Flow-Dependant erosion-corrosion often occurs under distributed flow conditions at geometrical irregularities such as fittings, valves and weld beads. Flow separation and reattachment produces high turbulence intensity and particle-wall interactions that can lead to high erosion –corrosion rates.
This paper presents the prediction of 2-D turbulent, single and two phase liquid/particle flow with recirculation, after a sudden constriction and expansion. The model is based on two-phase flow version of a standard k-e model of turbulence and a stochastic simulation of particle-fluid turbulence interactions. It is capable of successfully predicting local values of time-averaged fluid velocities and turbulence intensities, as well as predicting particle dispersion, and particle-wall interaction.
The numerical predictions of the flow structure are used to explain the results of an experimental erosion-corrosion study of water /sand mixture flowing in a pipe with a sudden constriction and expansion. Its is shown that in case of distributed single-phase flow, it is appropriate to correlate local near-wall parameters of flow with the metal lo rates. The simulations have shown that local near-wall intensity of turbulence is the important factor affecting mass transfer-controlled corrosion in distributed flow, rather than wall shear stress. In case of single-phase flow, comparisons revealed a significant effect of local turbulence intensity on corrosion rate of the base metal. In case of two case phase flow, maximum metal loss coincided with local maximums of particle-wall mean impact frequency.