Flow-assisted corrosion (FAC), an aspect of erosion/corrosion (E/C), is a mechanism of piping degradation that causes a loss of material from the inside of the piping and then thinning of the wall. FAC damage is believed to be accelerated by a single- or two-phase mixture flowing within the piping. A physical model is presented that attempts to predict the distributions of sites of FAC wear within the fitting; this model includes the E/C and the three-dimensional single- or two-phase-flow models. Based on the calculated results, the impact of centrifugal and gravitational forces on liquid droplet behavior can be reasonably simulated. Appropriate indicators derived from the E/C model are used to predict the FAC locations. Compared with the plant measured results, the proposed model can precisely predict the distribution of wear sites. The FAC pattern dominated by the upstream fittings can also be determined. The satisfactory agreement reveals that the indicators provided by the current models can be used to reasonably predict the FAC locations and explain the complicated phenomenon of FAC wear occurring within the fittings.