Local Skin Friction Reduction Using Microbubbles

Abstract

Skin friction reduction measurements using microbubbles were carried out in a two dimensional channel flow. Microbubbles are expected to reduce the skin friction which occupies a large part of the total ship drag. An adaptation to a real ship is difficult because of the very large amount of microbubbles. In order to adapt to a real ship we must search for more effective bubble conditions which are bubble size, bubble position and bubble scale effects. We measured the local skin friction reduction in a small high-speed water tunnel, systematically changing the main velocity and measurement position from the bubble injection point. At the same time, we measured the diameter of bubbles from the photographs.