects of phase difference on hydrodynamic interactions and wake patterns in high-density fish schools,” by Yu Pan and Haibo Dong, Physics of Fluids (2022). The article can be accessed at https://doi.org/10.1063/5.0113826 .
