PIV methodology for small scale measurement

Abstract

Measurement of velocity fields by PIV method is often limited by the scale of the measured model. This is doubly true for the stereo PIV method. Problems of measurement in small (but still macroscopic) scales are associated with optical distortions in the optical path of the camera. Additionally, there is a calibration problem for stereo PIV. Therefore, this paper is devoted to the description of PIV methodology for measurement in small geometrical scales. The idealized transparent model of hemodialysis vascular access was used in this paper. This model had realistic vascular access dimensions (6 mm in diameter). A special working blood-mimicking fluid (BMF) was mixed with a refractive index matching that of the model. The refraction and distortion of light passing through the interface between the model and the fluid was so small, that it was possible to calibrate the stereo PIV outside the measured model. The accuracy of this calibration is discussed and verified by measuring the velocity field on a straight section of the vascular access model for laminar flow.