The spatial-temporal sequence of 3D-3C(three-dimensional-three-component) simultaneous velocity field in a turbulent boundary layer was finely measured by tomographic TRPIV(time-resolved particle image velocimetry) in a water channel.A new concept of spatial local averaged velocity structure function was introduced to describe the dilation

compression and shear distortion and rotation of multi-scale eddy structures in turbulent flow.The three fluctuating velocity components of TBL (turbulent boundary layer) were decomposed into multi-scale components by spatial local averaged velocity structure function.A new turbulence coherent structure conditional sampling method was proposed based on the dilation and compression features of turbulent multi-scale eddy structures and the new concept of spatial local averaged velocity structure function.The eject and sweep process due to large-scale coherent structure burst was conditionally detected and the characteristic spatial topology modes of physical quantities

such as velocity and vorticity

during coherent structure bursts

were extracted from the tomo-PIV(particle image velocimetry) experimental dataset.A pair of counter-wise quasi-longitudinal horseshoe shaped vortex was discovered during coherent structure eject and sweep process.