Numerical Investigation of Flow Hydrodynamics Around the Gap Region of Finite Coastal Vegetation Patches

Abstract

This study investigates the role of coastal vegetation patches in reducing tsunami damage by addressing the "danger zones" that form between vegetation gaps. These gaps, where the velocity and turbulence of tsunami flows are higher, increase the risk of destruction. The research explores three gap configurations, including straight, inclined, and staggered, by using numerical simulations to evaluate the internal flow properties within these gaps. The Reynolds-Averaged Navier-Stokes (RANS) equations were used in setup with a seven-equation Reynolds stress model (RSM) for turbulence closure. The analysis, conducted using ANSYS Workbench, focuses on the flow dynamics around short submergent and tall emergent mangrove trees. Initially, the model was validated by comparing results with experimental data. The results showed that the inclined gap between vegetation patches (named as Case 2) reduced near-bed velocity by 18.6% and turbulence kinetic energy (TKE) by 40%, while the staggered gap (Case 3) provided the most effective mitigation, reducing velocity by 22.7% and TKE by 41.8%. These findings suggest that adjusting the gap configuration can optimize the effectiveness of coastal vegetation in mitigating tsunami damage. The study holds practical significance for policymakers and coastal engineers, as it provides insight into optimizing vegetation-based coastal defenses to reduce disaster risks, emphasizing the potential of staggered vegetation gaps with a mix of tree types as a promising strategy for enhancing coastal protection and promoting sustainable solutions for disaster resilience.