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Abstract

Turbulent flows and issues of turbulence modeling have long been intriguing and important in fluid researches and practices. The mean or instantaneous velocity gradient tensors with six independent components, or other tensorial variables involving gradients, play a key role in turbulence dynamics and models. The advancement of the knowledge of these parameters relies on measurement systems built on sophisticated flow diagnostic techniques that enable both detailed and complete measurements. However, such systems seem inevitably complicated to operate and costly to build and maintain. Therefore, we develop and optimize a dual-plane stereoscopic particle image velocimetry (DP-SPIV) system that is much more cost-effective than the conventional setup while maintain its full functionalities. Conventional DP-SPIV systems require two double-pulse lasers, four PIV cameras, and complex optical arrangements including a refractive-indexmatched prism that need delicate calibrations. We reduce the numbers of double-pulse laser, camera, and prism to one, three, and zero, respectively, with applications of birefringent optics, the continuity equation, and Scheimpflug condition. The complexities of optical arrangements, namely the polarizations and parallelism of the two light sheets and the prism, are also significantly reduced. The optimized system results in a cost-down of nearly one half and reduction of setup time to almost one order of magnitude shorter.

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