Movement of the nodal line of damping coastal seiches (original) (raw)

2018, Гідрологія, гідрохімія і гідроекологія (Hydrology, hydrochemistry and hydroecology)

Purpose of manuscript is to study the possible changes in effective length of open-ended water basin, conditioned by damping seiches, and to determine effects of this phenomenon. Method. Study was done by analytical and graphical methods of monitoring dynamic of wave, which described by its period and circulations of concomitant seiche current. Results. The calculations, performed on the example of the harbor of port of Ciudadela, showed an increase in the effective length due to the shift of the nodal line of damping seiche waves. With the spread of seiche oscillations, outside the harbor originate areas of current of alternating directions with length of half-period of oscillations; at the same time, outflow seiche current over time, which is equal to the half-period of oscillations, changes an inflow one. Due to damping of seiche oscillations, their period increases; the amplitude, velocity and length of the traversed by accompanying current path decreases. As a result of shift of node line everything, that falls into the seiche current, is moves from shore. Originality. On the basis of received data, it is put forward the hypothesis concerning the movement of the nodal line of damping coastal seiches. Shift of the nodal line may be caused at least by two independent reasons: growth of wave period and damping of the velocity of reversible movements of concomitant current. Practical significance. The obtained results can be used to construction of maps of seiche flows. This will allow, if not completely prevent the negative effects of damping coastal seiches, then at least reduce the negative effects. Work will find application in the design of hydraulic structures and optimize their operation; developing recommendations for swimmers and floating craft.