Method of using closed cell surfaces with enhanced drag-reduction properties

摘要

A method of controlling the flow resistance of a fluid disposed on a surface of a substrate. The method comprises contacting a fluid with a plurality of cells on a substrate and adjusting amounts of a surfactant and a medium in the fluid to thereby form a foam layer contacting the walls of the cells. Each of the cells has at least one dimension that is less than about 1 millimeter and is configured to hold the medium therein. Each of the cells has walls that laterally enclose an area of a surface of the substrate and has a top opening. Bubbles of the foam layer have fluid walls that include a surfactant, are filled with the medium, and remain substantially stationary on the top openings of the cells for a period on average of at least about 1 minute.