Testing for Erosion-Corrosion Under Disturbed Flow Conditions Using a Rotating Cylinder with a Stepped Surface

Erosion-corrosion is most severe in the vicinity of flow disturbances. In the past, erosion-corrosion under disturbed flow conditions has been studied experimentally in flow loops and numerically by performing flow simulations. In this study, a new, compact experimental setup was tested, intended for the study of erosion-corrosion under disturbed flow conditions, involving a rotating cylinder geometry with a sudden step. A thorough characterization of this new setup was initiated, involving wall mass-transfer measurements complemented with direct numerical simulation of the turbulent flow around it. A large variation of the wall mass-transfer rates behind the step was measured, similar in character to the one obtained in flow through a sudden pipe expansion. Flow simulations have confirmed that this flow geometry will create a qualitatively similar mean flow pattern as observed in a sudden pipe expansion flow involving flow separation and reattachment. Simulations also have shown that there is a large-scale unsteadiness in the turbulent flow structure downstream the step, a fact that might have a significant impact on erosion-corrosion. Further work on characterization of the new electrode involving erosion-corrosion measurements is in progress.