Genetic algorithm-informed microjet control for noise reduction in supersonic impinging jetsa)

Impinging jets are essential for vertical takeoff/landing aircraft to achieve the required lift. However, these impinging jets are highly unsteady and produce significant noise as a result of jet resonance. To mitigate this noise, a microjet-based control method is implemented on a Mach 1.5 supersonic nozzle to attenuate jet resonance. One microjet array is installed near the nozzle exit, and another microjet array is installed within the diverging section of the supersonic nozzle. Each array consists of 16 individually controllable microjets arranged in azimuthally aligned or staggered configurations. A genetic algorithm (GA) is applied to optimize the microjet configurations to minimize the overall sound pressure level (OASPL) at selected impingement distances. For the aligned configuration, the GA-optimized solution achieves a 10 dB reduction in OASPL compared to the baseline condition. This reduction represents an improvement of approximately 2 dB over that achieved when all microjets are activated at maximum pressure. Additionally, this improved noise reduction is accomplished while reducing the microjet mass flow rate by 26%. In the staggered configuration, the GA identifies that firing all microjets simultaneously provides the best OASPL reduction. Moreover, this configuration effectively reduces noise across a majority of impingement distances and varying nozzle pressure conditions.