Streamline segment statistics propagation in inhomogeneous turbulence

The streamline segmentation method proposed by Wang is applied to a turbulent wavy channel flow to investigate the impact of pressure-driven strain on the streamline segment probability distribution. While the asymmetrical shape of the probability distribution is known to react to streamwise strains, in regions of detached flow this impact is severely less pronounced. Using tomographic particle-image velocimetry measurements and numerical data in attached and detached flow, the origin for this observation is found in the strong compressive strain during attached flow. The responsible mechanism is determined by introducing a concept of streamline segment locality, adapting the propagation equation for streamline segment statistics to inhomogeneous flow and applying it to the numerical data. A locally increased segment cutting rate is identified to cause the reduced sensitivity of the segment probability distribution to the local strain.