Sharif Digital Repository

Wake aerodynamic of plunging airfoils have received less attention than the other unsteady phenomena. An experimental investigation was carried out to study the unsteady characteristics of flow field behind a model of a plunging airfoil in various conditions. The model has 0.25cm chord and is the 16m section of a 660kW wind turbine blade. All tests were conducted in the subsonic closed circuit wind tunnel in Iran. Invariable parameters were plunging amplitude, mean angle of attack and plunging frequency. The Wakes of plunging airfoil can be characterized as drag-producing, neutral, or thrust-producing .Our preliminary results show that the structure of vortex in the wake for the plunging... 

In last years, many researches are focoused on improving of suspension systems because of their importance in automotive afavourable performance. One of these advanced suspension systems are Magnetorheological suspension with nonlinear dynamic system and complicated behavior like Hysteresis Loops, so their modeling are notable.
In the first chapter as introduction, suspension systems and their aims are expressed briefly. Then Magnetorheological suspension structure and its function are mentioned. After review of researches that has done about its modeling and control , in the third chapter, different types of classic and generalized Prandtl-Ishlinskii models are introduced and... 

As a result of numerous earthquakes happened in recent decades, widespread failures were observed in conventional braced frames, which were mostly created due to buckling of the braces under compression. To find a solution to overcome this problem, Ribbed Bracing System (RBS) was developed by Golafshani et al. in 2004. In this study, continuing the experimental investigation and considering the previous outcomes, the RBS bracing was redesigned based on some modifications. Then, two half-scale RBS braces with pinned frames were constructed and tested under cyclic loading. RBS systems were utilized in two options, CC-RBS and SC-RBS, in X configuration, the first of which was constantly... 

Wettability of reservoir rock is one of the effective parameters in determining the mechanisms of production and consequently the amount of residual oil inside the porous media. In addition, the salinity of injected water is important factor in the recovery of reservoir oil in waterflooding.On the other hand, the role of the hysteresis on the residual oil saturation as well as the flow functions such as relative permeability curves is very important. In this project, the effects of reservoir wettability and injected water salinity on the hysteresis and residual oil saturation in two-phase water-oil flow systems are studied. Core-scale experiments were carried out using sandpacks and were... 

It is aimed in this study to numerically investigate the effect of contact angle on the heat transfer coefficient in oil-water two-phase flow. For this purpose, the finite element method (FEM) is used to solve the unsteady Navier-Stokes and energy equations. The level set method is also used to capture the interface between the phases. In the first part of the study, two-phase flow of the water and calibration oil is considered in a T-junction geometry at contact angles of 5°, 40°, and 75°. It is observed that the flow patterns formed in the microchannel depend on the initial flow condition which results in the hysteresis phenomenon. Investigating the effect of wall contact angle on the... 

Understanding many issues related to environmental geotechnics and soil sciences such as: instability and collapse of soil slopes, sinkholes, leakage from landfills and isolation of nuclear landfills, and optimization Agricultural processing depends on our knowledge of the behavior of unsaturated soils and their volume changes. To better understand the behavior of unsaturated soils, it is important to study the soil-water retention curve (SWRC) and the factors affecting it. These include factors such as porosity, grain size distribution, soil minerals, pore size distribution, and pore water chemistry, which affect soil-water retention curves and volume changes. Since the simultaneous effect... 

So far, many studies have been carried out on the core-scale regarding the effects of hysteresis on the macro-scale properties of systems including fluids and porous rock, however, many issues related to the physics of the problem (especially regarding the way fluids are distributed and the trapping of the non-wetting phase) at the pore-scale need further investigation. In the process of multiphase fluid flow in porous media, hysteresis refers to the dependence of the results of the fluids’ displacements on the history of fluid saturation and the direction of saturation changes (increasing or decreasing). The first step to investigate the hysteresis effect is to determine the amount of fluid... 

In the present study, the effect of the diffuser inlet-to-nozzle exit area ratio (A_d/A_e ) on the gradual starting performance of a second throat exhaust diffuser has been investigated experimentally. Experiments have been carried out with four conical nozzles with different expansion ratios and considering two approaches of gradual increase and gradual decrease of nozzle chamber pressure by a high-pressure air tank. Investigations show that at high area ratios before starting the diffuser, oscillations in the pressure of the test chamber are created due to the instability of the flow at the diffuser inlet. By frequency analysis of the vacuum chamber pressure, it is observed that as A_d/A_e... 

Due to environmental concerns about fossil fuels energy sources, countries are striving to replace fossil fuels with renewable energy sources. However, most alternative energy sources are highly dependent on weather and seasonal conditions. Underground hydrogen storage (UHS), unlike carbon dioxide storage which only experiences the gas injection phase, involves injection and production cycles. Therefore, it faces different challenges, each of which has different effects on the final hydrogen recovery rate and, consequently, cost estimation. Some of the major challenges ahead include the reservoir structure, heterogeneity of reservoirs, selection of suitable cushion gas, the impact of the... 

Mass or large-scale storage of hydrogen, as a clean source of energy, should be conducted in underground formations in order to be used as a reliable energy source at the peak of consumption. In this regard, underground formations such as aquifers and depleted hydrocarbon reservoirs are the most favorable and secured media for hydrogen storage. However, detailed understanding of the flow dynamics of hydrogen-water in these media is critical to maximize hydrogen storage and recovery and tackle the existing uncertainities which exist in the flow functions. To fill this gap, this research aims at a detailed pore-scale investigation of the effect of flow regime, hydrogen compressibility, and...