Abstract
Single-shot, tomographic imaging of the three-dimensional concentration field is demonstrated in a turbulent gaseous free jet in co-flow using volumetrically illuminated laser-induced fluorescence. The fourth-harmonic output of an Nd:YAG laser at 266 nm is formed into a collimated 15 × 20 mm2 beam to excite the ground singlet state of acetone seeded into the central jet. Subsequent fluorescence is collected along eight lines of sight for tomographic reconstruction using a combination of stereoscopes optically coupled to four two-stage intensified CMOS cameras. The performance of the imaging system is evaluated and shown to be sufficient for recording instantaneous three-dimensional features with high signal-to-noise (130:1) and nominal spatial resolution of 0.6-1.5 mm at x/D = 7-15.5.
Highlights
Laser-based techniques for point-wise, line, or planar measurements have been valuable for studying scalar structure of turbulent flows for quite some time, earlier measurements shown by Escoda and Long [1]
Single-shot, volumetrically-illuminated tomographic laser-induced fluorescence (LIF) measurements were presented in a free jet in co-flow
Eight views of the fluorescence signal were collected through stereoscopes mounted in front of four high-speed CMOS cameras coupled to high-speed dual-stage intensifiers to allow for temporally resolved volumetric reconstructions of the flow field
Summary
Laser-based techniques for point-wise, line, or planar measurements have been valuable for studying scalar structure of turbulent flows for quite some time, earlier measurements shown by Escoda and Long [1]. Because of relatively strong quantum yields and versatility, planar laser-induced fluorescence (PLIF) has been utilized for measurements of scalar mixing under a wide range of conditions, as summarized early on for gaseous flows by Van Cruyningen and associates [2] and for liquid flows by Crimaldi [3]. A single excitation pulse illuminates the entire volume within the time span of a nanosecond laser pulse, and up to eight intensified camera views are used to capture the fluorescence signal simultaneously from different horizontal and vertical angles. This provides a pathway to single-shot or high-speed, three-dimensional laser-based imaging with nanosecond time resolution even in flows without high nascent chemiluminescence or incandescence. The feasibility of tomographic imaging of laser-induced fluorescence, potential limitations, and strategies for improvement are presented and discussed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
