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51.
Environmental flows are generally characterized by complex bed morphology and high current speeds. Such configurations favor the formation of vortex structures that strongly affect hydrody-namics and sediment transport. Large-Eddy Simulation (LES) enables investigation of the dynam-ics of the largest turbulence scales and, thanks to enhanced calculation resources, has now become applicable for simulating environmental flows. In this paper, a LES approach is developed in a CFD code (TELEMAC-3D), which was originally developed to simulate free surface flows using RANS methods. The present developments involve implementing subgrid models, boundary con-ditions and numerical schemes suitable for LES. The LES version of TELEMAC-3D was validated by comparing results on the model with experimental data for flow past a cylinder. Then, the model was applied to a test case representing flow over dunes. After validating the hydrodynamics, the model was used to assess the bottom shear stress, using both a RANS and a LES approach. Com-parison highlighted the potential contribution of LES to investigating the hydrodynamic forces acting on the bottom. 相似文献
52.
Goodarz Ahmadi 《Mathematical Geology》1981,13(1):37-52
A previously developed continuum theory of granular media is applied to the problems of densification and liquefaction of saturated sand. An expression for the free energy of saturated sand is developed. The process of densification of sand subjected to cyclic shear stress is studied and several expressions for an increase of the solid volume fraction are obtained and discussed. The problem of the initial liquefaction of saturated sand samples under cyclic shear stress is then considered and several criteria relating the shear stress amplitude, over-burden pressure, time to liquefaction, and physical properties of the sand sample are established. Some semiempirical relations for field applications are also presented. 相似文献
53.
Appropriate emergency preparedness and response rely on social, economical, cultural, and political infrastructures, which
vary widely according to the level of the development of each country. Mental health damages are among the consequences of
absence of such infrastructure, which have not been studied comprehensively till to date. In most countries, planning for
natural disasters and earthquakes has been mainly focused on physical and economical impacts; however, lessons learnt from
recent earthquakes in Iran and other countries show that psychological impacts need to be considered more seriously. The first
responder to an emergency is really the affected community, which consequently should be mentally prepared by appropriate
training programs. These should include simple psychosocial interventions developed for people with average level of education
in a way to be easily understandable and practicable. After the Bam earthquake, local community volunteers have been selected
and trained to provide post-disaster mental health services. 相似文献
54.
Experimental and analytical investigations on bearing capacity of strip footing in reinforced sand backfills and flexible retaining wall 总被引:2,自引:1,他引:1
This study focuses on the experimental and analytical investigations of small-scale physical model tests. For this purpose, a set of tests were conducted with and without reinforcement on the top of the backfill. The specimens were different in terms of parameters like the number of geotextile layers, the vertical distance between layers and the strip footing distance from the wall. Soil failure in the bearing capacity step and the backfill shear zones was analysed using particle image velocimetry methods. Bearing capacity of the strip footings was studied using analytical procedures. The results indicate that a reinforcing top zone of the flexible retaining structures may be more appropriate than unreinforced case. The ultimate bearing capacity and wall deflection can be significantly improved by increasing the number of reinforcement layers. When the three layers of reinforcement are used, there is an optimum vertical spacing of the layers at which the bearing capacity is the greatest (h/H?=?0.12, d/H?=?0.33 and u?=?B). The study shows that the analytical solution and the results from the experimental models are in good agreement. 相似文献
55.
Azadeh Ahmadi Ali Moridi Elham Kakaei Lafdani Ghasem Kianpisheh 《Journal of Earth System Science》2014,123(7):1603-1618
Many of the applied techniques in water resources management can be directly or indirectly influenced by hydro-climatology predictions. In recent decades, utilizing the large scale climate variables as predictors of hydrological phenomena and downscaling numerical weather ensemble forecasts has revolutionized the long-lead predictions. In this study, two types of rainfall prediction models are developed to predict the rainfall of the Zayandehrood dam basin located in the central part of Iran. The first seasonal model is based on large scale climate signals data around the world. In order to determine the inputs of the seasonal rainfall prediction model, the correlation coefficient analysis and the new Gamma Test (GT) method are utilized. Comparison of modelling results shows that the Gamma test method improves the Nash–Sutcliffe efficiency coefficient of modelling performance as 8% and 10% for dry and wet seasons, respectively. In this study, Support Vector Machine (SVM) model for predicting rainfall in the region has been used and its results are compared with the benchmark models such as K-nearest neighbours (KNN) and Artificial Neural Network (ANN). The results show better performance of the SVM model at testing stage. In the second model, statistical downscaling model (SDSM) as a popular downscaling tool has been used. In this model, using the outputs from GCM, the rainfall of Zayandehrood dam is projected under two climate change scenarios. Most effective variables have been identified among 26 predictor variables. Comparison of the results of the two models shows that the developed SVM model has lesser errors in monthly rainfall estimation. The results show that the rainfall in the future wet periods are more than historical values and it is lower than historical values in the dry periods. The highest monthly uncertainty of future rainfall occurs in March and the lowest in July. 相似文献
56.
Dhaou AKROUT Hassène AFFOURI Riadh AHMADI Eric MERCIER Mabrouk MONTACER 《Resource Geology》2011,61(3):270-280
This paper presents geochemical analysis of drilled cutting samples from the OMZ‐2 oil well located in southern Tunisia. A total of 35 drill‐cutting samples were analyzed for Rock‐Eval pyrolysis, total organic carbon (TOC), bitumens extraction and liquid chromatography. Most of the Ordovician, Silurian and Triassic samples contained high TOC contents, ranging from 1.00 to 4.75% with an average value of 2.07%. The amount of hydrocarbon yield (pyrolysable hydrocarbon: S2b) expelled during pyrolysis indicates a good generative potential of the source rocks. The plot of TOC versus S2b, indicates a good to very good generative potential for organic matter in the Ordovician, Silurian and Lower Triassic. However, the Upper Triassic and the Lower Jurassic samples indicate fair to good generative potential. From the Vankrevelen diagram, the organic matter in the Ordovician, Silurian and Lower Triassic samples is mainly of type II kerogen and the organic matter from the Upper Triassic and the Lower Jurassic is dominantly type III kerogen with minor contributions from Type I. The thermal maturity of the organic matter in the analyzed samples is also evaluated based on the Tmax of the S2b peak. The Ordovician and Lower Silurian formations are thermally matured. The Upper Silurian and Triassic deposits are early matured to matured. However, Jurassic formations are low in thermal maturity. The total bitumen extracts increase with depth from the interval 1800–3000 m. This enrichment indicates that the trapping in situ in the source rocks and relatively short distance vertical migration can be envisaged in the overlying reservoirs. During the vertical migration from source rocks to the reservoirs, these hydrocarbons are probably affected by natural choromatography and in lower proportion by biodegradation. 相似文献
57.
Mohammad Reza Ghorbani Ahmad Reza Ahmadi Massimo Tiepolo Antonio Langone 《Chemie der Erde / Geochemistry》2013
In the Taleghan area of Alborz mountain range, two distinct units of alkaline rocks are identified. Whole rock major and trace element data does not provide a clue as to their common or different parental melts. However, major and trace element geochemistry of their included clinopyroxene phenocrysts, combined with the whole rock data, helped to infer that two parental magmas were involved in the evolution of volcanic succession in the Taleghan area. 相似文献
58.
The structural and sedimentological study of fault-propagation folds in Southern Tunisia highlights a special geometry of the growth strata (strata deposited simultaneously with the formation or growth of a fold). This distinct geometry is visible in the uppermost growth-strata beds and consists of one flank with unconformity as opposed to the other flank with perfect conformity. This geometry can be explained by the mechanism of fault-propagation folding, with asymmetrical flank dips and hinge migration kinematics. This kinematics was originally predicted by the fault-propagation fold model, which facilitates the study of this special geometry in a narrow domain of sedimentation-to-shortening ratios. A plot projection provides a generalisation of the results of all types of fault-propagation folds by revealing the expected geometry of the growth strata. This study constitutes one of the most complete examples of kinematic model validation on a field scale. 相似文献
59.
Mahmoud Mehramuz Hossein Zomorrodian Khadijeh Ahmadi Majid Mahood 《Arabian Journal of Geosciences》2013,6(10):3853-3864
The separation of residual gravity anomaly from regional gravity has considerably been studied for many years in gravity explorations. In addition, it is considered as a critical step in gravity data inversion. Some techniques have been developed for regional–residual anomaly separation both in space and frequency domains. One of these techniques for computing the regional anomaly is nonlinear filtering. In this paper, some techniques such as low-pass filtering, Butterworth, upward continuation, and nonlinear filtering are used to on synthetic gravity data in present of random noise and noise free for the purpose of residual–regional anomaly separation. The obtained results of techniques are compared with each other. The results have shown that separation methods are so efficient where synthetic models are located in shallow depth. Moreover, it is found that in comparison with other separation techniques, nonlinear filtering is more efficient in residual–regional anomaly separation and upward continuation technique is more efficient than Butterworth filter and low-pass filter. In addition, all of the obtained results have shown that Butterworth and low-pass filters are the same. 相似文献
60.
Conditioning stochastic simulations are very important in many geostatistical applications that call for the introduction of nonlinear and multiple-point data in reservoir modeling. Here, a new methodology is proposed for the incorporation of different data types into multiple-point statistics (MPS) simulation frameworks. Unlike the previous techniques that call for an approximate forward model (filter) for integration of secondary data into geologically constructed models, the proposed approach develops an intermediate space where all the primary and secondary data are easily mapped onto. Definition of the intermediate space, as may be achieved via application of artificial intelligence tools like neural networks and fuzzy inference systems, eliminates the need for using filters as in previous techniques. The applicability of the proposed approach in conditioning MPS simulations to static and geologic data is verified by modeling a real example of discrete fracture networks using conventional well-log data. The training patterns are well reproduced in the realizations, while the model is also consistent with the map of secondary data. 相似文献