Experimental Investigations of the Turbulent Boundary Layer for Biomimetic Protrusive Surfaces Inspired by Pufferfish Skin: Effects of Spinal Density and Diameter

作者：Dongliang Fan, Xiaoming Feng, Guizhong Tian, Yaosheng Zhang · 发表于：Langmuir · 年份：2021 · DOI：10.1021/acs.langmuir.1c01745 · 被引用次数：23 · 研究领域：Fluid Dynamics and Turbulent Flows、Particle Dynamics in Fluid Flows、Aeolian processes and effects

Pufferfish is known for its extension of tiny spine-covered skin that appears to increase skin drag and may act as turbulisors, reducing overall drag while serving a protective function. Therefore, the present study addresses a neglected aspect of how spines affect the turbulent boundary layer (TBL) for drag reduction in the pufferfish skin. Particle image velocimetry (PIV) was utilized to investigate the TBL structure on the biomimetic spine-covered protrusion samples inspired by the back skin of the pufferfish. The comparison samples of two sparse “ k -type” arrangements (hexagon and staggered) for three types of rough element sizes with roughness heights k + = 5.5–6.5 (nearly hydraulically smooth) and smooth case in bulk Reynolds numbers ( Re b = 37,129 and 44,554) were tested. The results of turbulence statistics of these samples indicate that both the sample (type hexagon) for large rough density (λ = 0.0215) with small roughness elements and the sample (type staggered) for small rough density (λ = 0.0148) with large roughness elements have a drag reduction rate of 5–11%. These two kinds of bionic surfaces have a similar morphology to that seen in the distribution of pufferfish spines and probably serve a similar hydrodynamic function. Vortex identification shows that the spines in the front section for large density with small rough elements stabilize the TBL and generate many small-scale vortices and the dense spines with large rough elements at the back section have t...