Control of mixing by boundary feedback in 2D channel flow

We address the problem of enhancing mixing by means of boundary feedback control in 2D channel *ow. This is done by 6rst designing feedback control strategies for the stabilization of the parabolic equilibrium *ow, then applying this feedback with the sign of the input reversed. The result is enhanced instability of the parabolic equilibrium *ow, which leads rapidly to highly complex *ow patterns. Simulations of the deformation of dye blobs positioned in the *ow indicate (qualitatively) that e:ective mixing is obtained for small control e:ort as compared with the nominal (uncontrolled) *ow. A mixedness measure P is constructed to quantify the mixing observed, and is shown to be signi6cantly enhanced by the application of the destabilizing control feedback. ? 2003 Elsevier Ltd. All rights reserved.