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Showing 12 results for Teymouri
Volume 5, Issue 3 (Summer 2023)
Abstract
Introduction
The land of Iran is located in a belt of dry and desert areas of the earth, which suffers the most unfavorable effects from climate change. Climate change is evident in the Zayandehrud basin, and its effects are evident in the decrease of rainfall and increase in temperature in recent years, as well as the continuation of droughts in the Zayandehrud watershed. With the reduction of river water flow, the allocation of water to the agricultural and environmental sectors in the middle and downstream parts has faced a problem. The need for water in this basin is high, so that during these years, the effort to obtain water in the Zayandehrud basin has entered a new arena in the form of tension, conflict, protests, and social unrest. One of the most important consequences of climate change is that it forces governments to plan inter-basin transfers. As a result of the water transfer policies without taking into account the religious rights and the environmental rights of the Zayandehrud bed and the Gavkhoni wetland, many social differences between the provinces have intensified.
Methodology
In terms of its purpose, the current research is an applied research that considering the historical, geographical, economic and political importance of the area, identifies the dimensions and effects of climate change in the Zayandehrud watershed and explains how climate change can increase crisis and tension in the watershed. This can be a useful guide for planners and decision makers in the field. In terms of method and nature, this research is descriptive-analytic, and the method of data gathering procedure is based on library sources, including books, magazines, and databases.
Research findings
The turning of snow into rain at the source of the Zayandehrud and the increase in evaporation has led to the reduction of lands in the downstream part of the river, so that the area of "agricultural" and "pasture" lands has decreased in the middle and downstream parts. The number of wells has increased dramatically in recent years. The number of wells in the middle and downstream parts has increased significantly in this period, the average depth of the wells in the basin has increased by 4.8 meters, which is 6.65 meters in the upstream part, 5.55 meters in the middle part, and 28.28 meters in the downstream part. An average of 6 meters has been added to the depth of the wells. The increase in inter-provincial tensions, of which prominent examples were observed between Khuzestan, Isfahan and Chaharmahal Bakhtiari provinces in recent years, is one of the most important political consequences of climate change, which forces governments to plan inter-basin transfers. Isfahan farmers are the most important group protesting the critical water situation in this basin. One of the most important concerns of the people of the region and the most important cause of strikes and conflicts in recent years is the reduction of water resources and the reduction of agricultural activity. In recent years, the farmers of the region have expressed their protests in various ways, such as breaking and breaking water pipes, strikes, demonstrations and blocking the road with tractors, referring to the province and other ways. Public tension and protests regarding water supply and optimal water management for the residents of Zayandehrud Basin are not limited to the residents and beneficiaries of Zayandehrud Watershed. Hydro-political issues of the Behesht Abad water transfer project in the upper part of the Karun Basin, which has been the cause of local, regional and even national disputes between people and officials at the source and destination. This has caused social and political differences between the residents and beneficiaries of the upstream watersheds and the mentioned watersheds, and due to the ethnic differences of the watersheds, this issue has turned into an internal hydro-political crisis that has created gaps between ethnic groups. Climate change has hit the agriculture sector the most. Also, the first procedural consequence is the increase in the amount of unemployment and the immigration crisis. Immigration has led to the dispersal of kinship relations and the loss of solidarity, ethnic cohesion, and the increase of individualism and isolation, and as a result marginalization and drug addiction. The drying of Zayandehroud riverbed due to climate change has caused numerous cracks and subsidence in different areas of the watershed in Isfahan province. The depth of these cracks is very deep and in some cases they have a depth of more than 10 meters. Cracks have caused serious damages to roads and agricultural land.
Conclusions
Climate change in the Zayandehrud basin is one of the factors that threaten the water resources in the basin. The climate change and decrease in rainfall and the expansion of agriculture and water-bearing industries has led to the destruction of nature and the geographical space and the lowering of the underground water level and even the transformation of permanent rivers into seasonal and seasonal into casual and dry rivers, and to compensate for this situation, the water transfer policy. This approach has caused political and security tensions in this region. Among the hydro-political issues of the water transfer projects in the mentioned catchment basin and its negative social-political consequences can be the intensification of local and regional conflicts and divergences, jeopardizing local and regional security, political activism of people and officials, ethnic diversity and political and regional sensitivities. One of the factors that play a basic role in creating negative political activism caused by water transfer is the strengthening of political regionalism, which itself is caused by weak management policies. This leads to the formulation of "negative hydro-politics" on a national and regional scale, and in turn has negative effects on local, regional and even national security issues.
Volume 10, Issue 2 (Spring 2019)
Abstract
Effluent from dairy industry has a high amount of nutrients such as nitrate and phosphate. In this work nitrate and phosphate removal from treated dairy wastewater in the presence of organic load was investigated. For this purpose, 400ml of synthetic wastewater was inoculated with 2ml of seed culture of microalgae Chlorella salina. During the growth period, nitrate and phosphate concentration in synthetic wastewater was measured for 1, 3, 5 and 7 days with the standard method (APHA). Results showed that removal of nitrate and phosphate by the microalgae from synthetic wastewater was 100% and 95%, respectively. Also, maximum biomass production in 7 days of experiment was about 0.7g/L. These values showed that Chlorella Salina could be potential candidates by showing their intrinsic merit for removal of phosphate and nitrate from dairy wastewater and can be used in treated outlet refinement from the dairy treatment plant to be used before entering to the environment.
Volume 17, Issue 65 (4-2024)
Abstract
Shahriar Mandanipour is one of the contemporary writers who was experimental in structure and form. For this reason, the reader is challenged with spaces in his stories that are essentially an arrangement of mixed and various spaces. Dealing with this type of space in a theoretical and sometimes practical way can be observed in Michel Foucault's approach, which he calls it heterotopian or other spaces. In this regard, this study first describes these types of spaces through writings of Foucault and other thinkers who have explored in this field. Then, it analyzes these spaces in the fiction of Mandanipour including Mummy and Honey, Midday Moon, Violet Orient, and Ultramarine Blue. This study concludes that Mandanipour, by bringing up such spaces in his stories, points to the hidden truth behind the homogenous structure of one space. Moreover, introducing a new way and knowledge beyond the limitations in homogeneous spaces, heterotopian spaces help the characters from the limitations not only in understanding themselves but also the world.
Extended Abstract
The different narrative language of Shahriar Mandanipour is perhaps the most characteristic of his story writing that calls attention to the first reading. This feature is due to his interest in structure and form, which is often expected from modern storytellers because they attempt to free themselves from established structures so as to mix a new structure with the old one for their new experiences. Assuming that their type of vision cannot be offered in traditional structures, he has developed a language in storytelling that distinguishes him from any other writer and creates a unique story space in the range of this language, as the author himself points out: “Language is the purpose of writing. Therefore, it is not a means for writing stories, and the author must be able to create a range of different languages” (conversation with Shahriar Mandanipour, 2012). This convergence of different languages makes his prose complicated and sometimes unrealistic, but at the same time, it allows the author to bring almost disparate worlds together. For this reason, in his stories, the border between reality and fantasy merges, and the reader's entry into the story is like entering a labyrinth of uncertain boundaries, and this is the result of the author's experimentalism in writing stories. Now, as Mir Abedini (1998, p. 74) emphasizes: “From his very first stories, he showed that he has a thought and tries to find a suitable structure and tone for this thought, and through experiencing the form, he reaches a new understanding of reality”. The world that Shahryar Mandanipour creates in his fictional works is sometimes derived from dreams and is hyper-realistic and sometimes from myth, folklore and Iranian culture, which is special in its way and plays a significant role in the development of Iranian fiction literature. The mixing of apparently dissimilar worlds can be considered one of the most basic narrative features of this storyteller. This study attempts to shed light on space and place in the stories of Mandanipur. In so doing, this study relies on the methodology of geocriticim or spatial studies. Then, heterotopias or other spaces are described, which are influenced by Michel Foucault, in order to explain and discuss the appearance of such spaces in Mandanipour's stories. Michel Foucault's heterotopian spaces have had an important impact on space-place studies. Introducing heterotopia versus utopia as a space that challenges the knowledge of homogeneous spaces. Placing these spaces together and revealing their internal contradictions can be considered a critical reading. This is Foucault's approach in continuation of his discussion about the opposition of power and resistance, which according to him, in every discourse of power, a conflicting and challenging discourse is formed, even though it is on the sidelines. Shahriar Mandanipour, a contemporary Iranian writer makes literary use of these spaces in his stories, which is a result of his new approach to modern and experimental writing. Desert, prison, library, book and literary space, cemetery, cinema, theater, cafe, hotel, park, table, and so forth are examples of heterotopian spaces in his stores. In these spaces, the characters of his stories seek to overcome life's crises, which are often tied to death, love, tradition, politics and power. These spaces help them to challenge the homogenous spaces because they already have limited their understanding of self and the world. These heterotopian spaces in his stories are sometimes of a critical and sacred type; sometimes of the type of spaces that are for those who do not follow the rules of society and are deviant in a way; sometimes the functions of these spaces undergo changes in the form of context and time; sometimes they challenge time; sometimes it is an illusion and to cover the lack of homogenous spaces; and sometimes it is of the type of space of literature, all of which have significant impact on the lives and thoughts of the characters in the stories. The use of these spaces in the writings reviewed in this article is in line with Mandanipour's desire to create a new style in writing, and somehow these spaces help Mandanipour to have a special and different style. Mandanipour's other writings, such as The Courage of Love (1998), Censoring an Iranian Love Story (2009), Moon Brow (2018), and Seasons of Purgatory (2022) also contain heterotopian spaces that can be the subject of further studies.
Extended Abstract
The different narrative language of Shahriar Mandanipour is perhaps the most characteristic of his story writing that calls attention to the first reading. This feature is due to his interest in structure and form, which is often expected from modern storytellers because they attempt to free themselves from established structures so as to mix a new structure with the old one for their new experiences. Assuming that their type of vision cannot be offered in traditional structures, he has developed a language in storytelling that distinguishes him from any other writer and creates a unique story space in the range of this language, as the author himself points out: “Language is the purpose of writing. Therefore, it is not a means for writing stories, and the author must be able to create a range of different languages” (conversation with Shahriar Mandanipour, 2012). This convergence of different languages makes his prose complicated and sometimes unrealistic, but at the same time, it allows the author to bring almost disparate worlds together. For this reason, in his stories, the border between reality and fantasy merges, and the reader's entry into the story is like entering a labyrinth of uncertain boundaries, and this is the result of the author's experimentalism in writing stories. Now, as Mir Abedini (1998, p. 74) emphasizes: “From his very first stories, he showed that he has a thought and tries to find a suitable structure and tone for this thought, and through experiencing the form, he reaches a new understanding of reality”. The world that Shahryar Mandanipour creates in his fictional works is sometimes derived from dreams and is hyper-realistic and sometimes from myth, folklore and Iranian culture, which is special in its way and plays a significant role in the development of Iranian fiction literature. The mixing of apparently dissimilar worlds can be considered one of the most basic narrative features of this storyteller. This study attempts to shed light on space and place in the stories of Mandanipur. In so doing, this study relies on the methodology of geocriticim or spatial studies. Then, heterotopias or other spaces are described, which are influenced by Michel Foucault, in order to explain and discuss the appearance of such spaces in Mandanipour's stories. Michel Foucault's heterotopian spaces have had an important impact on space-place studies. Introducing heterotopia versus utopia as a space that challenges the knowledge of homogeneous spaces. Placing these spaces together and revealing their internal contradictions can be considered a critical reading. This is Foucault's approach in continuation of his discussion about the opposition of power and resistance, which according to him, in every discourse of power, a conflicting and challenging discourse is formed, even though it is on the sidelines. Shahriar Mandanipour, a contemporary Iranian writer makes literary use of these spaces in his stories, which is a result of his new approach to modern and experimental writing. Desert, prison, library, book and literary space, cemetery, cinema, theater, cafe, hotel, park, table, and so forth are examples of heterotopian spaces in his stores. In these spaces, the characters of his stories seek to overcome life's crises, which are often tied to death, love, tradition, politics and power. These spaces help them to challenge the homogenous spaces because they already have limited their understanding of self and the world. These heterotopian spaces in his stories are sometimes of a critical and sacred type; sometimes of the type of spaces that are for those who do not follow the rules of society and are deviant in a way; sometimes the functions of these spaces undergo changes in the form of context and time; sometimes they challenge time; sometimes it is an illusion and to cover the lack of homogenous spaces; and sometimes it is of the type of space of literature, all of which have significant impact on the lives and thoughts of the characters in the stories. The use of these spaces in the writings reviewed in this article is in line with Mandanipour's desire to create a new style in writing, and somehow these spaces help Mandanipour to have a special and different style. Mandanipour's other writings, such as The Courage of Love (1998), Censoring an Iranian Love Story (2009), Moon Brow (2018), and Seasons of Purgatory (2022) also contain heterotopian spaces that can be the subject of further studies.
Hamid Yousefi, Ehsan Khavasi, Saba Teymouri, Parsa Nazmi, Zahra Mashhadi,
Volume 18, Issue 1 (3-2018)
Volume 18, Issue 1 (3-2018)
Abstract
Density currents flow due to the density difference between the current and surrounding environment. An important category of density currents is called turbidity currents, which density difference created as a result of suspended solid particle presence in fluid. In the present study, it is tried to use both Eulerian-Eulerian and Eulerian-Lagrangian methods, to take advantage of each one. In this way, the larger particle that have a more effective role in sedimentation mechanism due to the more falling velocity are calculated as Lagrangian and smaller particles by the Eulerian method. In order to obtain a criterion for particle assortment, seven currents with different particle sizes in the Eulerian-Eulerian model have been numerically simulated in a simple channel and it is compared with no particle case, and also the Eulerian-Eulerian method has been verified with experimental results and identified when the particle sizes is less than 12 micron, the sedimentation process is not appreciable, and the presence effect of these kind of particle can be ignored. Therefore, the Eulerian-Eulerian method is a suitable method for this case. The Eulerian-Lagrangian method validation has been performed with experimental results. Finally, the current inside the channel with a spectrum of particle dimensions is simulated and described the results by the proposed method (the combination of two methods). To perform numerical simulations, the development of open-source OpenFOAM codes has been used to take into account the effect of particle. Due to the current’s turbulence, a Large Eddy Simulation method has been used for turbulent modeling.
Volume 18, Issue 1 (may 2018)
Abstract
Data showed that by increasing the adsorbent dose, the availability of sorption sites eased resulting in greater percentage removal of the dye. The percent adsorption increased with increased contact time. Maximum quantitative removal of MB from an aqueous solution was obtained in 10 min for GFP contact time. The pH of an aqueous solution is an important factor in dye adsorption, as it affects the surface charge of the sorbent material and the degree of ionization of the dye molecule.The effect of pH on the amount of MB adsorbed onto fruit pulp was investigated over the pH range from 2 to 12. amount of dye adsorbed per unit mass of the adsorbent increased with increase in the initial concentration up to 25 mg/L. The When the of the solution was 2-6, the sorption of methylene blue was slightly weaker than at pH 6-12 due to poor dissociation of carboxyl Groups. The qe was found to increase with increasing pH. Optimal pH was determind 9. This can be on the basis of a decrease in competition between positively charged H and MB for surface sites and also by decrease in positive surface charge on the adsorbent, which results in a lower electrostatic repulsion between the surface and MB. SEM is one of the useful tools to examine the surface morphology of the biosorbent the SEM micrograph shows that the surface of GFP was porous.FTIR analysis showed that the main functional sites taking part in the sorption of MB included carboxyl and hydroxyl groups. Adsorption data are most commonly represented by the equilib-rium isotherm value, which is a plot of the quantity of the sorbate removed per unit sorbent (qeq) as the solid phase concentration of the sorbent against the concentration of the sorbate in the liq-uid phase (Ceq). The equilibrium isotherm value is of fundamental importance for the design and optimization of the adsorption sys-tem for the removal of a dye from an aqueous solution. Therefore, it is necessary to establish the most appropriate correlation for the equilibrium curve. Several isotherm models have been used to predict validity of the experimental data. The Langmuir isotherm is based on the assumption of monolayer adsorption on a structurally homogeneous adsorbent, where all the adsorption sites are identical and energetically equivalent, wherein the adsorption occurs at specific homogeneous sites within the adsorbent, and once a dye molecule occupies a site no further adsorption can take place at that site. The results indicate that the data for adsorption of dye (R2= 0/9738) fitted well with Langmuir isotherm. Studies suggest that GFP can be effectively used as a cost-effective adsorbent for removal of MB from aqueous solution. Batch adsorption studies show that removal is dependent upon process parameters like pH, sorbate and sorbent concentrations and contact time. The experimental equilibrium sorption data obtained from batch studies at optimized conditions fit well to Langmuir adsorption isotherm equation, indicating monolayer adsorption. FTIR analysis showed that the main functional sites taking part in the sorption of CV included carboxyl and hydroxyl groups. The number of experiments decreased of 256 to 64 by Taguchi method. Based on this that many textile industrial waste waters have an alkaline pH(8-12),this adsorbent can be used instead of effective compound. The present work shows that GFP is an efficient sorbents for the removal of methylene blue from aqueous solution and it may be an alternative to more costly sorbents such as activated carbon. The Taguchi method was efficient manner for optimizing process.
Volume 19, Issue 122 (April 2022)
Abstract
In this study, natural dye curcumin wasused to monitor the quality of packaged fish meat through color changing indicators and the color changes of the indicators were evaluated visually and with colorimeter during storage of fish samples at room temperature (for 60 hours) and in the refrigerator (for 12 days). In order to evaluate performance of paper indicators for monitoring the quality of fish, the quality characteristics of fish such as total viable count, pH, and TVB-N were evaluated. This indicator had very good characteristics such as less moisture absorption than the control, excellent stability during storage for 30 days, and high selectivity to pH changes. The FTIR results showed that the curcumin was well stabilized on cellulose filter paper. The results of color changes of the indicator during fish storage indicated that with increasing the storage time, the brightness (L *) of the indicator based on curcumin significantly decreased and red-green (a *) and yellow - Blue (b *) parameters increased. Colorimetric indicator based on curcumin indicated significant color changes from yellow to orange due to sensitivity to pH and detection of TVB-N and hydrogen sulfide compounds. According to the results obtained from the qualitative characteristics of fish in relation to performance and function of colorimetric indicator during fish spoilage, it can be concluded that curcumin provides a promising approach in intelligent packaging systems for meat products to monitor fish meat freshness.
Volume 19, Issue 127 (September 2022)
Abstract
Flaxseed oil is sensitive to oxidation due to its high content of polyunsaturated fatty acids. Antioxidant sources such as olive leaves can be used to stabilize it. Olive leaves contain lipase and lipoxygenase enzymes that need to be removed before use. Therefore, the aim of this study was to investigate the extraction of oil by cold pressing of flax seeds with blanched leaves steamed at levels (0 (control sample), 2.5, 5, 7.5 and 10% w/w) is. Acidity, peroxide, phenolic content, fatty acid composition, chlorophyll content, carotenoid content and oxidative stability of extracted flaxseed oil were investigated during storage. The results showed that by adding different levels of blanched olive leaves, the acidity and peroxide number decreased and the amount of carotenoids, chlorophyll, phenolic compounds content and oxidative stability of oil samples in different levels of blanched olive leaves significantly increased compared to the control sample(P <0.05). On the other hand, during the storage period in the treated samples, the acidity and peroxide number of the samples increased significantly (P <0.05) but this increase was less than the control sample. Also, fatty acid profiles showed that by adding blanched olive leaves, the linolenic acid (18: 3) was preserved during further storage. According to the obtained results, it can be said that with the addition of blanched olive leaves, phenolic compounds in the produced oil increased and also oxidative stability increased and beneficial compounds such as linolenic acid and more carotenoids were preserved and a useful oil can be produced and offered to the consumer market.
A. Bagheri-Bami, S. Amini , R. Teymouri ,
Volume 20, Issue 2 (February 2020)
Volume 20, Issue 2 (February 2020)
Abstract
The ball deep rolling process is used to improve the surface properties of the workpiece. In this research, the optimum state was determined using the design of the experiment to improve the properties including optimum hardness and roughness. It was determined 3 passes and the type of traditionally and ultrasonic process and proposed regression model at the speed of 1000mm/min. In this case, it showed the hardness of 131 micro vickers and also determined minimum roughness in the mean roughness of 0.179 microns and the maximum roughness of 1.01 microns. The microstructure and tensile tests have been investigated in the optimal sample, compared to the surface topographic reference sample. The microstructure has been shown the decreases from about 30-50 microns to about 300 nanometers in thickness at about 50 microns below the surface by scanning electron microscopy. The tensile stress and percentage increase in length were determined by 10% and 29% increase, respectively by the tensile strength test. Topography has also shown the reduction of roughness by 40%. The hardness of the subsurface was studied in the thickness of the workpiece and it was compared to the same traditional and modern optimum specimen. The result showed the effect of increasing the hardness due to the of the structure fracture and strain rate.
Volume 20, Issue 3 (5-2018)
Abstract
An experiment was carried out to study the effect of Hull-Less Barley (HLB) replaced for dietary corn at the rate of zero, 25, 50, 75, and 100% with two levels of Enzyme Cocktail (EC) supplementation (0 and 0.5 g kg-1 of diet) on performance of broiler chickens during the finisher period. Four hundred and fifty male broiler chickens aged 24-days were randomly assigned to 50 pens in a Complete Randomized Design (CRD) experiment, in a 5×2 factorial arrangement, with five replicates of 9 birds each. There were no significant differences in Average Daily Gain (ADG), Average Daily Feed Intake (ADFI), and Feed Conversion Ratio (FCR) of birds fed diets with zero, 25, 50, and 75% HLB replacement for corn, whereas the complete replacement of HLB for corn in diet significantly decreased ADG and ADFI and increased FCR. The GastroIntestinal Tract (GIT) organs relative weights and ileal chyme viscosity were significantly increased, and serum lipid metabolites concentrations significantly decreased by the increase in dietary HLB levels. A significantly shorter and thicker villi and thicker muscular layer in jejunum of chickens were observed when diet HLB level increased. The dietary EC supplementation significantly reduced the adverse effects of high dietary level of HLB on performance and GIT characteristics. It is concluded that HLB is a good alternative for broiler finisher diet, if substituted for up to 75% of corn. In addition, supplementation of EC in the finisher diet can decrease the adverse effects of high level of HLB on performance of broiler chickens.
Volume 21, Issue 3 (5-2021)
Abstract
In this study, the effects of the concrete rings as well as the far and near field earthquake on the frequency and seismic behavior of the intake tower have been investigated. For modeling and analysis with considering the interaction of water and structure, ANSYS software which is based on the finite element method is used. For a better analysis of these models, two far and near field earthquakes have been selected and scaled to the same maximum value acceleration. To evaluate the effects of concrete rings on the behavior of the intake tower, 33 intake tower models have been modeled by considering concrete rings in different numbers and height levels. In the following, 66 analyzes have been performed for three modes of the tower, including only the structure of the intake tower without a reservoir, the intake tower with the surrounding reservoir and without inside water, and the intake tower with the surrounding reservoir and inside of the tower is full. The results of displacement, stress, and base reactions of the intake tower under the relevant analyzes have been compared with each other. Based on the results, it was found that the effects of a near-field earthquake at maximum displacements and stresses are far greater than a far-field earthquake. However, the values of the responses depend on the frequency of the earthquake in addition to its proximity to the field. The results also showed that surrounding water and internal water have different effects on the seismic response of intake towers affected by near and far-field earthquakes. The presence of water increases the effective duration of the earthquake on the response of the intake tower, especially in the near field earthquake. The results showed that by adding circular rings, the frequencies of the intake towers undergo significant changes, which require seismic analysis to evaluate its effects. In the case of an intake tower without a surrounding reservoir and an intake tower with a surrounding reservoir and without inside water, the maximum values of displacement decrease with increasing the height of the concrete rings and decreasing the distance between them. For an intake tower with a surrounding reservoir and full inside, in the case of far-field earthquake analysis, the greatest reduction in displacement occurs for an intake tower with a ring at 25 meters, while for a near field earthquake, in this case, the amount of displacement is further reduced with an increasing height level of concrete rings. The pattern of changes in the first principal stresses for all the studied models is also in accordance with the changes in the values of the maximum displacement. The maximum values of the base reaction for the intake tower without surrounding reservoir and the intake tower with the surrounding reservoir and without inside water for near field earthquake are greater than for the far-field earthquake while for the intake tower with surrounding reservoir and full inside for far-field earthquake it is more than a near field earthquake which is due to the frequency content of the desired earthquakes. Eventually, the results showed that adding concrete platforms at high and close to each other has very good and positive effects also reduces the maximum values of stress, base reaction, displacement, and relative displacement.
Volume 21, Issue 4 (10-2021)
Abstract
This paper presents a non-hydrostatic two-dimensional vertical (2DV) numerical model for the simulation of wave-porous structure problems. The flow in both porous and pure fluid regions is described by the extended Navier-Stokes equations, in which the resistance to flow through a porous medium is considered by including the additional terms of drag and inertia forces. The finite volume method (FVM) in an arbitrary Lagrangian-Eulerian (ALE) description is employed to discretize the flow and transport equations. A two-step fractional method has been deployed to solve the governing equations. In the first step, the momentum equations in the absence of pressure field were solved to compute an intermediate velocity. The second fractional step consisted of bringing the pressure terms back into the equations, and calculating the pressure field by solving the extended continuity equation and the momentum equations excluding advective and diffusive terms and drag force components. By substitution of the approximations of the pressure derivatives into momentum equations, and subject to the continuity constraint, the pressure Poisson equation was obtained. The solution of the pressure Poisson equation led to a linear system of equations in the form of a block tri-diagonal matrix with the pressures as unknowns. The second step was completed by computing the updated velocity values. In the present numerical model, two types of boundary conditions, namely Dirichlet and Neumann boundary conditions were adapted to solve the governing equations. The Dirichlet boundary condition was set to zero for normal velocities at impermeable bottom and the Neumann boundary condition was considered to be equal to zero for normal gradient of the tangential velocities at impermeable bed and also the left side of the computational domain. At open boundaries, where required, by setting the dynamic pressure equal to zero at the end of the numerical domain, a free exit for water was considered. The newly developed model in the absence of porous medium was verified by comparing the numerical simulations with the analytical solutions of a solitary wave propagation in a constant water depth. The newly developed model was then employed to simulate the solitary wave interaction with a permeable submerged breakwater. Based on the numerical results, when the solitary wave front reaches the offshore side of the submerged breakwater, due to the hydraulic jump formation, the flow is separated from the top of the obstacle and small clockwise vortices are generated at the leading edge of the breakwater. As the wave passes over the breakwater, the primary vortex grows in size and penetrates into the deeper layers of water. It was also seen that, due to the drag and inertia resistance forces of the porous medium, the velocity inside the permeable breakwater was noticeably smaller than that on the top of the breakwater. The comparisons between the numerical results and experimental measurements for time histories of water displacements, spatial distributions of free surface elevation, velocity fields and velocity profiles in both horizontal and vertical components, showed the capability of the newly developed model in predicting wave interaction with permeable submerged breakwater.
Volume 22, Issue 4 (7-2022)
Abstract
Alkali-Aggregate Reaction (AAR) is a type of destructive and time-dependent chemical process in concrete that occurs between alkali ions in the cement and reactive minerals in certain types of aggregates. First recognized in 1930s, AAR is divided into two major categories of Alkali-Silica Reaction (ASR) and Alkali-Carbonate Reaction (ACR), both of which produce an expansive gel in the concrete which expands as a result of water absorption. The expansion of the AAR gel exerts significant internal pressure in the concrete, which may lead to internal and external cracks. With the occurrence of such cracks, many parameters affecting the stiffness and strength of the structure, such as compressive strength, tensile strength, and modulus of elasticity are diminished. As a result, the safety and serviceability of the structure may be seriously impacted. While advances in concrete materials science have led to means to prevent AAR in new construction, numerous existing structures worldwide, such as dams, power plants, and bridges, are affected by these reactions, the replacement of which may be impractical, or in some cases, impossible. As a result, it is crucial to simulate the behavior of such structures for reliable estimation of their safety and providing rehabilitation measures as necessary. One of the major indicators of AAR is the anisotropic expansion it generates inside the concrete member, which changes drastically based on the boundary conditions and internal and external restraint imposed on the expansions. As a result, the prediction of the anisotropic expansions is of utmost importance in successful simulation of AAR-affected reinforced concrete structures. This paper presents a practical simulation methodology for estimating the directional distribution of AAR expansions. The methodology makes use of the user subroutine capability in the finite element software Abaqus. A mathematical model is used to simulation AAR-related expansion based on the stress tensor, whereas concrete damage is simulated using the concrete damage plasticity model. The model is used to simulate a variety of AAR-affected reinforced and plain concrete cube and beam specimens for which the directional expansion data have been reported in the literature. Comparison between numerical and experimental results shows that the proposed methodology is capable of reliably simulating the AAR-induced expansions and the interaction between AAR expansions and the ensuing damage for a variety of reinforcement configurations. The model showed that the yield strength of reinforcing bars plays a major role in the directional distribution of expansion. However, changes in the mechanical properties of concrete were found to be inconsequential in the distribution of the expansions. Moreover, changes in distance between reinforcing bars and the reinforcement ratio in each direction were observed to affect the accuracy of the model. However, the model was found to be successful in reasonably capturing the trends in all case studies investigated. The results of this study are of great value to the simulation of AAR-affected reinforced concrete structures.
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