Suppression of Aerodynamic Tonal Noise from an Automobile Bonnet Using a Plasma Actuator

Paper #:
  • 2017-01-1825

  • 2017-06-05
Intense tonal noise often radiates from flows around a trailing edge with an upstream kink shape such as found in an automobile bonnet, where fluid-acoustic interactions occur. It was clarified that the tonal sound became intense at a specific angle of the kink. Moreover, in order to reduce this noise, the flow was controlled by a dielectric barrier discharged plasma actuator (PA), which was attached around the kink shape. The flow and sound pressure were measured by a hot-wire anemometer and a microphone in a low-noise wind tunnel. In the flow around the model without control by the PA, vortices are shed in a separated flow between the kink and the trailing edge, and acoustic waves are radiating due to the interference of vortices with the wall. Measured coherent output power (COP) based on the simultaneous measurement of velocity fluctuations and far-field sound pressure shows that the velocity fluctuations near the trailing edge are related with the tonal acoustic radiation. Experiments with the PA with different streamwise positions were performed. Additionally, by changes the direction of the PA, effects of the co-flow and counter-flow forcing configurations of the PA were investigated. As a result, intense tonal noise was reduced with the control of the PA with the streamwise distance of 10% from the kink with reference to the distance between the kink and the trailing edge in both configurations. The mean velocity profile under the control shows that the separation around the kink is suppressed. Also, by the measured distributions of the COP, the velocity fluctuations related with the tonal noise were clarified to become weaker.
Also in:
  • SAE International Journal of Passenger Cars - Mechanical Systems - V126-6EJ
  • SAE International Journal of Passenger Cars - Mechanical Systems - V126-6
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