Convective spread over the surface. Mass transport. Diffusion and dispersion. Loss of heat through surface. Models of flows without a free surface. Models of river training schemes. Model techniques. Control and operation. Measurement and instrumentation. Flow velocities. Water levels. Water pressures. Sediment Transport in Rivers.

Basic concepts and relevant parameters. The granular material. The flow: velocity distribution. Dimensional analysis of the two-phase phenomenon. Beginning of sediment transport - transport rate. Sand waves. Friction factor. Suspended load. River Models with Movable Bed. Model laws for bedload.

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Models with flat bed. Models with sand waves. Scaling of undistorted models. Scaling of distorted models. Modelling techniques. Choice of movable bed material. Calibration of the model. It is shown that scale effects can be important and can explain part of these differences.

The graph on the right and a formula to estimate the influence of scale and model effects on the overtopping discharge at steep rubble mound breakwaters like the Zeebrugge breakwater have been developed. The figure gives on the x-axis the overtopping discharge which would be obtained by simply upscaling the model value by Froude law. As a function of this upscaled overtopping discharge, the y-axis shows the ratio between the measured prototype overtopping discharge and the upscaled model discharge.

Hence, an approximation of the influence of scale and model effects on the overtopping discharge for the given structure and by extension for other steep rubble mound breakwaters can be made. The graph also shows a conservative curve giving the influence of the scale and model effects as a function of the upscaled overtopping discharge.

Both the small and large scale tests, with a length scale ratio of 5. The comparison of large and small scale test results led to a new correction procedure to correct for scale effects. The procedure was calibrated to the obtained data in order to establish new guidelines for overtopping scale effects. Model effects caused by differences in wave height distributions, wave skewness and wave set-up were identified. Because the wave characteristics are very important for small overtopping discharges, it is difficult to separate these model effects from scale effects.

Consequently two different normalization methods were used in order to determine the scale effects. The traditional normalization method gives an underestimation of the scale effects as for identical Hm0 wave heights the extreme waves are significantly larger in small scale. Even using this dimensionless plot, which underestimates the scale effects, larger dimensionless overtopping discharges in large scale for the low and normal wall were identified. This shows clearly a scale effect is present. The difference is most significant in the case of small armour crest freeboards high water level.

This analysis method leads to more conservative estimates of the scale effects. Also this analysis shows that the difference between large and small scale overtopping discharges is for identical average overtopping discharge most pronounced in case of small freeboards high water level. The difference is most significant when the wall is low, where more of the overtopping water flows through the armour crest, which gives more influence of drag. The wave steepness also significantly influences the overtopping flow.

For high wave steepness the main part of the overtopping water is thrown over as spray when the wave impact and breaks on the slope. For the low wave steepness much more water flows through the armour layer. This has an influence also on the observed differences in overtopping, with larger differences for the low wave steepness. For the high wall case the crest berm has, especially for low wave steepness, to be more or less filled with water before overtopping occurs. This reduces the influence of viscosity, and is probably the reason for only identifying small differences in overtopping discharges for this cross-section.

The conclusion is that the magnitude of the scale effects is very dependent on the top geometry of the structure. Numerical modelling The hydrodynamic aspects of an integrated model system for the prediction of coastal flooding developed as part of the UK Flood Risk Management Research Consortium are presented [77].

The input conditions are offshore wind, waves, tides and surge. Climate models from the Met Office provide boundary conditions for Regional Climate Models RCM which in turn provide boundary conditions for wave climate and the continental shelf models of National Oceanographic Centre. These models provide boundary conditions for modelling nearshore waves and water levels due to tides, surge and setup, which are the parameters driving overtopping, inundation and breaching at the coast.

The methods are applied to a particular flood event which occurred in Walcott in North Norfolk, UK on 9th November The coastline at Walcott is orientated approximately northwest-southeast and is prone to attack from the North Sea , especially when the wind blows from the northeast.

The danger increases when this wind is combined with a North Sea surge, which can raise the still water level of the sea by up to 2m above the predicted sea level. Such conditions have caused disastrous flooding in the town, as in and more recently in Figure 6: Map of the coastal domain a and of the local domain b [77].

It was used to hindcast the Walcott surge and wave event for November The wave model is a version of the third-generation spectral WAM model [82] which has been extended to be applicable on continental shelf-scale in shallow water [83]. For this application the wave model does not take into account the effect of interaction between waves, water level and currents, although this option is available and may be important in very high-resolution nearshore regions [84].

In both the model implementations, the wave model spectral resolution was 24 directions and 25 frequencies. WAM computes the evolution of the 2D spectra, which is then used to estimate the value of a number of integrated parameters e. Waves generated offshore and approaching the nearshore are subjected to shallow waters and varying bathymetry, leading to shoaling, refraction and loss of energy either due to bottom friction or to wave breaking.

Off Walcott, the tidal and surge regime is large enough to interact with wave propagation. To simulate all these physical processes, the TELEMAC suite [85] , containing a shallow water hydrodynamic solver and a wave action conservation equation solver is set up to model inshore water levels and wave spectra for November This open-source system is also chosen since it allows fine mesh resolution when needed through the FE mesh. To represent the physical processes influencing inshore wave propagation, a numerical approach based on the 3 rd generation wave model [86] , is adopted. The model takes into account bathymetric wave breaking, bottom friction, nonlinear wave-wave interactions, wind wave generation and white-capping.

The model produces integrated wave parameters and directional wave spectrum at a nearshore location. Composite modelling A case which considers permeable low crested beach parallel structures LCS is presented [4]. Nine irregular wave conditions generated with a Jonswap spectrum were tested for each structure, corresponding to three different wave heights and three different wave steepness [73]. First, the results of the two model approaches were assessed and compared. The 2DV PM gave good results at the structure front because they reproduce shoaling, refraction, reflection and breaking processes.

The PM results at the lee side of the structure are less good, because although it reproduces wave transmission, the PM does not simulate diffraction, longshore currents and sediment transport and it also does not accurately reproduce the water levels there, due to the piling-up effect of water, which gives rise to spurious results for this variable. The NM did not give good results at the structure front because although it reproduces shoaling, refraction and breaking, it does not simulate reflection. At the lee side of the structure, the NM allowed taking into account diffraction effects, which could not be included in the PM.

Moreover, it could give more realistic set-up results in the leeside of the structure, because the NM did not feature the piling-up. However, the NM did not accurately represent the wave transmission. Although other possible approaches were analyzed the CM approach followed existed in selecting the areas where either PM or NM gave the better performance. The assessment of the areas of better performance was process based, i.

Figure 7: Composite modelling approach. Some limitations and constraints observed in 2DV physical models were overcome with the employed approach. Thus, an overall better representation of hydro-morphodynamic conditions around the structure was obtained. This approach was applied successfully to both emerged and submerged permeable low crested structures Figure 8. Figure 8: Final bathymetry after 9 tests case of emerged structure [4].

Furthermore, some processes cannot be assessed or reproduced by this technique. For instance, diffraction is only reproduced by the NM and is therefore assessed qualitatively only , while the lower resolution of the NM does not allow to reproduce features such as ripples [74]. Evers, J. Grune, A. Funke Hybrid modelling as applied to hydrodynamic research and testing.

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## Recent Advances in Hydraulic Physical Modelling

Edge, B. Ed ASCE. Kirkegaard The future role of experimental methods in European hydraulic research: towards a balanced methodology. Journal of Hydraulic Research, Vol. Academic Press, London, pp. Goring, D. J Geophys Res C Continental Shelf Research, 29, Coast Eng 41 1—3 — Cont Shelf Res — Coastal Flooding — Impacts of coupled wave-surge-tide models. Natural Hazards, 9 2 , J Geophys Res 84 C4 — Hydraulics research report TR In: Proceedings of the 5th international conference on ocean wave measurement and analysis. Coast Eng —3, 95— Peregrine, D.

Fluid Mech. Geophys J R Astron Soc — In: Peregrine DH ed Floods due to high winds and tides. Wiley, Chichester, p J Geophys Res Cll — Circular 20, National Bureau of Standards, Mathematical models for simple harmonic linear water waves; wave refraction and diffraction. Fluid Mechanics, , — Coastal Engng. Holthuijsen, and T. Holthuijsen Computational Physics, 68, — Description v and Modeling of Directional Seas, Tech. Booij, and R. Dalrymple Houston, and H. Butler Modeling of Longshore Currents for Field Situations. Coastal Eng. Kashiyama Numerical Methods Fluids, 4, 71— Liu Waterway, Port, Coastal and Ocean Eng.

Sancho, I. Svendsen, and U. Numerical Modelling of Nearshore Circulation. Vreugdenhil Rip-current Generation Near Structures. Svendsen Sorensen, and H. Schaffer a. Part I. Schaffer b. Part II. Dalrymple, J. Kirby, A. Kennedy, and M. Haller Boussinesq Modelling of a Rip Current System.

Dalrymple, and I. Rip Channels and Nearshore Circulation.

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Study of sediment bypass at coastal structures by composite modelling. World Scientific, Volume 2, pp - Littoral 9th International conference, Venice, Nov. Composite modelling by applying an inverse technique in analysing interactions between beaches and structures. Conf on Hydroinformatics, Concepcion, Chile, January, , paper a, 10 pages. Wave attack on sea defences — potential benefits of a composite modelling approach. Journal of Coastal Research, SI 56, pp — Mathematical modeling of scour: A review.

Hydraulic Research, Vol 45, Issue 6, pp. Interaction between seabed and scour protection, Ph. Flow and scour around a half-buried sphere. In preparation. Hybrid modelling of scouring-deposition in front of a coastal structure. Journal of Coastal Research, SI 50, Physical and numerical modeling of beach response to permeable low-crested coastal structures. Journal of Coastal Research, SI 56, - Effects of new variables on the overtopping discharge at steep rubble mound breakwaters - The Zeebrugge case Coast.

Coastal Engineering, 65, Coupled wave and surge modeling and implications for coastal flooding. Advances in Geosciences. An s coordinate density evolving model of the northwest European continental shelf: 1, Model description and density structure. Cambridge University Press, Cambridge, p The spectral wave model, WAM, adapted for applications with high spatial resolution Coast. Journal of Marine Systems in press. Hydrodynamics of free surface flows modelling with the finite element method.

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Log in. Page Discussion. Read View source View history. Jump to: navigation , search. This page was last modified on 28 June , at Figure 2: Model integration leading to an integrated model [4].

## Book Recent Advances In Hydraulic Physical Modelling

Figure 4: Cross section of Zeebrugge rubble mound breakwater [76]. Figure 5: Ratio between prototype overtopping discharge and upscaled model overtopping discharge [76]. The main author of this article is Prinos, Panayotis Please note that others may also have edited the contents of this article. Citation: Prinos, Panayotis : Modelling coastal hydrodynamics. There are also several interactions between the mean circulation and wind-waves Peregrine and Jonsson The propagation of waves in shallow water is dependent on water depth and this means that the total water depth, which includes tide and surge, will affect wave propagation.

In fact, the tidal propagation is also modified in the presence of a surge, leading to tide-surge interaction Wolf [9]. Waves are modified by the presence of currents generated by tide and surge. They contribute to water level and mean circulation through wave setup and longshore currents, due to radiation stresses in shallow water Longuet-Higgins and Stewart Tides, caused by the gravitational effect of sun and moon, are periodic and very predictable. Surges, on the other hand, are quasi-periodic and caused by meteorological forcing.

The most important mechanism for surge generation is wind-stress acting over shallow water. Surges at the coast are produced by Ekman dynamics , behaving as forced Kelvin waves [8]. The size of the surge is proportional to the wind-stress divided by the water depth. The wind-stress is usually taken to be proportional to the square of the wind-speed with a drag coefficient which increases with wind speed accounting for some effect of surface roughness due to waves [10].

Due to transient effects there is also an increase in surge height with wind duration. Surges are, therefore, largest where storms impact on large areas of shallow continental shelves. In deep water, surge elevations are approximately hydrostatic with a 1 hPa decrease in atmospheric pressure giving about 1 cm increase in surge elevation [11].

Surges in the Mediterranean as a whole are likely to be much lower due to the much deeper water. However, they are important in local areas of shallow water, e. Some modification is caused by seiching, when winds trigger oscillations at the natural periods of enclosed sea areas, e. It has long been recognized that in shallow water areas with a large tidal range, the nonlinear effects of tide—surge interaction are important. Jones and Davies [12] and Horsburgh and Wilson [9] , among others, have described work on the effects of tide—surge interaction.

Figure 3 illustrates the mechanism by which tide-surge interaction leads to a surge peak on the rising tide. The tidal phase is advanced due to the deeper water caused by the presence of a positive surge level. The difference between the phase-shifted T0 and undisturbed tide T is added to the surge to give the net tidal residual red line , which has a peak 3 h before predicted high water. Figure 3: Illustration of tide-surge interaction. These may be summarized as: the effects of water levels and currents on waves and the effect of waves on tides and surges.

First, the effect of water levels on nearshore wave transformation are considered. As waves enter shallow water, when the depth is less than half the wavelength , the processes of shoaling and refraction change the wavelength and phase speed but the wave period remains constant in the absence of currents.

As energy propagates at the group velocity, by energy conservation the wave height first decreases then increases this is because of the group velocity property that it increases first with intermediate depth, only to decrease when the depth becomes shallower [15]. Finally, the energy dissipation processes of breaking and bottom friction start to limit the wave height. At the coast an increase in water depth will increase the wave height and also the distance to which waves can penetrate inland. Tide and surge currents can affect wave generation, propagation and dissipation. The effect on surface stress is to change the apparent wind and effective fetch.

There may also be an enhancement of the wave friction in the bottom stress [16] although Soulsby and Clarke [17] state this is negligible. Current gradients in the horizontal also cause wave refraction and currents produce a Doppler shift of frequency. In the presence of currents it is the wave action which is conserved rather than wave energy. All these processes are described in more detail in Wolf et al. Waves can affect the mean flow and water level in the nearshore zone through radiation stress causing longshore drift and wave setup Longuet-Higgins and Stewart Waves may affect the generation of surges by affecting surface roughness.

Janssen , introduced the concept of wave stress in which wave age affects the surface roughness and implemented it in the WAM model. Further investigation of this has been carried out by Brown and Wolf [10]. Waves may enhance the bottom friction experienced by currents in shallow water [16]. Physical, Numerical and Composite Modelling Physical Models Wind, waves and swell can be reproduced satisfactorily by a physical model which has to be chosen dependent on various project and site specific parameters like model test objectives proposed structure design and rationale behind the proposed structure.

These include typical cross sections, detailed drwings of the structure and material related information such as density of material and grain size information bathymetric details of the surrounding area 3D or the wave approach direction 2D so that a representative bottom configuration can be constructed. Good quality bathymetric data will assure that wave transformation is well simulated in the model environmental design conditions wave height, period, water level, wave spectra and wave direction structure performance criteria such as allowable damage level, maximum wave run-up, permissible wave transmission at design wave and water level conditions.

The use of physical models for understanding the impact of water waves is essential for the design of marine structures and assessment of coastal development due to natural causes as well as human intervention. For physical model tests wave characteristics have to be selected like the types of the waves to be used regular, irregular, multi-directional, etc.

The selection of wave conditions in the model must be carefully considered in relation to the actual problem. The largest possible scale for the available experimental facility is generally selected. Other limitations than physical dimensions may play an important role in scale ratio selection wavemaker capacity, towing speed etc. Wave characteristics from the actual project location shall be the basis for selection of representative sea states for a model test programme.

The selection also depends on the application. In some cases very long testing time is required to obtain enough information to derive design values. Free and bound long waves. Any structure or coastline is highly reflective when exposed to long waves. While long waves can often escape to deep water under natural conditions, they are inevitably entrapped in traditional laboratory experiments.

Active absorption systems can assist the transparency of offshore boundaries to long waves. Although solved in practice, there are serious practical problems in handling long waves by the wave generator. In shallow water the necessary stroke of the wave generator is very large and may therefore restrict reproduction off extreme sea states at a satisfactory model scale. Selection of 2D or 3D wave testing depends on the problem to be investigated, however, a general experience shows that 2D testing is sufficient for a large range of problems.

The general lack of good quality directional wave data is also used as a reason not to use 3D testing. In 3D wave basins the treatment of boundary effects such as wave reflection or damping at the boundaries of the wave basin requires larger efforts than in 2D modelling. Monitoring of 3D wave field within the basin can also be problematic. In 3D basins the wave conditions are more inhomogeneous in space than in 2D flumes.

Hence, wave conditions in the 3D basins require higher resolution monitoring of wave parameters. The planning and execution of tests and the measurement and the analysis of laboratory waves are essential parts of physical modelling. Numerical Models Storm surges are modelled in detail for a variety of reasons, including most, if not all, of the preceding components for real shorelines as a function of time.

One possible reason is the prediction of the or year storm surge at a coastal site for the design water levels for coastal structures or the establishment of hazards and insurance rates for coastal communities.

Another purpose, involving real-time modeling, is for hazard mitigation and public safety. The last problem is far easier than the first two, for often data concerning the storm parameters and the wind fields can be obtained. Owing to the lack of long-term water level records or any records at all, statistical surge information is usually unavailable. For actual surge occurrences, often not much data are available except from a few established tide gauge sites and site-specific evidence such as high water levels inside buildings, elevation of wave damage, and other indicators of storm water level.

For any surge model, an adequate representation of a wind field is necessary because the spatial extent of the wind and pressure fields associated with a storm is needed as input. Further, the path of the storm and its correct forward speed are necessary. Heaps [20] , Flather [21] and Pugh [22] reviewed earlier work on numerical modelling of storm surges. Limited area models are subject to errors in boundary conditions and tidal models may omit some tidal frequencies, local effects of the tide generating forces and load tide response of the solid Earth.

Shum et al. However, tidal models are still inferior to harmonic analysis and prediction for shallow water tides at locations where coastal tide gauge data are available. The tide—surge model predictions reflect this in using the model surge together with harmonic predictions for tides to provide the total water level [24]. A surge model inter comparison exercise de Vries et al. Work on the UK tide—surge model by Williams and Flather has also shown a need for enhanced wind-stress relative to Smith and Banke and recently Brown and Wolf [10] have shown this may be related to wave effects and also nearshore bathymetric resolution.

Numerical wave models can be distinguished into two main categories: phase-resolving models, which are based on vertically integrated, time-dependent mass and momentum balance equations, and phase-averaged models, which are based on a spectral energy balance equation. Moreover, none of the existing models, phase-resolving or not, considers all physical processes involved. The more recent research efforts have been focused on the development of unified phase-resolving models, which can describe transient fully nonlinear wave propagation from deep water to shallow water over a large area.

In the mean time, significant progress has also been made in simulating the wave-breaking process by solving the Reynolds Averaged Navier Stokes RANS equations with a turbulence closure model. These RANS models have also been employed in the studies of wave and structure interactions. Continuing efforts have been made to construct a unified model that can propagate wave from deep water into shallow water, even into the surf zone.

The forerunner of this kind of effort is the ray approximation for infinitesimal waves propagating over bathymetry that varies slowly over horizontal distances much longer than local wavelength. In this approximation, one first finds wave rays by adopting the geometrical optic theory, which defines the wave ray as a curve tangential to the wave number vector. One then calculates the spatial variation of the wave envelope along the rays by invoking the principle of conservation of energy. Numerical discretization can be done in steps along a ray not necessarily small in comparison with a typical wave length.

Since the ray approximation does not allow wave energy flux across a wave ray, it fails near the caustics or the focal regions, where neighboring wave rays intersect, diffract and possibly nonlinearity are important. While ad hoc numerical methods for local remedies are available, it is not always convenient to implement them in practice.

Within the framework of linear wave theory , an improvement to the ray approximation was first suggested by Eckart [25] and was later rederived by Berkhoff [26] [27] , who proposed a two-dimensional theory that can deal with large regions of refraction and diffraction. The underlying assumption of the theory is that evanescent modes are not important for waves propagating over a slowly varying bathymetry, except in the immediate vicinity of a three-dimensional obstacle. The mild-slope equation can be applied to a wave system with multiple wave components as long as the system is linear and these components do not interact with each other.

In applying the mild-slope equation to a large region in coastal zone, one encounters the difficulty of specifying boundary conditions along the shoreline, which are essential for solving the elliptic- type mild-slope equation. The difficulty arises because the location of the breaker cannot be determined a priori.

A remedy to this problem is to apply the parabolic approximation to the mild-slope equation [28] [29]. Therefore, the effects of diffraction have been approximately included in the parabolic approximation. The practical application of wave transformation usually requires the simulation of directional random waves. Because of the linear characteristics of the mild-slope equation and the parabolic approximation, the principle of superposition of different wave frequency components can be applied.

In general, parabolic models for spectral wave conditions require inputs of the incoming directional random sea at the offshore boundary. The two-dimensional input spectra are discretized into a finite number of frequency and direction wave components. Using the parabolic equation, the evolution of the amplitudes of all the wave components is computed simultaneously. Based on the calculations for all components, and assuming a Rayleigh distribution, statistical quantities such as the significant wave height can be calculated at every grid point.

The corresponding nonlinear mild-slope equation and its parabolic approximation have been derived and reported by Kirby and Dalrymple [28] and Liu and Tsay [30]. However, one must exercise caution in extending the nonlinear Stokes wave theory into the shallow water; additional condition needs to be satisfied. Assuming that both non-linearity and frequency dispersion are weak and are in the same order of magnitude, Peregrine [31] derived the standard Boussinesq equations for variable depth. Numerical results based on the standard Boussinesq equations or the equivalent formulations have been shown to give predictions that compared quite well with field data [32] and laboratory data [33] [34].

Because it is required that both frequency dispersion and nonlinear effects are weak, the standard Boussinesq equations are not applicable to very shallow water depth, where the nonlinearity becomes more important than the frequency dispersion, and to the deep water depth, where the frequency dispersion is of order one.

The standard Boussinesq equations written in terms of the depth averaged velocity break down when the depth is greater than one fifth of the equivalent deep-water wavelength. For many engineering applications, where the incident wave energy spectrum consists of many frequency components, a lesser depth restriction is desirable.

Furthermore, when the Boussinesq equations are solved numerically, high frequency oscillations with wave lengths related to the grid size could cause instability. To extend the applications to shorter waves or deeper water depth many modified forms of Boussinesq-type equations have been introduced [35] [36] [37]. Although the methods of derivation are different, the resulting dispersion relations of the linear components of these modified Boussinesq equations are similar. The modified Boussinesq equations are able to simulate wave propagation from intermediate water depth water depth to wave length ratio is about 0.

Despite of the success of the modified Boussinesq equations in intermediate water depth, these equations are still restricted to weakly nonlinearity. As waves approach shore, wave height increases due to shoaling and wave breaks on most of gentle natural beaches.

The wave-height to water depth ratios associated with this physical process become too high for the Boussinesq approximation. The appropriate model equation for the leading order solution should be the nonlinear shallow water equation. Of course this restriction can be readily removed by eliminating the weak nonlinearity assumption [39] [40]. These fully nonlinear equations can no longer be called Boussinesq-type equations since the nonlinearity is not in balance with the frequency dispersion, which violates the spirit of the original Boussinesq assumption.

In the previous paragraphs all the wave theories have been developed based on the assumption that no energy dissipation occurs during the wave transformation process. However, in most coastal problems the effects of energy dissipation, such as bottom friction and wave breaking may become significant. The mild-slope equation may be modified in a simple manner to accommodate these phenomena by including an energy dissipation function describing the rate of change of wave energy.

The energy dissipation functions are usually defined empirically according to different dissipative processes [41]. Similarly, in the numerical models based on Boussinesq-type equations, adding a new term to the depth-integrated momentum equation parameterizes the wave breaking process. While Zelt [42] , Karambas and Koutitas [43] and Kennedy et al. In the roller model the instantaneous roller thickness at each point and the orientation of the roller must be prescribed. Furthermore, in both approximations incipient breaking has to be determined making certain assumptions.

By adjusting parameters associated with the breaking models, results of these models all showed very reasonable agreement with the respective laboratory data for free surface profiles. However, these models are unlikely to produce accurate solutions for the velocity field or to determine spatial distributions of the turbulent kinetic energy and therefore, more specific models on breaking waves are needed.

Spectral models entail bringing the full directional and spectral description of the waves from offshore to onshore. These models have not evolved as far as monochromatic models and are the subject of intense research.

dingbirranorthca.tk Open source models Recent models often include the interactions of wave fields with currents and bathymetry , the input of wave energy by the wind, and wave breaking. For example, Holthuijsen, Booij, and Ris [50] introduced the SWAN model , which predicts directional spectra, significant wave height, mean period, average wave direction, radiation stresses, and bottom motions over the model domain.

The model includes nonlinear wave interactions, current blocking, refraction and shoaling , and white capping and depth-induced breaking. Numerical modelling of the nearshore circulation system including rip and longshore currents permits the study of both onshore and offshore motions as well as longshore motions and can in fact include the influence of rip currents. A variety of models has been developed, for example, Noda , Birkemeier and Dalrymple [51] , Vemulakonda, Houston and Butler [52] , Kawahara and Kashiyama [53] , Wu and Liu [54] and Van Dongeren et al.

These depth-averaged models in general solve the nearshore circulation field forced by bottom variations, although Ebersole and Dalrymple [56] examined the case of intersecting wave trains and Wind and Vreugdenhil [57] addressed the circulation induced between two barriers, pointing out the importance of correctly modeling the lateral shear stresses. The last model by Van Dongeren et al. Madsen, Sorensen, and Schaffer [59] [60] have shown that an extended Boussinesq wave model can predict surf zone hydrodynamics quite well when a wave-breaking algorithm is included.

Chen et al. The numerical model predicts the instabilities in the rip currents as seen in the physical model by Haller et al. Most of these nearshore circulation models were developed by finite difference methods, although Wu and Liu [54] use finite element techniques. Some of these models are being used for engineering work, although it should be pointed out that most of them are very computer intensive and require very small time steps on the order of seconds to reach steady-state solutions. Models typically have been developed only for monochromatic single frequency wave trains rather than for directional spectra.

Several open source codes Delft3D, ossdeltares. The Delft3D suite consists of various components to model the particular physics of the water system, such as the hydrodynamics, morphology and water quality. Delft3D allows you to simulate the interaction of water, sediment, ecology and water quality in time and space. The suite is mostly used for the modelling of natural environments like coastal, river and estuarine areas, but it is equally suitable for more artificial environments like harbours, locks, etc.

Delft3D consists of a number of well-tested and validated programmes, which are linked to and integrated with one-another. The Delft3D Wave component can be used to simulate the propagation and transformation of random, short-crested, wind generated waves in coastal waters which may extend to estuaries, tidal inlets, barrier islands with tidal flats, channels etc. The SWAN model is applicable in deep, intermediate and shallow waters and the spatial model grid may cover any model surface area of up to more than 50 km by 50 km.

The added value of Delft3D Wave is the capability of Delft3D Hydrodynamics, Morphology and Waves to perform a so-called online calculation, in which information is transferred from Flow and Morphology to Wave and back again. This online coupling allows for the simulation of complex water systems in which flow-wave wave currents interaction as well as wave setup or flow-wave-morphology effect of radiation stress on sediment transport and seabed changes are important.

SWAN is a phase-averaged wave model which is less or not applicable in regions where complex phenomena occur within relatively short distances, e. For those areas phase-resolving models are required to obtain more accurate wave predictions. Examples of these models are Boussinesq-type models and Multi-layer models. In practice Delft3D-Wave in combination with other modules is used to transform offshore information such as wind speed statistics to nearshore wave conditions, or more concrete, hydraulic loads on revetments, dune retreat, resulting ship motion, etc.

Several models and techniques are required for this transfer, that are coupled in a so-called coastal engineering platform.

The above cases are presented briefly in the following paragraphs. Sedimentation bypass for a harbour layout. Grunnet et al. Very local physical modelling and larger scale numerical modelling has been used to support and complement each other. A physical model in a shallow water wave basin was combined with detailed area modelling of the fields of the waves, the current, the sediment transport and the resulting morphological evolution of the bed. The resulting coastline evolution was further simulated by a regional coastline model a one-line model based on a littoral drift model.

The regional numerical wave model was used for transformation of the wave conditions to the local physical model area. The deposition of sediment in the harbour basin was determined in the physical model. Simulations were made with a coastline model to determine the regional coastline evolution caused by the blocking of the sediment by the harbour and the sedimentation in the harbour basin.

Reduction of uncertainties in physical modelling using a numerical error correction technique Sandy nearshore bottom profiles profiles can change significantly under severe storms, and it is therefore desirable to take bottom uncertainty into account in physical scale modelling of the most critical wave loads on coastal structures.