Making ships slippery like seaweed can reduce drag and save energy, a new simulation suggests.
If ships are to become more environmentally friendly, they need to cut through water more efficiently and reduce their fuel requirements. One option is to rethink the materials used to build ship鈥檚 hulls, given that about 60 to 70 per cent of the total resistance to a vessel鈥檚 movement can come from friction between the water and the hull.
Hyung Jin Sung at the Korea Advanced Institute of Science and Technology, South Korea, and his colleagues think seaweed could inspire a solution. It has a slippery surface when submerged in water because it contains cells that release mucus.
Advertisement
Practical simulations suggest surfaces mottled with microcavities that release lubricant, mimicking the mucus in seaweed, can reduce drag in water. 鈥淚 wanted to simulate the phenomena empirically,鈥� says Sung.
The simulations used material samples dotted with microcavities, each partially covered by a lip that extends from the cavity edge, creating a bottleneck. The microcavities were filled with a lubricant called Krytox GPL 103.
鈥淭he lubricant is not harmful to fish or other animals, so we can apply this idea to ships鈥� surfaces in real life,鈥� says Sung.
The larger the cavity鈥檚 bottleneck opening, the more the lubricant was released from the cavity and smeared along the material surface 鈥� which would make the surface less resistant as it moved through water. Increasing the thickness of the lip had a small effect too: it led to a thicker layer of lubricant smearing over the material.
鈥淚f the present design parameters are adopted, the drag reduction rate will increase significantly,鈥� says Sung. 鈥淲e observed almost 18 per cent reduction in drag.鈥�
The study focuses on a fundamental problem, says Zhiming Yuan of the University of Strathclyde, UK, but he cautions that the lab results may need tweaking to work in practice. 鈥淔rom the engineering point of view, it might not be realistic to use this lubricant-infused slip surface to reduce the drag of a ship, considering its large wet surface.鈥�
Physics of Fluids
