Abstract
Flow visualization experiments and numerical calculations were conducted to investigate the flow characteristics at orifice downstream, with contraction ratio of 0.6, related to pipe wall thinning phenomena in power plant piping systems, especially for flow accelerated corrosion (FAC). Turbulent kinetic energy was found out to be a presumable factor to affect on FAC, since its profile trend nearly matched with that of pipe wall thinning data at actual plant piping. Reattachment points of flow separation, created at orifice downstream, will be, at the utmost, 2.5 times of diameter (2.5D) with plant piping system condition, although they gradually shift towards downstream with increase of Reynolds number. From this result, for pipe wall inspection region at orifice downstream, 3.0D would be conservative enough, which is the regulated value in the current pipe wall thinning management standard for power plants.
