SYNTHETIC JET AERODYNAMIC CHARACTERIZATION

This document, as Output O 2.2.1-33 of the GRA – “Low-Noise Configuration” (LNC) Project of the “Clean Sky” JTI, is issued according to the Technical Annex 1B to the Grant Agreement 2011 of the GRA ITD. The document present results related with the experimental characterization of the synthetic jets actuators manufactured by the research group of Fraunhofer. The oscillating surface of the actuator is covered by a circular piezoelectric element that generates oscillating flow through a circular orifice having a diameter equal to 0.5mm. The test panel has three distinct actuators that can be activated singularly or can also be used in a multiple actuation. The investigation has been performed in still air conditions. Velocity measurements on the jets axis have been carried out varying the voltage amplitude and the oscillation frequency for each single actuator. A miniaturized total pressure probe having external diameter equal to 0.3 mm was used. Maximum velocity on the jet axis of the order of 20 m/s were measured for the three actuators in correspondence of the second resonance frequency of the actuators. Several distances from the exit section were tested, up to 40 diameters downstream. A combination of the two closest actuators was surveyed measuring the velocity distribution along the direction connecting the two orifice centres for x/d = 10 and x/d=20. An inclination of the three jets axis respect to the geometric centre of the orifice was finally highlighted.