Spectral distribution of three velocity components in high-Reynolds-number pipe flow using laser Doppler velocimetry measurements.

This article focuses on spectral analysis of turbulent pipe flow at high friction Reynolds numbers (Reτ ≈ 3000 to 20,000) using laser Doppler velocimetry (LDV) to measure all three velocity components: streamwise, wall-normal, and spanwise. The study addresses challenges inherent to LDV, such as random sampling intervals and interpolation methods, and validates its spectral results through comparison with established hot-wire (HW) anemometry data. Findings show good agreement for the streamwise component, including identification of characteristic k−1 and k−5/3 spectral regions and Reynolds number dependence of very-large-scale motions (VLSMs), while some discrepancies appear near the wall and at high wavenumbers for the wall-normal and spanwise components. This work presents the first unified spectral dataset for all three velocity components in high-Reynolds-number pipe flow obtained using the same facility and measurement technique, highlighting LDV's non-intrusive advantage over HW methods.