Influence of frequency characteristics of turbulence velocity fluctuations in complex flow field downstream of an orifice upon pipe wall thinning

Flow-accelerated corrosion (FAC) is one of the most severe events which cause pipe wall thinning in power plants. In this study, the frequency characteristic of turbulent velocity fluctuations was focused on as an influential factor of FAC because the size of scalloped appearance due to FAC depended largely on the wall thinning rate. PIV measurement was used for the flow downstream of an orifice and FFT analysis was applied to the velocity fluctuations in the axial and wall directions. As a result, it was found that there was not any evidence to combine the frequency characteristics and wall thinning properties. However, this result could be because of the distance at which velocity fluctuations were observed. (author)