An experimental study has been conducted in the Cal Poly ME 0.61 m x 0.61 m (2 ft x 2 ft) subsonic wind tunnel of the effect of a piezoelectric synthetic jet actuator at 10% chord on a NACA 0015 finite wing up to α = 20° at Re C = 100,000. It was observed that the actuation is able to delay the separation over the NACA 0015 finite wing model up to α = 20°. For all the Cμ values tested, the synthetic jet excitation is effective at F + = 1, 2.8, and 13.9 at α = 16°, but only at F+ = 13.9 at α = 20°. At α = 16°, the C p suction peak under the synthetic jet excitation at F + = 1, 2.8, and 13.9 all gradually reduce from C p ≅ -4 at in the inboard area to about Cp ≅ -3 near the wingtip, about 25% reduction. The situation is similar for F + = 13.9 at α = 20° except at 2y/b = 0.30, the most inboard testing position, where the excitation shows almost no effect. The surprising result is that slit is not the only actuation influencing the flow. For F + from 1 to 2.8, the synthetic jet is indeed the most effective configuration and is successful in causing flow attachment as seen in previous experiments. For F + = 13.9, however, the flow is successfully attached with the model vibration caused by the actuators alone without the slit at 16°. At 20°, this configuration was not successful in delaying separation.v
Improvements and results of a new method are presented that computes a pre-test estimate of the precision error of the drag coefficient of a wind tunnel model. The error estimate is defined as the part of the drag coefficient's precision error that is primarily associated with the precision error of the angle of attack measurement and physical characteristics of the chosen strain-gage balance. The method indirectly describes the precision error of the angle of attack measurement by using an assumed balance gage output variation of one microV/V. The physical characteristics of the balance, on the other hand, are described by partial derivatives of the axial and normal forces with respect to the strain-gage outputs. These derivatives can directly be obtained from the data reduction matrix of the balance. The precision error estimate itself is calculated by applying a simple explicit equation that uses the model reference area, the dynamic pressure, the angle of attack, the coefficients of the linear terms of the data reduction matrix, and the electrical output variation of one microV/V as input. Precision errors at constant angle of attack may be visualized as contour plots by plotting them, for example, versus the Mach number and the total pressure. Characteristics of NASA's MC60E balance are used in combination with the reference area of a generic wind tunnel model in order to demonstrate that error estimates are independent of both the balance load format and the units chosen for the description of balance loads, model reference area, and the dynamic pressure. Finally, experimental data from a wind tunnel test of the Ames Check Standard Model in the NASA Ames 11-ft Transonic Wind Tunnel illustrates the application of the method to real-world test data.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.