Validity of the Taylor hypothesis in a random spatially smooth flow

Abstract

The validity of the Taylor frozen flow hypothesis in a chaotic flow of a dilute polymer solution in a regime of elastic turbulence is investigated experimentally. By accurate time-dependent measurements of the flow field we study the velocity coherence between pairs of points displaced both in time and space and quantify the degree of applicability of the Taylor hypothesis. Alternatively, the frozen flow assumption is assessed by comparison of the measured velocity structure functions with the ones derived by a frozen flow assumption. The breakdown of the Taylor hypothesis is further discussed in both the context of strong velocity fluctuations and long-range spatial correlations, which are the result of the flow smoothness and lack of scale separation. Different choices of the advection velocity are tested and discussed.