‘Bubble Coat’ Reduces Drag On Underwater Objects

Using a coat of compressed air, researchers in South Korea have managed to significantly reduce drag forces on a moving body in water.

AsianScientist (Dec. 18, 2018) – A team of scientists in South Korea has developed a method to reduce the drag force of a moving body in a still fluid. They reported their results in the Journal of Fluid Mechanics.

When a body moves in air, the frictional drag is lower than that of the same body moving in water. Therefore, the body that moves in water can reduce drag significantly when it is completely enveloped in a gaseous cavity.

In this study, scientists led by Professor Cho Yeunwoo at the Korea Advanced Institute of Science and Technology used compressed air to create so-called supercavitation, which is a phenomenon created by encasing an object in a single large gaseous cavity. They then measured the drag force on the object as it moved through fluid.

The team found that the drag force for a moving body enveloped in air is about 25 percent of the drag force for a moving body without the air coating. The team noted that their findings can be applied to the development of high-speed underwater vehicles and the creation of air lubrication for ship hulls.

The article can be found at: Chung & Cho (2018) Ventilated Supercavitation Around a Moving Body in a Still Fluid: Observation and Drag Measurement.


Source: Korea Advanced Institute of Science and Technology ; Photo: Shutterstock.
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