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Dispersion of a scalar puff in turbulence: theory and experiment

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We study the diffusion of a puff of passive scalar in a homogenous and isotropic turbulent flow. We integrate the equation for the spreading of a Gaussian puff using numerical simulations done at Taylor-Reynolds number Reλ = 400. This equation is valid for small puffs, such that the turbulent velocity accross the puff can still be considered linear. The numerical simulations are compared to an experiment in which small Gaussian puffs of NO molecules in a turbulent flow of air are created using molecular tagging. We find striking agreement between simulations and experiment, and discuss the effect of intermittency.

Author(s):

[CANCELLED]    

Enrico Calzavarini    
Laboratoire de Mecanique de Lille
France

Willem van de Water    
Physics Department Eindhoven University of Technology
Netherlands