To provide a flow resistance reduction method which improves a flow resistance reduction effect between a solid and a liquid mainly on the subject of a laminar flow region which has a relatively low flow velocity and of which flow resistance can hardly be reduced until now and provide a flow resistance reduction surface.
It is considered that the reason why flow resistance increases when a relatively rough uneven part 5 is formed on the interface of a solid 1 as shown in Fig. (C) is that part of lumps of a liquid 2 intrudes into recessed parts and adheres to a solid 1. On the other hand, it is considered that the reason why the flow resistance increases when the interface of the solid 1 is a mirror surface 3 as shown in Fig. (A) is that the surface energy of the solid increases because of the mirror surface and the lumps of the liquid 2 spread over and adhere to the solid 1 as if a thin film were stuck, so that wettability is increased. In order to resolve those problems, a fine uneven part 4 is formed on the interface of the solid 1 as shown in Fig. (B), so that the surface energy is reduced and a superior water-repellent surface to which the liquid 2 hardly adheres is formed, and thereby, the flow resistance is reduced.