LAUSR

A novel approach, which utilizes astigmatism-based depth codification and discrete dual-plane illumination, is developed to provide quasi-volumetric velocimetry (2.5D3C) by means of Stereo-PIV. The technique is referred as Dual-Plane Stereo-Astigmatism (DPSA). It provides the full characterization of the velocity gradient tensor by overcoming the limitation of out-of-plane gradient determination. The principle of the DPSA approach relies on the joint recording of two, consecutive, planar measurement domains and the subsequent allocation of particles based on the particle image shape. For the identification of particles, a correlation-based particle identification approach (CPI), which addresses non-overlapping particles, is introduced. With regard to dense particle fields, a method for the iterative particle reconstruction (IPR) is adapted for DPSA. For displacement analysis, an alternative PIV evaluation strategy is introduced, which utilizes derived information of particle locations. The DPSA approach is tested experimentally and synthetically by the investigation of a spray-induced flow and a generic test case, respectively. Separate planar velocity fields are obtained by means of PIV and PTV evaluation. A performance analysis is carried out to assess the influence of noise, particle density and particle image size on the procedure of particle identification and allocation. The CPI technique provides adequate results for low to medium particle densities and further features a high robustness regarding particle identification with respect to background noise, optical aberrations and inconsistent particle images. The adapted IPR method, on the other hand, shows viable results for particle densities of up to 0.1 ppp.