미역의 점액질 표면이 가진 항력 저감 효과에 대한 실험적 연구

Abstract

Sea mustard has a slippery surface in which mucilage works as a lubricant. In this study, the drag reduction effect of the mucilage surface of sea mustard was investigated as a liquid-infused surface (LIS). The morphological structures of sea mustard were observed by using a scanning electronic microscopy (SEM) and the mucilage-secreting glands were observed with a transmission electron microscopy (TEM). As a result, the sea mustard skin surface has wrinkled structures and pores of the mucilage glands have re-entrant structure. Velocity profiles of the boundary layer flow over sea mustard samples were measured by using a particle image velocimetry (PIV) and particle tracking velocimetry (PTV) techniques to evaluate the corresponding slip length. Pressure drop in the channel covered with sea mustards was measured to estimate the slip effect. In addition, skin friction of the mucilage surface was measured to evaluate the corresponding drag reduction rate. The sea mustard surfaces tested in this study were found to have a relatively large slip length of 101μm and the pressure drop was about 25.6 % reduced due to the morphological peculiar characteristics and slippery mucilage surface. With these drag reduction effects, the mucilage surface exhibits skin friction reduction up to 35.2%. The present results would be helpful for understanding the drag reduction mechanism of sea mustard.