Physics of Fish Swimming

Physics of Fish Swimming
Fish Swimming Physique - Strategic swimmer. The red nose tetra fish (Hemigrammus bleheri) uses a snappy and coastal swimming pattern. Roberto/stock.adobe.com

Some fish species swim in a forward thrust pattern, where their bodies alternately undulate and remain stationary as they approach the shore. Although intermittent swimming is more difficult to simulate than continuous swimming, the researchers have now run in-depth simulations to understand the advantages of this mode for fish and its potential applications for fish-like robots. In the video of the simulations, a virtual fish is seen fidgeting and accelerating before calmly advancing to almost a stop. The researchers discovered that the reduction in drag caused by a more aerodynamic body position could compensate for the lack of propulsion during the docking phase. However, this tactic works best when parameters such as the forward length are optimized.

Although researchers have widely acknowledged that based on tests and analytical models, spaced swimming may be more effective, comprehensive simulation has been difficult, in part because of the unsteady character of the flow. A two-step protocol was established by Gen Li and colleagues from the Japan Sea-Earth Science and Technology Agency (JAMSTEC). In the first stage, they simulate a series of long spikes and shore runs with varying amplitudes and frequencies for fish surges. They then use the bits of this simulation information they copy and paste to reproduce random burst and shore swimming patterns.

Using this method, which they have done before, the researchers were able to determine the ideal values ​​of variables such as the frequency and amplitude of the waves without using a significant amount of processing power. They can compare the effectiveness of intermittent and continuous swimming in great detail. A long simulation used in the database is shown in the video. This simulation starts with 15 tailspin cycles and then continues for a while.

Many parameters can be monitored over time by Li and colleagues, including drag, input power, and thrust, which show rapid changes previously unnoticed. Researchers have found that sprints and fast swimming can use less energy than continuous swimming, but this tactic can become too ineffective if, for example, the length of each spurt and fast cycle is too great. Fish-like robot designers will need to carefully optimize their swimming parameters to reduce their energy consumption, because real fish undoubtedly have millions of years to develop this swimming pattern.

Source: physics.aps.org/articles/v16/8

 

 

 

Günceleme: 17/01/2023 12:43

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