Internal flow velocimetry of hydraulic coupling based on particle tracking velocimetry technology

In order to study the three-dimension flow characteristics of hydraulic coupling, the internal flow field of rectangular cavity-type hydraulic coupling was tested based on PTV（Particle Tracking Velocimetry） technology. Triple exposure technique on single frame was used to record three different lengths of particle motion trajectory. The internal flow direction of hydraulic coupling was judged accurately. Particle motion trajectory was extracted by edge detection algorithm, double threshold method was used to detect strong and weak edges. This method was proved efficient for detecting edges with sigle-pixel width and the displacements of particles were extracted directly, then the internal flow velocimetry was acquired, visualization of internal flow field and quantitative measurement were achieved. At the same time, the particle diameter can be estimated approximately.