Sustained simultaneous high-speed imaging of scalar and velocity fields using a single laser

A high-speed technique that combines planar laser induced fluorescence (PLIF) detection of biacetyl and particle image velocimetry (PIV) for simultaneous imaging of scalar and velocity fields is demonstrated at a frame rate of 12 kHz for up to 32500 consecutive frames. A single diode-pumped, frequency-tripled Nd-YAG laser was used for excitation. Wavelength-separated recording was achieved for Mie scattering from silicone oil droplets with a CMOS camera and for the red-shifted fluorescence from biacetyl with an image-intensified CMOS camera. Interference between PIV and PLIF tracers was found to be negligible. Cross-talk between PIV and PLIF signals was low and a strategy to completely eliminate it was devised and is discussed. The signal-to-noise ratio is about 9 for single-shot scalar images. Example image sequences were recorded in an atmospheric pressure air jet at Re = 2000.