Deltares - R&D Highlights 2009

Contact: herman.kernkamp@deltares.nl +31 (0)88 335 8521 arthur.vandam@deltares.nl +31 (0)88 335 7689 Unstructured grid modelling Hydrodynamic modelling for freshwater topics is generally based upon Sobek-1D2D. This program is particularly suitable for modelling river fl ow, channel fl ow, sewer fl ow and 2D fl ooding and it covers both sub- and supercritical fl ow regimes. Most work on estuarine and coastal issues, on the other hand, is performed using Delſt 3D, which is particularly suitable for model tidal propagation in seas and estuaries, storm surges, fl ows in rivers, harbours and lakes, salinity intrusion and thermal stratifi cation. Water height in continental shelf model run In the new hydrodynamics package Unstruc, we aim to combine the effi cient and well-proven methods of both packages into one hydrodynamics modelling system. It is based on a fully unstructured network, yielding optimal fl exibility. The curvilinear grid approach is adhered to as much as possible because of its high accuracy, but one can easily switch to an unstructured approach locally to circumvent its occasionally less benefi cial properties. To help users create these new types of networks, we have added curvilinear grid generation in channels or rivers and along coastlines, and triangular grid generation in intermediate areas. The various grid areas can be coupled automatically. Local refi nement of grids is now possible, as is automated refi nement based upon local bathymetry. Detail of Unstruc mesh in Sacramento delta The physical and numerical model features of Unstruc are being extended gradually by importing functionality known from Delſt 3D and SOBEK. In 2009, we conducted several initial tests with 3D (z-layer) problems based on the k-ε-model. Onedimensional fl ow networks can now also be coupled to the 2D fl ow areas, such as model small rivers leading into a lake. Two of our 2D-test applications are a full-scale continental shelf model and the Sacramento delta in the San Francisco bay area. 82

Courantnetwork: automatic bathymetry-based refi nement To facilitate the rolling out of Unstruc to users, fi le-based model input and model output were implemented. For this purpose, we adopted the international NetCDF standard. We are working on a standardisation of solution data for unstructured grids in cooperation with international parties. In 2010, we will add further modelling capabilities for 1D structures, such as weirs and pumps. In 2D modelling, we will extend the possibilities for boundary and initial conditions and discharges. We also intend to link Unstruc to the water quality package Delwaq and to extend 3D modelling, for example with fl exible layers in the vertical direction. 83

herman.kernkamp@deltares.nl, arthur.vandam@deltares.nl,
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