Puja Upadhyay

Control of high speed jet exhaust noise continues to be a research challenge for military as well as commercial high speed aircrafts. With aircrafts becoming faster, more powerful, and louder, the issue of jet noise has become even more pressing. This exhaust noise not only poses serious health concerns to the crew members working in close proximity of the aircraft, but is also a major source of noise pollution for the communities surrounding the airports. Exhaust from high speed jets, also known as free jets, is characterized by a highly unsteady flow field, high levels of turbulence, and radiated noise. The dynamics of high speed jets is mainly governed by large scale vortical structures in the shear layer. These structures present in the shear layer are known to be the most dominant source of aircraft noise. The primary goal of jet noise control is to modify the evolution of these high amplitude vortical structures in the shear layer, while keeping the thrust penalty and external energy expenditure to a minimum. The current study utilizes high-frequency Resonance Enhanced Microactuators (REM), which are pulsed fluidic actuators, to actively control the exhaust from high speed jets. These actuators are capable of producing high momentum output at frequencies that are an order of magnitude (or higher) than the natural instabilities in the jet flow field. The actuators are strategically distributed at the nozzle exit to excite and potentially modify the characteristics of the initial shear layer. The effect of high frequency forcing on the evolution of the jet is characterized by performing flow visualization and acoustic measurements. Preliminary near field acoustic results have been promising with reductions in low frequency noise. A uniform reduction in noise at all measurement angles is observed. Moreover, velocity field measurements revealed that control resulted formation of strong counter rotating vortex pairs. The formation of the vortex pairs is believed to be one of main mechanism associated with high frequency control that results lower growth rates of large scale structures.

  Upadhyay, P., Valentich, G. M., & Alvi, F. S., “Flow and Acoustic Features of a Mach 0.9 Jet using High-Frequency Excitaiton”, AIAA (in preparation, AIAA 2016).

  Upadhyay, P., Gustavsson, J.P.R., Development and Characterization of Ultra-High Frequency Resonance-Enhanced Microjet Actuators (manuscript in review).

  Valentich, G.M., Upadhyay, P., & Kumar, R., “Mixing Characteristics of a Supersonic Rectangular Jets”, (manuscript in preparation)

  Upadhyay, P., Davis, T.B, & Alvi, F. S., “Active Control of Mach 0.9 Jet Using High-Frequency Excitation”, AIAA 2015- 0299 (2015)

  Upadhyay, P., Gustavsson, J.P.R., & Alvi, F. S., “Development and Characterization of Ultra-High Frequency Resonance- Enhanced Microjet Actuators”, AIAA 2013-2476 (2013).

  Worden, T. J., Upadhyay, P., Gustavsson, J. P., & Alvi, F. S., “Studies on Microjet Control Effectiveness in High- Temperature Supersonic Impinging Jets”, AIAA Journal, 52, 8 (2014), 1757-1769.

  Worden, T. J., Upadhyay, P., Gustavsson, J. P., & Alvi, F. S., “Studies on Microjet Control Effectiveness in High- Temperature Supersonic Impinging Jets”, AIAA 2013-0680 (2013).

  Upadhyay, P., Valentich, G. M., & Alvi, F. S., “Flow and Acoustic Features of a Mach 0.9 Jet using High-Frequency Excitaiton”, 54th AIAA Aerospace Sciences Meeting, San Diego, CA (2016)

  Upadhyay, P., Davis, T.B, & Alvi, F. S., “Active Control of Mach 0.9 Jet Using High-Frequency Excitation”, 53rd AIAA Aerospace Sciences Meeting, Kissimmee, FL (2015)

  Upadhyay, P., Gustavsson, J.P.R., & Alvi, F. S., “Development and Characterization of Ultra-High Frequency Resonance- Enhanced Microjet Actuators”, 43rd Fluid Dynamics Conference, San Diego, CA (2013)