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    Theoretical and computational investigations of the optimal tip-speed ratio of horizontal-axis wind turbines
    (Elsevier - Division Reed Elsevier India Pvt Ltd, 2018) Bakirci, Mehmet; Yilmaz, Sezayi
    An important factor in the optimization of the geometry of a horizontal-axis wind turbine (HAWT) is the design tip-speed ratio (DTSR). Previous research has suggested that DTSR values between 6 and 8 are desirable. However, a different approach was used in this study. Two standard airfoils with aerodynamic properties that are specified in the wind turbine airfoil catalog were selected and six different HAWT geometries were generated using the Schmitz formula for three DTSR values. These geometries were investigated theoretically based on the blade-element momentum (BEM) theory and numerically by using computational fluid dynamics (CFD) to calculate the rotor power efficiency and the optimal tipspeed ratio (OTSR). The six HAWTs had an average maximum power coefficient of 0.54 and an OTSR of 8.2 when the airfoil properties given in the airfoil catalog were used; these values were 0.43 and 6.7, respectively, when the airfoil properties were calculated using CFD and 0.41 and 7.3 when the HAWTs were simulated using three-dimensional CFD. To determine the power coefficient and OTSR values based on the BEM theory, the maximum value of CL/CD should be carefully selected considering factors such as the Reynolds numbers. Based on these findings, it was concluded that the CFD results validated the BEM theorem; the differences between the results obtained by these methods were likely due to the assumptions used when applying the BEM theory. (C) 2018 Karabuk University. Publishing services by Elsevier B.V.
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    Using cfd to analyze wind velocity around buildings to determine the appropriate wind velocity
    (2023) Bakirci, Mehmet; Mohammed, Noor Adil
    A 2d numerical study has been conducted by using Ansys Fluent 2020R2 program to design 4 different cases(shapes) for buildings at a different initial velocity value (2,4,6 m/sec) .in order to find a way to benefit from the areas where the winds velocity is small and it not enough to operate the winds turbines. Where a velocity analysis has been carried out for the four cases, each of them separately, and the intensity of turbulence and pressure around the buildings has been calculated. The highest velocity has been obtained at case 3, where the velocity has been reached to 4 m/sec when Vinlet was equal to 2m/sec. The best case has been determined and the streamline and the vector for velocity have been presented for the best case. The area between the two buildings has been divided to six parts. for the best case of the buildings in order to find the area where the velocity flow is high to put the wind turbine . The dimensions, height and initial velocity for appropriate turbine ,have been determined. The initial and final velocities of the used turbine have been determined. Also, the annual energy calculations have been found to increase the speed by using the Weibull distribution. finally it has been determined the annual energy production for the selected region for the first case(region without two buildings) was 68 kWatt hours, but this value increase to 294 kWatt hours in the new case (the region when putting two buildings). That means, the power was increased by 76%.