Active control of streamwise vortices

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A proposal is made for producing and studying the streamwise vorticity introduced into jets and free shear layers by means of active flow control (AFC). The method is based on local attachment of separated shear layers to discrete flaps, which can be distributed around the circumference of the jet. For incompressible flows, attachment of the shear layers can be achieved by means of zero mass-flux perturbations introduced at the shoulder of each flap. Primary measurements will be LDA or PIV, and will be complemented by flow visualization. Flap surface pressures and/or flap loads will also be measured. To maximize the fundamental and practical returns of this research, the proposal is based on a three-phase approach with additional complexity being added at each phase. The main practical advantage of the methodology proposed here is that it requires only small perturbations to bring about strong streamwise vorticity and thereby vigorous three-dimensional mixing of the jet with its surroundings. This research has direct application to mixing, combustion and jet noise.The first phase of the research outlined in this proposal, is structured to provide a solid fundamental understanding as well as the practical insight required to advance the technology (years 1 and 2). The second and third phases will be more directly application-orientated (years 3 and 4).