Effectiveness of fluid injection on supersonic jet noise at high exhaust temperatures

Jet exhausts from high-performance supersonic military aircraft result in very high acoustic levels that can have a detrimental effect on the health and performance of the crew working in the vicinity of the aircraft, even with the currently deployed hearing protection. Due to this reason, most jet noise reduction technologies target noise reduction during takeoff and landing. The fluid insert technology is one such noise reduction technology that has been shown to effectively reduce supersonic jet noise in both downstream and upstream directions. This is achieved by steadily blowing a small portion of the bypass air at different locations in the diverging section of the nozzle using rows of injectors spaced uniformly around the azimuth. Previous experimental research has shown that these fluid inserts are more effective at higher jet temperatures. However, this research is limited to jet total temperature ratio (TTR) values of 3. All high-performance supersonic military aircraft are equipped with afterburners to improve performance during takeoff and combat situations. During the application of afterburners, the exhaust temperature ratios may reach as high as TTR = 7. Such temperature ratios are difficult to replicate in laboratory scale experiments. Large Eddy Simulations (LES) on the other hand are free from such experimental limitations. This paper studies the effect of fluid injection on jet noise at TTR values higher that 3 using LES.