Sharif Digital Repository

The occurrence and development of scour hole around bridge pier are the main causes of bridge destruction. To predict manner, occurrence, development and final situation of scour hole around pier is the most important in the hydraulic design of bridges. A large number of studies have been performed to estimate the scour depth around piers at simplified laboratory conditions. The available equations from these studies do partly not present acceptable solutions. This issue is especially of great importance to the pile groups. For accurate determination of scour depth, it is required to get a better understanding of the flow and governing mechanism around pier. Although the flow pattern... 

Numerical simulations and large eddy simulations (LES) of turbulent flow downstream of diversion dam , pool-riffle bedform in different geometrical ratios (different lengths of riffle and pool) with flow Reynolds number of 3.0 E+04 to 3.3E+04, downstream of special case study "Mill and Moghan diversion dam" with Froude number of 0.5 are presented The calculations are performed using a computational fluid dynamics model, FLOW-3D, which solves the Navier-Stokes equations in three dimensions with finite volume method. Numerical simulations are validated by comparing the numerical results of time-averaged flow patterns downstream of pool-riffle sequence with that of the experimental... 

Hydrodynamic behavior of gas-solid fluidization in large-diameter beds like FCC regenerator exhibits complex aspects. To investigate the gas-solid flow pattern of UOP's combustor-style FCC regenerator, a lab-scale regenerator was designed by a downscale factor of 0.045. The regenerator's operation and fluidization of FCC particles through it was examined and pressure axial distributions were measured and analyzed at different superficial air velocities. 3D CFD simulation of the regenerator was performed with Eulerian-Eulerian approach to investigate the effects of operating conditions, including superficial air velocity, catalyst mass flux, presence of recirculated catalyst, and the... 

The concurrent flow of oil and water is a common occurrence in the field of multiphase flow in different fields including petroleum industry. In such conditions an accurate assessment of pressure loss inside the well plays a vital role in efficient and effective production planning. Changes in well orientation, wellbore diameter, reservoir and fluid properties as well as fluid flow rates are among parameters in which will affect the flow patterns that can occur inside a well during its life time. These flow patterns are created as a result of a competition between viscous, gravity and capillary forces. Due to the fact that the dominant forces vary for different flow regimes, the pressure... 

The present study provids an experimental investigation on two-pase flow characteristics in microchannels. Experiment were conducted with a mixture of air and water in horizontal circular pyrex channel with 400µm inner diameter. The pressure drop and flow rates of the liquid and gas were measured using new method and images of the flow patterns recorded by high shutter speed camera. The gas and liquid superficial velocity ranges were 0.025-12.5m/s and 0.016-3.6m/s, respectively. The flow pattern map is developed from the observed flow patterns based on phases superficial velocity as wel as We numbers of liquid and gas phases. The flow pattern map is compared with those of larger channels.... 

The concurrent flow of oil and water is a common occurrence in the field of multiphase flow in different fields including petroleum industry. In oil and gas, production engineers often face a situation in which more than one phase is flowing through the producers. In such conditions an accurate assessment of pressure loss inside the well plays a vital role in efficient and effective production planning. Changes in well orientation, wellbore diameter, reservoir and fluid properties as well as fluid flow rates are among parameters in which will affect the flow patterns that can occur inside a well during its life time. These flow patterns are created as a result of a competition between... 

Fuel cell is a power generator like internal combustion engines, but the first point is that internal combustion engines produce mechanical power while fuel cells produce electrical power. Secondly, internal combustion engines use hydrocarbon derivatives such as gas as fuel and their exhaust fumes are toxic gaseous, but fuel cells use hydrogen as fuel and their exhaust are only water in either vapor or liquid form. One of the most important issues in fuel cells is optimum design of micro channels of bipolar plates which is different regarding the type and application of fuel cells. Optimum designing of micro channels on bipolar plates plays a key role in fluid mass transport through micro... 

In this research, the dynamic of flow, dispersion of contaminant and characteristic of wake in the presence of two flexible stems of polyurethane is investigated in a hydraulic flume. The stream velocity of 2.28, 4.47 and 7.58 cm/s are considered, which are equivalent to Reynolds number in stem diameter scale 173, 340 and 576. The spacing ratio of two stems are one, two and three in both transverse and longitudinal direction. Velocity fields are measured using Particle Image Velocimetry (PIV) technique. The size of wake area behind stems is determined using the flow field measurement. The results show that the spacing ratio l/d affects the wake area size and interactions of wakes. The... 

Flow measurement in both types of single phase and multiphase has a crucial place in a wide variety of industries, specially petroleum industry. for single phase flowmeters, improving their precision using different types of mechanical, mathematical and analytical techniques will be considered as an important step. Using multiphase flow meters will cause no need of volume catching and costly separators and also make us capable of taking well-timed decisions in production management. for making flow meters weather multiphase or single phase, there is a crucial need of a multiphase flow loop. To achieve that, an 8-meter-long flow loop using transparent Plexiglas pipes with inside diameter of... 

Many species in nature exist which human can reach the aims of flying and swimming by inspiring from them. Observations show that fish can use their especial undulating motions of body/fins to crusing, increase performance, suddenly acceleration, and maneuvering. To design a robot fish and benefit the characteristics and abilities of a live fish, using its real geometry and kinematics in the robot is vital. Therefore, simulations are essential to better exploiting the fish behavior, which can obtain useful consequences by using computational fluid dynamics. In this thesis, first the kinematics of sharks is investigated. Then, investigations are accomplished by utilizing an unsteady finite... 

Considering the importance of oil and gas industries in Iran, issues related to drilling and exploitation of oil and gas fields are among the country's priorities and challenges in industries, research centers and universities, and extensive research is conducted in this field. Since during the process of oil production from oil wells and reservoirs, the formation of multiphase flows, including two-phase fluid flow, is inevitable, investigating the behavior of multiphase fluids, which is a branch of fluid mechanics, is of special importance. In this regard, in continuation of the research conducted in the Faculty of Chemical and Petroleum Engineering of Sharif University of Technology, in... 

Numerical simulations and large eddy simulations (LES) of turbulent flow around single pile, circular tandem piles, circular and square side-by-side piles at different spacing ratios (centre to centre distance to the pile diameter) with flow Reynolds number of 105 on the fixed flat-bed are presented. The calculations are performed using a computational fluid dynamics model, FLOW-3D, which solves the Navier-Stokes equations in three dimensions with finite volume method. Numerical simulations are validated by comparing the numerical results of time-averaged flow patterns around single and side-by-side piles with that of the experimental measurements. At the downstream of single pile,... 

Vacuum assisted resin transfer molding (VARTM) is one of the most efficient and low cost process in composite industries. In this process, the preform is covered by a flexible vacuum bag and resin flows into the mold with applying vacuum pressure at the vent. The main objective in VARTM process is preventing voids and dry spots formation in final composite part because these defects may significantly deteriorate the mechanical properties of a structure. Flow front is an important parameter in this process which have a high influence on the void formation. Resin flow control is required to prevent dry spots or micro voids during the VARTM process. In general, the flow control is classified...