A Numerical Study of a 2D Multi-Component Corrosion Model in a Water Distribution System

The main purpose of this study is to present a fully transient multi-component water quality model through a numerical simulation of flow in a pipeline considering both hydraulic and water-chemistry issues. In other words, the objective is to numerically model the concentration of chemicals in the water distribution systems during the different conditions of flow. The chemicals are released in the system due to the reactions, which take place either in bulk flow or at the pipe-wall. The later is studied herein. This preliminary study explores on the effects of important parameters such as solution pH and initial concentration of dissolved oxygen on the chemical processes such as corrosion. In this light, considering the dissolved oxygen as main oxidant, the process is chemically modeled as simple anodic-cathodic reduction-oxidation reactions (redox reactions). The iron metal oxidized, creating ferrous ion (Fe2+) at anode. On the other hand, the reduction reaction produces hydroxide ion (OH–) at chatode. Due to concentration gradient, the ions migrate within the system in order to maintain the solution electrically neutral. Then, the ferrous ion reacts with hydroxide ion producing iron hydroxide, which deposits on the pipe-wall as corroded material. In this study, one- and two-dimensional simulation models are proposed, by which the concentration of each chemical is modeled by the advection-diffusion-reaction equation, which is then coupled with continuity and momentum equations for flow. Modeling the turbulence fluctuations by the five region turbulence model, a combination of finite difference and characteristic methods are used to numerically integrate the governing equations for chemical constituents and flow. Results for a case study are compared and show good agreement.