Research on energy extraction characteristics of an adaptive deformation oscillating-wing

Oscillating foil machines represent a type of flow energy harvesters which perform pitching and plunging motions simultaneously to harness the energy from incoming stream. In this paper, a new adaptive deformation oscillating wing was proposed and the theoretical performance of such a concept was studied here through unsteady two-dimensional simulations using an in-house developed computational fluid dynamics code. During operation, the proposed oscillating foil whose initial shape is symmetric can be deformed into a cambered foil, which aims to produce large lift force. Our numerical results suggest that the power efficiency of the proposed oscillating foil can be about 16.1% higher than the conventional oscillating foil without deformation. In addition, the effects of the maximum bending displacement and effective angle of attack on the efficiency of proposed oscillating foil were also discussed in this work

The effect of variations in first- and second-order derivatives on airfoil aerodynamic performance

The geometric factors which influence airfoil aerodynamic performance are attributed to variations in local first- and second-order curvature derivatives. Based on a self-developed computational fluid dynamics (CFD) program called UCFD, the influence of local profile variations on airfoil aerodynamic performance in different pressure areas is investigated. The results show that variations in first- and second-order derivatives of the airfoil profiles can cause fluctuations in airfoil aerodynamic performance. The greater the variation in local first- and second-order derivatives, the greater the fluctuation amplitude of the airfoil aerodynamic coefficients. Moreover, at the area near the leading edge and the shock-wave position, the surface pressure is more sensitive to changes in first- and second-order derivatives. These results provide a reference for airfoil aerodynamic shape design

Research on the aerodynamic characteristics of a lift drag hybrid vertical axis wind turbine

Compared with a drag-type vertical axis wind turbines, one of the greatest advantages for a lift-type vertical axis wind turbines is its higher power coefficient ( C p ). However, the lift-type vertical axis wind turbines is not a self-starting turbine as its starting torque is very low. In order to combine the advantage of both the drag-type and the lift-type vertical axis wind turbines, a lift drag hybrid vertical axis wind turbines was designed in this article and its aerodynamics and starting performance was studied in detail with the aid of computational fluid dynamics simulations. Numerical results indicate that the power coefficient of this lift drag hybrid vertical axis wind turbines declines when the distance between its drag-type blades and the center of rotation of the turbine rotor increases, whereas its starting torque can be significantly improved. Studies also show that unlike the lift-type vertical axis wind turbines, this lift drag hybrid-type vertical axis wind turbines could be able to solve the problem of low start-up torque. However, the installation position of the drag blade is very important. If the drag blade is mounted very close to the spindle, the starting torque of the lift drag hybrid-type vertical axis wind turbines may not be improved at all. In addition, it has been found that the power coefficient of the studied vertical axis wind turbines is not as good as expected and possible reasons have been provided in this article after the pressure distribution along the surfaces of the airfoil-shaped blades of the hybrid turbine was analyzed