Numerical Simulation of Supersonic Jet Noise with Overset Grid Techniques

Supersonic jets with a complex shock pattern appear in numerous technical applications. Most supersonic jets, especially in modern military or civil aircraft, are not perfectly expanded. Thereby, shocks are appearing in the jet core and interacting with the turbulent mixing-layers and emanating shock induced noise. Under certain conditions this upstream traveling noise can be amplified due to a closed feedback loop. These so called

screech tones

can reach sound pressure levels of up to 160 dB [11] and hence lead to immense noise pollution and even structural fatigue.

The focus of this research project lies in the numerical simulation of supersonic jet noise and finally the minimization of screech tones with an adjoint shape optimization approach of the nozzle geometry. To this end the nozzle geometry, based on a complex shape, has to be included in the computational domain. In the present paper the method of overset grid techniques is presented for the simulation of supersonic jet noise. Direct numerical simulations with a modeled nozzle inlet showed a good agreement of the screech frequency to a semi-empirical low found by Powell in 1953 [6].