Stereoscopic PIV measurements using low-cost action cameras

Abstract

Recently, large progress was made in the development towards low-cost PIV (Particle Image Velocimetry) for industrial and educational applications. This paper presents the use of two low-cost action cameras for stereoscopic planar PIV. A continuous wave laser or alternatively an LED was used for illumination and pulsed by a frequency generator. A slight detuning of the light pulsation and camera frame rate minimizes systematic errors by the rolling shutter effect and allows for the synchronization of both cameras by postprocessing without the need of hardware synchronization. The setup was successfully qualified on a rotating particle pattern in a planar and stereoscopic configuration as well as on the jet of an aquarium pump. Since action cameras are intended to be used at outdoor activities, they are small, very robust and work autarkic. In conjunction with the synchronization and image pre-processing scheme presented herein, those cameras enable stereoscopic PIV in harsh environments and even on moving experiments. Graphic abstract

Smartphone-based particle image velocimetry for cardiovascular flows applications: A focus on coronary arteries

“…Second, the combination of the (fixed) maximum acquisition frame rate of the smartphone camera and the use of a continuous light source resulted in particle blurring in correspondence of the stenosis ( Supplementary Figures S4, S7 ), with the consequence of underestimating local velocity values ( Figure 8 ) starting from 40 cm/s. To reduce particle blurring, a possibility could be offered by the adoption of a cw laser pulsed by a frequency generator, as suggested by Cierpka et al, 2021 , or a pulsed low-power light source ( Aguirre-Pablo et al, 2017 ; Käufer et al, 2021 ; Minichiello et al, 2021 ) to illuminate the image sensor for a short time, although this solution would require a synchronization unit. Particle blurring ( Oh et al, 2021 ) could potentially be reduced also by decreasing the exposure time.…”

“…Despite the proven capability of conventional PIV test benches in characterizing internal flows, their adoption in both research and industrial laboratories is hampered by the cost of the components (rough order of magnitude estimate of 100 k€). In recent years, attempts have been made to propose alternative PIV solutions based on low-cost components, thus overcoming cost-related barriers ( Cierpka et al, 2016 ; Aguirre-Pablo et al, 2017 ; Käufer et al, 2021 ; Minichiello et al, 2021 ). In this respect, the imaging system embedded in smartphones have captured the attention of researchers as potential substitute of high-speed cameras adopted in conventional PIV, leveraging the latest smartphone technological advancements and their relatively low cost.…”

SmartPIV: flow velocity estimates by smartphones for education and field studies

“…Kashyap et al (2020) validated the image recoding of different smartphones using an open PIV software and achived relative differences below 7% in comparison to numerical results. Käufer et al (2020) extended the planar PIV system to stereoscopic PIV using two consumer action cameras and a modulated cw-laser and Aguirre-Pablo et al (2017) even used smartphones and colored LEDs for a tomographic reconstruction of the velocity field in a jet. All these attempts were based on previously recorded videos that were later processed on a powerful workstation with conventional PIV software.…”

A compact in vitro test bench for cardiovascular flow analysis

“…In recent years, attempts have been made to use smart-PIV systems to overcome the limitations mentioned above. 1,2 In this respect, the imaging equipment of commercial smartphones, coupled with low-energy light sources, has recently proved to be a suitable component for PIV measurements in air and water flows. 1 In vitro modelling with artificial flow phantoms (scale 1:1) has been used to investigate the fluid mechanics of the circulatory system without the ethical and safety issues associated with animal and human experiments.…”