Enhancing diffuser augmented wind turbine performance: Aerodynamic optimization of diffuser’s cross-section via CFD and response surface methodology

This study develops a numerical framework for optimizing an airfoil-shaped diffuser for a Diffuser-augmented-wind turbine (DAWT) by combining computational fluid dynamics with Response Surface Methodology (RSM). The high-camber Eppler 423 airfoil was selected through CFD prescreening out of 24 cambered airfoils (6 to 10.6%). Four geometric parameters: angle of attack, chord length, maximum camber, and maximum thickness were systematically investigated. Rotor effects were captured using an actuator disc model. A Central Composite Design, Design of Experiment, guided the numerical experiments. A quadratic regression model was created and validated, showing strong correlation. Analysis of variance confirmed significant linear effects for angle of attack, chord, and maximum camber. It also identified significant interaction effects between angle of attack and chord length, angle of attack and maximum thickness, and chord length and maximum thickness. Numerical optimization produced an optimal profile that increased maximum camber by 6.1% while reducing maximum thickness by 22.3%. The optimized diffuser achieved a 15.85% increase in power coefficient and a 4.4% rise in mass flow rate. The compact configuration attained a pressure recovery coefficient of 0.76. The RSM model was validated against CFD results with only 1.2% deviation. These gains demonstrate the value of a system-aware design that captures both linear effects and critical parameter interactions. This work delivers optimized diffuser geometry and a robust computational design strategy for advancing high-performance DAWT technology.