Study of Seiche Oscillation Regimes in Sevastopol Bay

Abstract

Based on the ADCIRC hydrodynamic finite element model, various seiche oscillation regimes in a narrow extended deep-water bay are investigated with a case study of Sevastopol Bay. Long waves penetrating into the bay through its inlet are considered perturbations. Calculations are made for perturbations with periods of 2.5, 2.9, and 6.2 min, belonging to the eigenmodes of the bay with different spatial structure: transverse; longitudinal-transverse, and longitudinal, respectively. The impact of these perturbations leads to generation of not only resonance modes with periods close to the perturbation period, but also an intense Helmholtz mode that occurs after the perturbation ceases and leads to a significant increase in the amplitude of level oscillations. In studies of seiches caused by perturbations in the form of monochromatic long waves coming from the open sea, it was not possible to confirm that the greatest potential hazard to the coastal zone of an elongated deep-water bay is represented by the so-called extreme modes with a transverse structure. A mode with a structure close to transverse was generated, but its maximum amplitude was 2.5 times less than that of longitudinal-transverse and longitudinal seiches. The largest amplification of the incident waves was noted for the longitudinal-transverse mode with a period of 2.9 min.