One of the major issues in the thick airfoils like wings wide-body aircraft, propellers and wind turbine blades is having a wide functional range. Many conventional airfoils despite optimal performance at their design point, do not function properly outside of the design range. For example, if the wind turbine is in off design due to wind condition, efficiency loss and even damage to the turbine blades is possibe. Therefore turbine will be turned off. However, if the right cavity design is used, the turbine can have a good performance in vaiety of operating conditions. Also propellers which have wide efficient operating conditions can provide more flight altitude. In the present research, the effect of using an optimal aerodynamic cavity for the RISO airfoil on its performance is studied. For this purpose, genetic optimization algorithm is connected to ANSYS CFX as the flow solver in the analysis. Reynolds averaged equations are solved by a finite volume method and two discritizatin techniques with different order of accuracy. k?-SST model is used for turbulence modeling. Six geometric parameters including the location of cavity, its width, depth, profiles and the suction surface profile after the cavity are considered as design parameters and the cost function is defined as the maximum lift to drag coefficient ratio. Optimization is performed for six different parametric systems to study the effect of each geometrical parameter separately. After finding optimized values for the cavity geometrical parameters, numerical solution is obtained on a fine grid for unsteady flow for a wide range of Reynolds number to compare the performance of airfoil with aerodynamic cavity and airfoil without cavity. An experimental study is also carried out in a wind tunnel test section to measure lift and drag coefficients for the airfoil with and without cavity in various angle of attacks. The experimental result is used to validate the numerical results.In summery, Numerical and experimental results show that using aerodynamic cavity improves the lift to drag ratio up to 50% at 10 to 20 degrees angle of attack in comparison with the airfoil without cavity. Keywords: Airfoil with Cavity, Aerodynamic Coefficients, Increasing the Range of Functional, Optimization, Genetic Algorithms, Experimental Testing
