title: Fish mouths as engineering structures for vortical cross-step filtration.
abstract: Suspension-feeding fishes such as goldfish and whale sharks retain prey without clogging their oral filters, whereas clogging is a major expense in industrial crossflow filtration of beer, dairy foods and biotechnology products. Fishes' abilities to retain particles that are smaller than the pore size of the gill-raker filter, including extraction of particles despite large holes in the filter, also remain unexplained. Here we show that unexplored combinations of engineering structures (backward-facing steps forming d-type ribs on the porous surface of a cone) cause fluid dynamic phenomena distinct from current biological and industrial filter operations. This vortical cross-step filtration model prevents clogging and explains the transport of tiny concentrated particles to the oesophagus using a hydrodynamic tongue. Mass transfer caused by vortices along d-type ribs in crossflow is applicable to filter-feeding duck beak lamellae and whale baleen plates, as well as the fluid mechanics of ventilation at fish gill filaments.
authors.affiliation: Department of Biology, College of William and Mary, PO Box 8795, Williamsburg, Virginia 23187, USA.
authors.forename: S Laurie
authors.initials: SL
authors.lastname: Sanderson
authors.affiliation: Department of Biology, College of William and Mary, PO Box 8795, Williamsburg, Virginia 23187, USA.
authors.forename: Erin
authors.initials: E
authors.lastname: Roberts
authors.affiliation: Department of Biology, College of William and Mary, PO Box 8795, Williamsburg, Virginia 23187, USA.
authors.forename: Jillian
authors.initials: J
authors.lastname: Lineburg
authors.affiliation: Department of Biology, College of William and Mary, PO Box 8795, Williamsburg, Virginia 23187, USA.
authors.forename: Hannah
authors.initials: H
authors.lastname: Brooks
mesh_terms: D000818:Animals; D057005:Bioengineering; D001934:Branchial Region / Q000502:physiology; D005247:Feeding Behavior; D005374:Filtration; D006054:Goldfish / Q000033:anatomy & histology*; D057446:Hydrodynamics; D008954:Models, Biological; D009055:Mouth / Q000033:anatomy & histology*; D011312:Pressure; D012272:Ribs; D012754:Sharks / Q000033:anatomy & histology*