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1.
This paper describes the extension of a fluid-flow simulations method to capture the free surface evolution around a full-scale Tension Leg Platform (TLP). The focus is on the prediction of the resulting hydrodynamic loading on the various elements of the TLP in turbulent flow conditions and, in particular, on quantifying the effects of the free surface distortion on this loading. The basic method uses finite-volume techniques to discretize the differential equations governing conservation of mass and momentum in three dimensions. The time-averaged forms of the equations are used, and the effects of turbulence are accounted for by using a two-equation, eddy-viscosity closure. The method is extended here via the incorporation of surface-tracking algorithm on a moving grid to predict the free-surface shape. The algorithm was checked against experimental measurements from two benchmark flows: the flow over a submerged semi-circular cylinder and the flow around a floating parabolic hull. Predictions of forces on a model TLP were then obtained both with and without allowing for the deformation of the free surface. The results suggest that the free surface effects on the hydrodynamic loads are small for the values of Froude number typically encountered in offshore engineering practice. 相似文献
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The present study is focused on examination of the physical processes of convective cell evolved from a MCS occurred on 4 November 2011 over Genoa, Italy. The Quantitative Precipitation Forecasts (QPF) have been performed using WRF v3.6 model under different configurations and cloud permitting simulations. The results indicate underestimation of the amount of precipitation and spatial displacement of the area with a peak 24-h accumulated rainfall in (mm). Our main objective in the research is to test the cloud model ability and performance in simulation of this particular case. For that purpose a set of sensitivity experiments under different model initializations and initial data have been conducted. The results also indicate that the merging process apparently alters the physical processes through low- and middle-level forcing, increasing cloud depth, and enhancing convection. The examination of the microphysical process simulated by the model indicates that dominant production terms are the accretion of rain by graupel and snow, probabilistic freezing of rain to form graupel and dry and wet growth of graupel. Experiment under WRF v3.6 model initialization has shown some advantage in simulation of the physical processes responsible for production and initiation of heavy rainfall compared to other model runs. Most of the precipitation came from ice-phase particles-via accretion processes and the graupel melting at temperature T0 ≥ 0°C. The rainfall intensity and accumulated rainfall calculated by the model closely reflect the amount of rainfall recorded. Thus, the main benefit is to better resolve convective showers or storms which, in extreme cases, can give rise to major flooding events. In such a way, this model may become major contributor to improvements in weather analysis and small-scale atmospheric predictions and early warnings of such subscale processes. 相似文献
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In order to examine the extent of the As enrichment and the factors influencing this enrichment in the groundwater of Eastern Croatia, groundwater samples were collected from 56 production wells in two counties, Osijek-Baranja and Vukovar-Srijem, suspected to be more affected. Hydrochemical analyses were performed at all locations including in situ As speciation at 32 locations. Arsenic was detected in 46 out of 56 groundwater samples with total As concentrations up to 491 μg/L. Thirty-six of the studied wells yielded groundwater with total As concentrations that exceeded the WHO Maximum Contaminant Level for arsenic in drinking water of 10 μg/L. Only inorganic As species were detected with arsenite As(III) as the predominant form. The spatial distribution of As in the groundwater was significantly linked with geological, geomorphological and hydrogeological development of the alluvial basin of the Drava and Sava rivers. The most probable groundwater As sources are deeper sediments from the Middle and Upper Pleistocene. The results obtained suggest that biogeochemical processes controlling As concentration in the groundwater are complex and location-specific. Reductive dissolution of Fe oxides, desorption of As from Fe oxides and/or clay minerals as well as competition for the sorption sites with organic matter and phosphate could be the principal mechanisms that control As mobilization. The extent of those processes vary in the different parts of the Drava and Sava depressions and could be linked to different site related parameters, such as lithology, mineralogy, local hydrology and hydrogeology; thus different processes of As mobilization have been proposed for the different types of water in relation to groundwater evolution. 相似文献
4.
Kopa?ki Rit Nature Park is part of the Danube River natural floodplain and one of the last oases of wild life in the Danube River Basin. Due to its extraordinary value, it was inscribed on the list of Wetlands of International Importance in 1993. More than 2,000 species have been registered in this area, which consists of lakes, canals, grassland, marshland and forests. Even the number of investigations which have been performed on its biological and ecological features, hydrological and water resources characteristics, as a prerequisite for ecohydrological analyses, are still rather unknown in the scientific community. Mainly the Danube River and partly the River Drava cause flooding of Kopa?ki Rit and inundations enter the area from both the northern and southern parts. Results of hydrological and meteorological analysis show a decreasing trend of both mean and minimum, annual water levels in the Rivers Drava and Danube (respectively 1.8 and 1.38 cm/year). These reductions in water level can reduce the replenishment periods of Kopa?ki Rit Nature Park. In addition, a significant rise of mean annual air temperature and consequently water temperature (data 1988–2011) may be causing increasing evapotranspiration and loss of water within Kopa?ki Rit. But an encouraging counteracting finding is that, the results of frequency analysis show, even a discharge of 5-years’ return period on the River Danube inundates 70 % of the Danube floodplain and Kopa?ki Rit Nature Park. 相似文献
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A case study was carried out in 2000 in the shallow coastal area of the Northern Adriatic Sea (Gulf of Trieste) where untreated domestic sewage and industrial wastes are discharged at rate of 5500 m3·day?1. The sewage plume above the outfall was followed using faecal coliforms (FC) and overturning length scale (lT). The latter was rejected as a marker as the discharge conditions prohibit following the turbulence of sewage water. Intermittent sewage discharge is reflected in the minimal effect of eutrophication. Increase of phytoplankton biomass is thus only minor compared with the unpolluted area regardless of elevated concentrations of sewage‐derived nutrients (confirmed by correlation coefficients between FC and NH4+, TP, PO43?: 0.78, 0.71 and 0.67, respectively). Deteriorated trophic status, determined by the TRIX index, was observed only in the surface layer (average TRIX: 5.67). High FC content well above the regulation limit (up to 2.6 × 105 FC·100 ml?1) represents, therefore, the major negative impact of the improperly treated waste for the risk to human health. 相似文献
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锦州东港电力有限公司矿泉水水源地位于辽西中部断陷盆地锦州盆地的北端。地处中新生代上侏罗统及白垩系构成的对称向斜,NNE新华夏系断裂构造经由锦州盆地通过。工作区第四系覆盖6-14m,下伏孙家湾组(K2S)砂质泥岩、砂砾岩和义县组(K1y)火山碎屑岩、英安岩、安山岩及火山凝灰角砾岩。对该区进行地质水文资料综合分析的基础上,采用电阻率联合剖面、高密度电阻率法、电测深(电阻率、衰减时及极化率)多种物探电法综合勘查,确定断裂构造位置、产状及赋水性。经验证获得涌水量312t/d具有商业价值的矿泉水水源地。这一工作方法在辽西火山岩贫水区进行水资源勘查具有推广意义。 相似文献
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This study presents results of the first comprehensive research on ecotoxic trace metals (Cd, Pb, Cu and Zn) in aquatic anchialine ecosystems. Data show the influence of hydrological and geological characteristics on trace metals in highly stratified anchialine water columns. 相似文献
9.
Stanislav Frančišković-Bilinski Vlado Cuculić Halka Bilinski Hermann Häusler Philipp Stadler 《Chemie der Erde / Geochemistry》2013
Complementary geochemical and stable isotope investigations of the Gorski Kotar karst aquifer system in western Croatia were obtained for the first time, to answer the question whether both studied rivers drain the same aquifer system or not. The two main rivers, the Kupa and the Rje?ina, rise under the same mountain range, but belong to two different watersheds (Black Sea and Adriatic Sea). The karst aquifer of Gorski Kotar is a potentially important source of drinking water for two neighboring countries, Croatia and Slovenia (Central and South Europe), and is strongly influenced by both Mediterranean and continental weather conditions. It is a part of the Dinaric karst, which is “locus typicus” for karst worldwide and one of the most typical karst areas in the world. 相似文献
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Marijan Herak Ivo Allegretti Davorka Herak Krešimir Kuk Vlado Kuk Krešimir Marić Snježana Markušić Josip Stipčević 《Bulletin of Earthquake Engineering》2010,8(3):483-499
Horizontal-to-vertical spectral ratios (HVSR) of ambient vibrations measured in the ancient town of Ston (Croatia) on 99 locations, are shown to be well matched to the theoretical ones computed for body-waves as well as for the surface waves. This match is poorer for sites on the slopes of nearby hills. The ratios of measured peak horizontal ground acceleration during the damaging earthquake in 1996 (M L = 6.0) and the ones obtained using empirical attenuation laws is approximately equal to the mapped value of the dynamic amplification factor determined on the basis of observed HVSR in the vicinity of the accelerometric station. The HVSR of the accelerogram is very similar to the HVSR of the ambient noise. The damage to the building stock in the old town centre caused by the earthquake series of 1996 is closely related to the estimated soil amplification and its fundamental frequency. More measurements in buildings are needed to arrive at confident conclusions about possible soil-structure resonance. 相似文献