Moment-matching based model reduction for Navier-Stokes type quadratic-bilinear descriptor systems

We discuss a Krylov subspace projection method for model reduction of a special class of quadratic-bilinear descriptor systems. The goal is to extend the two-sided moment-matching method for quadratic-bilinear ODEs to descriptor systems in an efficient and reliable way. Recent results have shown that the direct application of interpolation based model reduction techniques to linear descriptor systems, without any modifications, may lead to poor reduced-order systems. Therefore, for the analysis, we transform the quadratic-bilinear descriptor system into an equivalent quadratic-bilinear ODE system for which the moment-matching is performed. In view of implementation, we provide algorithms that identify the required Krylov subspaces without explicitly computing the projectors used in the analysis. The benefits of our approach are illustrated for the quadratic-bilinear descriptor systems corresponding to semi-discretized Navier-Stokes equations. (C) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim