Numerical study on the haystack phenomenon of turbulence ingestion noise

The haystack phenomenon, i.e., humps and blue shifting in noise spectra, is commonly observed in the study of underwater turbulence-propeller interactions, which is a major contributor to noise radiation. However, its generation mechanism is still unclear, which is vital to develop noise control strategies. To address this issue, this work conducted numerical simulations concerning the interaction between turbulence and rotors. The propeller is simplified to a cascade model and the turbulence flow is represented by a time series of harmonic gusts for convenience. The simulations are validated against the Sears model for a gust-airfoil interaction problem. Initial results suggest a convolutional interaction mechanism between the spectra of incoming flow disturbances and the periodic sampling of the cascade, which approves the theoretical analysis from Huang (AIAA J. 2023). The results is helpful to understanding the physics of turbulence-ingestion rotor noise and designing the next generation underwater vehicles.