Abstract
In order to clarify the relationship between the drag reduction and the fine grooves on the wall surface, we measured pressure losses of tap water in a pipe with new water-repellent wall. The pipe walls are different in terms of width, length and intensity of development of the grooves on its surfaces each other. The surfaces of those water-repellent walls are excellent in durability comparing to those of highly water-repellent walls, whose endurance is a serious problem of the practical use of this wall. The experimental result shows that the drag reduction does not occur for the test pipes. It can be considered that the size of the grooves is larger than that of the drag reducing highly water-repellent wall.
