Streamline segment scaling behavior in a turbulent wavy channel flow

Abstract

A turbulent flow in a wavy channel was investigated by tomographic particle-image velocimetry measurements and direct numerical simulations. To analyze the turbulent structures and their scaling behavior in a flow undergoing favorable and adverse pressure gradients, the streamline segmentation method proposed by Wang (J Fluid Mech 648:183–203, 2010) was employed. This method yields joint statistical information about velocity fluctuations and length scale distributions of non-overlapping structures within the flow. In particular, the joint statistical properties are notably influenced by the pressure distribution. Previous findings from flat channel flows and synthetic turbulence simulations concerning the normalized segment length distribution could be reproduced and therefore appear to be largely universal. However, the mean streamline segment length of accelerating and decelerating segments varies within one wavelength typically elongating segments of the type which corresponds to the local mean flow. Furthermore, the local pressure gradient was found to significantly impact local joint streamline segmentation statistics as a main influence on their inherent asymmetry.