Combination of Holographic Interferometry and Digital Speckle Tomography for Analysis of Three-Dimensional Density Distributions

<jats:title>Abstract</jats:title> <jats:p>A digital speckle tomography has been combined with a holographic interferometry to improve the accuracy of reconstruction of density distributions. For the combined system, several beam splitters have been used to separate the laser beams from a continuous wave laser for the digital speckle tomography and the holographic interferometry so that measurements can be performed simultaneously by both of the experiments. The density distributions have been reconstructed by the tomography methods for both of the experiments. While the projection of the digital speckle tomography expresses the integration of the density gradients, those of the holographic interferometry can be obtained from the integration of the density itself. Thus, the steep region of the density distribution has been reconstructed by the use of the digital speckle tomography more accurately while the holographic interferometry has been used to calculate the density distributions for other regions from the simultaneous measurements of the combined system. Initially, the downward CO2 flow from one-nozzle and two-nozzle test sections have been investigated to confirm the accuracy. Then, the downward flow of CO2 from a circular small opening with a vertical partition (CO2-air exchange flow) has been analyzed for the transient three-dimensional density fields by the proposed combined system in this study.</jats:p>