Velocity derivatives in a high Reynolds number turbulent boundary layer. Part III: Optimization of an SPIV experiment for derivative moments assessment

TL;DR

This paper details the optimization and validation of an SPIV experimental setup to accurately measure derivative moments and estimate turbulence dissipation rates in a high Reynolds number boundary layer, including error analysis and comparison with DNS data.

Contribution

It introduces a comprehensive methodology for optimizing SPIV measurements of derivative moments and provides validation techniques for accurate turbulence dissipation assessment.

Findings

Quantified noise errors and developed de-noising methods.

Validated SPIV measurements against DNS and theory.

Provided guidelines for future PIV experiments on dissipation measurement.

Abstract

An SPIV experiment using two orthogonal planes simultaneously was performed in the LML boundary layer facility to specifically measure all of the derivative moments needed to estimate the dissipation rate of the Turbulence Kinetic Energy. The Reynolds number was $Re_\theta = 7500$ or $Re_\tau = 2300$. A detailed analysis of the errors in derivative measurements was carried out, as well as applying and using consistency checks derived from the continuity equation. The random noise error was quantified, and used to ``de-noise'' the derivative moments. A comparison with a DNS channel flow at comparable Reynolds number demonstrated the capability of the technique. The results were further validated using the recent theory developed by George and Stanislas 2020. The resulting data have been extensively used in parts I and II of the present contribution to study near wall dissipation. An important result of the present work is the provision of reliable rules for an accurate assessment of the dissipation in future PIV experiments.