The paper presents an effective method for the analysis of complex unsteady flow fields on the basis of the Karhunen-Loeve decomposition. The mathematical formulation of this method is explained and an applicable approximation proposed. The presented analysis method, the so-called analysis of coherent structures is used for the investigation of unsteady viscous flow calculations for a stator-rotor-stator turbine configuration with different clocking positions of the second stator row. An effective reduction and structuring of the complex unsteady flow fields is demonstrated and the possibility of modeling dominant physical mechanisms by selected coherent structures shown.