Coherent structures near the wall (streamwise vortices, low-speed streaks, and coherent Reynolds stress producing events) in an open channel flow at Re_(τ)=300 are investigated using stereo particle image velocimetry(SPIV) in a cross-stream plane. A time series of 3 velocity components in the plane is converted into an instantaneous full 3 dimensional velocity field by Taylor's hypothesis. It is observed that a pair of counter-rotating quasi-streamwise vortices cause coherent Reynolds stress contributions beside the vortices by their swirling motions. A kinked low-speed streak is also observed below the vortex pair. These structures are consistent with the conceptual model proposed by Jeong et al. (J. Fluid Mech. 332, 185 (1997)), and is the first quantitative experimental verification of the complete combination of configuration among these structures to our knowledge.
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