Parameters optimization of light field micro-particle image velocimetry

Abstract

The light field micro-particle image velocimetry (LF-μPIV) can record the instantaneous three-dimensional (3D) spatial position information of tracer particles in a single photographic exposure by a single camera, and thus achieve the instantaneous 3D velocity measurement of the micro-scale flow. The accuracy of the spatial positions of the reconstructed tracer particles is closely related to the spatial reconstruction resolution of the LF-μPIV system, and determines the measurement accuracy of the 3D velocity distribution. In this paper, the effects of the optical parameters of the LF-μPIV system and the spatial position of the tracer particle on the spatial resolution and reconstruction quality are numerically studied. The location of the measurement volume and the optical parameters of the LF-μPIV system are further optimized. Based on the optimized parameters, a LF-μPIV system is assembled. Finally, experiments are carried out to verify the feasibility of the optical parameters optimization from simulations and to evaluate the performance of the LF-μPIV system for three-dimensional velocity field in a micro-scale convergent channel. Results indicate that the lateral and axial reconstruction resolutions are higher in the outside and inside regions away from the focal plane, compared with those in the region near the focal plane of the objective lens, and is less affected by the microlens aperture, CCD sensor pixel size and objective lens magnification. The spatial reconstruction resolution of the LF-μPIV system at different depths is in good agreement with the simulation results, proving the effectiveness of the optical parameters optimization of the LF-μPIV system. The measurement results of 3D velocity field in a micro-scale convergent channel are consistent with the simulation results by ANSYS Fluent, further verifying the feasibility of the optimized LF-μPIV system for 3D velocity field.