On the coupling of uncoupled flow and transport solvers

The coupling of flow and transport solvers we are dealing with in this paper represents a whole intermediate processing step taking place between the two. We develop new techniques to ensure mass conservation of the transport while using totally different numerical schemes in the flow and in the transport solvers. We also present a method which allows the use of larger time steps for the transport computation than the one used for the flow leading therefore to faster computations and considerable reduction in disk space for the storage of flow data. These techniques are applied and tested in the numerical application of 2D and 3D problems.     

Efficient scheme for the shallow water equations on unstructured grids with application to the Continental Shelf

In this paper, a shallow-water flow solver is presented, based on the finite-volume method on unstructured grids The method is suitable for flows that occur in rivers, channels, sewer systems (1D), shallow seas, rivers, overland flow (2D), and estuaries, lakes and shelf breaks (3D). We present an outline of the numerical approach and show three 2D test cases and an application of tidal propagation on the Continental Shelf. The benefits of applying an unstructured grid were explored by creating an efficient model network that aims at keeping the number of grid cells per wavelength constant. The computational speed of our method was compared with that of WAQUA/TRIWAQ and Delft3D (the commonly used structured shallow-flow solvers in The Netherlands), and comparable performance was found.     

An accurate momentum advection scheme for a z-level coordinate models

In this paper, we focus on a conservative momentum advection discretisation in the presence of z-layers. While in the 2D case conservation of momentum is achieved automatically for an Eulerian advection scheme, special attention is required in the multi-layer case. We show here that an artificial vertical structure of the flow can be introduced solely by the presence of the z-layers, which we refer to as the staircase problem. To avoid this staircase problem, the z-layers have to be remapped in a specific way. The remapping procedure also deals with the case of an uneven number of layers adjacent to a column side, thus allowing one to simulate flooding and drying phenomena in a 3D model.     

Open Principle for Large High-Resolution Solar Telescopes

Vacuum solar telescopes solve the problem of image deterioration inside the telescope due to refractive index fluctuations of the air heated by the solar light. However, such telescopes have a practical diameter limit somewhat over 1 m. The Dutch Open Telescope (DOT) was the pioneering demonstrator of the open-telescope technology without need of vacuum, now pursued in the German GREGOR. Important ingredients for this technology are primary beam completely open to natural wind flow, stiff but still open design by principal stiff overall geometries in combination with carefully designed joints and completely open-foldable dome constructions based on tensioned strong cloth. Further developments to large sizes are made within the framework of the design study for a European Solar Telescope (EST).     

Middle Pleistocene glacial stratigraphy at Baxter Rivulet,western Tasmania,Australia

Mapping, analysis and interpretation of glacigenic sediments in the King Valley, Tasmania has led to a revision of the Pleistocene stratigraphy of Tasmania. The sediments provide evidence of a glaciation that occurred between the Middle Pleistocene Henty Glaciation and the Early Pleistocene Linda Glaciation. The Moore Glaciation is estimated, on the basis of weathering rinds, amino-acid dating and palaeomagnetism to have occurred between 400000 and 550000 yrs BP. At Baxter Rivulet, sediments of the Moore Glaciation rest unconformably on highly weathered till and weathered Ordovician limestone and are overlain by outwash gravel of the Henty Glaciation. The Moore Glaciation sediments can be divided into four formations on the basis of lithology, organic content and degree of chemical weathering. The Huxley Formation (oldest) was deposited by an ice advance of the Mt. Jukes Glacier and is overlain by the Baxter Formation. The Baxter Formation consists of a bed of organic silty sand which records a cool non-forested flora of an interstadial period. The overlying Pyramid and Moore formations are outwash gravels from the Mt. Jukes and King Valley glaciers respectively. Though deposited during the same general ice advance, these two gravels were deposited at different times and show that the glaciers of the West Coast Range had spatially differentiated responses to climatic change.     

Seismic time‐lapse effects of solution salt mining – a feasibility study

This article addresses the question whether time‐lapse seismic reflection techniques can be used to follow and quantify the effects of solution salt mining. Specifically, the production of magnesium salts as mined in the north of the Netherlands is considered. The use of seismic time‐lapse techniques to follow such a production has not previously been investigated. For hydrocarbon production and CO₂ storage, time‐lapse seismics are used to look at reservoir changes mainly caused by pressure and saturation changes in large reservoirs, while for solution mining salt is produced from caverns with a limited lateral extent, with much smaller production volumes and a fluid (brine) replacing a solid (magnesium salt). In our approach we start from the present situation of the mine and then study three different production scenarios, representing salt production both in vertical and lateral directions of the mine. The present situation and future scenarios have been transformed into subsurface models that were input to an elastic finite‐difference scheme to create synthetic seismic data. These data have been analysed and processed up to migrated seismic images, such that time‐lapse analyses of intermediate and final results could be done. From the analyses, it is found that both vertical and lateral production is visible well above the detection threshold in difference data, both at pre‐imaging and post‐imaging stages. In quantitative terms, an additional production of the mine of 6 m causes time‐shifts in the order of 2 ms (pre‐imaging) and 4 ms (post‐imaging) and amplitude changes of above 20% in the imaged sections. A laterally oriented production causes even larger amplitude changes at the edge of the cavern due to replacement of solid magnesium salt with brine introducing a large seismic contrast. Overall, our pre‐imaging and post‐imaging time‐lapse analysis indicates that the effects of solution salt mining can be observed and quantified on seismic data. The effects seem large enough to be observable in real seismic data containing noise.     

‘They are stealing my island’: Residents’ opinions on foreign investment in the residential tourism industry in Tamarin,Mauritius

The small nation of Mauritius in the Indian Ocean, once a poor sugar plantation island, has successfully diversified and expanded its economy since independence, by attracting foreign investment in manufacturing and modern service industries. Tourism is a major part of the ‘Mauritian Miracle’; in recent years residential tourism—attracting wealthy foreigners to take up semi‐permanent residence—has become a growth industry transforming coastal areas like Tamarin. Based on in‐depth interviews among 17 residents of Tamarin, this paper looks at how local people perceive the changes residential tourism is causing in the local area. It appears that while the majority is positive about economic changes like more jobs and income opportunities, and to some extent about improvements in infrastructure and services, there are growing misgivings about some of the social impacts. Notably, the increasing scarcity of land and rising house prices are making it impossible for growing numbers of local people to afford a place to live, resulting in growing squatter settlements in the area. Such growing social disparities challenge the Mauritian development model and may undermine its stability. These undesirable effects call for careful management of tourism development, incorporation of sustainability standards and attention to the position of major stakeholder groups, such as local residents.