Development of High Speed PIV using Dual-Camera System

M. Yamada, K. Sakakibara, Y. Miyamoto, and T. Saito

Graduate School of Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan, Email: ttsaito@ipc.shizuoka.ac.jp

ABSTRACT

In this study, a dual-camera PIV (particle image Velocimetry) system newly developed with two high- speed video cameras is applied to the flow field around a single bubble of 2.9 mm in equivalent diameter. Its performance is verified and discussed. The two cameras are adjusted as the two visualized images are in good correspondence using both calibration target and micro motion positioning stages. It is very difficult to achieve complete correspondence of the two visualization fields. The systematic discrepancy between the visualization field of the master camera and that of the slave camera causes a bias error. The authors correct the bias error by removing the discrepancy from the results obtained by dual-camera PIV measurement. In a PIV system of using a CW laser, a time interval of two time-series images depends on the camera frame rate. Compared with a conventional PIV system of using a double pulse laser, the time interval of the CW-laser-PIV images is longer. A time interval of two images for PIV affects the measurement accuracy significantly. Therefore, the time interval should be precisely controlled and short. In measuring unsteady flow, such as the surrounding liquid motion of a single rising bubble, higher time resolution is needed. The technique developed in the present study provides an arbitrary and fully controllable interval of two images by delaying the capture timing of a slave camera using a phase shift function generator. In addition, high time resolution is achieved using high-speed video cameras.

The authors perform simultaneous visualization measurement of the bubble motion and its surrounding liquid motion via this dual-camera PIV system. On the basis of the results, suitability of the dual-camera PIV system is discussed. By bubble shape analysis and PIV analysis, we confirm the left- right asymmetry of the bubble shape and the flow toward the bottom of the bubble.

Keywords piv, dual-camera, bubble, two-phase flow