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21.
The concept of equilibrium plan form and equilibrium profile has been widely used as an engineering tool in order to design beach nourishment projects. The scope of this paper is to further explore this “equilibrium beach” concept in crenulated bays, as a long-term tool for beach nourishment projects. The proposed methodology is based on González and Medina (2001) and combines the static equilibrium plan and profile for long-term analysis. This methodology includes a modified equilibrium plan form, which is able to define the orientation of the local wave front in the diffracting point, and also to locate the downcoast starting point of the static equilibrium beach from which the parabolic plan form of Hsu and Evans (1989) is valid. This methodology permits the application of any equilibrium profile formulation. An example of the application of this methodology and long-term formulations to the design of the Spanish nourishment project of Poniente Beach (Gijón) is presented. Ten years after its construction, the beach has still got a static equilibrium and remains pretty close to the predicted equilibrium beach in plan and profile. 相似文献
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This paper is devoted to the analysis of the hydrodynamic equilibrium of a headland or semi-elliptic shaped beach. It is shown that the state of equilibrium depends not only on the in- and outgoing sediment but also on the accommodation of the sediment within the embayment. The shape and relative depth of shoals, or settling zones, also directly affect the wave and current patterns inside the bay, within which the resultant breaker line almost stops wave-induced currents at some locations, whereas the magnitude of current increases at other locations. Several numerical tests are analytically conducted in a semi-elliptic beach with two symmetrical shoals of varying relative depth where circulatory current systems are detected and analyzed. Numerical modelling for wave climate and wave-induced current estimation is also presented in order to corroborate results and provide a tool for complicated and/or physical domains. The results lead to a redefinition of the concept of equilibrium for headland-bay beaches taking into account not only the net sediment transport but also the role of the formation and disappearance of settling zones, as well as sediment interchanges between the beach and shoals. 相似文献
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A criterion for initiation of sediment movement on a horizontal bed under non-breaking waves is established. Bagnold's sediment transport model is used. The dissipation rate of energy has been related to the length and velocity scales of the large-scale turbulence. The proposed equation is compared with the available laboratory results for fine and coarse material 0.1 mm < D ? 45 mm over a wide range of particle sizes, density ratios and liquid viscosities and a reasonable agreement between the two is obtained. An incipient motion hypothesis based on the development of vorticity is proposed. 相似文献
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A first approach to the behaviour, flow characteristics and stability, of mound breakwaters under oblique wave attack is undertaken by assuming that oblique incidence only affects the slope angle. For run-up and run-down this approach shows a reasonable degree of agreement with experimental data for small incidence angles (say up to 45°) becoming unreliable for large incidence angles. 相似文献
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This work aims to demonstrate an advancement towards the integrated modelling of surf zone hydrodynamics by means of a VOF-type numerical model (COBRAS-UC) based on the Reynolds-Averaged Navier–Stokes equations. In this paper, the numerical model is adapted and validated for the study of nearshore processes on a mildly-sloping beach. The model prediction of wave energy transformation and higher order statistics (skewness and asymmetry) are in good agreement with detailed laboratory observations from a barred beach [Boers, M. (1996). “Simulation of a surf zone with a barred beach; Report 1: Wave heights and wave breaking”. Tech. Rep.96-5, Comm. on Hydrol. and Geol. Eng., Dept. of Civil Engineering, Delft University of Technology]. Moreover, the numerical model allows us to study the low-frequency motions inside the surf zone. It is found that in order to achieve a satisfactory simulation of both short- and long-wave transformation, the numerical model must achieve: (i) the simultaneous second-order wave generation and absorption, (ii) the energy transfer between triad of components, (iii) the short- and long-wave energy dissipation inside the surf zone, and (iv) the wave reflection at the shoreline. Comparisons between numerical and experimental results demonstrate the model capability to satisfactorily simulate all the aforementioned processes. 相似文献
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G. Iglesias J. Rabual M.A. Losada H. Pachn A. Castro R. Carballo 《Ocean Engineering》2008,35(11-12):1113-1120
The prediction of rubble-mound breakwater damage under wave action has usually relied on costly and time-consuming physical model tests. In this work, artificial neural networks (ANNs) are applied to estimate the outcome of a physical model throughout an experimental campaign comprising of 127 stability tests. In order to choose the network best suited to the problem data, five different activation function options and 38 network architectures are compared. The good agreement found between the physical model and the neural network shows that an ANN may well serve as a virtual laboratory, reducing the number of physical model tests necessary for a project. 相似文献
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Temporal and spatial variability in the Guadalquivir estuary: a challenge for real-time telemetry 总被引：1，自引：1，他引：0
Gabriel Navarro Francisco Javier Gutiérrez Manuel Díez-Minguito Miguel Angel Losada Javier Ruiz 《Ocean Dynamics》2011,61(6):753-765
Meteorological, hydrological, and hydrodynamic data for 3 years (2008–2010) have been used to document and explain the temporal
and spatial variability of the physical–biogeochemical interactions in the Guadalquivir River Estuary. A real-time, remote
monitoring network has been deployed along the course of the river between its mouth and Seville to study a broad range of
temporal scales (semidiurnal, diurnal, fortnightly, and seasonal). This network consists of eight hydrological monitoring
stations capable of measuring temperature, conductivity, dissolved oxygen, turbidity, and chlorophyll fluorescence at four
depths. In addition, six stations have been deployed to study hydrodynamics, obtaining 20-cell water column current profiles,
and there is a meteorological station at the river mouth providing data for understanding atmospheric interactions. Completing
this data-gathering network, there are several moorings (tide gauges, current/wave sensors, and a thermistor chain) deployed
in the estuary and river mouth. Various sources of physical forcing, such as wind, tide-associated currents, and river discharge,
are responsible for the particular temporal and spatial patterns of turbidity and salinity found in the estuary. These variables
force the distribution of biogeochemical variables, such as dissolved oxygen and chlorophyll fluorescence. In particular,
episodes of elevated turbidity (when suspended particle matter concentration >3,000 mg/l) have been detected by the network,
together with episodes of declining values of salinity and dissolved oxygen. All these patterns are related to river discharge
and tidal dynamics (spring/neap and high/low tide). 相似文献
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Andreas M. Waser Rob Dekker Johannes IJ. Witte Niamh McSweeney Bruno J. Ens Jaap van der Meer 《Estuaries and Coasts》2018,41(2):507-520
Many subtidal predators undertake regular tidal migrations into intertidal areas in order to access abundant prey. One of the most productive habitats in soft bottom intertidal systems is formed by beds of epibenthic bivalves such as blue mussels (Mytilus edulis) and Pacific oysters (Crassostrea gigas). In the Dutch Wadden Sea, these bivalves might face substantial predation pressure by the shore crab (Carcinus maenas), which increased considerably in numbers during the last 20 years. However, the quantification of this species on bivalve beds is challenging, since most methods common for quantifying animal abundance in marine habitats cannot be used. This study investigated the potential of two methods to quantify the abundance of C. maenas on 14 epibenthic bivalve beds across the Dutch Wadden Sea. The use of the number of crabs migrating from subtidal towards intertidal areas as a proxy of abundance on bivalve beds yielded unreliable results. In contrast, crabs caught with traps on the beds were correlated with the abundance assessed on the surrounding bare flats by beam trawl and therefore provided usable results. The estimates, however, were only reliable for crabs exceeding 35 mm in carapace width (CW). The application of these estimates indicated that crab abundances on bivalve beds were influenced by the biogenic structure. Beds dominated by oysters attracted many large crabs (> 50-mm CW), whereas abundances of medium-sized crabs (35–50-mm CW) showed no relationship to the oyster occurrence. The combination of traps and trawls is capable of quantifying crab abundance on bivalve beds, which offers the possibility to study biotic processes such as predator-prey interactions in these complex structures in more detail. 相似文献