Conditional averaging on volumetric velocity fields for analysis of the pseudo-periodic organization of jet-in-crossflow vortices

Abstract

Volumetric velocimetry measurements have been performed on a round jet in crossflow (JICF). Two kind of conditional averaging process are presented : a global conditional average (GCA) and a local conditional average (LCA). Vortices crossing the JICF symmetry plane are used to quantify the jet pseudo-periodicity leading to the GCA and LCA definitions. Because they make possible to improve the velocity field resolution as well as to significantly reduce the experimental noise, these conditional averages are an interesting and efficient way to study the instantaneous swirling structures of this instantaneous flow.

PTV measurements of oscillating grid turbulence in water and polymer solutions

“…This could for example help to visualize 3D turbulent velocity structures rising from the grid to the interface, or compute instantaneous pressure, shear stress, or viscosity fluctuations. Such instantaneous reconstructions have already been achieved (in Newtonian fluids), for example by Cambonie (2012Cambonie ( , 2015 and co-workers for the study of pseudo periodic organization of jets in cross flows. Recently, major progress towards the possibility of Eulerian projections at high grid resolution have been made.…”