Natural Frequencies of Seiche in a Closed Trapezoidal Basin with Internal Barriers

A seiche is the free oscillation of water in a closed or semi-closed basin; it is frequently observed in harbors, bays and lakes. Enclosed basins can experience oscillations due to a variety of causes. The enclosed basin has certain natural frequencies of seiche, depending on the geometry of the water boundaries and the bathymetry of water depths. Therefore, the variation in water surface at a point becomes irregular as caused by the combination of several natural frequencies, which may be considered as the superposition of sinusoidal frequency components of different amplitude. This paper is mainly concerned with the motion of an incompressible irrotational fluid in a closed trapezoidal basin with internal impervious barriers. An analytical solution is presented for predicting the characteristic of generated waves in these types of basins. The equations of free water surface oscillations and its boundary conditions are reduced to a system of linear equations, which is solved by applying the small amplitude water wave theory. The flow potential, wave amplitude, flow patterns, and the natural period of waves generated in the basin with impervious internal barriers are found based on the basin geometry. It is shown that the natural period of basin is strongly dependent to the location of barriers and the size of barrier’s opening.