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Horizontally curved bridges have been observed to suffer severe structural damage during past earthquakes so determining the seismic performance of curved bridges is crucial due to the complex dynamic behavior of these structures because of their irregular geometry and non uniform mass and stiffness distributions. Analyzing and plotting the capacity curve of these structures can be costly and time-consuming. As a result, many efforts have been made to simplify the structural models of these bridges and reduce the computational workload required for their analysis. This article presents a straightforward method to convert the multi-degree-of-freedom system of these structures into an equivalent single-degree-of-freedom system, ensuring that the capacity curve of the equivalent structure closely matches that of the original structure with minimal error. In this study, the OpenSees program was used to extract the stiffness and mass matrices of a curved bridge structure. These matrices were then condensed into one-by-one matrices for mass and stiffness using dynamic condensation equations. The characteristics of these matrices were applied to a single-degree-of-freedom stick model. In this model, the obtained mass is placed at the top of a stiff rod (stick), which is connected to the ground by a spring (zero-length element) with the equivalent stiffness obtained. A nonlinear static pushover analysis of the bridge structure was performed to obtain the capacity curve. An equivalent bilinear curve was then drawn, and the yield shear force and yield displacement were determined. The nonlinear behavior of the single-degree-of-freedom structure was modeled using the Steel02 material available in the OpenSees library by zero length element utilizing the yield shear force and yield displacement magnitudes of the curved bridge. The capacity curve of the stick model, which has a single degree of freedom, showed an error percentage of 7% compared to the bridge's capacity curve. This indicates acceptable compliance with the capacity curve of the main structure, making the stick model a viable alternative for repeated analysis of the curved bridge structure. This study also included a sensitivity analysis to investigate the effects of increasing the curvature radius and decreasing the curvature angle of the bridge on its capacity and effective mass. Due to the dynamic condensation of the curved bridge structure, the influence of all degrees of freedom was considered in the stiffness and mass matrices, unlike methods that rely solely on the first vibration mode for dynamic condensation. Comparing the capacity curve of each structure with that of an equivalent single-degree-of-freedom system revealed that the structure's capacity increases with a larger curvature radius. In contrast, the lowest capacity was observed in the straight bridge scenario. Additionally, modal analysis of the studied models showed that increasing the bridge's curvature radius leads to a longer structural period, while a decreasing curvature angle has a similar effect. However, the period of the straight bridge was longer than all the other models. Furthermore, as the curvature radius increased, the mass contribution percentage of the first mode in the translational x-direction decreased, whereas the translational mass contribution percentage in the y-direction and the rotational mass contribution around the z-axis increased.

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- The effect of panel height on performance of ceiling radiant cooling system has been studied. Investigation has been done by employing solution of conservative equations, together with the radiant and thermal comfort equations. Calculation is performed for the typical hottest day of Tehran. Vapour condensation is one of the most important problems whit these systems. Therefore effect of panel height on condensation has been also studied, in a residential place with several different ranges of ventilation rate. The results show that appropriate design of the panel height can significantly reduce the rate of condensation.

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Hafez, le grand poète persan, utilise des allusions, des histoires et des récits dans ses poèmes. Le contenu de ses récits est la matière première et un plan d’expression pour transmettre des sens profonds qu'il utilise pour créer un concept important. En fait, en changeant l'allusion, Hafez fournit une analogie pour que les lecteurs n'interprètent pas sa poésie à son niveau littéral et superficiel. Pour ce faire, il choisit souvent ces analogies dans son époque même avant son temps qui sont communes entre l’énonciateur et l’énonciataire. L’objectif de cet article est de montrer que Hafez a créé un nouveau type de l’énonciation et du discours.
Cet article, en s’appuyant sur les théories sémiotiques, examine les vers narratifs de Hafez qui ont des propriétés élastiques et créent un espace cognitif condensé. L’histoire est implicitement et secrètement raconté. L'élasticité et de la condensation des énoncés en sémiotique est pour montrer les différentes dimensions qui dérivent du discours. Par exemple, l'élaboration ou le métalangage est le résultat de la largeur du discours, tandis que la nomination est le résultat de sa condensation. Les vers narratifs ont également cette dimension. À travers eux, le monde du passé et les événements historiques, diverses réalités significatives, sont représentées avec des éléments culturels. Le poète réduit la dimension du temps, reliant le passé au présent, et récite constamment des histoires du passé pour que l’énonciataire acquière une meilleure connaissance de lui-même et du monde

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In present study, volume of fluid method in OpenFOAM open source CFD package will be extended to consider phase change phenomena due to condensation process. Both phases (liquid – vapor) are incompressible and immiscible. Vapor phase is assumed in saturated temperature. Interface between two phases are tracked with color function volume of fluid (CF-VOF) method. ُSurface Tension is taken accounted by Continuous Surface Force (CSF) model and mass transfer occurs along interface is considered by Lee mass transfer model. Pressure-Velocity coupling will be solved with PISO algorithm in the collocated grid. This solver is validated with Stefan problem. In one dimensional Stefan problem, the desistance of interface motion from cold wall is compared by the analytical solution. Then condensate laminar liquid film flow over vertical plate is simulated in the presence of gravity. Numerical result shows calculated film thickness from numerical simulation is thinner than analytical solution. Also, it shows Nusselt number is a function of vapor specific heat which neglected in existing correlations, therefore analytical solution and experimental correlation should modified to consider this effect on the Nusselt Number.

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Dry Steam flow at blade passages of steam turbines' low pressure stages occurs due to rapid expansion, delay in condensation and the condition of supercooled dry steam and finally after nucleation and condensation shock, phase change from vapor to liquid droplets occurs which is called two-phase or wet steam flow. In this paper, the aim of developing finite-volume flow of wet Jameson is considered for the first time in two-dimensional study by using the advantages of CUSP's numerical method. In this paper, equations governing the formation of liquid phase are combined with equations of survival and by using CUSP's numerical approach in Jameson's finite-volume method (the integrated method) the positive features of both of these methods can be simultaneously used in the modeling of two-phase flow. To calculate nucleation, the classical equation of nucleation with appropriate correction and also Lagrangian solution for growth of droplets are used in integrated method. Additionally, condensation shock effect on the pressure distribution and the droplet size has been calculated and compared with experimental data. Given the importance of areas of shocks on the suction surface of the blade, the focus of integrated method is shifted to this area. The results of integrated two-phase model are examined in subsonic and supersonic flow output .In the shock area on suction surface blade, using the CUSP's method (the integrated method) shows a better coverage in predicting attributes of flow in target area in comparison with the experimental data by a reduction of 20 percent in numerical errors.

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In this paper, based on lattice-Boltzmann method (LBM), the steam condensation and growth of a droplet on the horizontal cold wall and falling down on vertical wall has been simulated. The Lee’s LBM model which is stable in the high density and viscosity ratios is used. This method is accompanied with solving the temperature equation and adding a phase change source term. The Lee model is based on Cahn-Hilliard theory which is assumed to be incompressible flow and therefore the velocities of the flow are divergence-free. when phase change occurs this condition will not be satisfied. A phase change source term is added on the interface of gas and liquid phase. Solution of temperature field in a passive scalar method of solving the flow field is separated and Boussinesq assumption would be influence the flow field of the temperature field. The density ratio of 25 is considered to be in this paper which is density ratio of steam and water. The model is extended to two dimensions (D2Q9) to simulate droplet condensation. The simulation results are compared in various grids. The effects of gravitational acceleration, equilibrium contact angle, the cold wall and also the mass conservation, have been investigated separately. Finally the stream field for the different time step has been analyzed.

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The prediction of distillation zone is very important in steam turbine blades and steam nozzles. In identification of distillery with equilibrium method, as the steam flow contacts the two-phase dome, the second phase formes and flow properties will pass the distillery without any jumping, therefor after crossing the saturation curve, the droplet formation transpires, but in non-equilibrium method by a sudden increase in pressure, called “condensation shock” a discontinuity in the flow characteristics is seen and after crossing the saturation curve, the formation of droplets starts. In this paper, numerical analysis of a vapor-liquid two-phase transonic flow in a convergent-divergent nozzle with and without shock is investigated. Effects of stagnation temperature at nozzle inlet, viscosity and geometry is studied using thermodynamic equilibrium and non-equilibrium methods and results compared with experimental datas. Roe numerical method is used for vapor-liquid two-phase flow numerical solution. The main properties of the flow at the boundary of elements is extrapolated by MUSCL third order acuracy and time discretization is performed using Lax-Wendroff explicit two-step method of second order accuracy. It is observed that the results of non-equilibrium solution, has more correspondence to experimental results and Condensation starts earlier in the nozzle with further expansion rate. By increasing the temperature at nozzle inlet, the place at which condensation starts goes forward. Also in comparision with non-viscous flow, the shock location in viscous flow comes closed to the throat.

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In this paper, the heat transfer enhancement by the nanoparticles in the film condensation of nanofluid over a cooled plate is studied numerically. Shooting method and modified-Euler scheme are employed to solve the condensation boundary layer equations. The effect of changes in the plate angle, nanofluid type, volume fraction of nanoparticles and Jacob number, on the velocity and temperature profiles and Nusselt number are investigated. Resulting graphs are compared and validated with the available theoretical results for the base fluid and nanofluid. The results show that the presence of nanoparticles in the liquid film of condensation increases the heat transfer from it. As the plate distances from the vertical position, the temperature change across the boundary layer is close to linear and thus, the heat transfer descends. Also it can be found that the average Nusselt number is almost constant up to the angle of 20o, and then reduces in a gradual manner, so that for instant, for water-TiO2nanofluid, by increasing the angle up to 60o, the temperature gradient is reduced by about 20 percent. Furthermore, it is seen that the relationship between the ratio of nanofluid to pure water Nusselt number and the nanoparticles volume fraction is linear, while the slope of the line for water-Cu and water-Ag is more than other studied nanofluids, i.e., these two nanofluids are more effective in heat transfer enhancement. The obtained results also confirm the fact that the Nusselt theory is only applicable in low Jacob numbers.

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In In this paper nanofluids condensation heat transfer on an inclined flat plate is investigated. To do this, thermal resistances of single droplets are calculated and the total heat flux is evaluated using population balanced theory. The nanofluids include alumina, titanium dioxide and silver as nanoparticles and water as a base fluid. Effects of different surface inclinations, nanofluids types, and nanoparticles concentrations are investigated on the heat transfer. Nanofluids properties consisting of thermal conductivity, density, dynamic viscosity, and latent heat are extracted from literature and introduced into the equations. The results are compared with some experimental data in the same conditions. The Nusselt theory is used to compare the heat transfer rate of filmwise condensation with dropwise condensation. Inspecting the results shows that the heat transfer coefficient of a vertical plate is maximum, and decreases with decreasing in inclination due to lower washing rate of small droplets by sliding droplets. The results also show that the heat transfer coefficients of various nanofluids are different but they are constant all over the surface. As well as, addition of nanoparticles to the base fluid increases heat transfer rate. It can be seen that water-silver nanofluid has the maximum heat transfer rate among three beforehand mentioned nanofluids in the same conditions and the heat transfer rate increases with increase in volume fraction of nanoparticle for a specific nanofluid.

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In present work, heat transfer and flow pattern map of dimpled and horizontal tubes were studied during phases of boiling and condensation of mandatory convection of hydrocarbon R600-a. Empirical relationship will be expressed based on empirical data obtained by such experiments and fit the experimental results and Matlab software to show flow pattern map for such refrigerant with proper accuracy. The cycle consists of a pump, two preheaters, two testing parts, two condensers, flow meter and reversing valve. In this study, experimental evaporator is a copper tube with internal diameter of 8.7 mm and length of 1200 mm. the heat required for fluid evaporation is supplied by thermal element twisted around it. Such tube has been designed in forms of dimpled and straight models to evaluate effect of placement of dimples inside tubes. The test was conducted by refrigerant mass flow between 155 and 470 kg/m^2 s and vapor quality between 0.05 and 0.78. Moreover, flow patterns and their transitions for refrigerant R-600a during flow boiling inside a helically dimpled tube and a smooth tube were visually observed and analyzed. Annular, intermittent, and stratified-wavy flow were recognized for plain tube whereas there was no stratified-wavy flow in flow pattern visualization of dimpled tube. Investigation clearly shows that the dimples in evaporation significantly impact the two phase flow pattern. Inside the helically dimpled tube the intermittent/annular transitions occurs at lower vapor quality value than for the smooth tube.

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Condensation phenomena in steam flow, can cause droplets with different sizes to form. For an exact prediction of two phase flow behavior, it is necessary to consider the effects of all droplets with different sizes on the steam. In this paper, nucleation equation in an Eulerian–Lagrangian framework has been used to analyze one–dimensional flow of wet steam in a supersonic convergent–divergent nozzle. Polydispersed and monodispersed radius methods for modeling the formed droplets are compared. In polydispersed method, all the formed droplets in the spontaneous condensation zone, are retained in the calculations, without being merged with other groups; but in monodispersed method, all groups are merged, and only one group with averaged radius is retained in the calculations. The polydispersed method has an advantage and can predict the complete droplet spectra. Results of comparing the two methods with experimental data indicates that the predicted radius in the polydispersed method, in every four investigated cases, is closer to experimental data, than that of monodispersed method.

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