Towards two-dimensional measurements of small scales (scalar and velocity) : principles and limitations. Application for a highly turbulent flow field

Bruno Renou, COmplexe de Recherche Interprofessionnel en Aérothermochimie (CORIA), Rouen, France

Optical techniques are now widely used to measure velocity and/or scalar fields. In particular, accurate determination of instantaneous spatial gradients of velocity and scalar is of a first importance for a large field of applications (turbulence, combustion, .). PIV (Particle Image Velocimetry), Rayleigh Scattering, PLIF (Planar Laser Induced Fluorescence) on a tracer, ., are likely the best techniques for such measurements, but their implementation, as well as the interpretation of the results require caution.

Proper assessment of the principle, the limits and the uncertainties of these techniques are of first importance to analyse experimental results. Some important issues concerning the optimization of the measurement to reduce the noise, the determination of the spatial resolution, the estimation of both scalar and turbulent energy dissipation rate will be tackled during the lecture. A short review of important results in the literature will also be used to illustrate these purposes.