Active control of streamwise vortices

提出了用主动流动控制(AFC)方法产生和研究引入射流和自由剪切层的流向涡量的建议。该方法是基于将分离的剪切层局部附着到离散襟翼上，这些襟翼可以分布在射流的圆周上。对于不可压缩流动，剪切层的附着可以通过在每个襟翼肩部引入零质量通量摄动来实现。主要的测量将是LDA或PIV，并将得到流动可视化的补充。还将测量襟翼表面压力和/或襟翼载荷。为了最大化这项研究的基本和实际回报，该提案基于三阶段方法，每个阶段都增加了额外的复杂性。本文提出的方法的主要实用优点是，它只需要很小的扰动就能产生强烈的流向涡度，从而使喷流与周围环境发生强烈的三维混合。这项研究直接应用于混合、燃烧和喷射噪声。本提案中概述的研究的第一阶段旨在提供坚实的基础理解和推进技术所需的实践洞察力(第一年和第二年)。第二和第三阶段将更直接地面向应用程序(第三和第四年)。

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).