Development of Automatic measurement system of the instantaneous 3-dimensional flow field by using PIV and MASCON model

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An advanced technique using PIV and MASCON model was developed to measure the instantaneous 3-dimensional flow field above flexible water plant. The measurement reveal that organized vortices are generated intermittently above the vegetation. A side view of the vortex shows an elliptical shape, and the part of the 3-dimensional structure above the vegetation layr consists of a pair of vortices inclined downward toward the front. The period of the vortex generated is explained in terms of linear stability analysis of flows with an inflectional velocity profile. The wavy motion of flexible vegetation is induced by movement of such organized vortices. The instantaneous flow field was visualized by using Application Visualization System effectively. It was confirmed that the technique developed in this study is a powerful tool to measure the 3-dimansional and unsteady flow field.To obtain the transport of fluid momentum and sensible heat induced by the organized vortices above the flexible plant, a field observation was conducted at a reed field. The observation suggests that the organized vortices are the major agency for exchange of fluid momentum, heat and other substance between in and above plant canopy.