Electroosmotic Pressure-Driven Flow through a Slit Micro-Channel with Electric and Magnetic Transverse Field

In the present study, flow through two-dimensional microchannel under an axial electric field, transverse electric and magnetic fields and with axial pressure gradient has been investigated numerically. Continuity and momentum equations were solved steadily with respect to the non-slip condition by using discrete finite volume method and a numerical code. The results show that in the presence of the axial electric field, applying transverse magnetic field reduces flow velocity. However, when the transverse electric field and axial electric field exist together, applying the transverse magnetic field increases the flow rate to a certain extent and then reduces the flow rate. Hartmann number like this amount of magnetic field is known as critical Hartmann number. Therefore, with the presence of transverse and axial electric fields and transverse magnetic field, the highest possible flow rate is for critical Hartmann number. It was also found that by increasing the pressure gradient within the microchannel, the critical Hartmann number decreases. Moreover, by increasing the transverse electric field, the sensitivity of critical Hartmann number to the pressure gradient decreases and its value tends to a specific number (about 1.5)

Flood prediction in southern strip of Caspian Sea watershed.

Modeling of hydrological process has become increasingly complicated since we need to take into consideration an increasing number of descriptive variables. Soil, topography, land-use, rainfall and flow are some of the variables which are difficult to be spatially measured. In recent years black box solutions like artificial neural networks have been used in modeling complex process of hydrologic events. The potential applications of multilayer feedforward back propagation neural networks for developing rainfall-runoff relationships for some homogeneous catchments located in the north of Iran were studied and compared with those of a multiple regression model. A total of 24 sites yielding 356 pairs of observed data were studied. The most popular network in hydrology, i.e., multilayer feedforward back propagation was used. Results show that among the different backpropagation learning algorithms used in this research, the Levenberg-Marquardt resulted in the best performance. Keywords: artificial neural networks, estimation of flood, flood frequency, hydrological modeling

A review of modelling methodologies for flood source area (FSA) identification

Flooding is an important global hazard that causes an average annual loss of over 40 billion USD and affects a population of over 250 million globally. The complex process of flooding depends on spatial and temporal factors such as weather patterns, topography, and geomorphology. In urban environments where the landscape is ever-changing, spatial factors such as ground cover, green spaces, and drainage systems have a significant impact. Understanding source areas that have a major impact on flooding is, therefore, crucial for strategic flood risk management (FRM). Although flood source area (FSA) identification is not a new concept, its application is only recently being applied in flood modelling research. Continuous improvements in the technology and methodology related to flood models have enabled this research to move beyond traditional methods, such that, in recent years, modelling projects have looked beyond affected areas and recognised the need to address flooding at its source, to study its influence on overall flood risk. These modelling approaches are emerging in the field of FRM and propose innovative methodologies for flood risk mitigation and design implementation; however, they are relatively under-examined. In this paper, we present a review of the modelling approaches currently used to identify FSAs, i.e. unit flood response (UFR) and adaptation-driven approaches (ADA). We highlight their potential for use in adaptive decision making and outline the key challenges for the adoption of such approaches in FRM practises

Spatial patterns and temporal variability of drought in Western Iran

An analysis of drought in western Iran from 1966 to 2000 is presented using monthly precipitation data observed at 140 gauges uniformly distributed over the area. Drought conditions have been assessed by means of the Standardized Precipitation Index (SPI). To study the long-term drought variability the principal component analysis was applied to the SPI field computed on 12-month time scale. The analysis shows that applying an orthogonal rotation to the first two principal component patterns, two distinct sub-regions having different climatic variability may be identified. Results have been compared to those obtained for the largescale using re-analysis data suggesting a satisfactory agreement. Furthermore, the extension of the large-scale analysis to a longer period (1948–2007) shows that the spatial patterns and the associated time variability of drought are subjected to noticeable changes. Finally, the relationship between hydrological droughts in the two sub-regions and El Niño Southern Oscillation events has been investigated finding that there is not clear evidence for a link between the two phenomen

Assessment the flood hazard arising from land use change in a forested catchment in northern Iran

The provinces of northern Iran that border the Caspian Sea are forested and may be prone to increased risks of flooding due to deforestation and other land use changes, in addition to climate change effects. This research investigated changes in runoff from a small forested catchment in northern Iran for several land use change scenarios and the effects of higher rainfall and high antecedent soil moisture. Peak discharges and total runoff volumes from the catchment were estimated using the US Soil Conservation Service 'Curve Number' (SCS-CN) method and the SCS dimensionless unit hydrograph. This method was selected for reasons of data availability and operational simplicity for flood managers. A GIS was used to manipulate spatial data for use in the catchment runoff modelling. The results show that runoff is predicted to increase as a result of deforestation, which is dependent on the proportion of the catchment area affected. However, climate change presents a significant flood hazard even in the absence of deforestation. Other land use changes may reduce the peak discharges of all return period floods. Therefore a future ban on timber extraction, combined with agricultural utilisation of rangeland, could prove effective as 'nature-based' flood reduction measures throughout northern Iran

‫روش‬ ‫ﻣﻘﺎﻳﺴﻪ‬ ‫ﻫﺎي‬ ‫اﺳﺘﺨﺮاج‬ ‫ﭘﻴﻤﺎﻳﺶ‬ ‫ﻫﻤﺰﻣﺎن‬ ‫ﺧﻄﻮط‬ ‫زﻣﺎن‬ ‫روﻧﺪﻳﺎﺑﻲ‬ ‫روش‬ ‫در‬ ‫اﺳﺘﻔﺎده‬ ‫ﺑﺮاي‬ - ‫ﻣﺴﺎﺣﺖ‬ ‫ﺷﻜﻮﻫﻲ‬ ‫ﻋﻠﻴﺮﺿﺎ‬ Isochrones Mapping Methods in Time-Area Routing Technique

Abstract The Time-Area method is a suitable technique for watershed routing and can be potentially used as a distributed model. As an advantage, it can also be used as a GIS-based method. The performance of the existing methods for deriving isochrone locations is compared in this study with that of the kinematic wave theorem. In most methods, travel time is proportional to the distance-to-outlet of any point raised to a power. Investigating the numerical value of powers, it is shown that exponent 1.5 of Laurenson's method yields the closest time-area hydrograph to that of the kinematic wave solution. Therefore, this paper showed that certain empirical isochrone delineation methods could be applicable provided that the travel length is measured towards the outlet

Source apportionment of the sediments entering dam using lithological and mineralogical studies

The present study was carried out to determine the possible origins of sediments entering Taleghan Dam in northern part of Iran, in order to avoid further sedimentation and helping in extension of the useful life of the proposed dam. This was performed by XRD analysis. To do so, first of all, sediment sampling points were positioned along the Taleghan River. The collected samples, after coding, were transferred to the laboratory for mineralogical testing. Then, the samples were exposed to X-ray diffraction analysis. The experimental results were compared with data from geology, land cover land use and slope maps in order to find the possible primary origins of deposits in the Taleghan Dam. Furthermore, the geological formations and physiographical parameter such as slope were also analyzed to test erodibility of the formations. The results showed that most sediment samples in Taleghan are of sedimentary sandstone, mainly containing the quartz and plagioclase minerals (quartz sandstone and arkose sandstone). The findings also showed that calcite and dolomite were abundant in the collected samples, while aragonite and anthracite were found to a lesser extent in the samples. Accordingly, acidic and alkaline formations, mudstone, and siltstone of Karaj area formations, the gypsum of upper red formation, particularly at places with steep slope with a dominance of rangeland land use type, are main origins of sediments in the Taleghan reservoir. In another hand, the control of sediments at these areas would substantially decrease total sediment yields of the entire basin as in the dam reservoir