Aerospace Colloquium

Complex flow phenomena are present in fluid flow systems underlying energy generation and propulsion, and control of such fundamental phenomena is key to development of efficient, robust systems. This talk will describe research at UCLA on flow instabilities and their control, in the spirit of this fundamental approach, with a focus on the canonical jet in crossflow (JICF) or transverse jet. New insights into JICF shear layer stability characteristics have created the potential for tailored flow control which can alter jet dynamics, molecular mixing and other important features of the jet flow. Quantification and interrogation of the flowfield involves use of acetone planar laser-induced fluorescence (PLIF) imaging and simultaneous stereo particle image velocimetry (PIV), with dynamical characteristics documented via Proper Orthogonal Decomposition (POD) analysis. Transitions in shear layer instabilities from convective to absolute to global instability are observed to depend on specific flow conditions, with attendant alterations in jet structure and symmetry that can have a significant effect on mixing metrics. These fundamental stability characteristics require alternative methods for reduced order model development as well as jet control, depending on the flow regime, which can optimize performance of the jet in various applications.