Dual-camera DPIV for flow studies past artificial heart valves

A video-based digital-particle-image-velocimetry (DPIV) system with a time-delayed dual-camera recording was built for investigation of the unsteady flow structure in a pulsating flow behind artificial heart valves. The delay between the master and slave image is arbitrary by adjusting a phase-shift in the phase synchronization of the consumer video-cameras which represents a cheap and easy way to perform video-based cross-correlation DPIV at high velocities like that in heart valve flows. A calibration procedure was necessary to correct for misalignment of the image acquisition system with regard to translation and tilt of both image planes. With a framing rate of 50 Hz and continuous recording, a large number of PIV recordings at a rate of 50 Hz can be captured which enables to resolve the flow evolution in detail as demonstrated by a sequence showing the generation and sweep down of starting vortices behind the leaflets for the Bjork-Shiley-Monostrut (BSM) and Sorin-Bicarbon (SE) heart valves during the opening phase. Long-term recording with the video system over several hundreds of beating cycles offers statistical investigation of cycle-resolved fluctuations and evaluation of shear stresses. In general, this system is very suitable for video-based DPIV at higher velocities when a pulsed and synchronized illumination is not available or difficult to implement.