An in-situ method for measuring surface topography and velocity field of flood flow discharged from high-dam reservoir

Large-scale flood flows discharged from high-dam reservoirs are extremely difficult to measure due to the presence of fast developing, highly fluctuating flow surfaces. This study presents a novel in-situ method suitable to monitor surface topography as well as velocity fields of such complex flows. The new method combines stereo photogrammetry and large-scale particle image velocimetry (PIV). The two-camera stereo photogrammetry adopts the SIFT approach for spotting and matching distinct points, and to enhance measurement accuracy and efficiency the internal and external camera parameters are calibrated separately. The large-scale PIV system traces texture of the surface flow through image acquisition, grey standardization, background removing, and median filtering. Real surface velocity field is constructed from velocity field and surface topography measured by two cameras simultaneously. Application of the new method to Xiangjiaba project has been successful.