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Theoretical analysis of the balaenid whale’s hydrodynamic filtering system
Dean Hu, Yawei Zhu, Gang Yang

Last modified: 2020-07-28


As continuous ram filter feeders, balaenid whales move forward to make the mixture of prey and seawater flow straight into the mouth in the feeding process. Then, through a complex flow field inside the mouth, prey is carried to the oropharynx and seawater is filtered out through the posterior openings. Balaenid whales separate prey from water without clogging their oral filters, whereas clogging often occurs in industrial filtration. Therefore, it is necessary to take inspiration from whale filtering and rethink traditional filtering systems. In this work, the flow profile and particle trajectories are analyzed to study the balaenid whale’s hydrodynamic filtering system. First, the average velocity of the anteroposterior canal within the mouth along the tongue (APT channel) and the lip (APL channel), as well as the lateral flow channel formed by the intra-baleen gap (IB channel), are obtained by our previous theoretical modeling analysis [1]. Then, appropriate velocity profiles in the anteroposterior and lateral directions are adopted to approximate the flow field inside the oral cavity of balaenid whales. Next, the particles trajectories are obtained by solving a set of second-order ordinary differential equations, which are established by analyzing the force equilibrium of particles in the above theoretical flow field. Finally, by combining the U-type foraging process, different particle input conditions are defined to analyze the feeding filter system of balaenid whales. The study suggests that the active backward flow of prey due to fluid dynamics, as well as the intermittent clearing of aggregates near the esophagus by balaenid whales, contribute to the non-blocking mechanism. The results of quantitative analysis can provide a guidance for the design of high-efficiency filtering systems.


Balaenid whale, Particle trajectory, Theoretical model, Filtering system

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