This study investigates the fluid forces acting on a circular cylinder in a laminar flow regime while using a passive control strategy. Three cases including the cylinder with one, two or three rigid splitter plates attached at its rear surface were considered and the location of horizontal plates (attachment angle) was varied between 0̊ and 90. A comprehensive parametric study was performed to identify the optimum arrangement of the plates using the commercial finite element software, Comsol Multiphysics. The results show that the location and the number of the plates have crucial effects on the wake control. Increasing the number of splitter plates from one to two symmetric parallel plates led to a reduction in drag force, vortex shedding frequency and fluctuation of lift force. A maximum drag reduction of 23% for dual-splitters and 15% for single-splitter was achieved, at an angle of 45° at Reynolds number 100. However, increasing the number of attached plates to three didn't have a significant effect on flow quantities when plates of the same length were utilized. The suitability of the third plate (the middle plate) was further studied by investigating the effect of length of the plate on flow quantities.

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The semi real-time observations of oil-in-water emulsification process in a Kenics static mixer were performed using a novel in-situ visualization system. The homogenization processes and emulsion characteristics were analyzed using images taken periodically in fixed time intervals during the emulsification process. Morphological evolution of droplets was monitored and the mechanism of droplet formation was studied, both experimentally and theoretically. A wide range of dispersed phase concentration as well as surfactant concentration were used in the experiments and their impacts on emulsion characteristics were determined. Different droplet formation mechanisms occurred during the experimental results are presented. The relationship between droplet sizes, flow rate, surfactant concentration and other impact factors was visually shown, and their role in controlling the emulsification process was revealed. The minimum droplet size obtained from the dispersed phase in emulsions was shown to be perfectly monitored and controlled by this technique.

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In this paper, the effect of crosswind flow and barrier placement on the performance of the condenser fan in a subway train is investigated. In addition, the amount of heat transfer on the condenser tubes is also analyzed. At different velocities of the train, variations in the velocity profile and drag force are determined for various geometries including triangular, rectangular, symmetric triangular barriers, and a barrier with parallel lines outside of the fan. Navier–Stokes, energy equations, and k– ω turbulence model have been used for the numerical modeling of the turbulent and incompressible flow. The results show that due to the created vortices behind the triangular and rectangular barriers, a negative velocity on the outflow of the fan is observed. Also, the symmetric triangular barrier minimizes the rotational flow on the top of the fan, and parallel paths have the most impact on the improvement of the fan's performance due to the elimination of all rotating flows. Finally, variations in temperature on the condenser tubes in the presence of barriers that are placed in the middle gap between the holes on the top of the condenser tubes are determined. These barriers move the crosswind flow toward the condenser tubes and decrease the output air temperature of the condenser.

This study investigates the heat transfer in the mode of natural convection from a pair of hot cylinders to a cold square enclosure. Effects of boundary conditions of the enclosure on the rate of heat transfer from a pair of isothermal hot cylinders are investigated at a Rayleigh number of 10 5 . The cylinders are arranged in a horizontal array at the middle height of enclosure. The commercial software, Fluent (V.6.3.26), is utilized to solve the problem using the Finite Volume Method. The streamlines as well as isothermal lines of the problem are reported. Moreover, the local Nusselt number on the walls of enclosure is calculated. The results show that the boundary conditions of the enclosure have crucial effects on the heat transfer of a pair of hot cylinders.