Fish mouths as engineering structures for vortical cross-step filtration

Area of Science:

• Biomimetics
• Fluid Dynamics
• Filter Feeding

Background:

• Suspension-feeding fish retain prey without filter clogging, unlike industrial crossflow filtration systems.
• Fish can retain particles smaller than their gill-raker filter pore size, a phenomenon not fully understood.

Purpose of the Study:

• To investigate the fluid dynamic mechanisms behind efficient particle retention in fish oral filters.
• To explore novel engineering structures that prevent clogging and facilitate particle transport in filtration systems.

Main Methods:

• Development of a vortical cross-step filtration model inspired by fish gill structures.
• Analysis of fluid dynamics using backward-facing steps and d-type ribs on a porous cone surface.

Main Results:

• The novel filtration model prevents clogging and efficiently transports concentrated particles via a hydrodynamic tongue.
• Vortices generated along d-type ribs in crossflow drive mass transfer, explaining particle capture.

Conclusions:

• The discovered filtration mechanism is applicable to various filter-feeding organisms, including duck beak lamellae and whale baleen.
• This biomimetic model provides insights into fish gill ventilation and can inspire advanced industrial filtration technologies.