5 kHz VLIF (Volumetric laser induced fluoresence) measurement in turbulent flows seeded with iodine

This work reports the experimental demonstration of 5 kHz visualization of turbulent flows in all three spatial dimensions (3D) based on volumetric laser induced fluorescence (VLIF). The measurements were performed based on the LIF signal of iodine (I2) vapor seeded in the flow. In contrast to established planar LIF (PLIF) technique, the VLIF technique excited the seeded I2 vapor volumetrically by a thick laser slab. The volumetric LIF signals emitted were then simultaneously collected by multiple cameras from different orientations, based on which a 3D tomographic reconstruction was performed to obtain the 3D distribution of the I2 vapor in the target flow. Single-shot measurements obtained in a duration of ~300 ns (limited by the pulse duration of the excitation laser) were demonstrated in a measurement volume of ~50 × 50 × 50 mm at a repetition rate of 5 kHz. These measurements demonstrated the feasibility and potential of VLIF for resolving the 4D spatiotemporal dynamics of turbulent flows.