Utilizing Low-Dimensional Dynamical Systems Models to Guide Control Experiments

In this paper we describe an effort in which the proper orthogonal decomposition (see Lumley 1967) based low-dimensional dynamical system of Glauser et al (1992) is utilized to guide control experiments for the jet. These ideas are then applied using the experimental setup of Corke and Kusek (1993). The experiment uses a closed-loop feed-back to control the flow field, including the possibility of converting the instabilities from convective to global. In the dynamical systems simulations, cascade phenomena are observed where streamwise wavenumbers act as trigger modes to excite various helical modes, in particular azimuthal modes 4, 5 and 6. When these higher helical modes were excited through the experimental control scheme, similar effects, such as mode competition and switching have been observed. These results clearly show the utility of using low-dimensional systems models to guide control experiments.