Simultaneous 3D temperature-velocity measurements in fluid flow using shake-the-box and phosphor thermometry
M. Stelter(1), B. Fond(2), F. Beyrau(1)
1: Institute of Fluid Mechanics and Thermodynamics, Otto von Guericke University Magdeburg, Germany
2: Department of Aerodynamics, Aeroelasticity and Acoustics (DAAA), ONERA, the French Aerospace Lab, Paris-Saclay University, Meudon, France
DOI:
This contribution implements algorithmic improvements for improved simultaneous three-dimensional temperature and velocity measurements in turbulent gas flows based on seeded sub-micron sized thermographic phosphor particles. Such instantaneous measurements of multiple flow parameters are valuable for direct investigations of non-isothermal turbulent flows and to validate numerical models. The present study focuses on improving our initial implementation of the concept, by implementing state-of-the art algorithms for camera calibration and particle tracking, and refining the processing of particle luminescence images. To investigate the benefit of improved algorithms on the overall performance of the measurement concept, the same image raw data as for the initial concept implementation is evaluated. Using volume self-calibration for the camera calibration leads to a more than twentyfold reduction of remaining errors in the camera models. Combined with two-pulse shake-the-box for 3D particle tracking, the number of successfully tracked particles is increased by a factor of ten. To obtain temperature results from individual particle luminescence emissions, the segmentation of the recorded luminescence images is improved by introducing a two-step masking scheme. Combined with a 3D flat-field correction scheme, this results in more than doubling the number of successfully processed temperature data points, while maintaining the same level of temperature error. This is a further step towards resolving non-isothermal 3D flow structures from individual instantaneous single-shot recordings.
