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Aerodynamic performance improvement of airfoilsis the first step towards enhancement ofthe wind turbine performance in electricity generation and energy conversion inrenewable energy applications. The flow behavioraround wind turbine blades profilecan be improved by introducing active and/or passive flow controls. This work numerically describes the impact of adding micro-cylinder, as a passive flow control around S809 airfoil, on aerodynamic performance under various operating conditions. A suitable combination of flow analysis and optimization technique has been used in the current work.The numerical simulation has been performed using ANSYSFluent 18.2 software. The airfoil was numerically analysed in flow atReynolds number of 106; aerodynamic coefficients (lift and drag coefficients) at different angle of attacks were validated with the experimental data reported by Somers in NREL. The Response Surface Method (RSM) is applied to obtain the optimum position of micro-cylinder to achieve maximum lift to drag ratio. It has been found that the total aerodynamic forces are sensitive to the location of the micro-cylinder. A significant enhancement of lift to drag ratio can be achieved by adding micro-cylinder in front of S809 airfoil especially at high Reynolds number.

In several food processing and chemical industries, liquid is pumped and kept in interrelating coupled tanks. However, automatic regulation of the liquid level and flow control between these tanks is a challenging problem because of the complexity and high non linearity of such system. This paper deals with the liquid level control of two horizontal coupled tanks system. A comprehensive comparative study is made for most popular sliding mode control (SMC) algorithms found in literature, namely Proportional-Derivative Sliding Mode Control (PD-SMC), Proportional-Integral-Derivative SMC (PID-SMC), Fractional Order SMC and finally dynamic SMC. Special emphasis is put on the effect of the sensor noise on the controller performance. Simulated experiments including robustness to variation in plant parameters and step input disturbances are made. Control algorithms parameters are selected to optimize designed performance indices by using MATLAB optimization toolbox. Simulation results reveal that dynamic SMC is superior to other control algorithms in the presence of sensor noise and has a significant reduction in the actuator chattering phenomenon.

Abstract. Vortex flows are subject to a number of major structural changes involving very large disturbances when a characteristic ratio of azimuthal to axial velocity components is varied. Vortex breakdowns are among the structural forms that may occur. This phenomenon is one of the hydrodynamic instability problems and it is encountered in many practical application, such as, aerodynamics (in aeronautics), combustion chamber, diffusers and nozzle.The objectives of the present research are to investigate the effect of Reynolds number (Re) and circulation number (Ω) on the observed modes of the vortex breakdown. The position of the vortex breakdown with two vertical cylinder tube length as well as for clockwise and anti-clockwise flow direction is also investigated.The results revealed that there are a total of six distinct modes of the disruption of the vortex core as Re and Ω of the flow were varied. The breakdown position was found to be dependent on both Re and Ω of the flow. Whereas, for all Re values an increase in Ω always results in moving the breakdown position upstream for all Re values. The breakdown position is smaller for anti-clockwise flow direction than that, when vanes were set at clockwise flow direction for long and short tube.