The Particle Image Velocimetry (PIV) is a superior technique to measure the velocity distributions in the vessel. However, in order to measure the three-dimensional velocity distributions using PIV, the three-dimensional positions of the tracer particles should be determined from the two-dimensional images. Therefore, two or more images are taken from different angles at the same time to cause the complex measurement systems, e.g., three cameras, synchronous recorder, stroboscope.
The author had developed the new PIV called VVH (Velocity Vector Histogram) method. In this method only two images taken from different angles are used to identify the particle three-dimensional positions. The uncertainty of the three-dimensional particle identification can be abandoned in the velocity vector histogram. The unidentified particle positions are considered as noise, and are omitted in the velocity vector histogram. Namely, the three-dimensional particle positions are determined using the velocity information.
The VVH method was applied to the complex three-dimensional flow. The relatively high velocity fields including a circulating flow were measured and the effectiveness of the VVH method were discussed. Several techniques to improve the accuracy and the dynamic range of the measured velocities were evaluated using the three-dimensional VVH method.