Session: 4.1.1 - Interactions in Bio-Inspired Propulsion

Paper Number: 158116

158116 - Hydrodynamic Analysis of Fish Schools in the Vertical Plane 

Abstract: 

The hydrodynamic interactions of fish schooling are a popular field amongst biologists and engineers alike. Formations within the horizontal plane have dominated the literature, however, recent experiments have highlighted the need to study vertical formations. Fish are not constrained to swim within the same horizontal plane and have been shown to adopt different vertical heights relative to each other. Long-duration experiments quantified that a vertical ladder, where fish remain in the same vertical plane with a vertical and streamwise displacement between each other, was the most frequently adopted for schooling giant danios. 

Computational models are placed in the stagger formation to conduct high fidelity fluids simulations using an in-house developed flow solver. In this solver, the 3-D Navier-Stokes equations are discretized using a cell-centered, collocated arrangement of the primitive variables and are solved using a finite difference-based Cartesian grid immersed boundary method. The numerical procedures maintain 2nd order accuracy in both space and time. This direct numerical solver allows us to resolve in detail the near and far wake structures produced by the giant danios which is important for analyzing the performance and wake patterns resulting from the interactions of the fish. For this study the Reynolds number is fixed at 4000 which is within the range of biologically relevant Reynolds numbers for slow giant danio schooling. The parametric study in this paper revolves around the vertical ladder formation and understanding the effects of the vertical ladder angle, at a fixed vertical distance between fish, on performance. 

Most prior studies of fish schooling have only considered formations that occur in the same horizontal plane; thus, this paper will provide new knowledge on the body-body interactions occurring between fish in the vertical plane. The results will discuss the role of the ladder angle in leveraging the body-body interactions for drag decrease and thrust increase. These findings will inform beneficial formations that could be adopted by bio-robotic schooling swimmers.  

Presenting Author: Alec Menzer University of Virginia

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