On the assimilation of Martian total ozone retrievals

The technique of data assimilation gives us an opportunity to further our understanding of important photochemical processes in the Martian atmosphere, through the creation of a reanalysis product that can be used to investigate the temporal and spatial agreement between model and observations and determine any possible causes of identified differences. In this study [1], we have assimilated, for the first time, total ozone retrievals into a Mars Global Circulation model (GCM) to study the ozone cycle

Pesticide policies, practices and initiatives - can the UK’s know-how be transferred to Chile?

Non peer reviewedFinal Accepted Versio

Efficient computation of steady, 3D water-wave patterns

Numerical methods for the computation of stationary free surfaces is the subject of much current research in computational engineering. The present report is directed towards free surfaces in maritime engineering. Of interest here are the long steady waves generated by ships, the gravity waves. In the present report an existing 2D iterative method for the computation of stationary gravity-wave solutions is extended to 3D, numerically investigated, and improved. The method employs the so-called quasi free-surface boudary condition. As test cases we cosider gravity-wave patterns due to pressure perturbations imposed at the free surface of a steady, uniform horizontal flow. The effects are studied of the distance of the imposed pressure distribution to the far-field boundary, the magnitude of the imposed pressure perturbation, and the mesh widths. In all experiments, our focus is on the convergence behavior of the free-surface iteration process

Tidal energy leasing and tidal phasing

In addition to technical and economic constraints, tidal energy leasing is generally governed by demand for sites which contain the highest tidal streams, and does not take into account the phase relationship (i.e. the time lag) between sites. Here, the outputs of a three-dimensional tidal model are analysed to demonstrate that there is minimal phase diversity among the high tidal stream regions of the NW European shelf seas. It is therefore possible, under the current leasing system, that the electricity produced by the first generation of tidal stream arrays will similarly be in phase. Extending the analysis to lower tidal stream regions, we demonstrate that these lower energy sites offer more potential for phase diversity, with a mean phase difference of 1.25 h, compared to the phase of high energy sites, and hence more scope for supplying firm power to the electricity grid. We therefore suggest that a state-led leasing strategy, favouring the development of sites which are complementary in phase, and not simply sites which experience the highest current speeds, would encourage a sustainable tidal energy industry

Efficient computation of steady, 3D water-wave patterns, application to hovercraft-type flows

Numerical methods for the computation of stationary free surfaces is the subject of much current research in computational engineering. The present report is directed towards free surfaces in maritime engineering. Of interest here are the long steady waves generated by hovercraft and ships, the gravity waves. In the present report an existing 2D iterative method for the computation of stationary gravity-wave solutions is extended to 3D, numerically investigated, and improved. The method employs the so-called quasi free-surface boundary condition. As test cases we consider gravity-wave patterns due to hovercraft-type pressure perturbations imposed at the free surface of a steady, uniform horizontal flow. The effects are studied of the distance of the imposed pressure distribution to the far-field boundary, the magnitude of the imposed pressure perturbation, the mesh widths, as well as the presence of a no-slip boundary intersecting the free surface. In all experiments, our focus is on the convergence behavior of the free-surface iteration process

Commercial Light Water Reactor Tritium Extraction Facility Geotechnical Summary Report

A geotechnical investigation program has been completed for the Circulating Light Water Reactor - Tritium Extraction Facility (CLWR-TEF) at the Savannah River Site (SRS). The program consisted of reviewing previous geotechnical and geologic data and reports, performing subsurface field exploration, field and laboratory testing and geologic and engineering analyses. The purpose of this investigation was to characterize the subsurface conditions for the CLWR-TEF in terms of subsurface stratigraphy and engineering properties for design and to perform selected engineering analyses. The objectives of the evaluation were to establish site-specific geologic conditions, obtain representative engineering properties of the subsurface and potential fill materials, evaluate the lateral and vertical extent of any soft zones encountered, and perform engineering analyses for slope stability, bearing capacity and settlement, and liquefaction potential. In addition, provide general recommendations for construction and earthwork

Realistic wave conditions and their influence on quantifying the tidal stream energy resource

AbstractWhen selecting suitable sites for tidal stream energy arrays a wide range of factors must be considered, from the magnitude of the tidal stream resource, to realistic oceanographic conditions. Previous computational and laboratory-scale investigations into the impact of waves upon tidal turbines (such as turbine blade loadings) and turbine arrays (such as array configuration) typically assume that waves propagate “inline” to the tidal current (waves following or waves opposing the tidal current with a 20° tolerance limit). We investigated the wave climate at typical tidal stream energy sites across the British Isles. The wave climate was simulated at 18 sites using a 7-year (2005–2011) SWAN wave model simulation of the northwest European shelf seas. The principal semi-diurnal lunar constituent (M2) was also estimated at these sites using the three-dimensional ROMS tidal model. A significant proportion of the wave climate (between 49% and 93% of the time), including extreme wave events (>10m wave heights), was found to be propagating in a direction which was “oblique” to the major axis of tidal flow (i.e. waves which propagate at an angle to the tidal current with a 20° tolerance limit) at all 18 selected sites. Furthermore, the average “inline” wave climate was 2.25m less in height and 2s less in wave period in comparison to the oblique wave climate. To understand the direct effect of waves upon the tidal stream resource, the dynamically wave-tide coupled COAWST modelling system was applied to an idealized headland case study, which represented the typical tide and wave conditions expected at first generation tidal stream energy sites. Waves were found to alter the simulated tidal velocity profile, which, because tidal stream power is proportional to velocity cubed, reduced the theoretical resource by 10% for every metre increase in wave height (R2 94% with 22 degrees of freedom) – depending upon wave period and direction. Our research indicates that wave angle should be considered when quantifying the impact of waves upon tidal turbines, such as computational fluid dynamic (CFD) studies, or laboratory-scale experiments of wake characteristics and turbine fatigue loading. Further, dynamically coupled tide-wave models may be necessary for a thorough resource assessment, since the complex wave-tide interaction affected the tidal resource; however, in situ observations of tidal velocity profiles during a range of wave events will be essential in validating such modelling approaches in the future

Manure and sorbent fertilisers increase on-going nutrient availability relative to conventional fertilisers

The key to better nutrient efficiency is to simultaneously improve uptake and decrease losses. This study sought to achieve this balance using sorbent additions and manure nutrients (spent poultry litter; SL) compared with results obtained using conventional sources (Conv; urea nitrogen, N; and phosphate–phosphorus; P). Two experiments were conducted. Firstly, a phosphorus pot trial involving two soils (sandy and clay) based on a factorial design (Digitaria eriantha/Pennisetum clandestinum). Subsequently, a factorial N and P field trial was conducted on the clay soil (D. eriantha/Lolium rigidum). In the pot trial, sorbent additions (26.2 g of hydrotalcite [HT] g P− 1) to the Conv treatment deferred P availability (both soils) as did SL in the sandy soil. In this soil, P delivery by the Conv treatments declined rapidly, and began to fall behind the HT and SL treatments. Addition of HT increased post-trial Colwell P. In the field trial low HT-rates (3.75 and 7.5 g of HT g P− 1) plus bentonite, allowed dry matter production and nutrient uptake to match that of Conv treatments, and increased residual mineral-N. The SL treatments performed similarly to (or better than) Conv treatments regarding nutrient uptake. With successive application, HT forms may provide better supply profiles than Conv treatments. Our findings, combined with previous studies, suggest it is possible to use manures and ion-exchangers to match conventional N and P source productivity with lower risk of nutrient losses