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1.
The note extends and completes the analysis carried out by Briganti and Dodd [Briganti, R., Dodd, N., 2009. Shoreline motion in nonlinear shallow water coastal models. Coastal Eng. 56(5–6) (doi:101016/j.coastaleng.2008.10.008), 495–505.] on the performance of a state of the art Non-Linear Shallow Water Equations solver in common coastal engineering applications. The case of bore-generated overtopping of a truncated plane beach is considered and the performance of the model is assessed by comparing with the Peregrine and Williams [Peregrine, D., Williams, S.M., 2001. Swash overtopping a truncated beach. J. Fluid Mech. 440, 391–399.] analytical solution. In particular the influence of shoreline boundary conditions is investigated by considering the two best performing approaches discussed in Briganti and Dodd [Briganti, R., Dodd, N., 2009. Shoreline motion in nonlinear shallow water coastal models. Coastal Eng. 56(5–6) (doi:101016/j.coastaleng.2008.10.008), 495–505.]. Different distances of the edge of the beach from the bore collapse point are tested. For larger distances, the accuracy of the overtopping modelling decreases, as a consequence of the error in modelling the tip of the swash lens and, consequently, the run-up. A sensitivity analysis using the numerical resolution is carried out. This reveals that the approach in which cells shallower than a prescribed threshold are drained and wave propagation speeds for wet/dry Riemann problem are used at the interface between a wet and a dry cell (referred as Option 2ea in [Briganti, R., Dodd, N., 2009. Shoreline motion in nonlinear shallow water coastal models. Coastal Eng. 56(5–6) (doi:101016/j.coastaleng.2008.10.008), 495–505.]) performs consistently better than the other. 相似文献
2.
《Coastal Engineering》2006,53(5-6):543-544
The equations for shoreline motions are derived and the difference between the derived equations and those derived by Prasad and Svendsen [Prasad and Svendsen, 2003, Moving shoreline boundary condition for nearshore models Coastal Engineering, 49 :239-261.] is discussed. An alternative approach to treat the moving shoreline boundary condition is proposed based on the new derivation. 相似文献
3.
《Coastal Engineering》2002,45(2):89-110
Experimental and numerical analyses have been used to assess the validity and potentialities of the integral swash zone model by Brocchini and Peregrine (Proc. Coastal Dynamics '95, ASCE 1 (1996) 221) which is extended to include seabed friction effects previously neglected. Applications of the model to experimental data show it represents a simple and useful tool for modelling swash zone flows. The model allows for computation of integral swash zone properties and shoreline motion from local variables defined at the seaward limit of the swash. For most properties, correlation between local and integral properties is very good (correlation coefficient about 0.80).A suitable parametric form of frictional forces in the swash zone is defined on the basis of both experimental data and analytical investigation. Numerical tests showed that the proposed parameterization models well integral frictional forces within the swash zone. The parametric friction force improves capabilities of the integral swash zone model of representing real swash motions. This is particularly evident when considering the momentum equation: the correlation coefficient between the rate of change of the onshore momentum in the swash zone and its forcings increases from about 0.85 to about 0.95 due to the inclusion of the seabed friction. 相似文献
4.
Maximum run-up,breaking conditions and dynamical forces in the swash zone: a boundary value approach
On the basis of the approximate analytical solution for the nonlinear shallow water equations of Antuono and Brocchini [M. Antuono & M. Brocchini, The boundary value problem for the nonlinear shallow water equation, Stud. Appl. Maths, 119, 71–91 (2007).], we propose useful regression curves for the prediction of maximum run-up and dynamical forces in the swash zone on a frictionless, uniformly sloping beach. For the first time the dependence of the results on both the wave height and the wave steepness is analyzed in detail providing formulae able to describe a wide class of wave inputs. Finally, the regression formulae are validated through comparison with maximum run-up laws and breaking conditions already available in the literature, the present model results appearing to better account for nonlinear effects. 相似文献
5.
The numerical model COBRAS-UC [Losada, I.J., Lara, J.L., Guanche,R., Gonzalez-Ondina, J.M. (2008). Numerical analysis of wave overtopping of rubble mound breakwaters. Coastal Engineering, Vol 55 (1), 47–62.] is used to carry out a two-dimensional analysis of wave induced loads on coastal structures. The model calculates pressure, forces and moments for two different cross-sections corresponding to a low-mound and a conventional rubble-mound breakwater with a crown-wall under regular and irregular incident wave conditions. Predicted results are compared with experimental information provided in Losada et al. [Losada, I.J., Lara, J.L., Guanche,R., Gonzalez-Ondina, J.M. (2008). Numerical analysis of wave overtopping of rubble mound breakwaters. Coastal Engineering, Vol 55 (1), 47–62.] and Lara et al. [Lara, J.L., Losada, I.J., Guanche, R. (2008). “Wave interaction with low mound breakwaters using a RANS model”. Ocean engineering (35), pp 1388–1400; doi:10.1016/j.oceaneng.2008.05.006.] on a 1:20 scale. Good agreement is found, and the differences between both typologies are explained in detail. Additionally, numerical results are also compared with several semi-empirical formulae recommended for design at both the 1:20 model scale and two prototype cross-sections. Results suggest that COBRAS-UC is able to provide realistic stability information that can be used to complete the approach based on currently existing methods and tools. 相似文献
6.
《Coastal Engineering》2001,42(3):219-239
This paper describes an adaptive quadtree-based 2DH wave–current interaction model for evaluating nearly horizontal wave-induced currents in the surf-zone. The model accounts for wave breaking, shoaling, refraction, diffraction, wave–current interaction, set-up and set-down, mixing processes (turbulent diffusion), bottom frictional effects, and movement of the land–water interface at the shoreline. The wave period- and depth-averaged governing equations, which conserve mass, momentum, energy and wave action, are discretised explicitly by means of an Adams–Bashforth second-order finite difference technique on adaptive hierarchical staggered quadtree grids. Grid adaptation is achieved through seeding points distributed according to flow criteria (e.g. local current gradients). The model is verified for nearshore circulation at a sinusoidal beach and nearshore currents at a multi-cusped beach. Reasonable agreement is obtained with experimental data from da Silva Lima [da Silva Lima, S.S.L., 1981. Wave-induced Nearshore Currents. PhD Thesis, Department of Civil Engineering, University of Liverpool] and Borthwick et al. [Borthwick, A.G.L., Foote, Y.L.M., Ridehalgh, A., 1997. Nearshore measurements at a cusped beach in the UK Coastal Research Facility, Coastal Dynamics '97, Plymouth, 953–962]. The modelling approach presented herein should be useful in simulating nearshore processes in complicated natural coastal domains. Of particular value is the local grid enrichment capability, which permits refined modelling of important localised flow behaviour such as rip currents and surf-zone circulation systems. 相似文献
7.
Based on the classical Boussinesq model by Peregrine [Peregrine, D.H., 1967. Long waves on a beach. J. Fluid Mech. 27 (4), 815–827], two parameters are introduced to improve dispersion and linear shoaling characteristics. The higher order non-linear terms are added to the modified Boussinesq equations. The non-linearity of the Boussinesq model is analyzed. A parameter related to h/L0 is used to improve the quadratic transfer function in relatively deep water. Since the dispersion characteristic of the modified Boussinesq equations with two parameters is only equal to the second-order Padé expansion of the linear dispersion relation, further improvement is done by introducing a new velocity vector to replace the depth-averaged one in the modified Boussinesq equations. The dispersion characteristic of the further modified Boussinesq equations is accurate to the fourth-order Padé approximation of the linear dispersion relation. Compared to the modified Boussinesq equations, the accuracy of quadratic transfer functions is improved and the shoaling characteristic of the equations has higher accuracy from shallow water to deep water. 相似文献
8.
9.
This paper provides a stochastic method by which the random wave-induced scour depth at the trunk section of vertical-wall and rubble-mound breakwaters can be derived. Here the formulas for regular wave-induced scour depth provided by Xie [Xie, S.L., 1981. Scouring patterns in front of vertical breakwaters and their influence on the stability of the foundations of the breakwaters. Report. Department of Civil Engineering, Delft University of Technology, Delft, The Netherlands, September, 61 pp.] for vertical-wall breakwater and Sumer and Fredsøe [Sumer, B.M., Fredsøe, J., 2000. Experimental study of 2D scour and its protection at a rubble-mound breakwater. Coast. Eng. 40, 59–87] for rubble-mound breakwater are used. These formulas are combined with describing the waves as a stationary Gaussian narrow-band random process to derive the random wave-induced scour depth. Comparisons are made between the present method and the Sumer and Fredsøe [Sumer, B.M., Fredsøe, J., 2000. Experimental study of 2D scour and its protection at a rubble-mound breakwater. Coast. Eng. 40, 59–87.] random wave scour data for rubble-mound breakwater, as well as the Hughes and Fowler [Hughes, S.A., Fowler, J.A., 1991. Wave-induced scour predictions at vertical walls. ASCE Proc. Conf. Coastal Sediments vol. 91, 1886–1899] random wave scour data and formula for vertical-wall breakwater. A tentative approach to random wave-induced scour at a vertical impermeable submerged breakwater is also suggested. 相似文献
10.
《Coastal Engineering》2006,53(7):545-555
In the paper, the three-dimensional structure of the wave-induced momentum flux in irrotational waves propagating over a two-dimensional, irregular bathymetry is analyzed. The expansion method developed by de Vriend and Kitou [de Vriend, H.J., Kitou, N., 1990a. Incorporation of wave effects in a 3D hydrostatic mean current model. Delft Hydraulics Report H-1295. de Vriend, H.J., Kitou, N., 1990b. Incorporation of wave effects in a 3D hydrostatic mean current model. Proc. 22nd Int. Coast. Eng. Conf. ASCE, 1005–1018.] for unidirectional waves has been extended to derive expressions for velocity components in three-dimensional waves over sloping bottom. The vertical wave-induced momentum flux resulting from this solution has been shown to be vertically-varying (contrary to the 2D-V case) and to act as a counterbalance for the vertical variability of the other wave forcing terms in the momentum equations. Thus, the total wave forcing remains depth-invariant, but—contrary to the ‘traditional’ solution based on the radiation stress concept—it does not depend explicitly on the direction of wave propagation and is a simple function of gradients of wave energy and water depth only. One of the most important consequences of this fact is the lack of the longshore-current-generating force in the case of non-dissipative waves approaching a shore with a bottom profile uniform in the along-shore direction. To illustrate the meaning of the new solution, the wave forcing due to waves approaching a barred beach has been analysed in detail. Also, the present solution has been shown to give the same results as the one obtained by extending of the approach by Rivero and Arcilla [Rivero, F.J., Arcilla, A.S., 1995. On the vertical distribution of 〈ũw˜〉. Coast. Eng. 25, 137–152.] to three dimensions. 相似文献
11.
12.
The Nankai Trough located southeast of Shikoku Island, Japan, exhibits a zone of exceptionally high heat flow. In the central part of the Nankai Trough the fossil spreading centre of the Shikoku Basin is subducted beneath the southwest Japan arc. We have modelled the temperature and maturation history along the Muroto Transect reaching from the tip of the thrust zone out into nearly undeformed Quaternary and Tertiary sediments seawards of Nankai Trough. We used two balanced cross-sections defining the sections before and after overthrusting as input for 2D-basin modelling. We can show that rapid burial and overthrusting during the Quaternary in combination with a heat flow history following the cooling curve of a 15 Ma old oceanic plate is not sufficient to explain the measured maturity of organic material in the sediments. Several heat flow scenarios derived from theoretical concepts [Yamano, M., Kinoshita, M., Goto, S., Matsubayashi, O., 2003. Extremely high heat flow anomaly in the middle part of the Nankai Trough. Physics and Chemistry of the Earth, Parts A/B/C 28, 487–497.] and previous modelling approaches [e.g. Brown, K.M., Saffer, D.M., Bekins, B.A., 2001. Smectite diagenesis, pore water freshening, and fluid flow at the toe of the Nankai wedge. Earth and Planetary Science Letters 194, 97–109; Spinelli, G.A., Underwood, M.B., 2005. Modeling thermal history of subducting crust in Nankai Trough: constraints from in situ sediment temperature and diagenetic reaction progress. Geophysical Research Letters 32(L09301): doi:10.1029/2005GL022793; Steurer, J., Underwood, M.B., 2003. Clay mineralogy of mudstones from the Nankai Trough reference sites 1173 and 1177 and frontal accretionary prism site 1174. In: H. Mikada et al. (Eds.), pp. 1–37. Available from: <http://www-odp.tamu.edu/publications/190196SR/VOLUME/CHAPTERS/211.PDF>] were tested. The best match between observed maturity levels, temperature and heat flow measurements is reached for a heat flow history which initially assumes the cooling of a 15 Ma old oceanic lithosphere but is reheated to 170–180 mW/m2 during the phase of rapid burial in the Quaternary. This can be achieved either by assuming the onset of hydrothermal circulation in the cooling crust or by reheating caused by off-axis volcanism at about 6 Ma [Yamano, M., Kinoshita, M., Goto, S., Matsubayashi, O., 2003. Extremely high heat flow anomaly in the middle part of the Nankai Trough. Physics and Chemistry of the Earth, Parts A/B/C 28, 487–497.]. 相似文献
13.
《Coastal Engineering》2006,53(2-3):157-170
Influence of various factors affecting the longshore currents induced by obliquely incident random waves is examined through numerical calculation. Seven numerical models for random wave breaking process are found to yield large differences in the wave heights in the surf zone and longshore current velocities. The turbulent eddy viscosity formulation by Larson and Kraus [Larson, M. and Kraus, N.C. (1991): Numerical model of longshore current for bar and trough beaches, J. Waterway, Port, Coastal, and Ocean Eng., ASCE, 117 (4), pp. 326-347.] functions almost equal to that by Battjes [Battjes, J.A. (1975): Modeling of turbulence in the surf zone, Proc. Symp. Modeling Techniques, pp. 1050–1061.], but the formulation by Longuet-Higgins [Longuet-Higgins, M.S. (1970): Longshore current generated by obliquely incident sea waves, 1 and 2, J. Geophys. Res., 75 (33), pp. 6779–6801.] produces excessive diffusion of longshore currents into the offshore zone. The generation and decay process of the surface roller is indispensable in the longshore current analysis. The random wave transformation model called PEGBIS (Parabolic Equation with Gradational Breaker Index for Spectral waves) by Goda [Goda, Y. (2004): A 2-D random wave transformation model with gradational breaker index, Coastal Engineering Journal, JSCE and World Scientific, 46 (1), pp. 1–38.] produced good agreement with several laboratory and field data of longshore currents. 相似文献
14.
The influence of the seaward boundary condition on the internal swash hydrodynamics is investigated. New numerical solutions of the characteristics form of the nonlinear shallow-water equations are presented and applied to describe the swash hydrodynamics forced by breaking wave run-up on a plane beach. The solutions depend on the specification of characteristic variables on the seaward boundary of the swash zone, equivalent to prescribing the flow depth or the flow velocity. It is shown that the analytical solution of Shen and Meyer [Shen, M.C., Meyer, R.E., 1963. Climb of a bore on a beach. Part 3. Runup. J. Fluid Mech. 16, 113–125] is a special case of the many possible solutions that can describe the swash flow, but one that does not appear appropriate for practical application for real waves. The physical significance of the boundary conditions is shown by writing the volume and momentum fluxes in terms of the characteristic variables. Results are presented that illustrate the dependence of internal flow depth and velocity on the boundary condition. This implies that the internal swash hydrodynamics depend on the shape and wavelength of the incident bore, which differs from the hydrodynamic similarity inherent in the analytical solution. A solution appropriate for long bores is compared to laboratory data to illustrate the difference from the analytical solution. The results are important in terms of determining overwash flows, flow forces and sediment dynamics in the run-up zone. 相似文献
15.
Storm-induced readjustment of an embayed beach after modification by protection works 总被引：2，自引：1，他引：1
This paper examines storm-induced morphological and hydrodynamic changes after a submerged and a detached breakwater were constructed at La Barceloneta beach (Barcelona, NW Mediterranean) in 2006–2007. The shoreline configurations before and after beach nourishment and the construction of the protective structures were compared using a video dataset comprising 29 storm events spanning the pre- (2001 to 2005, n?=?17) and the post-breakwater situation (2006 to 2011, n?=?12), and hydrodynamic modelling based on the SMC coastal modelling system. As a result of the protection works, La Barceloneta was subdivided into two beaches separated by an artificial salient. The analysis of shoreline response to storms has been improved by using the shoreline hyperbolic tangent fit to represent the beach planform. Comparing the pre- and post-breakwater situations on the basis of these shoreline fits facilitated the identification of beach rotation processes because interference by smaller-scale morphological features was eliminated (e.g. the formation, changes in shape or migration of mega-cusps). In the current post-breakwater situation, there is evidence for a change in the behaviour of the north-eastern beach triggered by the submerged breakwater built in 2007. Furthermore, a counter-clockwise beach rotation has occurred at the north-eastern beach, whereas the south-western beach has experienced a clockwise beach rotation. This morphodynamic behaviour is caused by a new, complex wave-induced circulation system comprising two dominant alongshore currents flowing in opposite directions. In contrast to the pre-breakwater situation, the alongshore component of the radiation stress does not accomplish beach rotation in the post-breakwater situation. 相似文献
16.
A simple numerical model, based on the Reynolds stress equations and k–ε turbulence closure scheme, is developed for the coastal wave and current bottom boundary layer. The current friction velocity is introduced to account for the effect of currents on waves. The implicit Crank–Nicolson finite difference method discretizes the governing equations. Vertical changing step grids with the constant ratio for two adjacent spatial steps are used together with the equal time steps in the modeling. Vertical profiles of mean current velocity and wave velocity amplitude are obtained. These modeled results are compared with the laboratory experimental data of Van Doorn [1981. Experimental investigation of near bottom velocities in water waves with and without a current. Report M1423, Delft Hydraulics Laboratory, Delft, The Netherlands; 1982. Experimenteel onderzoek naar het snelheidsveld in de turbulente bodemgrenslaag in een oscillerende stroming in een golftunnel. Report M1562, Delft Hydraulics Laboratory, Delft, The Netherlands]. It has been shown that modeled and observed (Van Doorn, T., 1981. Experimental investigation of near bottom velocities in water waves with and without a current. Report M1423, Delft Hydraulics Laboratory, Delft, The Netherlands; 1982. Experimenteel onderzoek naar het snelheidsveld in de turbulente bodemgrenslaag in een oscillerende stroming in een golftunnel. Report M1562, Delft Hydraulics Laboratory, Delft, The Netherlands) mean velocity profiles within the wave and current bottom boundary layer are in better agreement than outside. Modeled and observed (Van Doorn, T., 1981. Experimental investigation of near bottom velocities in water waves with and without a current. Report M1423, Delft Hydraulics Laboratory, Delft, The Netherlands) wave velocity amplitude profiles within the wave and current bottom boundary layer are in better agreement than outside. Modeled wave velocity amplitudes are in good agreement with the laboratory experimental data of Van Doorn [1982. Experimenteel onderzoek naar het snelheidsveld in de turbulente bodemgrenslaag in een oscillerende stroming in een golftunnel. Report M1562, Delft Hydraulics Laboratory, Delft, The Netherlands]. 相似文献
17.
The paper develops and analyzes two fully nonlinear boundary conditions that incorporate the motion of the shoreline in nonlinear time domain nearshore models. A moving shoreline essentially means the computational domain is changing with the solution of the flow. The problem is solved in two steps. The first is to establish an equation that determines the motion of the shoreline based on the local momentum balance. The second is to develop and implement into a shoreline model the capability of accommodating a changing computational domain. The two models represent two different ways of addressing this step: one is to track the position of the shoreline in a fixed grid by establishing a special shoreline point which generally is not a fixed grid point. The second is by a coordinate transformation that maps the changing domain onto a fixed domain and solves the basic equations in the mapped domain. The two shoreline conditions are tested against three known solution for nonlinear shoreline motion. Two are the 1-D solutions to the nonlinear shallow water (NSW) equations by Carrier and Greenspan [J. Fluid Mech. 4 (1958) 97], one representing the response to a transient change in the offshore water level, the other the motion due to a periodic standing wave, both on slopes steep enough to allow full reflection. The third is the 2-D horizontal (2DH) computational solution by Zelt [Coast. Eng. 15 (1991) 205] for the run-up of a solitary wave on a cusped beach. In all cases, both models are shown to behave well and give high accuracy results for suitably chosen grid and time spacings. 相似文献
18.
A new model for the boundary layer development and associated skin friction coefficients and shear stress within the swash zone is presented. The model is developed within a Lagrangian reference frame, following fluid trajectories, and can be applied to both laminar flow and smooth turbulent flow. The model is based on the momentum integral approach for steady, flat-plate boundary layers, with appropriate modifications to account for the unsteady flow regime and flow history. The model results are consistent with previous measurements of bed shear stress and skin friction coefficients within the swash zone. These indicate strong temporal and spatial variation throughout the swash cycle, and a clear distinction between the uprush and backwash phase. This variation has been previously attributed the unsteady flow regime and flow history effects, both of which are accounted for in the new model. Fluid particle trajectories and velocity are computed using the non-linear shallow water wave equations and the boundary layer growth across the entire swash zone is estimated. Predictions of the bed shear stress and skin friction coefficients agree reasonably well with direct bed shear stress measurements reported by Barnes et al. (Barnes, M.P., O’Donaghue, T., Alsina, J.M., Baldock, T.E., 2009. Direct bed shear stress measurements in bore-driven swash. Coastal Engineering 56 (8), 853–867) and, for a given flow velocity, give stresses which are consistent with the bias toward uprush sediment transport which has consistently been observed in measurements. The data and modelling suggest that the backwash boundary layer is initially laminar, which results in the late development of significant bed shear during the backwash, with a transition to a turbulent boundary layer later in the backwash. A new conceptual model for the boundary layer structure at the leading edge of the swash is proposed, which accounts for both the no-slip condition at the bed and the moving wet–dry interface. However, further development of the Lagrangian Boundary Layer Model is required in order to include bore-generated turbulence and to account for variable roughness and mobile beds. 相似文献
19.
《Coastal Engineering》2006,53(10):825-843
A newly developed two-phase flow model was applied to simulate the sediment movement under 2nd-order Stokes wave sheetflow conditions with different sediment sizes and wave periods. As for the distribution of eddy viscosity and sediment diffusion coefficient, the difference between onshore and offshore phases was considered by using an equivalent sinusoidal velocity amplitude for the asymmetric velocity profile. Sophisticated comparisons between laboratory measurements [O'Donoghue, T., Wright, S., 2004b. Flow tunnel measurements of velocities and sand flux in oscillatory sheetflow for well-sorted and graded sands. Coast. Eng., 51 (11–12), 1163–1184.] and the present numerical simulation were performed for sediment concentration, sediment velocity, sand flux and net transport rate. Four existing engineering models, together with the present two-phase flow model, were introduced for net transport rate prediction. Taking both the net sand transport rate magnitude and direction into account, the present process-based two-phase flow model provided the best estimations, which can simulate both the onshore net transport for medium/coarse sand cases and offshore net transport for fine sand cases with the agreement by a factor of 2 for almost all the considered cases. 相似文献
20.
Realistic modelling of marine ecosystems is necessary for improving our understanding of the ocean’s biogeochemical state and for predicting their response to anthropic perturbations. An essential step in achieving this task is the use of mechanistic formulations to describe the biogeochemical processes involved in the dynamics of marine pelagic ecosystems. This study provides a review on some modelling strategies for some of the key processes involved in the dynamics of phytoplankton. It encompasses the most advanced work in terms of mechanistic understanding and, therefore, mainly deals with photosynthesis (including photoacclimation and photoinhibition), respiration, and nutrient uptake (including multi-limitation of algal growth by nutrients). We highlight, that in many ecosystem models, phytoplankton processes are still described more or less empirically, mainly due to a lack of biochemical knowledge, or if a mechanistic formulation exists, the parameters are often difficult to assess experimentally. As a result of this investigation, a preliminary structure for a generic phytoplankton model is delivered in the last section of this paper. This model includes a mechanistic representation of photosynthesis/photoinhibition based on photosystem II status, as well as new formulations for photoacclimation and dissolved organic matter exudation processes. The model sensitivity analysis with regard to its parameters and a comparison with chemostat experimental data are presented in a companion paper [Baklouti, M., Faure, V., Pawlowski, L., Sciandra, A., 2006. Investigation and sensitivity analysis of a mechanistic phytoplankton model implemented in a new modular numerical tool (Eco3M) dedicated to biogeochemical modelling. Progress in Oceanography]. Finally, this new class of multi-element, multi-species phytoplankton models will provide the basis for future studies on ecosystem modelling. 相似文献