Entrance/exit losses and cross-sectional stability of double inlet systems
| Autor: | R. L. Brouwer, J. van de Kreeke, Henk M. Schuttelaars |
|---|---|
| Rok vydání: | 2012 |
| Předmět: |
geography
geography.geographical_feature_category media_common.quotation_subject Phase (waves) Mode (statistics) Perturbation (astronomy) Mechanics Aquatic Science Oceanography Inlet Inertia Stability (probability) Physics::Geophysics Physics::Fluid Dynamics Amplitude Geotechnical engineering Geology Stability Model media_common |
| Zdroj: | Estuarine, Coastal and Shelf Science. 107:69-80 |
| ISSN: | 0272-7714 |
| Popis: | This study investigates the effect of entrance/exit losses on the cross-sectional stability of double inlet systems. The inlet is in equilibrium when the sand transport into the inlet equals the sand transport out of the inlet. The velocity amplitude corresponding with the equilibrium cross-sectional area is referred to as the equilibrium velocity (∼1 m s−1). This equilibrium is stable when after a perturbation the cross-sections of both inlets return to their original equilibrium value. The amplitudes of the inlet velocities are obtained using a lumped-parameter model in which the basin water level fluctuates uniformly (pumping mode) and where the inlets are schematized to prismatic channels. The system is forced by a semi-diurnal tide, where amplitude and phase may differ between the two inlets. Previous studies concluded that for double inlet systems no stable equilibriums can be found. However, in these studies entrance/exit losses were neglected. In the present study entrance/exit losses are included in the dynamic equation of the inlets. Using an analytical model it is shown that entrance/exit losses and a difference in the two ocean tidal amplitudes are a prerequisite for the existence of stable equilibriums. Furthermore, the effects of the addition of bottom friction and inertia to the dynamic equation are investigated using a mathematical continuation method. The results show that, provided entrance/exit losses are considerably larger than bottom friction and inertia, stable equilibriums are possible. These conclusions are supported by observations in the Ria Formosa, southern Portugal. Care should be taken in using the stability model described in this paper as a predictive tool due to simplifications in the model and the uncertainty in determining certain parameter values including inlet length, entrance/exit loss coefficient, bottom friction factor and equilibrium velocity. To alleviate these shortcomings suggestions are made for future research. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect