The evaluation method of full-scale ship performance using low-friction ship bottom paint

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H02368
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 24020:Marine engineering-related
• Research Institution: Kobe University
• Principal Investigator: Katsui Tokihiro 神戸大学, 海洋底探査センター, 教授 (80343416)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 低摩擦型塗料 / 粗度抵抗 / 粗度関数 / LDV / 船舶性能

Outline of Final Research Achievements

The present study investigates the roughness function of the painted surface under assumption that painted surfaces are considered to be wavy surfaces. The roughness functions for three kinds of painted surfaces which have different ratio of wave length to wave height were estimated based on a newly developed method using rotating cylinder measurement. The velocity distribution of turbulent boundary layer of the painted rotating cylinder surfaces were measured using laser doppler velocimeter and the rotating torque of cylinders were also measured to estimate the frictional velocity of the painted surfaces. The estimated roughness functions for painted surfaces based on velocity profile and frictional velocity indicate that it is getting lower for the painted surface with lower ratio of wave length to wave height. The shape of roughness functions for painted surfaces is convex at higher roughness Reynolds number and this attitude is quite different from the sand-grain rough surface.

Free Research Field

船舶海洋工学

Academic Significance and Societal Importance of the Research Achievements

現在、船舶の脱炭素化に向けた動きが活発化しており、その一連の動きの中で既存船に対しても二酸化炭素排出量に規制がかかるようになっている。このため、船舶の燃費性能向上がこれまで以上に必要とされており、その一つの手法として低摩擦型塗料の開発が進められている。低摩擦型の塗料は有望な手法と目される一方、その実船燃費低減量を定量的に評価する手法がないことが難点であった。本研究では塗膜粗面を波状粗面と捉え、その波長波高比によって粗度関数がどのように変化するかを実船粗度レイノルズ数域で初めて調査した。これにより、低摩擦型塗料の性能評価法について新たな指針を示すことができたと考える。