Starting: December 2013
The transport of a passive
scalar such as a pollutant, by a high Reynolds number turbulent flow is intimately related to the statistical properties of the fluid particles trajectories. The recent developments of high speed
cameras enabling to track the motion of particles in high velocity flows, gave access to the Lagrangian properties of turbulence (i.e. turbulence seen from the particle’s point of view). In the
last 15 years, studies focusing on homogeneous systems have renewed the experimental approach of turbulence. But most situations of practical interest are inhomogeneous. It is the case of the
atmospheric boundary layer (the few hundred meters above the Earth’s surface), where the flow is extremely turbulent and shows a vertical gradient of velocity.
In this project, a high aspect ratio channel flow will be used as a benchmark case of turbulent boundary layers. This flow exhibits symmetry properties that will make the experimental study simpler. Eulerian measurements will be carried out to fully characterize the flow, and the study will then focus on Lagrangian properties, starting with the acceleration. The dispersion of fluid particles at longer timescales will then be addressed, and the experimental data will be compared to numerical simulations performed by I. Vinkovic and M. Gorokhovski in Ecole Centrale Lyon.
The aim is to better understand the influence of the velocity gradient on the fluid particles trajectories, in order to accurately model the transport properties in this region of the atmosphere.
Polystyrene particles (10 µm) doped with Rhodamine in a turbulent flow. The flow is illuminated by YAG laser sheet and the
fluorescent particles are isolated from the illuminated background by a red filter (exposure time: 1/250 sec).
Juan Ignacio Polanco, Ivana Vinkovic, Nickolas Stelzenmuller, Nicolas Mordant, Mickael Bourgoin: Relative dispersion of particle pairs in turbulent channel flow. International Journal of Heat and Fluid Flow, (In press)
Nickolas Stelzenmuller, Juan Ignacio Polanco, Laure Vignal, Ivana Vinkovic, and Nicolas Mordant: Lagrangian acceleration statistics in a turbulent channel flow. Phys. Rev. Fluids 2, 054602 – Published 2 May 2017
Bourgoin, M, Baudet, C, Kharche, S, Mordant, N, Vandenberghe, T, Sumbekova, S, Stelzenmuller, N, Aliseda, A, Gibert, M, Roche, P-E et al.: Investigation of the small-scale statistics of turbulence in the Modane S1MA wind tunnel. CEAS Aeronautical Journal, 2017
Lagrangian statistics in a turbulent channel, ETC16, 2017, Stockholm
Lagrangian statistics in turbulent channel flow: implications for Lagrangian stochastic models, APS DFD, 2016, Portland
Lagrangian study of inhomogeneous turbulence: Experimental results, EFMC 11 2016, Séville
Une étude Lagrangienne de la turbulence inhomogène, GdR Turbulence, 2016, Paris
An experimental Lagrangian study of inhomgeneous turbulence, APS DFD, 2015, Boston
Etude lagrangienne de la dispersion dans un canal plan turbulent, CFM 2015 Lyon
Mesures lagrangiennes dans un écoulement de canal plan turbulent, GdR Turbulence, 2015, Grenoble