排序方式： 共有66条查询结果，搜索用时 15 毫秒
11.
Numerical approximation based on different forms of the governing partial differential equation can lead to significantly
different results for two-phase flow in porous media. Selecting the proper primary variables is a critical step in efficiently
modeling the highly nonlinear problem of multiphase subsurface flow. A comparison of various forms of numerical approximations
for two-phase flow equations is performed in this work. Three forms of equations including the pressure-based, mixed pressure–saturation
and modified pressure–saturation are examined. Each of these three highly nonlinear formulations is approximated using finite
difference method and is linearized using both Picard and Newton–Raphson linearization approaches. Model simulations for several
test cases demonstrate that pressure based form provides better results compared to the pressure–saturation approach in terms
of CPU_time and the number of iterations. The modification of pressure–saturation approach improves accuracy of the results.
Also it is shown that the Newton–Raphson linearization approach performed better in comparison to the Picard iteration linearization
approach with the exception for in the pressure–saturation form. 相似文献
12.
Bart Christiaen Rebecca J. Bernard Behzad Mortazavi Just Cebrian Alice C. Ortmann 《Marine pollution bulletin》2014
Many studies show that seagrass δ15N ratios increase with the amount of urbanization in coastal watersheds. However, there is little information on the relationship between urbanization and seagrass δ15N ratios on a global scale. We performed a meta-analysis on seagrass samples from 79 independent locations to test if seagrass δ15N ratios correlate with patterns of population density and fertilizer use within a radius of 10–200 km around the sample locations. Our results show that seagrass δ15N ratios are more influenced by intergeneric and latitudinal differences than the degree of urbanization or the amount of fertilizer used in nearby watersheds. The positive correlation between seagrass δ15N ratios and latitude hints at an underlying pattern in discrimination or a latitudinal gradient in the 15N isotopic signature of nitrogen assimilated by the plants. The actual mechanisms responsible for the correlation between δ15N and latitude remain unknown. 相似文献
13.
14.
Hamed?KetabchiEmail author Davood?Mahmoodzadeh Behzad?Ataie-Ashtiani 《Hydrogeology Journal》2016,24(4):1045-1055
A closed-form analytical computation of groundwater travel time (GWTT) for two-layer oceanic small island aquifers is developed assuming steady-state and sharp-interface conditions. The two-layer geology impacts on the GWTT are investigated using the developed analytical solution to achieve a greater transparency of such conceptualizations. The results demonstrate that the inclusion of geologic layering leads to large changes in the GWTT. Sensitivity analyses, using specified dimensionless parameters, are employed to assess the influences of hydraulic conductivity, recharge rate, upper layer thickness, and seawater/freshwater density difference parameters, which influence the GWTT. These evaluations reveal that the GWTT is mainly influenced by the recharge rate and the upper layer thickness compared to the other influential parameters when the typical parameter ranges are considered. 相似文献
15.
GPS Solutions - Computerized tomography provides valuable information for imaging the ionospheric electron density distribution. We use a wavelet neural network with a particle swarm optimization... 相似文献
16.
Laboratory investigations have been performed on the submarine landslide generated waves by performing 120 laboratory tests. Both rigid and deforming-slide masses are considered. The effects of bed slope angle, initial submergence, slide geometry, shape and deformation on impulse wave characteristics have been inspected. Impulse wave amplitude, period, energy and nonlinearity are studied in this work. The effects of bed slope angle on energy conversion from slide into wave are also investigated. Laboratory-based prediction equations are presented for impulse wave amplitude and period in near and far-field and are successfully verified using the available data in previous laboratory and numerical works. 相似文献
17.
In this study, a scheme is presented to estimate groundwater storage variations in Iran. The variations are estimated using 11 years of Gravity Recovery and Climate Experiments (GRACE) observations from period of 2003 to April 2014 in combination with the outputs of Global Land Data Assimilation Systems (GLDAS) model including soil moisture, snow water equivalent, and total canopy water storage. To do so, the sums of GLDAS outputs are subtracted from terrestrial water storage variations determined by GRACE observations. Because of stripping errors in the GRACE data, two methodologies based on wavelet analysis and Gaussian filtering are applied to refine the GRACE data. It is shown that the wavelet approach could better localize the desired signal and increase the signal‐to‐noise ratio and thus results in more accurate estimation of groundwater storage variations. To validate the results of our procedure in estimation of ground water storage variations, they are compared with the measurements of pisometric wells data near the Urmia Lake which shows favorable agreements with our results. 相似文献
18.
Behzad Fatahi Thu Minh Le Behnam Fatahi Hadi Khabbaz 《Geotechnical and Geological Engineering》2013,31(5):1421-1435
In this study, effects of two types of geofibers, namely polypropylene and recycled carpet, on three dimensional shrinkage properties of cement treated kaolinite and bentonite clays are investigated. Cement treated clay specimens were prepared with cement contents of 5, 10, and 15 % by weight of dry soil for kaolinite samples, and 30, 40 and 50 % for bentonite samples. To investigate and understand the influence of different fiber types and contents, three different percentages of fiber content (i.e. 0.1, 0.2 and 0.5 % polypropylene fibers; and 0.5, 0.75 and 1 % carpet fibers) were adopted. The results of shrinkage tests on 126 cylindrical samples of cement treated clay with various cement and fiber contents were analysed to understand the relationships between these parameters and the shrinkage percentage of treated soil. Results of this study indicate that combination of cement and fiber is effective in reducing the volume change of clayey soils undergoing drying process. In the applied ranges of cement and fiber contents, the influence of cement addition on the shrinkage reduction is more significant than the addition of fibers for the treated kaolinite. However, addition of fibers in curtailing the shrinkage of bentonite clay is more significant than the cement addition. 相似文献
19.
Abolfazl Moradi Behzad Tokhmechi Vamegh Rasouli Mohammad Fatehi Marji 《Geotechnical and Geological Engineering》2017,35(3):1035-1050
Production of hydrocarbons from shale formations has been made possible mainly due to hydraulic fracture (HF) technology. It increases the permeability of reservoir rocks around a well by connecting fractures and improving conductivity. HF behavior especially in presence of natural fractures have recently given much attention in studies. This paper investigates HF propagation and its associated parameters in various conditions. A higher order displacement discontinuity method is used to achieve higher accuracy in the results. First, behavior of crack opening displacement (COD) of an HF i.e. HF width in various conditions is studied. COD is a key parameter in determination of an HF operation success. It is proportional to production rate of oil and gas wells and provides a path for proppant entrance into the fractures. An equation considering many important parameters, based on numerous numerical modellings of various mechanical and geometrical effects on COD is proposed with coefficient of determination and standard error of 94.35% and 4.37 × 10?4 respectively. The next part of the paper studies the HF propagation in a naturally fractured reservoir. These natural fractures alter the stress fields and hence affect the propagation of a hydraulic fracture. In fact, it is shown that in certain orientations of hydraulic fractures and natural fractures, the effect of natural fractures disappear or completely changes propagation path. Using a combination of several interaction criteria, a new modeling of HFs and NFs interaction is presented. The modellings showed that spacing and angle of intersection can significantly affect HFs propagation. The results of COD and HF propagation in presence of natural fractures may be considered in HG design and primary orientation of perforated fractures. 相似文献
20.
Behzad Amir-Faryar M. Sherif Aggour Richard H. McCuen 《Geomechanics and Geoengineering》2017,12(1):60-71
Numerous model forms have been used to predict the dynamic behaviours of soils, mainly the shear modulus and material damping. These models are used to represent normalised shear modulus reduction and material damping curves. The majority of the existing models are empirical and were proposed for specific soil types, strain ranges, etc. Some are limited to the data used in fitting, but fail to provide a good fit to other sets of data. The available model functions are not universal, which means that a model developed for one soil type may not be applicable for use with other soil types. In this paper, two universal mathematical models were proposed to predict the normalised shear modulus reduction and material damping curves. The mathematical model forms are sufficiently flexible to be widely used with different soil types. The models were evaluated using verification data of eight different soil types, i.e., data that were not used to fit the model parameters. The results indicate that the proposed model forms can accurately model the dynamic soil properties within the typical earthquake range. The advantage of developing the two universal models are two-fold, first the forms are applicable for sand, clay, and fibre-soil composite and second with further testing of soils, the model coefficients could ultimately be used to further understand the physical processes in soil behaviour, especially damping. 相似文献