The statistical study of vortex structure in turbulent boundary layer flow based on Tomographic PIV
Abstract
In present work, tomographic particle image velocimetry (Tomo-PIV) is applied to achieve a three-dimensional three-component (3D3C) velocity measurement on the plate turbulent boundary layer at <italic>Re</italic><sub><italic>τ</italic></sub>=1768. 250 velocity fields with size of 80 mm×16 mm×45 mm are obtained. The swirl strength <italic>λ</italic><italic><sub>ci</sub></italic> is used to identify vortices. The orientation of vortex is indicated by the projections of the swirl vector on different directions. Linear stochastic estimation (LSE) and pre-multiplied power spectra function are used to analyze the vortex structures in TBL. The vortex structures distribute periodically along the shear layer between high and low speed regions. Proper orthogonal decomposition (POD) is utilized to separate the flow field of different scales. The velocity distribution of the large scale field agrees well with the original velocity field, while the distribution and spectra of the vorticity of the small scale field are consistent with the statistical feature of the original velocity field.
