Numerical modeling and assessment of flood mitigation structures in idealized coastal communities: OpenFOAM simulations for hydrodynamics and pressures on the buildings

This research employs a Computational Fluid Dynamics (CFD) model utilizing the olaFlow solver to investigate the efficacy of flooding mitigation structures, such as a seawall (SW) and submerged breakwater (SB), in safeguarding an idealized coastal community against tsunami-like waves-induced overland flows. The numerical model results were validated through a series of large-scale laboratory experiment. A range of surges and wave conditions, encompassing non-breaking, impulsive breaking, and broken waves interacting with the beachfront berm, were examined. The outcomes reveal excellent consistency between simulated and measured wave hydrodynamic and loading parameters, including free surface displacements, velocities, forces, and pressures. Beyond the scope of the laboratory experiment, the numerical simulations shed light on the intricacies of overland flow patterns around macro-roughness elements. These simulations highlight that the overland flow passes the macro-roughness elements, generating the jet-type channelized flow with stronger velocity and lower water elevation in the middle of the landward area. The study also elucidates the impact of tsunami-like waves on the first row of buildings, with maximum runup heights ranging from two to four times the incident wave heights. Moreover, the combined installation of seawall and submerged breakwater (SWSB) mitigated baseline runup heights by 10% and 45% for breaking and broken wave conditions, respectively. Conversely, a 20% runup amplification was observed in the non-breaking wave condition compared to the baseline configuration. Additionally, the research explores the vertical distribution of wave-induced pressures on the seaward-most building row, strongly influenced by water level variations. Maximum pressures exhibited a linear decrease from low to high pressure transducer elevations in low-water-level conditions, contrasting with a significant increase in high-water-level conditions. These findings provide valuable insights for coastal community planning and resilience strategies, emphasizing the importance of tailored mitigation measures in coastal regions vulnerable to tsunami-like wave events.