Florent Laporte

Investigation of Ambient Turbulence Effects on Vortex Evolution using LES

The effects of ambient turbulence on vortex dynamics are studied using a validated,threedimensional, large-eddy simulation model. The objective of this study is to understand the mechanisms of interaction between vortices and turbulence and to obtain quantitative data about the aging process. Numerical simulations are performed in order to isolate the effects of ambient turbulence on a configuration consisting of a single vortex or vortex pair. A set of simulations has been conducted by placing vortices in a field of homogeneous isotropic turbulence for a range of turbulence intensities. The results reveal typical phenomena of vortex/turbulence interaction such as gradual, quasilinear circulation decay due to turbulent diffusion, vortex deformation, appearance of asimuthal vertical structures and the occurrence of longand short-wavelength instabilities. Several parameter studies have been performed in order to quantify a critical parameter which affects the strength of vortices and/or predicts the occurrence of instabilities.

A Numerical Study of the Elliptic Instability of a Vortex Pair

The elliptic instability developing in a laminar vortex pair with a high ratio of the vortex core size to the separation distance between the vortices is studied by direct numerical simulations. The computations allows the prediction of both the linear regime of the instability development and the non-linear regime including the transition to a locally turbulent flow.