This study is an original way to use the proper orthogonal decompostion (POD) in order to establish a low order model of the determinist and random part of a turbulent flow for which the large scale instationnarity is pseudo periodic.An experimental study of the wake behind a semi circular rod by 2 time Particule Image Velocimetry (PIV2T) provides a statistical overview of the wake.POD analysis of the velocity field allows to characterize the spatial mode and the phase parameter describing the large scale instationnarity which governs the deterministic part.The modeling of the temporal evolution of the coefficients associated with the modes is carried out by either harmonics for the deterministic part, or stochastic functions for the random part.Modeling is in agreement with experimental measurements of the first statistical moments in one point and for the space and time correlation functions of the velocity field.
