About Computational Modeling of Structures Submerged in Flows in Sub-Grid Scale

In the computational modeling of water environments there are cases where slender vertical structures, like bridge piers, are part of the modeling domain. In this work, four strategies for modeling the presence of bridge piers were studied: Mesh Refinement (MR), Nodal Island (NI), Additional Stress Term (AST) and Increasing Bottom Roughness (IBR). For each method, advantages and disadvantages were discussed. AST was the most favorable of the techniques studied due to the fact that it drastically decreases the time of computation, as well as providing the possibility to choose the drag coefficient according to the pier geometry and hydrodynamic condition. Comparing the results of longitudinal centerline velocity profiles, it has been observed that the AST method provides similar results to the RM method from a distance of 100 m downstream of the pier. For this reason, the research concludes that the AST method is appropriate to evaluate the flow distant from the structures, outside the near wake. This work presents a sensibility study of the pier drag coefficient to make the reader aware of the influence of this parameter.