title: Shark-skin surfaces for fluid-drag reduction in turbulent flow: a review.
abstract: The skin of fast-swimming sharks exhibits riblet structures aligned in the direction of flow that are known to reduce skin friction drag in the turbulent-flow regime. Structures have been fabricated for study and application that replicate and improve upon the natural shape of the shark-skin riblets, providing a maximum drag reduction of nearly 10 per cent. Mechanisms of fluid drag in turbulent flow and riblet-drag reduction theories from experiment and simulation are discussed. A review of riblet-performance studies is given, and optimal riblet geometries are defined. A survey of studies experimenting with riblet-topped shark-scale replicas is also given. A method for selecting optimal riblet dimensions based on fluid-flow characteristics is detailed, and current manufacturing techniques are outlined. Due to the presence of small amounts of mucus on the skin of a shark, it is expected that the localized application of hydrophobic materials will alter the flow field around the riblets in some way beneficial to the goals of increased drag reduction.
authors.affiliation: Nanoprobe Laboratory for Bio- and Nanotechnology and Biomimetics (NLBB), Ohio State University, 201 West 19th Avenue, Columbus, OH 43210-1142, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Dean
authors.forename: Bharat
authors.initials: B
authors.lastname: Bhushan
mesh_terms: D000818:Animals; D040761:Biomimetic Materials; D055592:Biophysical Phenomena; D017276:Friction; D057446:Hydrodynamics; D057927:Hydrophobic and Hydrophilic Interactions; D008954:Models, Biological; D009093:Mucus / Q000502:physiology; D011108:Polymers; D012212:Rheology; D012754:Sharks / Q000033:anatomy & histology* / Q000502:physiology*; D012879:Skin Physiological Phenomena; D013499:Surface Properties
chemical_list: D011108:Polymers