Modelagem numérico-computacional multiníveis de processos de corrosão em sistemas fluidodinâmicos

Abstract

Flow accelerated corrosion is a phenomenon observed in industrial operations that can lead to the failure of fluid dynamic systems and generate significant financial losses. In industrial turbulent corrosive systems, determining the regions of greater magnitude of velocity, turbulent kinetic energy and shear stresses contribute to identifying the most susceptible places to corrosion. In the present study, the URANS methodology was applied to simulate the phenomenon of corrosion and the fluid dynamics of these systems. Thus, the following equations were solved: mass balance, linear momentum and a scalar balance equation for corrosion modelling. It should be noted that for the turbulence closure modelling, the following were considered: LRN k-ε AKN and k-ω SST. In the present study, multilevel methods were analyzed to obtain a methodology that would provide greater computational efficiency for the study of this multi-physics phenomenon. The multilevel method implemented in the MFSim software has the characteristic of solving the equations that represent the phenomena in different meshes considering the characteristic lengths of each phenomenon. The application of the method is justified due to the high number of Sc of turbulent flows with corrosion. In the first analysis of the present study, a manufactured solution problem was considered to verify the MFSim code. After verifying the code, the multilevel method was evaluated, and a reduction in computational costs of approximately 90% and slight deviations from the passive scalar were observed. In the second part of the study, the multilevel method was analyzed in flows: sudden expansion, impingement jet and around a sphere. For the sudden expansion, it was observed that the mass transfer coefficients presented a minor deviation considering a mesh 16 times thicker for the fluid dynamics. Furthermore, the computational cost reduction was approximately 90% with the multilevel method, and it was possible to obtain mass transfer coefficient results with slight deviations considering the Immersed Boundary method. In the impingement jet flow analysis, moderate deviations of the mass transfer coefficient were obtained in the stagnation region. Furthermore, it was possible to get a good representation of the multi-physics phenomenon considering a mesh four times thicker for fluid dynamics with a computational cost reduction of 90%. For the simulations of the flow over the sphere, a mesh four times thicker was defined for the fluid dynamics, which resulted in slight deviations of Sh considering correlations usually applied in the literature. Regarding the multilevel method, it was possible to simulate this flow with a simulation time of approximately 30% smaller. The results obtained in MFSim point to a significant reduction in computational cost with the application of the multilevel method, making it possible to analyze industrial problems with lower computational costs.