Abstract
Acoustic excitation was used for method to prompt reattachment on airfoils. However several studies have been made on acoustic excitation, little attention has been given to the reattachment process in terms of turbulent intensity in separation shear layer. Then we will discuss the effect of sound on separation shear layer in this paper. According to the performance test and velocity measurement in boundary layer, we confirmed that the lift coefficient increase and drag coefficient decrease by acoustic excitation. We can interpret this phenomenon in the following way: Firstly, the separation boundary layer is disturbed by radiating the sound. This sound of frequency equals to the period of flow fluctuation in separation boundary layer. Secondly, turbulent intensity increased near the reattachment point. Finally, Reattachment is prompted. Additionally, we recognized that the effective frequency is 160Hz〜180Hz, effective sound pressure level is approximately 63dB for MEL12m84.
