Uncertainty of the PIV Testing Results for Gas Flow Field Caused by Tracer Particles and Seeding Method

The quality of flow visualization is very important for PIV. A lot of testing results indicate that the slip between tracer particles and continuous phase is very severe for high velocity gradient flow field and yield uncertain testing results. In addition, improper seeding method of tracer particles often results in false results. The systematical investigation on the above‐mentioned problem has been done based on the theory of dilute phase gas‐particle flow. The results indicate that tracer particles must be have the slip with the fluid as long as the velocity gradient presents, even the particle is sufficiently accelerated, and it has severely influence on the reliability of PIV testing results for the flow field with high velocity gradient or (and) larger tracer particles size. The relative error caused by the slip of particles and fluid is in proportion to the particle Stokes time and the particle velocity gradient, but it is in inverse proportion to the correction factor for Stokes‐drag force. The a...