Estimation of hydrodynamic coefficients for flow around cylinders in side-by-side arrangement with variation in separation gap

A finite-volume method (FVM) using a multi-block grid technique has been applied to investigate the hydrodynamic coefficients and to categorize the two-dimensional flow pattern around a pair of adjacent cylinders (known here after as double cylinders). Matching grids were used at the interface between blocks (cylinders), and the boundary conditions are imposed around the periphery to exchange physical values across the interface. To validate the developed numerical method, a case with laminar viscous flow around a single cylinder was carried out, the results showed good agreement compared to previously published data. Hydrodynamic coefficients, Strouhal number, and stagnation point change were thoroughly investigated as a function of the separation between the two cylinders. It is found that the changes of hydrodynamic coefficients due to variations in separation are well characterized by the five different vortex flow patterns, which can also be used to explain the flow and vortex pattern around the double cylinders.     

Near infrared coronal line emission in Nova Herculis 1991

Near infrared coronal line emission at 1.98 ± 0.02Μm due to [Si VI] detected in the spectrum of Nova Herculis 1991 about 17 days after optical maximum is reported. The early appearance of coronal emission is yet another unusual feature of this fast nova in which early onset of dust formation processes and X-ray detection five days after outburst have already been reported. The coronal line observations reported here are consistent with X-ray detection and support a hot shocked circumstellar envelope at the periphery of the dust formation zone in the nova.     

A high speed photometer in the optical region for lunar occultation studies

High speed photometry during the lunar occultation of a stellar system provides an effective means of achieving high angular resolution in one dimension at the sub arc second level which is well suited for resolving close binary projected separations in the range of 10–100 milliarc seconds. An optical fast photometer designed for such a purpose is described and some results from the initial observations taken with the system including the resolution of a projected separation of 55 milli arcsecond in one binary system are detailed.     

Resolution issues in numerical models of oceanic and coastal circulation

The baroclinic and barotropic properties of ocean processes vary on many scales. These scales are determined by various factors such as the variations in coastline and bottom topography, the forcing meteorology, the latitudinal dependence of the Coriolis force, and the Rossby radius of deformation among others. In this paper we attempt to qualify and quantify scales of these processes, with particular attention to the horizontal resolution necessary to accurately reproduce physical processes in numerical ocean models. We also discuss approaches taken in nesting or down-scaling from global/basin-scale models to regional-scale or shelf-scale models. Finally we offer comments on how vertical resolution affects the representation of stratification in these numerical models.     

Analysis of karst hydrodynamics through comparison of dissolved and suspended solids' transport

In karst systems, rain events often result in a decrease of the conductivity (a tracer of dissolved phase transport) and an increase in turbidity (a tracer of suspended solids transport) at wells and springs. This study shows that the comparison of suspended solids and solute transport by the coupled approach of $T\text{–}C$ curves (Turbidity–Conductivity) and autocorrelations gives evidence of the transport processes in the karst network and allows understanding the karst hydrodynamics. To cite this article: D. Valdes et al., C. R. Geoscience 337 (2005).     

Effects of Spectral Nudging on Oceanic States in a Coarse-Resolution Model

A 1-degree global model is used to investigate the skill of spectral nudging at coarse resolution by performing two numerical experiments, one with spectral nudging and the other without. In the spectral nudging experiment, the model temperature and salinity are nudged to an observed climatological monthly-mean field. The study compares the model mean state, as well as the interannual and decadal variability of oceanic quantities with observations, (e.g., sea surface height (SSH) and sea surface temperature (SST)). Spectral nudging is found to be effective in constraining model drift from the observed mean state of temperature and salinity in the global ocean, which has been reported in previous studies. The present study further shows that spectral nudging significantly improves the model skill of topostrophy (a measure of currents flowing along the topography) in water depth below 2000?m with no clear improvement elsewhere. Despite its known ability to damp oceanic variability at various time scales, spectral nudging can still represent the interannual and decadal variability of SSH and SST well, to a degree comparable to the other experiment.     

Wind-Flow Dynamics Over a Vineyard

Wind-flow dynamics has been extensively studied over horizontally uniform canopies, but agricultural plantations structured in rows such as vineyards have received less attention. Here, the wind flow over a vineyard is studied in neutral stratification from both large-eddy simulation (LES) and in situ measurements. The impact of row structure on the wind dynamics is investigated over a range of wind directions from cross-row to down-row, and a typical range of row aspect ratio (row separation/height ratio). It is shown that the mean flow over a vineyard is similar to that observed in uniform canopies, especially for wind directions from cross-row to diagonal. For down-row winds, the mean flow exhibits noticeable spatial variability across each elementary row-gap pattern, as the wind is channeled in the inter-row. This spatial variability increases with the aspect ratio. With down-row winds the turbulent structures are also more intermittent and generate larger turbulent kinetic energy and momentum flux. The displacement height and roughness length of the vineyard vary with the aspect ratio in a way similar to their variation with canopy density in uniform canopies. Both parameters take smaller values in down-row wind flow, for which the canopy appears more open. The analysis of velocity spectra and autocorrelation functions shows that vineyard canopies share similar features to uniform canopies in terms of turbulent coherent structures, with only minor changes with wind direction.     

The Social Nature of Participatory Ecological Monitoring

Participatory ecological monitoring brings together conservationists and members of the public to collect data about changes in nature. This article scrutinizes the “social nature” of such monitoring, considering not only its impacts for nature, but also society, and importantly the ways in which these interact. Drawing on the field of nature–society studies we present a framework with which to explore case studies from the community forests of Nepal. We document the importance of multiple knowledges of nature, including what is referred to as “local monitoring” and its relation to the scientific procedures promoted in participatory monitoring; the consequences of participatory monitoring as a situated and embodied practice, such that it may (re)produce social inequalities; and the place of monitoring within the wider socioecological regime, with regard to possible unintended consequences for both nature and society. This article thus expands our understanding of the complexities of this increasingly popular approach to conservation.