Diffuser augmented wind turbines (DAWTs) are incredibly beneficial to low wind speed areas. The duct that surrounds the turbine improves the power output by accelerating the approaching wind directing the wind through the blade. The power output of DAWT mainly depends on the duct length by turbine diameter (L/D) ratio, duct angle, axial distance, and tip clearance between the blade and duct. This article gives an insight into the performance variation of DAWT for various duct L/D ratios. Numerical simulations were performed on DAWT using ansys fluent, and the performance characteristics were studied for different duct L/D ratios, duct angles, and axial distance. The investigations found that axial distance of 0.06D for duct L/D ratios between 0.15 and 0.60 gives improved performance. It was found that the optimal duct angle is a function of the L/D ratio, and as the L/D ratio increases, the duct angle increases. A geometric procedure was used to find the pattern in which the angle increases in other L/D ratios. The geometric procedure helps to keep the duct’s inner profiles merging for duct L/D ratios 0.15 to 0.6 by maintaining constant axial distance. By keeping the ducts as per the proposed procedure resulted in angles 22 deg, 38 deg, 45 deg, and 52 deg for duct L/D = 0.15, 0.3, 0.45, and 0.6. The performance of WT with 30 deg angled ducts and proposed angled ducts was compared. The proposed angled ducts had improved power output than 30 deg angled ducts. The proposed axial distance and duct angles help to use the duct length effectively, which shortens the duct and enhances power output.