CFD-DEM simulation of the hydrodynamic filtration performance in balaenid whale filter feeding

Abstract Solid-liquid separation is a key link in environmental chemical and process engineering, including water purification, pollution treatment, etc. Traditional industrial filters are often clogged and damaged because they cannot be cleaned or replaced in time. Filter-feeders, on the other hand, are rarely clogged. Therefore, it is of great significance to draw bionic inspiration from biological filtration to guide the design of traditional filters. In this study, a computational fluid dynamics (CFD) and discrete element method (DEM) coupled model is adopted to investigate the filtering mechanism in balaenid whale feeding. In this model, DEM is used for the particle and the Navier-Stokes equation is used for the fluid. The effects of particle space and shape, as well as particle-particle/wall interaction, are considered. Then, the model is validated by comparing some crucial information with the theoretical results of previous literature. Finally, the effects of four key parameters on the filter feeding characteristics are analyzed, including the fringe layer permeability, prey incident direction, size and shape. The results show that the large permeability, random incidence direction, large size and real irregular shape all lead to more particle collisions. Besides, the captured prey is prone to form an uneven, backward aggregation trend. The large permeability and size make the trend of posterior aggregation more obvious. However, there are no significant differences in the number of the captured prey at each location for different types of incident directions or prey shapes. But the variation of the captured prey distribution in the real shape case is not as smooth as in the simplified sphere case, which shows that the increase in collisions changes the trajectories of some particles to some extent. This study provides a new idea for bionic design in solid-liquid separation field.