High subsonic jet flow physics and noise

Due to stringent commercial and military guidelines within the aerospace community, there exists a heightened interest in jet noise reduction. Recent studies have shown that active flow control (both open and closed loop) may provide a key component of future solutions to reduce jet noise. The work presented here includes the coupling of near-field pressure and velocity, with far-field acoustic measurements, alongside active flow control techniques (both open and closed loop) in the form of actuation at the jet nozzle lip. The data set of interest includes a high subsonic, turbulent compressible jet flow field, captured with high resolution time-resolved (10kHz) Particle Image Velocimetry measurements simultaneously sampled with near and far-field pressure. By combining low-dimensional reduced order models and flow control strategies, the goal is to gain insight into what mechanisms in the near-field jet plume are responsible for the far-field noise. Data analysis toolkits to aid in this investigation include various techniques such as proper orthogonal decomposition and wavelet filtering. Various flow cases and configurations will be investigated and discussed; preliminary findings suggest source identification is possible and low-dimensional loud modes of the flow can be modified with closed-loop flow control, leading to a reduction in far-field noise.