Spectral Analysis of Large Scale Structures in Fully Developed Turbulent Pipe Flow

Abstract

AbstractThe present work focuses on spectral analysis of the streamwise velocity fluctuations obtained, utilizing the Cottbus Large Pipe (CoLaPipe) test facility for R+ ≤ 3500, where R+ is the Reynolds number based on the wall friction velocity, uτ, and the pipe radius, R. Measurements of the streamwise spectra have been conducted using a single hot‐wire probe. Few runs have been also performed using Particle Image Velocimetry (PIV) as a structure visualization evidence and for spatial correlation purposes. The spectral analysis is being carried out to reveal few insights into pipe flow structure, allowing to follow the foot prints of such structures as well as providing estimates of their energy contents. The cumulative energy is examined as a function of the streamwise wavelength, describing the most energetic motions found in spectral data at various wall normal locations. For the current Reynolds number range, the Very Large Scale Motions (VLSM) and the Large Scale Motions (LSM) were evident as localized peaks in pre‐multiplied spectra, having mean wavelengths approximately of 12R, and 3R, respectively. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)