首页|Convection of multi-scale motions in turbulent boundary layer by temporal resolution particle image velocimetry
Convection of multi-scale motions in turbulent boundary layer by temporal resolution particle image velocimetry
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NSTL
Taylor & Francis
Experiments of particle image velocimetry (PlV) in the turbulent boundary layer at Re-tau- = 400 similar to 1000 have been conducted to investigate the convection characteristic of turbulent structure and the validity of Taylor's hypothesis. Views of 6(delta) x 1.26 (delta = delta 99, the boundary layer thickness) were captured by four streamwise-arranged cameras. Distributions of streamwise turbulent kinetic energy on a streamwise scale were investigated by continuous-wave transform, and scales were found where the portion of streamwise turbulent kinetic energy approaches maximum. Fluctuating velocities (instant velocity minus average velocity on time dimension) were divided into large-scale motion (LSM) and small-scale motion (SSM) portions, bounded by 1 delta. Convection velocities of LSM and SSM are determined by the spatiotemporal correlation method, and they are larger than local average velocities in near-wall regions, but smaller than local average velocities in wake regions. Statistical characteristics between velocity fields reconstructed by Taylor's hypothesis and original fields were compared by the autocorrelation method, and the reconstructed field's patterns are longer than original field's patterns, while their heights do not have clear distinction. The correlation of original velocity fields and reconstructed fields shows that LSM can hold on over 3 delta and SSM over 1 delta in streamwise convection separation for regions of gamma/delta > 0.2, given a threshold value (correlation coefficient C = 0.6).
NSTL
Taylor & Francis
