Sharif Digital Repository

In this study a new SPH model for solving free surface and fluid-fluid interaction problems is presented. The numerical model is capable of simulating two dimensional hydraulic problems with arbitrary boundary and initial conditions and large number of particles. It has the ability to model multi-fluids domain with different densities and viscosities. Several corrections are implemented in SPH formulation such as treatment of free surface and correction of viscous term in order to conserve the angular momentum. Several examples are conducted in fluid-fluid domains to measure the capability of model in this area of study. This new model use Incompressible SPH method for more accurate... 

Groundwater in coastal aquifers is one of the essential resources of freshwater in coastal regions, where are heavily populated or industrialized areas, and have critical ecosystems.The management of these resources is a priority to preserve groundwater from serious natural and human-induced threats such as salinization caused by seawater intrusion. The combined simulation-optimization techniques can be used for this purpose in determining optimal planning and management strategies. The implementation of such techniques for complex real-world and large -scale problems has major difficulties in terms of both computational efficiency (solution quality and required computational time) and... 

Approximately, 60 percent of the world's populations are living at the distance of 60 kilometers of the coasts. In coastal zones, coastal aquifers are the most important resources of the available freshwater while expected that the short-term or long-term impacts of the climate changes threat such aquifers. In general, it is predicted that climate changes e.g. sea-level rise (SLR) cause to increase seawater intrusion (SWI) in the coastal aquifers. In this study, both continental and island coastal aquifers are considered. The objective of this research is the investigation of SWI behavior occurred in the coastal aquifers due to climatic change parameters and aquifer properties. For... 

Groundwater is the most important freshwater resource in the coastal zones. There are some factors contaminate fresh groundwaters. Sea water intrusion (SWI) is one of the most important components of groundwater salinization. Also Submarine groundwater discharge (SGD) occurs when hydraulic gradient is from landside to seaside in coastal aquifers. There are many factors intensify SWI and SGD. In this research at the first part, coastline shape effect on SWI and SGD is investigated. For to this 4 different aquifers with different coastline shapes as stepped coastline, vertical coastline, steep slope coastline, and mild slope coastline are simulated with the same hydraulic parameters and... 

In this study a locally mass conservative finite volume method (FVM) is employed to simulate the coupled model of flow and geomechanics for the land subsidence problem. At the first step, a FV numerical method is implemented to solve a Biot consolidation model with discontinuous coefficients one dimensionally. The studies show that the FV scheme leads to a locally mass conservative approach which removes pressure oscillations especially along the interface between materials with different properties and yields higher accuracy for the flow and mechanics parameters. Then this numerical discretization is utilized to investigate different sequential strategies with various degrees of coupling... 

Groundwater resources in arid and semi-arid regions, which the most parts of them have not had enough surface water, is of great importance. Due to the paramount importance of these vital resources, many scholars have conducted various studies on groundwater contamination and, especially, on nitrate as the best indicator of groundwater contamination because of its ability to transport, its low absorption, and its durability in water. In this study, using qualitative methods, groundwater contamination of Mashhad aquifer was evaluated, and then in order to obtain better adjustment with urban areas, these methods were modified which resulted in better correlation with measured nitrat. Based on... 

In many countries of the world, especially dry and semi-arid areas, coastal aquifers are used to provide fresh water. Many of these areas have also become urbanaized, which has made the need for freshwater more important. Seawater Intrusion (SWI) is the greatest limitation that influences the exploitation of groundwater in coastal aquifers, where with SWI, the amount of freshwater supply and other existing pumping wells are not used. The present study attempts to model SWI in karst and fractured coastal aquifers. For this purpose, two models with Discrete Fracture/Conduit Network approach in Fortran and also in COMSOL Multiphysics software have been developed to study the density-variable... 

The goal of this study is to explore the density-driven flow and study the effect of fracture as well as chemical processes and reactions on convective transport. Convective flow is used in connection with the density-driven flow where the flow is driven by density differences in the fluid, which can be affected by the ambient rocks. Several studies of density-driven flow in porous media have focused on the effect of heterogeneity on the mixing convection; however, they neglect the key processes of geochemical reactions in fractured porous media. This study aims to address this gap by investigating the combined effect of heterogeneity (as fractures) and the existing geochemical reactions on... 

Lake Urmia water level fell dramatically from 2006 to 2014. Since then the declining trend of water level has stopped but the lake has remained in a critical situation. Moreover, Lake Urmia became supersaturated with total salinity averaging more than 350 g/l. Salt precipitation and dissolved materials brought by inflowing rivers have formed a layer of sediment with low hydraulic conductivity on the lakebed. We conducted a series of numerical simulation scenarios to study the groundwater flow pattern in the vicinity of the hypersaline Lake Urmia using COMSOL Multiphysics®. In the first step, we performed the simulations in steady-state conditions. Secondly, we simulated the lake level fall... 

The goal of this research is to investigate the phenomenon of saltwater up-coning into pumping wells in fractured porous media. For this aim, two series of regular orthogonal fracture networks and different vertical and horizontal fracture apertures are simulated using an axisymmetric (2D vertical cross-section) model with a sharp interface approach. The effect of changing the pumping rate and the hydraulic conductivity has been examined to recognize other effective characteristics of the aquifer and pumping well on the saltwater up-coning. These simulations have been performed in COMSOL Multiphysics. The results indicate that the saltwater extent under the pumping well can be affected... 

Quantitative estimation of baseflow is necessary for hydrological modeling of a watershed, ground-surface water interaction, water supply reliability, and vulnerability, especially during a dry period, and answering questions pertaining to the responses of human-based activities on natural ecosystems. Extensive research effort spanning more than 50 years provided collections of field, manual, and computer-based methods for baseflow separation study. In this study, a comprehensive review is carried out on the nine digital filters, six graphical methods, four tracer-mass-balance methods, fourteen recession analysis methods, and two frequency analysis methods. Sensitivity analyses of baseflow... 

Digital Elevation Models (DEM) is a crucial element of hydraulic models, including floods. Due to the lack of high-precision topographic data, including ground-based mapping hydraulic modeling is challenging. In recent years, remote sensing data, extensively used by many researchers in hydraulic modeling due to global coverage and free access. One of the most critical questions in hydraulic modeling is the efficiency of these DEMs in flood simulation. This research focused on using remote-sensing-based DEMs, such as SRTM-30m and 90m, ASTER-30m, and ALOS-12.5m DEMs, on the performance of the HEC-RAS-2D model in the Gorganrood river.The results showed that ALOS and SRTM-30m DEMs' accuracy and... 

Lake Urmia located in the NW of Iran, has lost 96 percent of its volume in 20 years and become a national crisis. During this shrinkage, the lake level has fallen by 8 m, and its concentration has increased up to 380 g/l. Regarding the vast area Lake Urmia basin is covered, the hydrological characteristics of the basin varies a lot, which affects the aquifers response to the seawater intrusion. In order to study the seawater intrusion in the lake’s aquifer, 18 cases with different hydraulic gradients, hydraulic conductivities and bathymetries were defined. All of these cases were run under three different scenarios in sequence. First, steady state scenario is preformed, then the lake level... 

Having information about the amount of water storage is essential to estimate the amount of water available for use in agriculture, industrial, etc. The purpose of this study is to propose a method for estimating the water budget in large-scale basins using remote sensing data. Using ground-based measurements to obtain water budget components is a challenging issue. This may be due to the limited access to in-site data in temporal and spatial resolution, especially in large scale basins. In recent years, with the increasing growth of satellite data, the application of remotely sensed data to estimate changes in water storage is increasing. In this study, due to the limitation of access to... 

Dense non-aqueous phase liquid accounts for a large share of groundwater pollution. In oil-rich countries, including Iran, the emission of this type of pollutant is mainly through leakage from concrete and steel tanks belonging to refineries and gas stations. The dissolution of these pollutants in groundwater and the vapor intrusion into residential homes increased the importance of developing efficient treatment methods. To choose the best method, it is necessary to gain sufficient knowledge of how these types of contaminants are distributed in the subsurface and how contaminants change and move over time. Heterogeneity, especially in the form of fracture, is one of the challenges to... 

Within the past few years, soil and groundwater resources contamination by petroleum-based products has become of great concern in the environmental engineering literature as a serious environmental problem throughout the world. Amongst petroleum hydrocarbons, groundwater contamination by Non-Aqueous Phase Liquids (NAPLs) is one of the most important environmental problems. In order to effectively remediate contaminated sites, knowledge of the distribution of the NAPLs is essential. The success of the remedial design will be dependent on the ability to predict the subsurface distribution of the NAPLs. Release of these compounds from spills and leaky underground storage tanks into subsurface... 

Local scour around bridge piers is one of the main causes of bridge failures Application of existing equations to complex flow patterns is problematic and often leads to questionable results in the field applications. A lack of understanding of the complex flow field and erosion mechanisms seems to be at least partly responsible for this state. Despite the rapid expansion of the literature on the flow around cylindrical piers, there are still challenges for flow field comprehension and estimating design scour depths around complex bridge piers. Due to geotechnical and economical reasons, bridge designs often leads to a complex foundation. Laboratory studies of local scour around complex... 

The occurrence and development of scour hole around bridge pier are the main causes of bridge destruction. To predict manner, occurrence, development and final situation of scour hole around pier is the most important in the hydraulic design of bridges. A large number of studies have been performed to estimate the scour depth around piers at simplified laboratory conditions. The available equations from these studies do partly not present acceptable solutions. This issue is especially of great importance to the pile groups. For accurate determination of scour depth, it is required to get a better understanding of the flow and governing mechanism around pier. Although the flow pattern... 

Potential landslides located in the borders of each water body may generate massive and destructive impulsive waves called landslide-generated waves (LGWs) which can be a major threat to human life and his possessions, offshore and coastal installations, dam bodies and hydraulic structures. This research is devoted to numerical modeling of LGW hazards with focus on the impulse wave generation stage including landslide movement, landslide/water surface interactions and consequent tsunami generation. The main purpose of this work is to study the effects of landslide deformability on the impulsive wave characteristics numerically in an introduced state-of-the-art numerical structure. The... 

Landslide is a natural hazard associated with economic losses and fatalities. The geometric of the slope, the soil properties, hydrological factors, and groundwater are important factors that affect the stability of a slope. The landslide investigation is important due to the identification and prevention of damages. Thus, more researchers studies on this subject. The new questions in this field are “how can simulate the vegetation effects in slope stability analysis?” and “what effects do precipitation and infiltration have on landslide triggering?”. Although the classic methods of slope stability analysis provide the initial information for the design, they have limitations in answering...