Turbulent/non-turbulent interface in high Reynolds number pressure gradient boundary layers

TL;DR

This study uses high-resolution PIV measurements to analyze the turbulent/non-turbulent interface in high Reynolds number boundary layers under adverse and zero pressure gradients, revealing broader TNTI distribution with adverse pressure gradients.

Contribution

It provides detailed measurements of the TNTI in high Reynolds number turbulent boundary layers with pressure gradients, comparing adverse and zero-pressure gradient cases.

Findings

TNTI exists over a broader range in adverse pressure gradient conditions.

The dataset enables accurate detection of the TNTI in thick boundary layers.

Implications for turbulence statistics based on TNTI detection are discussed.

Abstract

We report two-dimensional particle image velocimetry experiments in high Reynolds number turbulent boundary layers imposed with a moderately strong streamwise pressure gradient. The unique aspect of these data are the highly resolved measurements across the outer region of a physically thick boundary layer, enabling accurate detection of turbulent/non-turbulent interfaces (TNTI). The present dataset is used to detect the TNTI of an adverse pressure gradient turbulent boundary layer and compare its characteristics with that for a zero-pressure gradient boundary layer, at a nominally similar friction Reynolds number. It is found that the TNTI exists across a broader range of wall-normal distance in presence of an adverse pressure gradient, as compared to the zero-pressure gradient case. Implications on conditionally averaged turbulence statistics are discussed based on detection of the TNTI.