Experimental Fluid Mechanics goes 3D: New Numerical Methods for Quantitative Instantaneous 3D Imagery of Fluids


G. Le Besnerais, F. Champagnat, P. Cornic, A. Plyer, B. Leclaire, A. Cheminet, C. Illoul, G. Losfeld, Y. Le Sant, D. Donjat, F. Nicolas, F. Micheli (ONERA)

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We review recent developments made between three departments at ONERA (DTIM, DAFE, DMAE) with regard to 3D imagery used in fluid mechanics experiments. We first discuss 3D PIV (Particle Image Velocimetry) and present  original contributions on the modeling of the imaging process, the reconstruction of the 3D volume of particles and the estimation of the 3D motion field between two time instants. These three contributions emphasize the pointwise character of particles in PIV, in contrast with classical Tomo-PIV approaches, and have been shown to outperform state-of-the-art methods, yielding more accurate 3D velocity estimations. Then, we consider 3DBOS (Background Oriented Schlieren), which is aimed at estimating the instantaneous 3D density field of a moving fluid. We have recently proposed an original one-step numerical approach for 3DBOS. This method has been successfully used in several experiments conducted in various ONERA facilities, in particular in the F2 and S1MA wind tunnels. Finally, we draw some important perspectives, especially for the study of compressible flows by combining both techniques.