Numerical calculation for the flow of submerged bodies under a free surface

The flow field generated by a Rankine body moving under a free surface in afinite-depth water is calculated by potential theory. Velocity field generated by a source located at the origin is calculated first by using highly efficient and adaptive quadratures of the QUADPACK library. This solution is used for generating the flow around a Rankine body by locating a source and an equal strength sink along the body axis. Results agree well with the existing literature.     

A survey on semisubmersible wind loads

The methods and assumptions of calculating wind drags and overturning moments on semisubmersible offshore drilling rigs are investigated. The empirical methods and the wind tunnel testing are compared.     

Strength Behavior of Fine Grained Soil Reinforced with Randomly Distributed Polypropylene Fibers

Admixtures and reinforcement materials are frequently used in practice to stabilize coarse and fine grained soils and to improve their engineering properties. However, a limited number of studies have been carried out on fiber-reinforced fine grained soils. In this study, a series of unconfined compression tests, direct shear tests, and California Bearing Ratio tests were carried out to investigate the effect of randomly distributed polypropylene fiber on the strength behavior of a fine grained soil. The content of polypropylene fiber was varied between 0.25 and 1% by total dry weight of the reinforced samples. It was observed that unconfined compression strength, cohesion intercept and California Bearing Ratio increased with the addition of fibers. On the other hand, the results of the tests indicated that shear strength angle was not affected significantly by the fiber reinforcement.     

Verringerung der Schwermetall‐ und Sulfatbelastung in sauren bergbaubelasteten Gewässern durch Aluminiumpräzipitate

Attenuation of Heavy Metals and Sulfate by Aluminium Precipitates in Acid Mine Drainage During the mixing of acid mine waters with nearly neutral tributaries, often precipitates are formed which are high in iron or aluminium. These precipitates cover the river bed for many kilometres. Near the town of Lehesten (Thuringian slate mining area), leachates of slate quarries and waste rock dumps contain high amounts of aluminium, sulfate, copper, nickel, zinc, manganese, and H⁺ ions as a result of the oxidation of incorporated pyrite. These leachates enter the brooks Loquitz, Kleine Sormitz, and Rehbach leading to the phenomenon named above. The contribution of the forming aluminium‐rich precipitates on the attenuation of sulfate and heavy metals by sorption or coprecipitation was studied by analysing the composition of water and sediment samples as well as samples of suspended matter. Sulfate is often considered as conservative tracer in acid mine drainage. However, sulfate does not behave conservatively in this system what might be explained by the adsorption of sulfate to the aluminium precipitates. Instead, conservative behaviour was found for calcium, potassium, chloride, zinc, manganese, and nickel. A formation of jurbanite can be excluded because of the low sulfate contents. The sulfate content of the sediment depends on the pH. At low pH values (4.8) the S/Al ratio corresponds to the theoretical ratio in basaluminite and decreases with rising pH. Sulfate is weakly bound to the solid phase and can easily be replaced by OH^– ions. A formation of basaluminite is possible at low pH values with a fluent transition to aluminium hydroxide. Therefore the precipitates are assumed to consist predominantly of aluminium hydroxide with sulfate being adsorbed to the surface.     

Spatiotemporal variability of four precipitation-based drought indices in Xinjiang,China

Global increases in duration and prevalence of droughts require detailed drought characterization at various spatial and temporal scales. In this study, drought severity in Xinjiang, China was investigated between 1961 and 2012. Using meteorological data from 55 weather stations, the UNEP (1993) index (I _A), Erinç’s aridity index (I _m), and Sahin’s aridity index (I _sh) were calculated at the monthly and annual timescales and compared to the Penman-Monteith based standard precipitation evapotranspiration index (SPEI_PM). Drought spatiotemporal variability was analyzed for north (NX), south (SX), and entire Xinjiang (EX). I _m could not be calculated at 51 stations in winter as T _max was below 0. At the monthly timescale, I _A, I _m, and I _sh correlated poorly to SPEI_PM because of seasonality and temporal variability, but annual I _A, I _m, and I _sh correlated well with SPEI_PM. Annual I _A, I _m, and I _sh showed strong spatial variability. The 15 extreme droughts denoted by monthly SPEI_PM occurred in NX but out of phase in SX. Annual precipitation, maximum temperature, and relative and specific humidity increased, while air pressure and potential evapotranspiration decreased over 1961–2012. The resulting increases in the four drought indices indicated that drought severity in Xinjiang decreased, because the local climate became warmer and wetter.

     

Assessing radial transmissivity variation in heterogeneous aquifers using analytical techniques

Pumping tests are one of the most commonly used in situ testing techniques for assessing aquifer hydraulic properties. Numerous researches have been conducted to predict the effects of aquifer heterogeneity on the groundwater levels during pumping tests. The objectives of the present work were as follows: (1) to predict drawdown conditions and to estimate aquifer properties during pumping tests undertaken in radially symmetric heterogeneous aquifers, and (2) to identify a method for assessing the transmissivity field along the radial coordinate in radially symmetric and fully heterogeneous transmissivity fields. The first objective was achieved by expanding an existing analytical drawdown formulation that was valid for a radially symmetric confined aquifer with two concentric zones around the pumping well to an N concentric zone confined aquifer having a constant transmissivity value within each zone. The formulation was evaluated for aquifers with three and four concentric zones to assess the effects of the transmissivity field on the drawdown conditions. The specific conditions under which aquifer properties could be identified using traditional methods of analysis were also evaluated. The second objective was achieved by implementing the inverse solution algorithm (ISA), which was developed for petroleum reservoirs to groundwater aquifer settings. The results showed that the drawdown values are influenced by a volumetric integral of a weighting function and the transmissivity field within the cone of depression. The weighting function migrates in tandem with the expanding cone of depression. The ability of the ISA to predict radially symmetric and log‐normally distributed transmissivity fields was assessed against analytical and numerical benchmarks. The results of this investigation indicated that the ISA method is a viable technique for evaluating the radial transmissivity variations of heterogeneous aquifer settings. Copyright © 2013 John Wiley & Sons, Ltd.     

Homogeneity analysis of Turkish meteorological data set

The missing value interpolation and homogeneity analysis were performed on the meteorological data of Turkey. The data set has the observations of six variables: the maximum air temperature, the minimum air temperature, the mean air temperature, the total precipitation, the relative humidity and the local pressure of 232 stations for the period 1974–2002. The missing values on the monthly data set were estimated using two methods: the linear regression (LR) and the expectation maximization (EM) algorithm. Because of higher correlations between test and reference series, EM algorithm results were preferred. The homogeneity analysis was performed on the annual data using a relative test and four absolute homogeneity tests were used for the stations where non‐testable series were found due to the low correlation coefficients between the test and the reference series. A comparison was accomplished by the graphics where relative and absolute tests provided different outcomes. Absolute tests failed to detect the inhomogeneities in the precipitation series at the significance level 1%. Interestingly, most of the inhomogeneities detected on the temperature variables existed in the Aegean region of Turkey. It is considered that theseinhomogeneities were mostly caused by non‐natural effects such as relocation. Because of changes at topography at short distance in this region intensify non‐random characteristics of the temperature series when relocation occurs even in small distances. The marine effect, which causes artifical cooling effect due to sea breezes has important impact on temperature series and the orograhpy allows this impact go through the inner parts in this region. Copyright © 2010 John Wiley & Sons, Ltd.