Abstract
The application of control tools to fluid problems often requires model reduction to correctly capture the input-output behavior of the associated initial-value problem In this study a model combining global modes (for the unstable subspace) and balanced modes (for the stable subspace) is considered. We show that this model succeeds in removing the global instability or the flow over an incompressible cavity. Comparison with other reduced models clearly demonstrates the superiority of this approach for control problems.