A spline-based technique for estimating flow velocities using two-camera multi-line MTV

Applications of spline-based data reduction techniques for molecular tagging velocimetry (MTV) are explored for the case in which two cameras are employed. To accommodate two cameras, an affine warp-mapping scheme that correlates the two camera views is introduced, and the associated uncertainties quantified. Spline-based techniques are examined for both multiple line and grid-based images. The high spatial resolution of the multiple line method enables accurate measurements of the velocity gradient and spatial correlations in a single direction. Such information is required to accurately obtain turbulent integral and Taylor micro scales. Comparison with previous multiple line methods indicates that even with the additional uncertainties associated with two cameras, the present spline technique improves sub-pixel resolution by about a factor of three. This improvement is required to accurately obtain turbulent integral and Taylor length scales.