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Wind energy has become the most popular renewable based power plant for the last decades due to its environment benighted and large natural availability. Although modern wind turbine successfully installed worldwide, some areas with low speed wind characteristic might require a special innovation to increase the amount of conversion of extracted wind energy into electric power. One of among popular techniques for the low speed wind turbine is Diffuser Augmented Wind Turbine (DAWT) which are continued to develop from time to time for example by using numerical simulation as an early stages before manufacturing. In this paper a numerical simulations are performed to investigate the effect of attached flange
on wind velocity characteristics. Numerical simulations were carried out for the flow field around various flange diffuser type structures to improve the performance of a DAWT. The present studies specifically investigate the effect of attached flange to outlet diffuser with various flange’s angle (0°, 10°, 20°, 30°) on the wind velocity characteristics. Numerical studies were conducted using the Computational Fluid Dynamics (CFD) method. The
studies demonstrate that the curved diffuser with flange 10° generates the strongest increment of the wind velocity compared to the other configurations. The maximum velocity inside the diffuser increases up to 115.14%. It is found that the wind velocity at the diffuser centreline is not
capable to represent the overall velocity of each section. The curved diffuser with flange 10° shows the highest increment of the average wind velocity along diffuser with the greatest increment of 102.4 % at x/L = 0.36, and the highest increment wind velocity at the diffuser centreline section at x/L = 0.18 is 115.14%.

Keywords: CFD, DAWT, Diffuser, Flange, Wind energy, Wind turbine