An experimental investigation of the dynamic performance of two new rotor blade airfoils was undertaken in a transonic wind tunnel. The EDI-M109 and EDI-M112 airfoils were tested at 0.3 ≤ M ≤ 0.5 for pitching motions with amplitude 0.5 • ≤ α ± ≤ 8 • and frequencies 3.3 Hz ≤ f ≤ 45 Hz. The results show the dynamic stall performance of both new airfoils, and the effect of frequency, amplitude, and higher order pitching motion on these results is described. The pitching moment peak size was found to have an approximately linear correlation to the normalized mean angular velocity, and thus test cases with the same maximum angle of attack and oscillation frequency had similar dynamic stall qualities. The correlation between low aerodynamic damping for high-frequency, low-amplitude pitching motion, and poor dynamic stall performance is shown to be low. The pitching moment peak of the EDI-M112 airfoil is shown to be smaller for M = 0.3 and 0.4, and peak for the EDI-M109 airfoil is lower at M = 0.5. The dynamic performance of the airfoils is compared to the OA209.
The airfoil sections of helicopter rotors experience a wide range of flow conditions in forward flight from transonic flow on the advancing blade to subsonic flow and high angles of attack on the retreating blade. Most notably, the dynamic stall phenomenon has been a research topic for decades and various models have been introduced to predict the unsteady characteristics of the rotor blade undergoing unsteady separation. The objective of the present paper is to compare twodimensional (2D) dynamic stall computations, suitable for airfoil design studies considering unsteady characteristics, with computational fluid dynamics simulations of the wind tunnel environment taking into account three dimensionality and wall effects. Differences between experiment and 2D computations can be partly attributed to sidewall effects, which alter the effective angle of attack at the midsection pressure measurement plane. To gain more insight into these effects, investigations are presented, which show the wind tunnel wall boundary layers and separation effects at the sidewall-airfoil junction.
During the development process of wind turbines, there is a rising demand for detailed flow and multi-physics analyses. Especially the system level computational fluid dynamics (CFD), focusing not on a single component or aspect, but on the turbine as a system of geometric and dynamic properties can be used to improve the turbine quality and time to market. In this paper the integration of the system level CFD into the development process of Enercon wind turbines is introduced. Further two example applications are detailed presenting the benefits of CFD based nacelle anemometer calibration and a risk assessment study based on aero-servo-elastic CFD simulations.
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