فهرست مطالب e. jabbari

The Multiquadric Radial Basis Function (MQ-RBF) method, despite its advantages, has not yet been developed to be used for Dam-Reservoir-Foundation Interaction (DRFI) problems. In this study, this mesh-less method was developed for solving the DRFI systems in the frequency domain. A new domain decomposition technique was also used for analyzing dynamic interaction problems for the first time in MQ-RBF. In this regard, the computational domain is divided into dam, reservoir, and foundation subdomains. Then, the MQ-RBF method is separately applied to each subdomain. For applying the dynamic interaction between two adjacent subdomains, two Multiquadric shape functions must be considered for each computational center on their interaction boundary. Besides, each shape function is also defined using the computational centers in the subdomain. One of the important challenging issues in RBFs is the determination of the Optimal Shape Parameter (OSP). Thereafter, some new relations in terms of the earthquake frequencies are proposed for the OSPs in different cases of the interaction systems. In this regard, a few frequency magnitudes were considered and, consequently, different relations were presented for all frequencies using the obtained OSPs. It is found that, the OSP does not depend on the shear modulus of neither the dam nor the foundation. Moreover, the OSP value are not sensitive to the fluid compressibility and do not depend on the number of subdomains. Apparently, these properties reduce the computational costs and facilitate the MQ-RBF application. In order to validate the capabilities of the approach, nine numerical examples are solved in which the Roots Mean Square Error (RMSE) criterion has been evaluated for comparing the results with those of the exact and FD methods. Results show that the proposed method is of acceptable accuracy, i.e. more accurate than FD even with much more FD computational nodes. Also, it is shown that the errors increase by increasing the earthquake frequency value while the FD errors seem to be unacceptable in frequency values close to the resonance frequency, unlike those of the MQ-RBF.

In this study the fluctuating loads of the control gate in the experimental model of the bottom outlet of a dam was evaluated. The production, transportation, and dissipation of turbulent flow eddies based on Kolmogorov theory were investigated by image processing of the flow under the control gate, time series of velocity and static pressure fluctuations. According to the results 1- the flow turbulence at 10% opening of the control gate can be related to large eddies of middle and lower half streamlines of the upstream conduit. 2- The flow turbulence at 30% opening of the control gate can be related to large eddies of lower half streamlines of the upstream conduit. 3- The flow turned turbulent at 50% and 70% opening of the control gate can be related to large eddies of upper half streamlines of the upstream conduit. It can be concluded that the middle and lower streamlines of the upstream conduit play a major role in eddies production and flow turbulence at smaller openings of the control gate. In contrast, the upper streamlines of the upstream conduit play a major role in eddies production and flow turbulence at larger openings of the control gate. Large eddies are produced by shear layers created by velocity gradient at the guide slots of gate. The large eddies are transported by side guide slots toward the gate create strong secondary flows. After the collision of strong secondary flows with the main flow, the resulting turbulence leads to fluctuating static pressures. These fluctuations lead to the fluctuating loads on the control gate. Wavelet analysis of the time series provides the magnitude and frequency of pressure waves. Then, wavelet analysis and imaging of the gate flow reveal the causes of the turbulent flow formation process. The size and frequency of these large eddies range from 7.5 mm to 25 mm and 0.1 Hz to 2 Hz, respectively.

Khorram Abad plain is located in the folded Zagros zone and its River, as one of the main rivers discharging to Karkheh River, flows through this plain. This region is highly influenced by the neotectonic activities of this fault since Khorram Abad’s hidden and active fault is located in this region. Therefore, the current study aimed at the investigation of the effect of this fault’s activities on the morphological activities of Khorram Abad River.

This is an empirical study that is quantitative in terms of used data and calculations. Remote-sensing techniques, geometrical indices, aerial photos, satellite images, and field studies are used in the current research. For this purpose, the river’s route was divided into five subzones to be more precise. Then, the aerial photos taken in 1955 were compared to Google Earth’s 2016 images in GIS. Geometrical indices such as the gradient of the river’s slope and sinuosity of the mentioned five subzones were calculated by the digitization of the river’s route in AutoCAD; the profiles and the changes in the alluvial terraces were measured through field observations.

Khorram Abad River’s geometrical indices indicated that Khorram Abad’s anticline and its upstream regions are upheaving and the downstream regions are subsiding or staying in their previous positions. This ascending trend has been followed by an increase in the average riverchr('39')s slope has changed the number of the tributaries and geometrical properties of the river.

The primary reason for the morphological changes in the Khorram Abad River is the geological movements. Then, the movements of Khorram Abad hidden thrust fault were the most important factors changing the morphology of Khorram Abad River in the studied period.

Studies have shown that most of the particles sprayed on emergency respirational patients, accumulate inside the endotracheal tube and its connector. In this paper, applying Computational Fluid Dynamics (CFD) and Response Surface Method (RSM), an optimized geometry is introduced for higher efficiency of the drug delivery for patients with emergency respiratory diseases. In CFD modeling, finite volume method and for two-phase flow modeling, Lagrangian method is used. Reynolds averaged Navier–Stokes equations with Reynolds stress turbulence model are solved using SIMPLE pressure correction algorithm within the computational domain. The velocity fluctuations are simulated using the Discrete Random Walk (DRW). For optimization process, six different parameters including three dimensions of the connector of the tube: connector length, connector diameter and injection diameter, injection velocity of the drug particles, air flow velocity and particle size are investigated. Using Design of Experiments (DOE) and RSM, the output efficiency of the model and second-order regression equation model are derived and accuracy of the model is confirmed. Then the effect of each input parameter on the efficiency is investigated. Dringer algorithm is applied to optimize the process and the best combination of input parameters yielding the highest efficiency is introduced.

In this research, the behavior of the morning glory crest and throat were investigated in the event of flood. Spillway structure and dam reservoir fluid were respectively simulated using the finite element method and finite volume method in ANSYS software. The morning glory structure's behavior was performed in three scenarios: a) the static analysis scenario of the dam empty reservoir, b) the static analysis scenario of the full reservoir while there is no flow over the spillway crest, and c) the dynamic analysis scenario of structure-fluid interaction in two parts: 1- starting of the flood flow on the morning glory spillway, and 2- the steady state flood flow on the morning glory spillway. The concrete structure analysis was linearly done in all three scenarios. Based on the results, the most critical condition for the structure in terms of maximum tensile stress was 5.3 MPa in the first part of the third scenario. The maximum compressive stress was 12.3 MPa in the second part of the third scenario. Spillways are one of the most important and vital structures in the life of a dam. The efficiency and proper functioning of such structures requires a precise and responsible design. The morning glory spillways have a great deal of importance due to the standing structure inside the dam reservoir. The weight and hydrodynamic loading on the body of spillway concrete structure during a flood complicates the interaction analysis of the structure and the fluid. By using numerical methods in computational fluid dynamics and structural analysis, we will be able to predict the behavior of structure and fluid hydrodynamics parameters. In model's fluid domain, choosing the type of Navier---Stokes equations proportional to the efficient RANS mathematical model of turbulence, is very sensitive. Mainly one equation turbulence models such as the Spalart-Allmaras or two-equation models, such as K-Epsilon or K-Omega, are based on Boussinesq hypothesis. Boussinesq hypothesis explains how to estimate the components of the fluid stress tensor for the above-mentioned turbulence equations. This assumption, by simplifying the computation process, only a in some parts of the fluid domain, analyzes the turbulence as anisotropic.

 In this paper, multi-objective optimization (MOO) of heat transfer and flow field in cross-flow heat exchangers with triangular and square arrangement is performed using Computational Fluid Dynamics (CFD) techniques and Non-dominated Sorting Genetic Algorithms (NSGA II). At first, fluid flow is solved numerically in 150 various heat exchanger using CFD techniques. Finally, the CFD data will be used for Pareto based multi-objective optimization of fluid flow in cross flow heat exchanger using NSGA II algorithm. In the MOO process there are two geometrical parameters and the conflicting objective functions are to simultaneously maximize the amount of heat transfer and minimize the pressure drop. The Pareto front including optimum design variables and objective functions for two triangular and square heat exchangers are shown in results. It is shown that the achieved Pareto solution includes important design information on fluid flow in the heat exchangers.

One of the most important pillars of optimized multi-purpose reservoir optimization models is the definition of a penalty or loss function. Due to the variety of operating goals and the complexity of the system, they often use alternative functions instead of using profit and cost functions, which only consider certain goals. These functions are the sum of several expressions that reflect the penalty or damages corresponding to the deviation from the desired values ​​(needs). In this case, one of the most important steps in developing an optimization model is to determine the coefficients and capabilities (parameters) of these functions. This paper uses a dynamic stochastic programming (SDP) model to optimize the operation of a multi-purpose tank. With the help of this model, the parameters of the damage function have been evaluated through sensitivity analysis. For this purpose, the criteria of reliability, reversibility, and vulnerability have been used. Studies show that these parameters are much more sensitive to changes in the power of functions than the coefficients of functions.