Host: The Japan Society of Mechanical Engineers
Name : Dynamics and Design Conference 2023
Date : August 28, 2023 - August 31, 2023
One type of aerodynamic noise caused by airflow is edge tone, which is generated when airflows collide with edge-shaped objects and are separated at the edges. This edge tone is called self-excited sound, but the self-excitation mechanism has not yet been clarified, and quantitative modeling is not yet possible. Therefore, this study examines a mathematical model of edge tones and analyzes the self-excitation mechanism. The hypothesis of the self-excitation mechanism proposed in this study is as follows. "A dipole source above and below the edge induces a vertical particle velocity on the jet axis, which causes the jet to oscillate vertically. The jet vibrates perpendicularly. The oscillation of the jet causes the dipole sources above and below the edge to grow moment by moment, and the value of the particle velocity perpendicular to the axis also increases, resulting in self-excited oscillation of the jet." In the computational model, the dipole source is assumed to be a point source in the opposite phase, and the impulse response of the particle velocity to an impulse input of volume velocity is calculated using the Fourier series transform. As a result, a self-excited phenomenon was generated by assuming a dipole source with an assumed waste time at the edges.
