ABSTRACT
Drag reduction is a key problem in marine vehicles and fluid transportation industries. Reducing drag strategies and mechanisms need to be further investigated. To explore a bionic approach for reducing flow resistance, experimental and numerical simulation research was conducted to study the drag reduction characteristics of the Paramisgurnus dabryanus surface microstructure. In this study, the large-area flexible surface of the bionic loach scale was prepared by the template method of one-step demoulding. The water tunnel experiment results show that compared with the smooth surface, the drag reduction rate of the bionic surface ranges from 9.42% to 17.25%. And the numerical simulation results indicate that the pressure gradient and low-speed vortex effect created by the bionic loach scales can effectively reduce the friction drag. The results of experimental data and numerical simulation both prove that the bionic scales of Paramisgurnus dabryanus can achieve the underwater drag reduction function. This research provides a reference for drag reduction in marine industries and fluid delivery applications.
ABSTRACT
Reducing machinery surface friction resistance can improve the efficiency of energy utilization. The lotus leaf, as everyone knows, has a strong capacity for self-cleaning and hydrophobicity. In this paper, the bionic surface of the lotus leaf was prepared in large-area, and its drag reduction performance was studied by both numerical simulation and experimental analysis. Experimental results showed that the maximum drag reduction rate of the bionic surface was 6.29% which appeared at a velocity of 3 m s-1. The contact state between liquid and bionic surface changed from Cassie state to Wenzel state with the increase of water flow velocity. The surface free energies of the bionic surface and smooth surface were 1.09 mJ m-2 and 14.26 mJ m-2, respectively. In the droplet rolling experiment, the water droplet was a hemisphere when it rolled on the smooth surface, while it was an ellipsoid on the bionic surface. This study provides a theoretical basis for the structural design of bionic drag reduction surfaces, which are expected to be applied in underwater vehicles.
