抄録
Characteristics of open-channel turbulent flow downstream of a falling works were experimentally investigated by using image analysis methods. Trench section with various aspect ratios was installed just downstream of the falling work in order to understand the local effect of the trench shape to the main flow. In the experiment, twodimensional flow field in a longitudinal cross-section was measured either by particle tracking velocimetry (PTV) or particle image velocimetry (PIV) depending on flow situations. The measurements were conducted by using a highresolution video camera with 12 fps (frame per second). It was made clear that open-channel flows downstream of a falling work shows a drastic change in their surface shape as the aspect ratio of trench becomes greater than a specific value. In the experiment, it was discovered that a hydraulic jump created downstream of the trench section shows quite a periodic oscillation for a small range of aspect ratios. It was also shown that the imaging techniques used in the experiments are capable of measuring largely deformed free-surface flow with a reasonable accuracy.
