SUPER-resolution flow diagnostics for Scalar Transport And Dissipation – SUPERSTAD

To predict and understand heat and mass transport in turbulent flows found in reactors or in nature, lab experiments are needed in which fine enough measurements would be performed to avoid smoothing over small turbulent structures. In this project we propose to qualify and apply an optical technique which exploit the signals from individual sub-micron luminescent particles, seeded into the flow and illuminated by a thin laser light sheet. For each laser shot, the particles form an intricate web of luminescence thermometers where each thermometer is positioned in the three dimensions with a resolution better than the camera pixel, that is a few microns. The 3-components of the velocity vector will also obtained at each particle location using 3D particle tracking velocimetry approaches developed at ONERA.

To validate the concept, measurements will be performed in a laboratory jet and compared against those obtained by short ultra-fine and cold wire thermometers, very recently developed at ONERA. The luminescent particles will also be optimized considering wet chemical synthesis routes developed. Finally, the newly developed diagnostics will be applied in a canonical highly turbulent heated jet to demonstrate the ability to access temperature and velocity fluctuations product terms and directly measure the 3D temperature variance dissipation rate. These datasets will shed the light into the physics of scalar transport in high Reynolds number flows, and serve to develop and test turbulence models to improve the accuracy of LES and RANS simulations.