This study explores noise reduction in jets impacting surfaces. Different surface patterns (corrugated with various pitch lengths) were compared to a flat surface. Corrugated surfaces with wider pitches (63mm-35mm) achieved an 8 dB noise reduction by eliminating "tonal" noise, while narrower pitches (31.5mm-17.5mm) reduced total noise by 17 dB through decreased turbulence. Advanced analysis confirmed these findings and identified the "helical instability mode" as beneficial for noise reduction.

Numerical simulations revealed how flow patterns on different surfaces affect noise. The flat surface generated strong shock waves due to its extended jet core, leading to higher noise levels. Finally, optimization is carried out for nozzle pressure, distance, and surface pitch for minimum noise. Response surface methods were more accurate than traditional methods for this optimization.

This work is published in the International Journal of Turbo and Jet Engines, De Gruyter. The DOI is http://dx.doi.org/10.1515/tjj-2023-0071. The work related to optimization is published in Journal of Brazilian Society of Mechanical Sciences and Engineering, Springer. The DOI is http://dx.doi.org/10.1007/s40430-023-04568-1