Harmonic generation in Palu Bay, Indonesia

Harbor resonance, which occurs when an incoming wave's period matches the natural period of the harbor, can be severely damaging to the surrounding areas. Using shallow water equations, we estimated the (natural) resonant period of a bay, particularly one with a hyperbolic-cosine squared bottom shape. There are two scenarios discussed: a constant-width harbor and a non-constant-width harbor. The resonant period is determined analytically by employing the separation of variables method. Further, using the staggered finite volume method, we constructed a computational scheme and performed numerous simulations to recreate and analyze wave resonance. Moreover, we investigated the parameter dependence of resonant wave features. In both constant-width and non-constant-width harbors, only the depth and length of the harbor affect the resonant period and wave amplitude. Meanwhile, changes in the harbor's maximum width do not have any impact on either feature, despite the fact that changes in width do. The application of the model to the real bathymetry of Palu Bay in Central Sulawesi, Indonesia, proves that resonance occurrences could aggravate the potential danger of tsunami waves whose period coincides with the bay's resonant period. We believe that by applying the model proposed in this study, we will be able to predict the potential occurrence of resonance in specific bays and therefore design an appropriate coastal defense system.