Impact of smaller scales on the scalar dissipation rate in direct numerical simulations of wall bounded flows

Passive scalar dynamics in a turbulent channel flow is studied with Direct Numerical Simulation at friction Reynolds number Re_tau=160 and Prandtl number Pr=1. The goal of the study is to assess the grid spacing requirement for an accurate estimation of various turbulent statistics, with a special focus on the scalar dissipation rate. All scalar fields are computed in parallel using a single velocity field resolved with the finest resolution, thus reducing the statistical variability.