1112 Influence of free stream turbulence intensity and its eddy scale with the unsteady aerodynamic characteristics of an airfoil and aerodynamic sound characteristics generated from the airfoil flows

Abstract

Recently, it has been a problem of aerodynamic noise radiated from wind turbine blades, and noise prediction of the wind turbine is important. Then, airfoil noise under the various inflow conditions is measured by using the active turbulence generators (ATGs) in this study. The ATGs have 3 size of rotating plates with changing various swing angles in order to be varied independently turbulence intensity and eddy scale. And, we manufacture active turbulence generators (ATGs) which are 16 axis types to improve the non-uniformity of wind velocity with ATGs. In this paper, it is reported that the turbulence intensity and the eddy scale of inflow can be changed at 7% to 20% and at 18% to 30%, respectively. Also, it is cleared that sound pressure level of airfoil noise are increased by 5 to 15 dB in broadband frequency range of 100 to 5000 Hz in case of increase of turbulence intensity, and that the sound pressure level are increased by 5 to 15 dB in the range of 100 to 300 Hz in case of increase of eddy scale. And non-uniformity of wind velocity with the ATGs which are 16 axis types is 7%.