Numerical analysis of jet noise for nozzles with different throat sizes

Abstract

To propose a method for testing the dynamic change rate of the throat diameter based on the characteristics of the jet noise field, this study measured the effect of the size variation of the throat diameter on the jet noise during engine nozzle operation. Steady-state flow field simulation and transient noise simulation based on the Ffowcs Williams–Hawkings equation were carried out using large-eddy simulation for nozzles with different sizes of the throat diameter. The jet noise’s sound pressure level (SPL) is discussed and analyzed. By performing a Fourier transform on the noise signal obtained from the simulation, the influence rule of throat diameter size on the magnitude and frequency characteristics of jet noise is analyzed. The results show that the jet noise signal mainly manifests in the low-frequency region. With a gradual increase in frequency, the corresponding amplitude will first increase and then decrease. The effect of the change in the nozzle throat size on the structure of the jet wave system is more prominent; with the increase in the throat diameter, the SPL of the jet noise tends to increase, and the peak frequency of the SPL tends to decrease. The size of the nozzle throat diameter affects the change in the main frequency of the noise, which decreases as the nozzle throat diameter becomes larger.