Drag reduction mechanism of Paramisgurnus dabryanus loach with self-lubricating and flexible micro-morphology

Abstract

Underwater machinery withstands great resistance in the water, which can result in consumption of a large amount of power. inspired by the character that loach could move quickly in mud, the drag reduction mechanism of Paramisgurnus dabryanus loach is discussed in this paper. Subjected to the compression and scraping of water and sediments, a loach could not only secrete a lubricating mucus film, but also importantly, retain its mucus well from losing rapidly through its surface micro structure. In addition, it has been found that flexible deformations can maximize the drag reduction rate. this self-adaptation characteristic can keep the drag reduction rate always at high level in wider range of speeds. therefore, even though the part of surface of underwater machinery cannot secrete mucus, it should be designed by imitating the bionic micro-morphology to absorb and store fluid, and eventually form a self-lubrication film to reduce the resistance. In the present study, the Paramisgurnus dabryanus loach is taken as the bionic prototype to learn how to avoid or slow down the mucus loss through its body surface. This combination of the flexible and micro morphology method provides a potential reference for drag reduction of underwater machinery.

Preparation of a bionic lotus leaf microstructured surface and its drag reduction performance

“…It can be concluded that the drag force gradually increases with the increase of fluid velocity. According to eqn (4) , 26 the drag reduction rate of the bionic surface can be calculated. where η is drag reduction rate, F ts is the resistance of the smooth surface, F tb is the resistance of the bionic surface.…”

Dual‐composite drag‐reduction surface based on the multilayered structure and mechanical properties of tuna skin

“…This could be because vortexes are formed around the bionic fish scale so that the high‐speed flow fluid was far from the near‐wall region. Therefore, the sudden increase in the turbulence was greatly weakened, and the drag‐reduction effect was obtained (Bai, Zhang, Song, Boyce, & Ortiz, 2016; Wu et al, 2020). Figure 9c shows the velocity magnitude of the bionic dual‐composite surface, in which the outer layer covers the flexible epidermis layer of the tuna and the inner surface comprises hard scales.…”

Slime-Groove Drag Reduction Characteristics and Mechanism of Marine Biomimetic Surface

“…In addition to the drag reduction of loach surface structure, the flexible deformation mode of loach body also contributes to further increase the drag reduction rate. Loach, due to its self-adaptive characteristics, can always keep the drag reduction rate at a high level within a wide speed range [ 107 ], and the maximum drag reduction capacity can even reach 33.63% [ 108 ].…”

“… Microscopic morphology of loach body: (a) loach, (b) scale morphology, (c) different positions on the same scale, (d) groove structure, and (e) groove cross section [ 107 ]. …”

“…Yong et al [113] realized the bionic surface with the interaction of groove and mucus on the silicon surface by a femtosecond laser, as shown in Figure 25(a). A femtosecond [107]. Applied Bionics and Biomechanics laser (50 FS, 1 kHz, 800 nm) with a numerical aperture of 0.45 was focused on for progressive scanning.…”