Investigation of the supression of turbulent vortex formation and the frictional drag reduction effect on ship hull due to hydrogel painting

船体水凝胶涂料在海水中形成水合层，具有多种功能。在本研究中，我们根据与湍流涡旋结构形成的关系，揭示了水凝胶涂层表面的减摩效果。在实验中，我们制作了一个内筒表面涂漆的旋转环形圆柱装置，并测量了作用在内筒上的扭矩。实验数据表明，随着涂层厚度的减小，水凝胶涂层的减阻效果增强。此外，还对具有局部滑移速度和流体穿透壁面的槽道流动进行了数值模拟，发现湍流旋涡结构的尺度和边界层厚度对减阻效果有很大影响。

Hydrogel painting for ship hull makes hydration layer in sea water and has various functionalities. In this study, we revealed the effect of frictional drag reduction with hydrogel painting surface based on the relation with turbulent vortical structure formation. In experiment, we made a rotating annular cylinders apparatus with painted surface on the inner cylinder, and measured the torque acted on the inner cylinder. From experimental data, it was shown that the drag reduction effect of hydrogel painting became strong when the thickness of painting layer became small. In addition, we carried out the numerical simulations of channel flow with local slip velocity and penetration of fluid into wall, and found that the drag reduction effect depended on the scale of turbulent vortex structure and the thickness of boundary layer.