# Hydrodynamic Mechanisms Underlying the Burying Behavior of Benthic Fishes: Numerical Simulation and Orthogonal Experimental Study

## TL;DR

This study explores how benthic fish bury themselves in sediment using pectoral fin movements, offering insights for designing self-burying underwater robots.

## Contribution

A novel numerical model and orthogonal experiments reveal the hydrodynamic mechanisms and key factors influencing fish self-burial behavior.

## Key findings

- Rapid pectoral fin flapping fluidizes sediments, enabling benthic fish to bury themselves.
- Body size significantly impacts burial performance due to stronger fluid disturbances in larger fish.
- Kinematic parameters have a greater effect on self-burial than environmental factors like particle size.

## Abstract

To avoid predators, benthic fish will stir up the sediment on the seabed by flapping their pectoral fins, thus burying themselves. This self-burial concealment strategy can offer bionic enlightenment for the benthic residence method of Unmanned Underwater Vehicles (UUVs). In this paper, based on the observation results of the self-burial behavior of benthic fish, a two-dimensional fluid-particle numerical model was developed to simulate the processes of sediment transport induced by pectoral fin flapping. In addition, an orthogonal experimental design was employed to analyze the effects of body length, flapping amplitude, flapping number, flapping frequency, and particle size on burial ratio, input power, and burial efficiency. The results reveal that rapid pectoral fin flapping enables benthic fish to fluidize sediments and achieve self-burial. Among the influencing factors, body size has the most significant impact on coverage ratio and input power, as larger fish generate stronger tip vortices and fluid disturbances, making local flow velocities more likely to exceed the critical starting velocity. In contrast, particle size has the weakest effect on burial performance, while kinematic parameters exert a far greater impact on self-burial than environmental parameters. The research results can offer references for the biomimetic design of self-burying UUVs.