Investigation of the Regimes of Seiche Oscillations Sevastopol Bay

Based on the ADCIRC hydrodynamic finite element model, various regimes of seiche oscillations in a narrow extended deep-water bay are studied using the Sevastopol Bay as an example. Long waves penetrating into the bay through its entrance are considered as perturbations. Calculations are made for perturbations with periods of 2.5; 2.9; 6.2 min, belonging to the eigenmodes of the bay with different spatial structure: transverse; longitudinal-transverse, longitudinal, respectively. The impact of these perturbations leads to the generation of not only resonant 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 the 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 danger to the coastal zone of an elongated deep-water bay is represented by the so-called extreme modes having a transverse structure. A mode with a structure close to transverse was generated, but its maximum amplitude turned out to be 2.5 times less than that of the longitudinal-transverse and longitudinal seiches. The greatest amplification of the incident waves was noted for the longitudinal-transverse mode with a period of 2.9 min.