Modeling Microturbulences at Surface Imperfections as Related to Flow-Induced Localized Corrosion

In a first approach, a mathematical model was developed for the calculation of critical parameters for flow-induced localized corrosion (FILC) in small cavities (length 0.5 to 3 mm, depth 0.5 to 3 mm) in tubings at flow velocities on the cavity surface of 0.5 to 1.5 m/s. For Reynolds numbers below 2000, the model calculations yielded the highest flow intensities (velocities, pressure variations, and shear stresses) at sites in the cavities where FILC occurs in corrosive systems. Based on special assumptions, the maximum shear stress at the leading edge of small cavities can be calculated from general flow data outside the cavity yielding enhancement factors for the wall shear stress depending on the average flow rate and the geometry of the cavity. The results are rationalized by comparison with experimental data.