Single sensor fiber-based high-speed tomographic particle image velocimetry

Abstract

Particle image velocimetry (PIV) has been heralded as an accurate means of measuring velocimetry information for the study of flow-field phenomena. Many discoveries have been made utilizing the diagnostic technique; however, most of the work has been focused on two dimensions. In turbulent flows, time-resolved three-dimensionality is more often fact than exception. To accurately describe such flows, the PIV technique has been expanded to three-dimensional (3D) by use of tomography. The approach, however, is costly and suffers from lack of versatility, requiring full optical accessibility, which limits its use in laboratories, specifically for time-resolved measurements. Presented in this Letter is a novel technique for capturing time-resolved tomographic imaging for time-resolved, 3D information (four-dimensional) to measure velocity. The technology leverages fiber-optics and a high-speed camera to capture four image views of a volume domain to reconstruct and resolve a 3D flow field. A camera sensor is split into four quadrants by a fiber coupling, and the distal ends are structured for 3D light-field capture. The key is the compactness, flexibility, and ruggedness of the collection optics. This allows the tomographic PIV technique to be applied to challenging flow fields with limited optical access and in harsh environments.