Showing 25 results for Reservoir
Volume 1, Issue 1 (3-2013)
Abstract
Today fingerprinting techniques are increasingly adopted as an alternative and more direct and reliable means of assembling sediment source information. One of the principal assumptions of sediment fingerprinting is that potential catchment sediment sources can be distinguished on the basis of their physical, geochemical and biological properties or fingerprint properties. However, while the source fingerprinting approaches necessarily assume conservative behaviour of the fingerprint properties, some in-stream alteration of these properties during both transport and short-term storage is probably inevitable. This potential limitation must be judged in the context of the problems associated with the use of sediment fingerprinting techniques. Samples of sediment source and reservoir sediment collected during the present study have been used to determine the conservative behavior of fifteen fingerprint properties. Comparison of fingerprinting property concentrations of intensive properties used in fingerprinting indicates there is an increase in content of the N, P, C, Co, Cr, clay minerals (smectite, illite, kaolinite), Low Frequency Magnetic Susceptibility (XLF) and Frequency Dependent Magnetic Susceptibility (XFD) and decrease in clay mineral chlorite and base cations Ca, Mg, Na and K. The results indicate that N, Na and smectite properties have no significant difference in reservoir sediment samples than that in sediment source samples and therefore are useful for fingerprinting investigations in these catchments.
Volume 5, Issue 1 (3-2017)
Abstract
The optimal allocation of the Chahnimeh water resources among different sectors, viz. domestic, agricultural and environmental consumptions, was determined using the goal programming method in GAMS, based on the present condition in the area. Results showed an increase of 15.4, 44.5 and 230% in allocation of water to domestic, agriculture and environment sectors, respectively, in this method as compared to the present allocation. Besides, implementation of the second water transferring line to Zahedan city would resultin a 66% increase in the water transferring rate to this city without any change in water supply for domestic sector in Zabol city and the surrounding villages. The scenario of 20% reduction in water per capita consumption led to about 5.9 million cubic meters saving in water supply from Chahnimeh reservoirs to the domestic sector. According to the projected population growth for 2025 in the study area, water consumption in domestic sector will increase by 15.9%. Results showed that the goal programming can be applied as a useful tool to analyze the effect of different scenarios on water demand and supply management and, hence, to allocate water for different sectors in a most appropriate way.
Volume 9, Issue 4 (10-2007)
Abstract
Rock has been advantageously employed in hydraulic structures such as rockfill dams, gabion weirs and drain works. One rockfill dam applications can be flood control in wa-tershed management. The objectives of building rockfill detention dams are flow storage for a specific period and lowering of the outflow hydrograph. As this type of dam consists of coarse particles, seepage flow will deviate from Darcy’s law and mostly be turbulent. Under the practical conditions of watershed management, it might be necessary to build successive rockfill dams, where a final outflow hydrograph with lower peak flows and longer duration is needed. Due to their reciprocal effects, the hydraulics of successive rockfill detention dams are complicated. This paper describes a routing flow model through successive rockfill dams considering the storage among them and their effects on each other. In the developed model, the velocity has been introduced to the 1-D continuity equation as an exponential relationship between Reynolds number (Re) and the Darcy-Weisbach friction factor (f). By introducing the inflow hydrograph and rockfill character-istics as input data to the model, the outflow hydrograph can be determined through the storage routing method. The results of the developed model show good agreement with the experimental data collected for this investigation. The results show that the degree of peak reduction of the routed hydrograph depends on the number of successive rockfill dams, the distance between them, the average size of the rockfill material, and the dam dimensions.
Volume 11, Issue 0 (3-2007)
Abstract
Many of well known Iranian hydrocarbon reserves are concentrated in the anticlinal oil traps of the Asmari Formation. Fractures are too important in fluid flow simulation, because of their impacts on anisotropy and heterogeneity of the Asmari carbonate reservoirs. In order to fracture network modeling of the Asmari reservoirs, it’s necessary to have information about many parameters that most of them can not be got from the well data. Therefore, the extracted data from the remote sensing studies of the Asmari outcrops can be as a basis for determining these parameters.
The remote sensing imagery is one of the main techniques available to geologists for locating and extracting fracture systems. The Kuh-e Asmari anticline in marginal part of the Zagros Fold-thrust belt has been selected for remote sensing studies of the faulting/ fracturing systems in the Asmari outcrops. In this study, Landsat (ETM+) images, ASTER images (with high spectral resolution), IRS-PAN images (with high spatial resolution), and a detailed Digital Elevation Model (with scale 1:25,000) covering the Kuh-e Asmari anticline were used. The geometrical correction, data processing and image enhancement of the satellite images were carried out in ER Mapper 6.4. Furthermore, to improve the fracture study, some 3D models were made by draping satellite images on the DEM. In this study, many data were extracted about the fracture traces. The results were delivered as figures,maps, 3D models and statistical graphs. The statistical and structural analysess of the Kuh-e Asmari anticline showed faulting/ fracturing systems which have been formed by different mechanisms, and in different times. The results of this study can be used for fracture pattern modeling and prediction hydrocarbon flow in the Asmari reservoirs.
Volume 11, Issue 3 (7-2009)
Abstract
Reservoir dams are among the main storage systems employed in agriculture for the several past decades. Proper operation of these reservoirs is important for irrigation espe-cially in such arid and semi-arid areas like Iran, and particularly during dry years. A computational framework for reservoir simulation and flood routing is hereby presented. A key aspect of the reservoir simulation is the ease of use by managers and model users. In this paper, an object-oriented toolkit for building computer models for simulation of reservoir operation and flood routing in Boukan reservoir dam is used. The modeling ap-proach taken in this paper is significantly different from that typically employed in the development of water resources planning and management models. The medium in this kind of model provides a graphical object-oriented interface that allows the user(s) to model complex systems without even requiring a profound proficiency in computer pro-gramming. The Object Oriented Programming (OOP) environment chosen to develop the model of Boukan dam reservoir was STELLA Software. The probability of flood occur-enceis also taken into account for a prediction of more accurate results.
Volume 11, Issue 4 (12-2011)
Abstract
Hydrodynamic pressure on the upstream face of the concrete dams under the effect of
earthquake is one of the most important parameters, in planning dams' structure in earthquake
zone. Because of the reservoir effect, dynamic analysis of concrete dams is more involved
than other common structures. This problem is mostly sourced by the differences between
reservoir water, dam body and foundation material behaviors. As a result, researches in this
case must be able to evaluate the response of dam with consideration of dam’s interaction
with reservoir and its foundation. This problem has been studied vastly by different
researchers.
The first research on the analysis of concrete gravity dam has been done by Westergaard in
1930 and hydrodynamic pressure on the dam face was obtained by some simplifications.
There were a lot of other researches which studied the seismic behavior of the dam-reservoir
system, including nonlinear behavior of the dam under pressure and also cavitation. In each
research, different modeling methods are presented which are divided into two main groups.
In first method which is called Eulerian method, pressure is the main unknown variable in
reservoir nodes. In the second method that its main unknown variable is displacement of
nodes is called lagrangian method. Each of the methods contain some advantageous and
disadvantageous.
The purpose of this paper is to evaluate possible advantages and disadvantages of both
methods. Specifically, application of the above methods in the analysis of dam-foundationreservoir
systems is leveraged to calculate the hydrodynamic pressure on dam faces. Within
the frame work of dam- foundation-reservoir systems, dam displacement under earthquake for
various dimensions and characteristics are also studied. To achieve this purpose, visual
C#.NET 2003 computer programming language is used in this investigation that produces
possibility of dynamic analysis of concrete dams under earthquake with system modeling by
both methods. Nine node elements for reservoir and eight node elements for dam and
foundation are used for both methods. Also newmark average acceleration method is used for
solving dynamic’s equilibrium equation.
Modares Civil Engineering Journal (M.C.E.L) Vol.11, No.4, Winter 2011
131
In this paper the response of the tallest, non-overflow monolith of Pine Flat dam in California,
which is 122 m high, to horizontal and vertical component of earthquake is computed. A
water depth of 116 m is considered in full reservoir condition, and the water has the following
properties: unit mass, 1000 kg /m3 , bulk modulus, K 2.07*109 kg/m2 , and pressure wave velocity,
w c 1440m/ s . The finite element model of reservoir consists of 12 isoparametric elements and it
extends upstream a distance of 366 m, three times the dam height. The dam consists of 20
isoparametric elements. The concrete of dam has the unit mass of 2500kg /m3 , young’s
modulus ofE 2.275*1010kg /m3, and poisson`s ratio of 0.25. The concrete of foundation has the
unit mass of , young’s modulus ofE 4.45*1010 kg / m3 f , and poisson`s ratio of
0.25 f . The peak acceleration of S69E and vertical components are 0.18g and 0.1g,
respectively.
The results of both Lagrangian and Eulerian methods for Pine Flat dam are quantitatively
evaluated and compared in different condition and following results are achieved:
1- In Lagrangian Method, there is only one variable in equilibrium equation and mass and
stiffness matrixes are symmetric. But there is not such a condition in Eulerian method. Also,
the numbers of unknown parameters are different in two methods. By considering these
differentiations, needed time for analysis of Pine Flat Dam under Taft earthquake ,with
mentioned characteristics, by Lagrangian method is 1.17 times more than needed time for
Eulerian method.
2- The effect of material on reservoir's bottom in absorbing energy and `reducing system's
response was considerable especially under vertical component of the earthquake. Results
indicate that this case is not affected by reservoir modeling method. By applying this effect,
the response will decrease about 15% under horizontal component and 60% under vertical
component of the earthquake.
3- By evaluating the effect of reservoir bottom's slope, it is concluded that in the case of rigid
foundation, the response by Lagarngian modeling is about 10% more than Eulerian one. With
the increase of slope, the response will decrease under horizontal component of earthquake
but it will decrease or increase about 13% under vertical component of the earthquake. In
other words, reservoir bottom slope has little effect on response of the system under both
vertical and horizontal component of earthquake. But this effect is not negligible.
4- It is included from the analyses that by decreasing the depth of reservoir the response will
decease up to 50 percent under horizontal component of earthquake. This amount is 80
percent under vertical component. Also in the case of decreased depth, response of
Lagarngian method is about 10% more than Eulerian method.
5-In all analysis, the assumption of rigid foundation results in greater answers than the cases
of flexible foundation.
Volume 11, Issue 4 (12-2023)
Abstract
Aim: The purpose of this research is to formulate a program and design a suitable model for environmental monitoring of water quality in order to reduce the costs of water quality monitoring and evaluation in No.1 Zabol Chahnimeh.
Material & Methods: In this study eight sampling stations were selected in the bed of the reservoir No.1 in order to monitoring and measuring physical, chemical and microbial parameters. Sampling was conducted systematically on a month basis for one year. Then the data were analyzed with the help of multivariate statistical methods such as cluster analysis, Principal Component Analysis (PCA) and factor analysis.
Findings: Using multivariate statistical methods, No. 4, 5, 6 stations were selected as the main stations for sampling and factors of temperature, turbidity, DO, COD, magnesium, sodium, calcium, phosphate, chlorine, nitrite, sodium Absorption Ratio and pH was determined as the main water quality indicators. It was revealed that temperature, DO, nitrate and turbidity parameters should be sampled monthly, but the other parameters could be sampled periodically or even quarterly to model an optimal monitoring of water quality in reservoir No.1 during a year.
Conclusion: In general, the evaluation of the quality status of this valuable water resource by reducing the number of sampling stations, eliminating some unnecessary parameters and reducing the frequency of sampling completely and without defects and at a much lower cost is done for this reason, having the lowest costs and proper timing, management of the main reservoir will be possible considering all effective parameters.
Volume 12, Issue 4 (10-2010)
Abstract
This study is focused on developing an integrated optimization-simulation based genetic algorithm model (IOSGA) to develop the operational policies for a multi-purpose reservoir system. The objective function of the optimization model is considered to be a linear function of Reliability (Rel), Resiliency (Res), and Vulnerability (Vul) of the river-reservoir system. Genetic Algorithm (GA) is employed to solve the optimization model in which the coefficients of reservoir operation policy equations are considered as decision variables. These coefficients are formulated in the form of fuzzy numbers to be able to capture the variations in releases and in water demands. Due to significant variations of agricultural water demands during different months and years, a water demand time series is considered as one of the inputs of the optimization model. Zayandeh-Rud River-reservoir system, in central part of Iran, is considered the case study. The results of the proposed approach are compared with those of the classic three cyclic algorithm in which the reservoir releases are the decision variables of the optimization model and the IOSGA model in which the coefficients of reservoir operation policies are considered to be classic (non-fuzzy) numbers. The results of the study indicated that the developed algorithm can significantly reduce the time and costs of modeling efforts and the run-time of the GA model, while it has also improved the overall performance of the system in terms of Rel, Res, and maximum Vulnerability (VulMax) and the coefficient of efficiency (CE) and standard error (SE).
Volume 13, Issue 2 (5-2013)
Abstract
Abstract:
No dam could be safely designed without functionality dependence on reliable performance of a number of appurtenant structures.
Gates are the main appurtenant structures responsible for controlling water flow from the reservoir. Earthquakes induce acoustic and surface waves in the reservoir and cause hydrodynamic pressure on the adjacent gates. Hydrodynamic pressures might surpass hydrostatic pressure on some locations of the dam upstream face. Some engineers use the hydrodynamic pressure solution concerning to axi-symmetric offshore and coastal structures for the design of such hydro-mechanical gates. Flexibility of these gates may magnify the hydrodynamic pressure due to severe generation of vibrations separate from the dam body itself even for those installed within the dam bodies. This statement reflects the design philosophy of secondary structures. Fundamental frequency of such gates are usually reduced due to the presence of infinite fluid in their vicinity. Therefore the study of their behavior is somehow complicated during the earthquake. Design regulations of hydraulic structures, demand the hydrodynamic pressure as a design action and usually admits its simple calculation from the Westergaard formula. In this article, by using floor response spectrum in gate level which is used to design the secondary systems and also the spectral acceleration parameter in gate level which is used based on predominant frequency of gate-reservoir, the common relation of gate design against hydrodynamic pressure has been corrected. Then a new non-dimension factor is suggested for sliding rectangular gates in different levels of dam body that is related to the performed analyses and log-normal distribution of data..
In general for various conditions the dimensionless coefficient of Westergaard formula changes from 0.875 to widely varying values between 0.25 to 2.5 when using the base acceleration. However when the spectral acceleration of the floor response spectrum is used for the fundamental frequency of gate-reservoir, this coefficient is more precisely determined for vertical rectangular gates.
Volume 13, Issue 9 (12-2013)
Abstract
At a Compressed Natural Gas (CNG) filling station, natural gas is stored in the high pressure reservoirs. The pressures within these reservoirs have huge effects on fast filling process of a natural gas vehicle’s (NGV) cylinder and the difficulties associated with the filling process. The accurate modeling of the fast-fill process is a complex procedure which should be thoroughly studied to optimize the filling process. Here, a theoretical analysis has been developed to study the effects of various parameters on the CNG filling process and the conditions. The analysis is based on the first and second laws of thermodynamics, conservation of mass and the AGA8 equation of state. The required properties of natural gas mixtures have been calculated making use of the AGA8 equation of state (EOS) and thermodynamics relationships. It is found that, the composition of natural gas is very effective on the CNG filling process and final in-cylinder values. For various Iranian natural gas compositions, the optimized filling stations' reservoirs pressure has been found.
Volume 14, Issue 2 (3-2012)
Abstract
Sediment yield data, collected for most regions in Iran has been insufficient and not so reliable and there is still not any sufficiently reliable methodology available for sediment yield assessment in the country as a whole. On the other hand, an attainment of reliable sediment yield data is a must and key requirement for the design of effective sediment management as well as control strategies. Sediment deposition in reservoirs is assumed as a very useful tool in providing such data. The main objective of the present research was to discuss a combination of both source fingerprinting technique and reservoir sediment survey to provide reliable data on sediment yield of geological formations for three small catchments in Semnan Province, Iran. Throughout the study, the volume and mass of deposited sediments in reservoirs were initially assessed. Fingerprinting technique was employed to identify the contribution to, as well as the specific sediment deposition yield of each geological formation into reservoir sediments. Results indicate that there is a high spatial variation in Specific Sediment Yield (SSY) among the geological formations in all the three catchments varying from 2.98 t ha-1 year-1 to 0.16 t ha-1 year-1. The results also emphasize the importance of Quaternary Units and Upper Red Formation as the dominant surface sources within some vast areas of the catchments.
Volume 15, Issue 6 (11-2013)
Abstract
A Fully Fuzzy Linear Programming (FFLP) formulation for the reservoir operation of a multipurpose reservoir in presented in the ongoing paper. In the real world, water resources systems usually have complexities among social, economic, natural resources and environmental aspects, which lead to multi-objective problems of significant uncertainties in system parameters, objectives and in their interactions. These uncertainties in FFLP reservoir operation model are considered by being treated as fuzzy sets. In the present study, an FFLP reservoir operation model is developed where all parameters and decision variables are fuzzy numbers. The developed model is demonstrated through a case study of Jayakwadi reservoir stage–II, Maharashtra, India with the objectives of maximization of annual releases for irrigation and hydropower generation. The FFLP reservoir operation model is solved to obtain a compromised solution by simultaneously optimizing the fuzzified objectives and the corresponding degree of truthfulness, using linear membership function. The degree of correspondence (Correspondence) obtained is equal to 0.78 and the corresponding annual releases for irrigation amount of 367 Mm3 and while annual releases for hydropower generation being 216 Mm3. the present study clearly demonstrates that, use of FFLP in multipurpose reservoir system optimization presents a potential alternative to attain an optimal operating policy.
Volume 15, Issue 9 (11-2015)
Abstract
In this paper two automated and robust algorithms for generation of unstructured grids suitable for miltiscale finite volume method in oil reservoirs is presented. The multiscale finite volume method is an efficient numerical method for flow simulation in porous media. The multiscale finite volume method has been extensively studied on structured grids. In this research multiscale finite volume method is extended to unstructured grids. Development of the MSFV method to unstructured grids provides advantages of flexibility and compatibility with geological structures. In this method calculations are carried out on three grids, fine grid, primal coarse grid and dual coarse grid. One of the main challenges to extend the multiscale finite volume method to unstructured grids is to generate primal and dual coarse grids. In this paper an algorithm for partitioning of unstructured grid and generating primal coarse grid is proposed. Also a new algorithm for generating dual coarse grid is presented. Finally, the proposed algorithms for generating multiscale unstructured grids are employed for flow simulations in porous media. Numerical results show that the multiscale finite volume method with generated multiscale unstructured grids of this research can accurately predict the fine scale solution.
Volume 16, Issue 2 (6-2016)
Abstract
The purpose of constructing and using a dam reservoir is storage and conservation of water. Sedimentation declines this object and can arise many problems such as reduction in capacity for flow regulation, reservoir lifetime and flood control volume, blocking intakes in reservoirs and damage of tunnels and turbines, and many other types of sediment-related problems can occur both upstream and downstream of dams. Several techniques have been proposed to prevent entrance of sediment to the reservoirs and removing deposited sediment from reservoirs. However, actual observations of world reservoirs sedimentation rates have revealed that the problem still remains. The “burrowing-type sediment removal suction pipe method” is widely considered among the new methods introduced in the last decade. This study investigated the suction pipe geometrical and mechanical characteristics on the efficiency of the burrowing-type sediment removal suction pipe method. The the suction pipe geometrical and mechanical characteristics of this experimental study includes the bottom holes spacing ratio and suction pipe bends part’s density. The suction pipe with different density at its bend part, used as a new technique conserving distance between bottom holes and sediment. The average concentration of suction flow during the experiment time known as the efficiency of the Hydrosuction sediment removal method. In this research, A series of experiments are carried out to reveal the effect of the bottom holes spacing and density of suction pipe bend part of the Hydrosuction method efficiency. The suction pipe used in this research is a flexible PVC pipe with an internal diameter of 61 mm. The ratio of bottom hole diameter to pipe diameter is 0.25, and the spacing ratio between bottom holes varies from 0.5 to 1. This study, also, used a layout of holes that the bottom holes extended both the upstream and downstream of the pipe bend part. This research also investigates the time series of suction flow concentration and suction cone volume. The results showed that the decrease of the bottom holes spacing ratio from 1 to 0.5 increases the efficiency of the method and the suction flow has its maximum average concentration (efficiency) at spacing ratio 2, with an amount of 1.58 %. Also, the density of pipe bend part has a remarkable effect on Hydrosuction method efficiency. Examination of pipe bend part density showed tha, with the increase of density of bend part from 1.77 to 2.16, the efficiency increases and it decreases just the pipe bend part density’s dimensionless parameter have greater value than 2.16. Suction flow concentration showed that, mostly, the maximum concentration occurs at the beginning of the test and then the concentration curve has an ascending branch, a maximum point and descending branch, respectively. After commencing the test, the suction flow concentration has a rapidly increasing trend untill the pipe reaches to the level of reservoir bottom, then the concentration decreases gradually. Volume ratio of flushing cone to sediment filled under suction pipe location has its maximum value at holes spacing ratio of 2 that its value, in this research, reaches to 5.
Volume 18, Issue 1 (3-2018)
Abstract
In the present work, the three dimensional fluid flow inside a hydrocarbon reservoir block along with the fluid flow inside the wellbore of a production well drilled in this reservoir block is numerically simulated. To do this, the single-phase incompressible fluid flow in the hydrocarbon reservoir in terms of Darcy’s law (porous media flow) along with the fluid flow inside the wellbore in terms of Navier-Stokes equations (free flow) are simultaneously solved. The effects of boundary conditions imposed on the faces of the reservoir block, the off-centered wellbore, and the reservoir rock permeability on the fluid flow behavior inside a reservoir block are investigated. In each case, the well index is numerically approximated, using the pressure and velocity distributions in the reservoir block and the wellbore pressure, and compared with analytical well index. The numerical results indicate that the well equivalent radius and also the well index not only depend on the geometrical properties of reservoir block and well bore and the rock absolute permeability, but also depend on the boundary conditions imposed on the reservoir block faces and the well drilling location.
Volume 18, Issue 1 (5-2018)
Abstract
Abstract. One of the most vital, essential human being requirements is water, which it has become increasingly sensitive owing to population growth, the need to develop agriculture and industry, and restriction in water resources. Considering this, the need to store water and to use its potential for generating hydroelectric power, which it can be achievable by constructing dams, will be necessitated. Concrete dams play a significant role in Infrastructure in each country. One important part of dams exiting in the world are made of gravity dams and earthquake seems to be the major threat for them in earthquake-prone areas. Hence, the dam fracture, with much stored water, might have brought many conspicuous threats about in these zones. Also, any structural damage could lead to some negative economic effects. These facts have increased the scholars’ attention to the mechanical behavior of dams during the decades. The Seismic analysis of gravity concrete dams, usually, had been considered in an ideal form by means of 2D Monolith in mechanism design and an earthquake effect coefficient. Lately, the research focus, however, has been more on linear time history analytics and fracture analysis of concrete dams in 3D. The numerical modelisation of huge structures such as dams is a proper tool for Seismic analysis and performance evaluation. The valley shape is one of the important parameters in the selection of the dam structure. This parameter plays a crucial role in both Seismic stimulation and its results. In this paper, a 3D finite element model of Pine-flat gravity dam, without interruption seams with a non-linear behavior of the dam’s material, is considered. . Loading has two stages: static and dynamic. In this modelisation, static loading includes both the weight of dam body and the load of filled Hydrostatic tanks. After static loading, loading of Seismic dynamic is begun. Owing to the importance of valley shape, the changes/ deformations of valley width and the dam response to every three elements of ground is investigated. The impact of the ratio changes of width in dam height, as well as the importance of the transverse component of ground motion, along the vertical and horizontal, has been explored. Interaction effects of dam-reservoir-foundation is considered in the considered analysis and ultimately, the output of which is compared with two dimensional model results. The aim of this study is comparing two and three dimensional seismic response of concrete gravity dams and also necessity of providing more realistic models for considering the effects of cross stream modes. Also, not only are interaction effects of dam-reservoir-foundation, the nonlinear behavior of concrete, studied different Valley shapes, and the effect of them on non-liner response investigated, but also the Seismic stability of gravity concrete dams under longitudinal, vertical and the chosen transverse record earthquake are separate and simultaneously studied. The effects of dam-reservoir-foundation interaction, nonlinear behavior of mass concrete, also different shapes of valley are studied and their effect on nonlinear response and seismic stability of concrete gravity dams are evaluated under two and three-component earthquake records.
Volume 18, Issue 1 (5-2018)
Abstract
Dams are one of the most important structures which are built to prepare water for different usages such as drinking, agriculture, industrial, flood control and hydro power generation. Due to the importance of dams and increasing number of terrorist attack, Stability of dam structures against blast loading is important. Dam responses depend on magnitude of released energy and if the dam structure could not be able to resist and maintain its stability against this energy, irreparable consequences will happen. Explosion is a sudden release of energy which could be like gases combustion, nuclear explosion or any kind of bombs. TNT unit usually used as reference to determine the explosion power. Some of basic properties of an explosion are random location of explosion, transient loading and short time loading (up to few seconds). When blast loading happened, energy will released suddenly and this released energy include thermal radiation and wave scattering in air and earth. The waves which scattered in the air are the main factor to structural damage. These waves move faster than sound wave velocity and impact the structure. Due to reflex from structure surface, the pressure of these waves increased and also some air waves penetrate to structural elements from openings such as doors and windows. This process continues until all available parts of the structure affected by pressure waves. In this research, the effects of blast loading on Karun 4 dam are investigated. To this purpose, dynamic analysis of dam-reservoir-foundation system is performed by finite element model using ABAQUS software. Dam-reservoir-foundation modeled three dimensional in which reservoir length is three times greater than dam height. The foundation modeled as a hemi-sphere with a radius of three times greater than dam height. Non-linear material behavior also considered by using concrete damage plasticity method. The CONWEP theory is used to model blast loading. To verify the blast modeling theory and software abilities, a steel plate which investigated under blast loading in references has been modeled and the results shows same responses with the paper. The responses of dam are investigated under two different reservoir conditions include full and empty conditions. Analysis also done for three different explosion points in three different elevations. Explosion points are near base, mid height of dam and near dam crest respectively. All these points have 10 m distance from dam structure. TNT mass used in each noticed conditions, is the minimum amount of TNT which cause damage in dam body. The results indicate that the responses of the dam is very sensitive to mesh dimensions. The results also show, water level has not great effect on explosive mass which is needed for structural damage of the dam. In both full and empty reservoir conditions, when explosion happened near the dam crest, the displacement is more than other cases. It is noteworthy that when the explosion happened near the crest, the maximum displacement of the crest and the point in front of the explosion point, occur in same time but when the explosion point is in middle and also near the base, theses displacements are not in same time.
Volume 18, Issue 3 (9-2018)
Abstract
In the present paper a new numerical simulation method based on finite volume is developed for calculating hydrodynamic pressure distribution in the reservoir of dams during earthquake excitation. An explicit finite volume scheme is applied for discretization of dynamic governs equation. In the proposed method the asymmetry effect of reservoir shape on hydrodynamic pressure distribution can be considered. In the simulation quadrilateral elements with center cell algorithm is used. Because of the negligible changing of hydrodynamic pressure in the cross direction with averaging, the average differential partial equation in central vertical plan of reservoir is solved. The absorption effects of bottom sediment and lateral wall are included in the analysis and an exact far end boundary condition is applied in the truncation boundary. Different approaches to the solution of the coupled field problems exist solution of the entire set of equations as one discretized system, referred to as the monolithic approach. This approach is often inefficient due to its attempt to capture with one discretization methodology the completely different spatial and temporal characteristics of fluid and the structure. The second approach often mentioned is the notion of strong coupling, referring to solvers which might use different discretizations for the fluid and the structure but which employ sub-iteration in each time step to enforce coupling between the fluid and the structure. In these methods, the governing equations for fluid and structure are discretized separately in each of the sub-domains and coupled using a synchronization procedure both in time and in space without sub-iteration. Weakly –coupled schemes have been extensively applied to a variety of different fluid-structure interaction problems of engineering interest in past ten years. wo vital issues when coupling two domains are: the method of data transformation between domains and what information must be transferred. The property of fluid adjacent of a structure such as density and viscosity are also key parameters in the efficiency of a numerical scheme.A dense fluid coupled with a structure cause a strong coupling and required some special technique to overcome corresponding difficulties. Key questions with this approach include properly enforcing boundary conditions at the solid-fluid interface, and accurately transmitting tractions between the solid and fluid. The biggest complaint about the explicit staggered partitioned solution procedure is the typical instability associated with the method,that is generally caused by the time lag between the integration of the fluid and structure equations. In the typical partitioned method, the fluid and the structure equations are integrated in time, and the interface conditions are enforced asynchronously. In the solution of coupled problems using partitioned methods, it is necessary to find a cost-minimization (optimization) compromise between a few passes solution with small time steps and a more iterated solution with larger time steps. This compromise may depend, among other things, in the degree of nonlinearity of the structural problem, which may require equilibrium iterations independently of the interaction effects. From the computational point of view, a one–pass solution with no iteration would be optimal, but stability consideration may prove this impractical.
Volume 18, Issue 6 (12-2018)
Abstract
The Seismic analysis of concrete dams had been considered in an ideal form by means of two dimensional Monoliths in analyse and design procedures and structures had been subjected to ground motions with defining seismic coefficient. Lately, the research focus, however, has been more on linear time history analytics and fracture analysis of concrete dams in 3D space. With the advancement of knowledge in the field of earthquake engineering and the development of more precise methods for estimating the intensity of possible earthquakes, The methods of analyzing and evaluating the seismicity of the structures have been improved and the effects of more parameters can be considered in assessing the risk of each structure. In the present study, the seismic response of a concrete arch-gravity dam under the influence of earthquake stimulation is investigated in a three dimensional finite element analysis. The effects of dam-reservoir-foundation interactions are considered and the nonlinear behavior of the concrete and also the different patterns of the arc radius of the dam are studied. Finally, the contribution of response of each of the sustainability factors to seismic stimulation is evaluated. The Seismic analysis of concrete dams had been considered in an ideal form by means of two dimensional Monoliths in analyse and design procedures and structures had been subjected to ground motions with defining seismic coefficient. Lately, the research focus, however, has been more on linear time history analytics and fracture analysis of concrete dams in 3D space. With the advancement of knowledge in the field of earthquake engineering and the development of more precise methods for estimating the intensity of possible earthquakes, The methods of analyzing and evaluating the seismicity of the structures have been improved and the effects of more parameters can be considered in assessing the risk of each structure. In the present study, the seismic response of a concrete arch-gravity dam under the influence of earthquake stimulation is investigated in a three dimensional finite element analysis. The effects of dam-reservoir-foundation interactions are considered and the nonlinear behavior of the concrete and also the different patterns of the arc radius of the dam are studied. Finally, the contribution of response of each of the sustainability factors to seismic stimulation is evaluated. The Seismic analysis of concrete dams had been considered in an ideal form by means of two dimensional Monoliths in analyse and design procedures and structures had been subjected to ground motions with defining seismic coefficient. Lately, the research focus, however, has been more on linear time history analytics and fracture analysis of concrete dams in 3D space. With the advancement of knowledge in the field of earthquake engineering and the development of more precise methods for estimating the intensity of possible earthquakes, The methods of analyzing and evaluating the seismicity of the structures have been improved and the effects of more parameters can be considered in assessing the risk of each structure. In the present study, the seismic response of a concrete arch-gravity dam under the influence of earthquake stimulation is investigated in a three dimensional finite element analysis. The effects of dam-reservoir-foundation interactions are considered and the nonlinear behavior of the concrete and also the different patterns of the arc radius of the dam are studied. Finally, the contribution of response of each of the sustainability factors to seismic stimulation is evaluated.
Volume 19, Issue 5 (12-2019)
Abstract
The presence of halite karst systems in dam reservoirs can be one of the crucial sources of pollutants for the water resources. Karstic regions are those with dissolving caves. If dam is constructed in the regions with reactive rocks it is likely to be endangered by karst phenomenon, dissolution and corrosion of current waters. construction of dams and reservoirs in these formations are associated with high risk. Comprehensive and accurate understanding of the salt dissolution processes facilitates the description of salt karst formations dissolution process in dam reservoirs.
This research was performed based on three basis: field studies, experimental investigation and numerical modeling. For determination of dissolution coefficient, the physical model of reservoir was built in form of trapezoidal channel and samples of salt rock in the reservoir were used in the physical model of karst formation. This model was implemented in different conditions and the results of dissolution amount and salt concentration were measured for different time scales. At the next stage, the physical model was simulated in numerical model for determining of dissolution coefficient. The numerical model ran with different dissolution coefficients and results were compared with experimental results. With this comparison and adaptation of results, the dissolution rate of halite karst determined and then used in the numerical simulation of main reservoir. With simulation of main reservoir using dissolution coefficient obtained from laboratory study, the effect of salt karst formation on reservoir’s water quality was analyzed. The influences of effective parameters such as dissolution rate, air temperature, discharge and relative humidity on the water quality of dam reservoir were studied along with carrying out a wide range of sensitivity numerical analysis. To this purpose, a versatile finite volume tool ‘MIKE’ was used. Using the experimental study and numerical simulation and implementation of results, the dissolution coefficient of salt karst formation was calculated about 0.2 cm/h. Numerical model results showed that early months of operation were not critical to the project and salt concentration in reservoir was in the range of 0.8 to 0.9 of allowable limit. But considering the changes occuring in reservoir’s conditions, the process of salinity distribution increases and salt concentration increases with time. By comparing the salt concentration in reservoir and in numerical model, it was found that the average error percentage of concentration values was about 13.65 percent and the numerical model showed the values lower than the reservoir in most times.
The sensitivity analysis of parameters affecting the salinity distribution, showed that these parameters have a significant impact on salinity distribution and salt concentration in reservoir. It was found that with 10 percent changes in studied parameters, dissolution rate with 21%, air temperature with18%, discharge with 21.1% and relative humidity with 6.1% caused changes in salt concentration of reservoir. According to the results it is evident that dissolution rate and discharge were the most important factors that influence the behavior of salinity distribution in dam reservoir.