  This study focuses on assessing smartphone camera characteristics for
developing an economic smartphone-based Particle Image Velocimetry (PIV)
system. In the investigation, flow around a cylinder was visualized using two
commercially-available smartphones (OnePlus 5T and iPhone X) cameras and
low-intensity laser diodes. Hydrogen bubbles generated from electrolysis
(termed Bubble Image Velocimetry) of aluminum electrodes were used as seeding
medium. OpenPIV, an open-source toolbox, was used for processing captured
images and obtaining the flow fields. A parametric analysis of the two
smartphones was conducted across varying camera characteristics such as ISO,
exposure compensation and frame rate. The results obtained through
experimentation were compared with the results of a validated computational
fluid dynamics (CFD) study with the same flow conditions and were found to be
in good agreement, with deviation ranging from 1% to 3.5% for iPhone X and 1%
to 7% for OnePlus 5T. It was observed that a higher frame rate results in
greater accuracy of the measurement. Further, an exposure compensation of -1 EV
and an ISO of 400 was found to produce results with the least error as compared
to CFD values.

Image and Video Processing;Instrumentation and Detectors