Efficient methods for computing spectral projectors for linearized hydrodynamic equations

International audienceThis paper presents efficient methods for computing the spectral projectors for hydrodynamic equations, linearized at a steady state and approximated with respect to space. The focus is on the spectral projectors corresponding to a given part of the finite spectrum. In the case when the size of the problem is not too large, a QR-based method is proposed and compared with the $QZ$ method. In the large scale case, two variants of the Jacobi-Davidson method, with a deflation procedure, are developed. In both cases, the computed spectral projectors can be used to construct low-order models suited for the context of hydrodynamic stability. Numerical results are reported