Sharif Digital Repository

Meteorological droughts due to the concurrent occurrence of low-precipitation and high-temperature events can lead to severe negative impacts on agriculture, economy, ecosystem, and society. This study proposes a novel framework to characterize such drought conditions based on the joint variability of precipitation–temperature, particularly under climate change. Generalized hierarchical linear model is used to downscale precipitation and temperature at multiple stations from the outputs of nine General Circulation Models (GCMs) under Representative Concentration Pathways (RCPs) 4.5 and 8.5. A bivariate drought index called Precipitation–Temperature Deciles Index (PTDI) is developed using... 

Meteorological droughts due to the concurrent occurrence of low-precipitation and high-temperature events can lead to severe negative impacts on agriculture, economy, ecosystem, and society. This study proposes a novel framework to characterize such drought conditions based on the joint variability of precipitation–temperature, particularly under climate change. Generalized hierarchical linear model is used to downscale precipitation and temperature at multiple stations from the outputs of nine General Circulation Models (GCMs) under Representative Concentration Pathways (RCPs) 4.5 and 8.5. A bivariate drought index called Precipitation–Temperature Deciles Index (PTDI) is developed using... 

An unstructured grid, finite-volume, and three-dimensional (3D) primitive equation ocean model has been developed to predict oceanic pollutant dispersions in depth and surface of the Caspian Sea for non-chemical reactions of dissolved constituents. The model consists of momentum, continuity, temperature, salinity, and density equations. Physical and mathematical closure has been achieved using Mellor and Yamada turbulent closure sub-models. Since determining a practical definition of salinity that enjoys acceptable accuracy is difficult; therefore, various definitions have been used in this work. A recent definition of salinity stated in the UNESCO Practical Salinity Scale of 1978, PSS78,... 

Dynamic hydrosalinity models are available, but are not used extensively on a large scale soil which receives wastewater from industrial areas, partly because adequate database are expensive to be obtained. Thus, for this reason, there is an urgent need to assess the salt and other pollutant loads collected in wastewater flows into the soil and/ or ground water systems. A conceptual hydrosalinity model was used on two major underlying principals of mass balance and steady state. This model was initially tested on the 4,117 km2 plains west of the Yazd-Ardakan district in the central part of Iran. This model was used at a time when the soil and ground water salinity problem was serious due to... 

Lake Urmia is a thalassohaline ecosystem. It is an extremely simple ecological pyramid. This makes it a very sensitive ecosystem. This ecosystem has been facing various threats regarding the amount of water released from the associated basin. To calculate the lake water requirement with an ecological approach, we identified three variables: ecology, water quality, and water quantity indices as environmental indicators. The ecological index represented by Artemia urmiana is considered as an independent variable; while, the water quality index represented by concentration of NaCl, and the water quantity index represented by water elevation are regarded as dependent variables. The salinity... 

A solar natural vacuum desalination system was experimentally investigated. Using a barometric water column and creating an equilibrium with atmospheric pressure and gravity, vacuum conditions were maintained inside the evaporation chamber throughout the day, which led to the beginning of evaporation at lower temperatures and as a result, lower energy consumption compared to conventional methods. Solar evacuated tubes were used to more efficiently absorb solar radiation and raise the temperature of saline water. In addition, at the system startup, a vacuum pump was utilized to fill the water column and create vacuum conditions. Then, the existing vacuum in the system was maintained naturally... 

Arrayed Ti6Al4V nanotubes (TNT) coated with hydroxyapatite (HA) were synthesized via electrochemical anodization method. Paracetamol was loaded onto TNT-HA electrode. Effects of anodization, nanotube formation and hydroxyapatite deposition on sorption and release of the drug were investigated. Saturation time of paracetamol on the anodized samples was 30% shorter than the hydroxyapatite-coated samples. Release behavior of the loaded drug was studied by (a) plunging the probe into phosphate buffered saline (PBS), (b) sampling the drug-loaded PBS at different times and (c) analyzing the solution via ultraviolet-visible (UV-vis) spectroscopy. Results showed that HA electrodes hold higher... 

The effect of an efficient biosurfactant produced from Pseudomonas aeroginosa MR01, a bacterial strain isolated from oil excavation areas in southern Iran, on the recovery of residual oil trapped within carbonate rocks, was investigated. In a core holder set-up, bearing a number of limestone-and dolomite-containing core samples, biosurfactant flooding resulted in oil recoveries as large as 20% to 28% Residual Oil (R.O). Biosurfactant injection in less permeable rocks in a range of 0.5 to 32 md was more successful, in terms of oil production. In the case of the least oil recovery via biosurfactant flooding, incubation of the core with a biosurfactant solution at reservoir conditions,... 

Increasing demand of fresh water, and limitation water resources, with respect to world economic growth brings up the importance of utilization of saline water. At the current research the sensitivity analysis of ROSA was conducted. For this analysis, a single stage reverse osmosis is designed for well water specifi cation in southern Tehran under following condition: Feed fl ow: 40 m3/h and membrane Element: BW30–400 FR. The sensitivity analyses for all chemical element of base water were performed. As a result of sensitivity analysis shortest sensitivity gap, belongs to boron, and longest sensitivity gap, belongs to calcium. Which refl ects, under the same conditions, the least element to... 

Dam construction in arid and semiarid regions is generally related to the risk of increased salinity, due to water passage in contact with salty formations. Hence, it is important to take reservoir thermal and salinity stratification into account in operational rules. In the present study, a simulation–optimization model was developed to determine the amount of water release from various outlets to discharge the brine from hypolimnion layer considering the downstream water quality limitations. The most appropriate time, rate, and concentration to release brine were determined based on water consumption conditions and downstream water demand and river ecology characteristics. The proposed... 

Various urban, industrial, and agricultural pollutions discharge more than river self-purification potential damages river ecosystem and increases water treatment costs. As different decision-makers and stakeholders are involved in the water quality management in river systems, a new bankruptcy form of the game theory is used to resolve the existing conflict of interests related to waste load allocation in downstream river. The river restoration potential can allocate to the conflicting parties with respect to their claims, by using bankruptcy solution methods. In this research, dischargeable pollution loads to Karun River are determined by pollution sources in various scenarios using... 

Collapsible-dispersive soil is one of the most challenging types of problematic soils having the adverse effects of both collapsible and dispersive soils for construction. A natural occurrence of this type of soil was recently encountered along some part of the Chabahar-Zahedan railway line in Southeast of Iran. Indeed, the construction phase was stopped after facing several geotechnical problems along the railway embankment partly constructed such as local and general subsidence, non-uniform settlements of structural elements, etc. Relatively high natural porosity as well as pore water salinity were found responsible for those problems. Therefore, this study aims to conduct a three-phase... 

Using our recently developed model, for the first time in the literature, the effect of fluid/fluid and rock/fluid interactions on the performance of Low Salinity Waterflooding (LSWF, as an Enhanced Oil Recovery process) at pore-doublet scale is investigated. The model is incorporated into OpenFOAM and both the Navier-Stokes equation for oil/water two-phase flow and the advection-diffusion equation for ion transport (at both fluid/fluid and rock/fluid interface) are solved via direct numerical simulation (DNS). The model is validated against imbibition and drainage pore-doublet experiments reported in the literature, and then applied to investigate the sole effect of wettability alteration... 

Laboratory experiments have shown that performance of waterflooding in oil reservoirs could be significantly increased by lowering the ionic strength and/or manipulation of its composition, which is generally known as low salinity waterflooding (LSWF). The involved mechanisms in additional oil production can be generally categorized in two categories, fluid/fluid and fluid/rock interactions. The distribution of the phases and the involved displacement mechanisms would be strongly affected by the inter-relations between capillary and viscous forces. Although there have been recent advances in the simulation of the LSWF at core scale and beyond and some models are included in commercial... 

Using our recently developed model, for the first time in the literature, the effect of fluid/fluid and rock/fluid interactions on the performance of Low Salinity Waterflooding (LSWF, as an Enhanced Oil Recovery process) at pore-doublet scale is investigated. The model is incorporated into OpenFOAM and both the Navier-Stokes equation for oil/water two-phase flow and the advection-diffusion equation for ion transport (at both fluid/fluid and rock/fluid interface) are solved via direct numerical simulation (DNS). The model is validated against imbibition and drainage pore-doublet experiments reported in the literature, and then applied to investigate the sole effect of wettability alteration... 

Laboratory experiments have shown that performance of waterflooding in oil reservoirs could be significantly increased by lowering the ionic strength and/or manipulation of its composition, which is generally known as low salinity waterflooding (LSWF). The involved mechanisms in additional oil production can be generally categorized in two categories, fluid/fluid and fluid/rock interactions. The distribution of the phases and the involved displacement mechanisms would be strongly affected by the inter-relations between capillary and viscous forces. Although there have been recent advances in the simulation of the LSWF at core scale and beyond and some models are included in commercial... 

Low salinity waterflooding (LSWF) is a process in which by lowering the ionic strength and/or manipulation of the composition of the injection water, the long term equilibrium in oil/brine/rock system is disturbed to reach a new state of equilibrium through which the oil production will be enhanced due to fluid/fluid and/or rock/fluid interactions. In spite of recent advances in the simulation of the LSWF at core scale and beyond, there are very few works that have modelled and simulated this process at the pore scale specially using direct numerical simulation (DNS). As a result the effects of wettability alteration and/or Interfacial Tension (IFT) change on the distribution of the phases... 

The main idea behind the application of Low salinity polymer flooding (LSPF) enhanced oil recovery (EOR) method is that diluted brine improves the oil recovery by wettability alteration from oil-wet (OW) towards water-wet (WW) condition, while polymer enhances the mobility of the displacing phase. However the possible effect of polymer on the fluid/fluid and fluid/rock interactions are not investigated systematically in the literature. The main objective of the present reserach is to examine the possible effect of hybrid application of low-salinity and polymer on the brine/rock and brine/oil interfaces properties. Formation water (FW) and sea water (SW) and its two different dilutions, i.e.... 

The dynamics of droplet detachment from a surface is a fundamental topic studied in coating engineering, fluid mechanics, and subsurface engineering applications. This topic has direct relevance to wettability alteration using the modified ionic composition of water in contact with oil droplet, low salinity waterflooding (LSWF). Previous experimental studies of LSWF have shown a very long timescale in wettability alteration which cannot be explained using bulk diffusion coefficient. In the present study, we address both the time scale of detachment, as well as the impact of buoyancy and interfacial forces (referred to as Bond number) on droplet detachment by proposing an advanced... 

Preformed particle gels (PPGs) in solutions have been widely used to suppress excess water production in mature oil reservoirs and, in turn, to improve the amount of oil recovery in brown oil fields. In this study, PPG solutions were meticulously formulated and synthesized in order to be utilized in harsh environments in terms of pressure, temperature, pH, and salinity from a free radical polymerization process. In this work, nanosilica gel at different weight percentages was added to improve the mechanical and thermal stability properties of the PPG at harsh condition: high pressure, temperature, and strain. Moreover, the effects of nanosilica gel at various concentrations, ranging from 0.0...