Issues in Active Flow Control: Theory, Simulation and Experiment

Abstract

Open-to-discussion opinions and issues relevant to unsteady active flow control technology are discussed from a theoretical, numerical and experimental perspective. Feasible routes to structured progress, using global flow instability as efficiency enhancement tool, are presented; emphasis is placed on the crucial issue of geometric fidelity and appropriate boundary conditions. Direct Numerical Simulation and the two orders-of-magnitude more expensive Optimal Control Theory are perceived as useful for detailed understanding of physics in simple academic configurations; both are impractical at Reynolds numbers of aerodynamic significance, where hybrid methods, combined with Global Instability analysis may become useful. A generic flow control process and a template roadmap are put forward and illustrated using experimental examples.