جستجوی مقالات مرتبط با کلیدواژه « Hydrodynamic coefficients » در نشریات گروه « علوم پایه »

Groundwater is one of the main sources of water supply for agriculture, drinking and industry in Iran, especially in areas with arid and semi-arid climates. Therefore, due to the high importance of groundwater resources, it is necessary to know the hydrodynamic parameters in order to determine the natural flow of water and manage the optimal utilization of groundwater resources. Considering the role of the Daloon-Meydavood aquifer in providing part of the water needed in the study area, especially for agricultural purposes, the hydrodynamic parameters of this aquifer were estimated using the methods of grain size analysis, geophysics and pumping test. The parameters were calculated by all three methods and validated using the flow rate of the exploitation wells. In all three methods, the hydrodynamic parameters (Hydraulic conductivity, Specific yeild, transmissivity coefficient) are the highest in the north and northeast and the lowest in the south and northwest. The results showed that 2 methods including  grain size analysisand pumping test had the most similarity with the discharge map of the exploitationwells.

One of the most important concerns in aquifers adjacent to oil facilities is pollution caused by LNAPL leaks. Because these compounds have less weight than water, they float on the surface of the water as a layer and move along with the water flow. Recovery of LNAPLs is always difficult and expensive. This study aims to manage the recovering costs by determining the hydrodynamic coefficients of LNAPL. The hydrodynamic coefficients include transmissivity and specific yield. In this study, for the first time, instead of the term specific yield, the term oil specific yield has been used according to the type of fluid in the aquifer. The Rockwork model was used to calculate the oil specific yield and LDRM (LNAPL Distribution and Recovery Model) model was used to calculate LNAPL transmissivity coefficient. The inputs of the LDRM model include soil and LNAPL parameters, porosity, hydraulic conductivity of water saturation, van Genuchten parameters, mass densities of water and LNAPL, surface tensions of water-LNAPL, LNAPL-air and water-air, viscosities of water and LNAPL. From the inputs, LNAPL transmissivities and recoverable and total LNAPL specific volumes were extracted as output results. With the help of the obtained results, maps of LNAPL transmissivities, thickness and recoverable volume of LNAPL were prepared and the best recovery locations were introduced.

Hydraulic conductivity and Specific storage are known as the most important hydraulic characteristics of aquifers. Recently, due to software advances, the use of numerical models in the operation of groundwater aquifers has expanded. Modeling is one of the best tools for studying and simulating the state of water resources. One of the advantages of modeling is the simultaneous determination of several parameters such as hydraulic head, flow path and etc. Likewise, via modeling, it is possible to simulate the reaction of the basin against changes such as natural or artificial recharge and the amount of pumping, and by applying appropriate solutions, determine the best performance of the system then use it to manage the basin. In the present study, MODFLOW numerical model and GMS user interface were utilized to simulate and calibrate the model. Accordingly, the hydrodynamic properties of the Shabestar plain aquifer were evaluated regionally. As a result, the RMSE values of hydraulic head for the steady-state and non-steady-state models were 0.59 (m) and 0.95 (m), respectively. The obtained results demonstrated that the more heterogeneous the aquifer, the more diverse the hydrodynamic coefficients will be, and this variation does not follow a specific trend due to the existence of geological formations, the density and the porosity of the formations.

malkhalifeh aquifer is located in south of chaharmahal and bakhtiyari province , in sannadaj- sirjan zone as tectonic setting. this area very important as agricalture in the chaharmahal and bakhtiyari.This study investigated the geology and hydrogeological features of Mal-e Khalifeh in order to make more appropriate decisions about the utilization of water resources in this area based on groundwater level fluctuations and storage capacity. The research was carried out utilizing all of the reports, statistics, and data available in the archives of Chaharmahal and Bakhtiari Regional Water Company, Rural Water and Sewerage Company, as well as data obtained through measurements, experiments, and field studies. Mal-e Khalifeh study area, study code No. 2313, is one of the Great Karun drainage basin study areas with an area of 844.6 square kilometers, located in the southeastern part of the Great Karun in Lordegan, Iran. This area is managed by Chaharmahal and Bakhtiari Regional Water Company. The following conclusions were obtained by evaluating the features of plain aquifers, including the type of aquifer floor rock, the type of aquifer, hydrodynamic coefficients, groundwater level fluctuations, floor depth and floor rock, and groundwater exploitation status: - According to the map made from the amount of water transfer, the amount of transferability increases from the edges to the center of the plain, and in general, the middle section of the plain is ideal for reservoir utilizing. Suitable places for exploitation can also be identified in the northern and southern areas. - The minimum and maximum groundwater depths, according to the map, are 2.7 and 53.6 meters, respectively, with a maximum depth in the northern areas (western Amiran piezometer) and a minimum depth in the plain's southern areas (Qarah). According to the map, to reduce the groundwater level, groundwater generally flows from east to west and from north to the center and south of the plain. This changing trend is consistent with surface currents and demonstrates the impact and compliance of piezometric wells and aquifers with surface currents. The results of the above map analysis suggest that the currents created in the north of the plain are the main source of inflow to Mal-e Khalifeh Plain. - The region's maximum water level is around 1735.13 meters to the north and northwest of the plain, while the minimum water level is around 1659 meters in the south and southwest at the drainage basin outflow. The analysis of the groundwater drop map for the long-term period (October 1988 to October 2018) also indicated that the maximum aquifer drop in the north of the plain (Milas-Kondar intersection) was 21.29 m and the lowest drop in the south of the plain was 21.29 m. (Piezometers of Kundar-Abu Ishaq and Qarah intersection). This indicates the average annual decline in water level of 0.17 meters in recent years and a drop of around 1.26 meters in the census year (2017-2018). - The hydrograph of the groundwater unit declined by 0.84 in the water year 2017-18, resulting in a volume reduction of 0.82 million cubic meters in the aquifer reserve for that year. In addition, from October 1991 to October 2018, the average annual change in groundwater was roughly -0.24 meters, which reduced the reservoir's average annual volume by 0.24 million cubic meters. Furthermore, the overall amount of aquifer drop from the start of the long-term study period to the present was 6.59 meters, and the total volume of reservoir loss was 6.43 million cubic meters. - The amount of this parameter dropped from the northern regions to the southern parts and the plain outflow, according to the map of electrical co-conductivity. - Hydrogeochemical studies revealed that groundwater had adequate and acceptable drinking water quality. Furthermore, for agricultural purposes, the water quality for both dry and rainy periods was in c2s1, which is adequate and useable for agricultural purposes. In the long term, the Mal-e Khalifeh aquifer chemograph revealed a rise in salinity of plain groundwater. During the statistical period, the average electrical conductivity increased. According to this graph, the average electrical conductivity improved by 40% in the last 5 years when compared to the start of the statistical period. - The volume of the reservoir was 0.55 million cubic meters after considering and calculating the parameters of groundwater balance. According to the findings, the quality of groundwater in the Mal-e Khalifeh Plain is generally good for drinking and agricultural usages, with the primary issue being aquifer volume loss, which should be thoroughly explored. Considering the long-term aquifer hydrograph, which shows changes in aquifer volume of 0.24 million cubic meters per year on average, it is clear that this difference is due to some assumptions in the preparation and regulation of the groundwater aquifer balance, and due to the fact that the parameters used should be estimated, it was practically impossible to calculate it accurately during the above balance studies. In the general balance calculations, the rate of decline of groundwater reserves was 16.77 million cubic meters, which, given the aquifer's characteristics, area, and the trend of changes in the aquifer's hydrograph, reflects a considerable decrease in water reserves in the aquifer. The following items 1. Reduction of water storage in groundwater balance calculations by 16.77 million cubic meters 2. 3.5 times difference between the number of long-term aquifers and the annual number of 2017-18 water years with the average long-term 3. Decline of groundwater level in the plain with an average annual drop of about 0.84 4. Also, a 40% increase in the average electrical conductivity are due to the decrease in rainfall in recent years and the increase in exploitation by permitted exploitation wells and unauthorized wells in the plain. This suggests salinity, which reduces the amount of groundwater supplies and necessitates additional planning for water resource management. With this in mind, basin and water resource management in this area appears to be more important than ever, and should be technically controlled by modifying aquifer exploitation and using artificial inflow and aquifer operations.

One of the most prevalent ways for studying the submarine’s hydrodynamic behavior, like maneuvering, is calculating the hydrodynamic coefficients the hydrodynamic coefficients. In this paper calculation of hydrodynamic coefficients (up to third order) of an AUV using Computational Fluid Dynamics (CFD) and Finite Volume Method(FVM) was performed. Therefore, a Myring body was chosen to simulate the unsteady maneuvering for surge, sway and yaw motions. The turbulence effects were modeled by k-ω sst turbulent model. The Planar Motion Mechanism (PMM) in two situations has been implemented to calculate the forces and moments for sway and yaw motions. Creating body motions in computational domain, the Overset mesh was used. Furthermore, the grid study was performed for investigating of the simulation accuracy. Then for calculating the coefficients, some six order polynomial equations were interpolated for forces and moments versus velocity and acceleration. The numerical results were compared with the results of (Prestero, 2001) . The relevant error for damping coefficients was between 0.8 to 12 percent. These values for added mass coefficients were between 0.8 to 37 percent.

Estimation of aquifer hydrodynamical parameters is one of the important issues in groundwater resource management. It is essential to determine the aquifer's hydraulic properties in order to understand and recognize the natural flow pattern of an aquifer and groundwater measurement. As aquifer characteristics, transmissivity and the storage coefficient may vary spatially due to the existence of different subsurface materials, resulting in geological heterogeneity. Assessment of transmissivity and the storage coefficient, as the most significant hydrodynamical parameters, allows for a quantitative prediction of aquifer response to recharge and discharge rate. There are many different methods for hydrodynamical parameter estimation, which include a variety of methods such as: empirical formulas, laboratory methods, geophysical methods, tracking experiments and pumping tests. However, among all these techniques, the application of pumping test data is the most useful and common method, with the ability to reflect a wide range of aquifer. Using drawdown-time pumping test data can calculate the aquifer parameters which is able to employ different methods. The Cooper Jacob equation is used to determine the transmissivity and the storage coefficient for a confined aquifer using pump test results. In this research, a modified fuzzy least-squares regression (MFLSR) method uses imprecise pump test data to obtain fuzzy intercept and slope values which are then used in the Cooper Jacob method. Fuzzy membership functions for the transmissivity and the storage coefficient is then calculated using the extension principle. The modified fuzzy least-squares regression that is coupled with the Cooper Jacob method allows the analyst to ascertain the uncertainty that is inherent in the estimated parameters in an aquifer.