Filtration by reticulate sea fans under diverse flow conditions

Reticulate sea fans are intricate colonies of tiny polyps crucial to the marine ecosystem for their role in suspension feeding, waste removal, and gas exchange. Previous research demonstrated that recirculating flow patterns behind polyps enhance particle capture rates. However, the characterization of flow around and through physical models of a reticulate seafan, and its impact on filtration efficiency under various flow conditions, remains unclear. To address this, 2D-2C PIV measurements were conducted on six reticulate sea fan models, including rigid and flexible ones with Effective stiffness ranging from 0.00062 to 0.115. Data were collected at continuous flow speeds with pore-based Reynolds numbers (Re) from 50-300 and seafan inclination angles of 90° - 60°. The findings indicate that less inclined sea fans and higher Re led to increased flowrates downstream, suggesting stiffer sea fan models offer better filtration. Using the Planktos Agent-Based Modeling Framework, capture rates in small- and large-scale flows were calculated. On average, the capture rate in small-scale flows through the pores was higher than that of large-scale flow over the colony under the same conditions. Experiments into the effect of oscillation as it relates to filter performance of the sea fan will be presented.