Sharif Digital Repository

This paper represents a numerical study on the effects of landslide initial submergence and its geotechnical and rheological properties on the characteristics of landslide-generated waves (LGWs) and landslide deformation. A number of 117 numerical experiments are performed using a two-layer Coulomb Mixture Flow (2LCMFlow) model on a real-sized numerical flume as a simplified cross section of the Maku dam reservoir, located in the Northwest of Iran. Three different initial locations are considered for landslide representing a subaerial (SAL), a semi-submerged (SSL), and a submarine (SML) landslide. Based on the numerical results, the majority of SMLs and in some cases SSLs generate tsunami... 

Seismic analysis of complex structures such as concrete dams has been the subject of numerous studies. One of the challenges in seismic analysis of such systems is proper modelling of massed foundation. Since concrete dams’ foundations are usually layered, this makes the homogenous half-space assumption relatively unrealistic. In this paper, the effects of massed layered foundation on seismic response of concrete gravity dams in dam-reservoir-foundation systems are investigated. Seismic finite element analysis of the system carried out using domain reduction method. This approach is compared with another available method named, free-field column. First set of analysis considers the effect of... 

One of the main concerns in using commercial software for finite element analyses of dam-foundation-reservoir systems is that the simplifying assumptions of the massless foundation are unreliable. In this study, an appropriate direct finite element method is introduced for simulating the mass, radiation damping and wave propagation effect in foundations of dam-foundation-reservoir systems using commercial software ABAQUS. The free-field boundary condition is used for modeling the semi-infinite foundation and radiation damping, which is not a built-in boundary condition in most of the available commercial software for finite element analysis of structures such as ANSYS or ABAQUS and thus... 

Seismic analysis of complex structures such as concrete dams has been the subject of numerous studies. One of the challenges in seismic analysis of such systems is proper modelling of massed foundation. Since concrete dams’ foundations are usually layered, this makes the homogenous half-space assumption relatively unrealistic. In this paper, the effects of massed layered foundation on seismic response of concrete gravity dams in dam-reservoir-foundation systems are investigated. Seismic finite element analysis of the system carried out using domain reduction method. This approach is compared with another available method named, free-field column. First set of analysis considers the effect of... 

Capillary imbibition is an important recovery mechanism in naturally fractured reservoirs when water-filled fractures surround water-wet matrix blocks. A large amount of studies of imbibition process is simply total or partial immersion of nonwetting phase saturated rock in aqueous wetting phase. However, water advance in fractures during water flooding or water encroachment from an active aquifer introduces time dependent boundary conditions where invariant exposure of rock surface to water is not representative. In this work, a laboratory simulated matrix-fracture system was used to investigate different aspects of imbibition in the presence of fracture fluid flow (namely dynamic... 

By reducing the exploration of new oil reservoirs, enhanced oil recovery from previous oil reservoirs is a solution to supply energy demand. In order to develop the production, various technologies and methods have been proposed such as steaming, direct heating, flooding by nano-fluid, chemical injection, polymer injection and etc. In the present study, nanofluid flooding has been attempted on a rock reservoir with incomplete cone geometry and its performance has been evaluated on oil recovery. The porous media is considered heterogeneous in simulation in accordance with oil reservoirs. The heterogeneous geometry considered in this study is incomplete cone that is heterogeneous in a random... 

In this study, flooding of oil reservoir by implementing Nanoscale colloidal solutions as a working fluid is simulated. All oil reservoirs are heterogeneous porous media; therefore, in this investigation for more accurate prediction of the problem, the porous media is considered heterogeneous. The governing equations of this problem are solved by finite element method (FEM). Moreover two-phase equations of Darcy and mass transfer equations are used. In this paper, the effect of temperature and volume fractions of nanoparticles on the rate of oil recovery is investigated. The SiO2, Al2O3, and CuO nanoparticles are used in the enhanced oil recovery (EOR) process. Also, in order to solve the... 

Engineered water (EW) flooding is one of the enhanced oil recovery (EOR) techniques in carbonate reservoirs. In this method, the wettability of reservoir rock is altered by controlling the amount of various ions in the injected brine. The thermodynamics of wettability is related to the surface interactions and stability of water film on a rock surface. It can be identified by calculating disjoining pressure isotherms. In this study, core flooding tests, contact angle and zeta potential measurements along with the disjoining pressure isotherm calculation by the DLVO theory were used to investigate the wettability alteration of dolomite rock. Four brines include reservoir formation water... 

Petroleum industry is moving toward enhancing oil recovery methods, especially water-based methods, including low salinity and smart water flooding which water with an optimized composition is injected into the reservoir for improving oil recovery. Injection of water into the target formation is also a common operation in geothermal energy production. As the water is being injected into the reservoir, pressure and temperature change along the well column and cause scale formation. Mineral scale precipitation and deposition is a common problem for water injection wells which reduces the effective radius of the wellbore and affects the injection efficiency. In this paper, modeling scale... 

The chemical, thermal, and mechanical degradation of polymer chains under high salinity, temperature, and shear rates in oil reservoirs are the current challenges of the polymer flooding process. To answer such a complex requirement, recently, acrylamide (AM)-based thermoassociating graft copolymers (TAP) were synthesized that presented excellent performance as a viscosity enhancer, especially under high temperature and salinity conditions. The purpose of this study was to further investigate the effect of salinity, shear rate, mechanical strength, and adsorption of these TAPs on viscosity-enhancing performance at different temperatures. Finally, the performance of the TAPs was studied in... 

Air-water two-phase flow usually occurs during a sudden rise in water level at a tunnel or during the falling of the water level at an upstream reservoir while entering the conduit. When this happens, different flow patterns are generated, due to the hydraulics of flow and fluid properties. An analytical/numerical model, based on the assumption of a rigid incompressible water column and a compressible air bubble, is derived, to simulate pressure fluctuation, void fraction, air/water flow rate and water velocity in a closed conduit, including water depth at the upper reservoir, due to air bubbles becoming trapped in the water, for the highest possible number of flow patterns. It is a... 

In this paper, different injectivity scenarios were experimentally investigated in a coreflooding system to observe the efficiency of each method in laboratory conditions. Surfactant flooding, CO2 injection, carbonated water injection (CWI), active carbonated water injection (ACWI), after water flooding were investigated through the coreflooding system. First, it is necessary to optimize the surfactant concentration and then use it in ACWI injection. To do this, linear alkylbenzene sulfonic acid (LABSA) was used as a cationic surfactant at different concentrations. It was observed that 0.6 PV concentration of LABSA had an optimum result as increasing the surfactant concentration would not be... 

Seismic modeling of massive structures requires special caution, as wave propagation effects significantly affect the responses. This becomes more crucial when the path-dependent behavior of the material is considered. The coexistence of these conditions renders numerical earthquake analysis of concrete dams challenging. Herein, a finite element model for a comprehensive nonlinear seismic simulation of concrete gravity dams, including realistic soil-structure interactions, is introduced. A semi-infinite medium is formulated based on the domain reduction method in conjunction with standard viscous boundaries. Accurate representation of radiation damping in a half-space medium and wave... 

Real-time measurement of soil water pressure has been recognized as an essential part of investigating water ow in unsaturated soils. Tensiometry, amongst di erent measuring techniques, is a common method for direct evaluation of water pressure. However, the lower limit of measurable water pressure by a conventional tensiometer becomes even more limited by increasing its length in the vertical installation. This paper describes the development of a Vacuum-Re lled Tensiometer (VRT) for monitoring soil water pressure independent of installation depth. This is achieved by xing the distance between pressure sensor and ceramic cup together with incorporating an ancillary vacuum-re lling assembly... 

In this paper the effects of the first reservoir filling on rockfill dams were studied numerically. To simulate the problem a simplified coupled formulation based on Biot's theory associated with unsaturated soils was presented. The finite element method was applied to the governing equations for the spatial discretization, followed by a generalized Newmark scheme used for the time domain discretization. The three effects of reservoir filling, collapse settlement produced by wetting the rockfill, water load on the dam body and buoyancy in the upstream shell were introduced. The nature of collapse settlement and how to numerically capture that by using the proper constitutive model is... 

Because of the complex nature of carbonate reservoirs, the required conditions for effective Low Salinity Water Flooding (LSWF) in these reservoirs need further and in depth investigation. In the present study, three calcite cores, i.e. Cal-1, Cal-2, and IL, with the same chemical composition are subjected to tertiary low salinity water flooding (LSWF), while the crude oil and composition of flooding brine kept the same. The experimental results show significant difference in the amount of enhanced oil recovery, as IL had the most additional oil recovery (20.8 % of IOIP), followed by Cal-2 (10.5 % of IOIP) and Cal-1 (3.9 % of IOIP). The results of contact angle, zeta potential, and effluent... 

Public concern over environmental issues such as ecosystem degradation is high. However, restoring coupled human-natural systems requires integration across many science, technology, engineering, management, and governance topics that are presently fragmented. Here, we synthesized 544 peer-reviewed articles published through September 2020 on the desiccation and nascent recovery of Lake Urmia in northwest Iran. We answered nine questions of scientific and popular interest about causes, impacts, stabilization, recovery, and next steps. We find: (1) Expansion of irrigated agriculture, dam construction, and mismanagement impacted the lake more than temperature increases and precipitation... 

Controlling evaporation plays an essential role in arid and semi-arid water resources systems where it accounts for a considerable amount of reservoirs outflow. In this study, we have evaluated evaporation reduction efficiency of different kinds of self-assembled nano-thickness films. The films consist of six different combinations of stearyl and cetyl alcohols with additives such as jojoba oil, stearic acid, and calcium hydroxide. The study lasted from July to August and utilized two pairs of class A evaporation pans: one pair was semi-floating on Chitgar lake water surface while the other one was located on the shore. The experimental results showed that a monolayer containing 3:1 stearyl... 

In this work, a two-dimensional fourth-order Boussinesq-type numerical model is applied to estimate the impact of landslide-generated waves in dam reservoirs. This numerical model has recently been extended for simulating subaerial landslides. The extended model is validated using available three-dimensional experimental data, and a good agreement is obtained. The numerical model is then employed to investigate the impact of landslide-generated waves in two real cases, the Maku and Shafa-Roud dam reservoirs in the northwestern and the north of Iran, respectively. Generated wave heights, wave run-up, maximum wave height above dam crest, and dam overtopping volume have been estimated for each... 

Flood as a natural disaster causes heavy human and economic losses and social unrests in most areas of the world. As flood control cost and flood damage compensation is a heavy burden over countries' budget, traditional flood design methods are being replaced by more reliable risk-based methods employing comprehensive risk analysis. In this respect, flood damage estimation is an important step in flood control systems design and analysis. In large river basins with complex reservoir systems and various land uses, flood damage estimation is complex, data-intensive, time demanding, and uncertain task requiring an intensive hydrologic and hydraulic analysis. In this study a simple approach is...