The effect of nonsinusoidal trajectory on the propulsive performances and the vortex shedding process behind a flapping airfoil is investigated in this study. A movement of a rigid NACA0012 airfoil undergoing a combined heaving and pitching motions at low Reynolds number (Re = 11,000) is considered. An elliptic function with an adjustable parameter S (flattening parameter) is used to realize various nonsinusoidal trajectories of both motions. The two-dimensional (2D) unsteady and incompressible Navier–Stokes equation governing the flow over the flapping airfoil are resolved using the commercial software starccm+. It is shown that the nonsinusoidal flapping motion has a major effect on the propulsive performances of the flapping airfoil. Although the maximum propulsive efficiency is always achievable with sinusoidal trajectories, nonsinusoidal trajectories are found to considerably improve performance: a 110% increase of the thrust force was obtained in the best studied case. This improvement is mainly related to the modification of the heaving motion, more specifically the increase of the heaving speed at maximum pitching angle of the foil. The analysis of the flow vorticity and wake structure also enables to explain the drop of the propulsive efficiency for nonsinusoidal trajectories.

In this study, airfoil shape optimization of a wind turbine blade is performed using the ANSYS Fluent Adjoint Solver. The aim of this optimization process is to increase the wind turbine output power, and the objective function is to maximize the airfoil lift to drag ratio (Cl/CD ). This study is applied to the NREL phase VI wind turbine, therefore, the S809 airfoil is used as a reference profile. First, for the validation of the applied numerical model, steady-state simulations are carried out for the S809 airfoil at various angles of attack. Then, the optimization is performed with the airfoil set at a fixed angle of attack, , considering three Reynolds numbers, Re =3 105,4.8 105 and 106. Next, computations are performed for the fluid flow around the optimized airfoils at angles of attack AOA= 6.1° ranging from 0° to 20°. The results show that (i) the lift to drag ratios of the optimized airfoils are significantly improved compared to the baseline S809 airfoil, (ii) this improvement is sensitive to the Reynolds number, and (iii) the Cl/CD ratios are also improved for another angle of attack values. Thereafter, the optimized airfoils are used for the design of the NREL Phase VI blade and the aerodynamic performances of this new wind turbine are assessed using the open-source code QBlade. These latter results indicate that when the blades are designed with the optimized airfoils, the wind turbine aerodynamic performances increase significantly. Indeed, at a wind speed of 10 m/s, the power output of the wind turbine is improved by about 38% compared to that of the original turbine.

In this work, synthetic jet parameters are optimized using response surface methodology (RSM) to improve aerodynamic performances of a S809 profile placed in a flow at a Reynolds number Re = 10 ⁶ with an angle of attack of 15.2°. The synthetic jet actuator is positioned on the upper surface of profile at a distance 5% of the chord length from the leading edge. The considered optimization parameters are: amplitude jet (a _j ), jet frequency (f _j ) and jet angle (α _j ). The RSMs are constructed based on a quadratic meta-model established from a BOX-BEHNKEN design. The genetic algorithm (GA) is used to explore the surface and determine the parameters giving best performances. Navier-Stokes equations are solved in unsteady calculation of a two-dimensional domain using ANSYS Fluent software. Turbulence is accounted using the k-w SST model. The obtained results, show that optimization of jet parameters can significantly improve control efficiency. The size of the recirculation zone decreases and CL to CD ratio of the profile is improved by 150%.

In this study, numerical simulations are performed to investigate the effect of the position and jet angle of the synthetic jet on the aerodynamic characteristics of a wind turbine blade profile. The study is applied to the NREL S809 profile with a 1m chord, set at an angle of attack of 15.2° in a flow at a Reynolds number Re=106. The synthetic jet is placed on the extrados of the profile and modeled by a sinusoidal function. The flow around the blade profile is simulated by solving Navier–Stokes equations using the commercial software ANSYS Fluent based on the finite volume method. Turbulence is simulated using the two-equation SST model. The results show that the considered jet parameters have a strong effect on the aerodynamic characteristics of the profile. Applying an optimal combination of synthetic jet parameters significantly improves the aerodynamic performance of the profile.