Large-eddy simulation and 3D proper orthogonal decomposition of the hydrodynamics in a stirred tank

•Large eddy simulation is carried out in a tank stirred by a propeller.•POD analysis is applied in the 3D stationary and in the rotating reference frames.•The 3D coherent flow structures are investigated.•FFT analyses are performed in every computational cells to study macro-instabilities.•FFT of the POD time coefficients and FFT of velocity monitors are compared.