Subconvective Contributions to Wall Shear Stress Fluctuations in Zero-Pressure-Gradient Turbulent Boundary Layers at High Reynolds Number

Many vehicles of practical interest operate at high Reynolds numbers, where turbulent boundary layers exhibit dynamics that differ fundamentally from those at low Reynolds numbers. In particular, very large-scale motions become increasingly energetic and may influence wall shear stress fluctuations. This poses a problem for current models, which rely heavily on low-Reynolds-number data and fail to accurately capture the contribution of these large scales.

To investigate this, we conducted experiments in the high-pressure wind tunnel at Stanford University, achieving friction Reynolds numbers on the order of $Re_{\tau} = 10^4$. Wall shear stress was measured directly using synchronized, flush-mounted, multi-point sensors. We find that low-frequency spectral content increases significantly with Reynolds number. These results are compared with near-wall hot-wire measurements from the University of Melbourne, where high Reynolds numbers are achieved through extended development lengths, in contrast with Stanford’s pressurized approach. Additionally, comparisons with direct numerical simulation data assess consistency across methodologies. We use these data to examine the impact of sensor resolution and filtering at high Reynolds numbers and to develop correction strategies and practical guidelines that ensure accurate measurements.