The proposal for this CAREER award was motivated by the need for a comprehensive research strategy to address the problem of bridge pier and abutment scour, the leading cause of bridge failures that devastated the nation's transportation infrastructure during recent severe floods. Due to the enormous complexity of this problem, for such a strategy to be effective it must integrate field and laboratory experiments with three-dimensional computational modeling. It is the objective of this work to develop an advanced computational fluid dynamics model by combining the latest advancements in numerical and turbulence modeling of complex, three-dimensional flows with a novel approach for modeling the sediment transport processes that lead to scour. The numerical methodology will rely on the unsteady, three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations closed with advanced turbulence models, which resolve the near-wall flow, account for turbulence anisotropy, and can simulate bed roughness. Such level of turbulence modeling is essential for reproducing the structure and intensity of the foundation-induced, large-scale vortices that drive the scouring process. A coupled Lagrangian/Eulerian approach will be developed for modeling the transport of sediment particles and simulating the temporal development of scour. Efficient numerical methods, featuring multigrid acceleration and preconditioning strategies, will be used to solve the time-dependent governing equations. Data from existing laboratory experiments will be used to calibrate and validate the numerical model. This research will lead to an advanced computational framework that can be used to enhance our understanding of the complex mechanisms that induce scour in the field at a level of detail not previously accessible by field and laboratory experiments alone. The numerical model, employed in conjunction with experimental studies, will facilitate the evaluation of bridge designs for scour susceptibility and the development of scour countermeasures that are based on in-depth understanding of the flow physics. Therefore, this work could potentially have a significant impact on the current state-of-the-art, which relies almost exclusively on empirical correlations derived from small-scale laboratory measurements. Furthermore, the numerical model will help guide future improved experiments by clarifying issues such as the effect of scaling the results of small-scale experiments to full-scale conditions, and the time development of scour toward equilibrium. The educational contributions of this CAREER plan will include, among others, the following: i) a new curriculum for Civil and Environmental engineers in the area of computational fluid dynamics and hydraulics; ii) projects for directly involving undergraduates in research; and iii) a graduate-level textbook on the numerical simulation of incompressible turbulent flows.
