Hybrid time series from PIV for characterization of turbulent flow fields: ASTRA -- Approach using Spatially and Temporally Resolved Advection

TL;DR

This paper introduces ASTRA, an advection-based method leveraging Taylor's hypothesis to enhance temporal resolution in PIV data, enabling detailed two-point turbulent flow analysis beyond current limitations.

Contribution

The paper presents a novel advection-based approach that significantly increases temporal resolution of PIV data using Taylor's hypothesis, allowing advanced flow analysis.

Findings

Major increase in temporal resolution of PIV data.

Successful two-point analysis of turbulent flows.

Validation with hot-wire measurements confirms accuracy.

Abstract

Particle Image Velocimetry (PIV) has become increasingly popular to study structures in turbulent flows. PIV allows direct extraction and investigation of spatial structures in the given flow field. Increasing temporal resolution of PIV systems allows a more accurate capture of the flow evolution. Despite the very good spatial resolution of PIV, current systems can only match the multiple $kHz$ sampling rates of hot-wire or Laser Doppler Anemometer (LDA) measurements for a very short period in temporal analyses of flow. In this study, an advection-based approach is presented which uses Taylor's hypothesis of "frozen turbulence" for small scale turbulent patterns. Compared to the underlying raw data a major increase of the temporal resolution for extracted time series is shown. The quality of the presented approach is shown for two-point analyses, which would not be possible with presently known methods. To demonstrate this, different turbulent flow cases behind a fractal grid are studied. For the validation of the results corresponding hot-wire measurements at various positions along the centerline were used.