Measurement of mixing fluid flows with optical tomography.

We present what is, to our knowledge, the first instantaneous optical tomographic reconstruction of a nonstationary fluid flow. Holographic interferometry is used to measure optical path length through a coflowing helium jet in air along several views. The spatial distribution of the helium concentration is determined from these measurements. Eighteen views through a 7-cm-diameter, 7-cm-high cylindrical volume are recorded, yielding a spatial resolution of 3 mm with an error of less that 3%. When a 1-W argon-ion laser is used, the temporal resolution is 300 μsec.