Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Research on Drag Reduction Performance of Bionic V-groove Based on Finite Element Method
Shukang Tong , He Zhang , Bowen Jin , Zhuyun Shao
Shanghai Maritime University
Shanghai , China

experiments; (Xu, Zhang et al. 2021) analyzed the influence of different
rib shapes on the drag reduction effect by numerical simulation. (Hu andSong 2007) found that the groove structure perpendicular to the flow also
has drag reduction effect, and proposed the ' rolling bearing ' model inthe groove. (Jiao 2017) observed the fish scales of Ctenopharyngodon
idellus and found that there were crescent grooves on the surface
perpendicular to the flow direction. He found that this structure wasreduced by 28.5% by modeling analysis.(Wen 2020) studied the surface
groove of P. Dabryanus and carried out the fluid-solid coupling
numerical simulation of the flexible groove, but his model ignored thatthe span length of the groove was much larger than its size.
In addition, because of the different properties of fluid medium( seawater, freshwater, oil, etc. ) in reality, the Reynolds number of theinterface surface is different, and the scale of the groove is also different.
For example, (Toms 1949) found that adding high molecular weight
additives in fluid can greatly reduce resistance ( Toms effect ). (Chungand Graebel 1969) studied the structure of turbulence for pipe flow of
dilute polyethylene oxide and polypropylene solution by laser
anemometer, concluded that polymer additives can delay the transition
from laminar flow to turbulent flow, so as to achieve drag reduction.
Since different fluids have different requirements for wall structure,
water is used as the fluid for preliminary study in this paper.
Through previous studies, it is found that the groove size of vertical flow
is basically 1-50 μm. However, there is no exact research on which scale
the groove has the best drag reduction effect, and there is also a lack of
research on the influence of different Height-Width Ratios of the grooveon the drag reduction effect. In this paper, the groove size and different
Height-Width Ratios of grooves are studied, and the drag reduction
characteristics of flexible groove surface are studied in combination withthe material properties of fish scales.
This study has great significance for reducing the resistance of thenavigator, and can improve the performance and endurance of thenavigation.

ABSTRACTWith the further study of drag reduction, people pay more and more
attention to bionic drag reduction. By observing some aquatic organisms,
scientists found that the groove structure perpendicular to the flow
direction has a certain drag reduction effect. Some researchers have alsodone a series of studies by simulating the skins of these aquaticorganisms, but the scale at which these microtextures have the best dragreduction performance and the effect of the Height-Width Ratio ofmicrogrooves on drag reduction have not been accurately studied. At thesame time, the current research is based on rigid structure, which ignores
the influence of micro texture materials on drag reduction effect. In orderto solve the above problems, this paper uses finite element software tostudy the drag reduction effect of grooves with different scales, different
Height-Width Ratios and flexible grooves. It is found that the best dragreduction effect can reach 15 % when the scale of micro groove is
5μm;When the Height-Width Ratio of groove is greater than 1.2, the dragreduction effect is the best, which can reach about 15 %; The dragreduction effect of flexible groove in low speed flow is obvious, which
can reach 12.38 % at 1m / s flow rate.

KEY WORDS: Bionic drag reduction; flexible surface; surface texture;computational fluid dynamics.

INTRODUCTION
With the concept of green ships, energy conservation and emissions
reduction getting more and more attention, people focus on reducing
energy consumption of ships or underwater vehicles. The main resistanceof ships and underwater vehicles is the friction resistance between thesurface and water. Reducing the resistance can not only reduce energy
consumption to improve the voyage, but also improve the speed of thevehicle to a certain extent. As early as the 1980s, (Reif and Dinkelacker1982) found that shark skin had a special ridge structure along thedirection of water flow;(Walsh 1983, Walsh and Lindemann 1984)
simplified the rib structure to a V-shaped rib structure, and found that thedrag reduction rate of the rib structure could reach 8 % through

SELECTION OF FLUID MODEL
It is generally believed that in a pipe with diameter d, the flow is laminar
if the Reynolds number Re<2300. If Re>2300 fluid disturbance will3435