An active flow control experiment was conducted on a cropped NACA 0018 airfoil to study 3D effects and maneuverability aspects
made possible by a segmented actuation system installed in the airfoil. The 14 piezo-fluidic actuators were installed at the
corner of the cropped region, inclined at 30° to the local surface, facing downstream. Operating all actuators at unison significantly
increased lift and generated a pitch-down moment. Operating all actuators at the same magnitude but varying the phase along
the span generated larger lift-increment, with respect to the uniform phase excitation. Significant rolling moment can be
generated when only half-span of the wing is actuated. The latter effect, as indicated by the 3D pressure distribution, persists
to the leading edge even though the excitation was introduced close to the trailing edge. When a pair, out of the possible
fourteen actuators is not operating, very little of the control authority is lost. This is an important finding when issues like fault tolerance and robustness
of fluidic-piezo actuators are considered. 相似文献
Cellulose - Synthetic polymers and plastics which are currently used as barrier materials in packaging applications are neither renewable nor biodegradable. Nanopaper, which is obtained by breaking... 相似文献
Epoxidation made easy : Subnanometer gold clusters immobilized on amorphous alumina result in a highly active and selective catalyst for propene epoxidation. The highest selectivity is found for gas mixtures involving oxygen and water, thus avoiding the use of hydrogen. Ab initio DFT calculations are used to identify key reaction intermediates and reaction pathways. The results confirm the high catalyst activity owing to the formation of propene oxide metallacycles. Al green, Au yellow, O red, and C gray.
