A numerical study of scalar dispersion downstream of a wall-mounted cube using direct simulations and algebraic flux models

► The computed DNS statistics indicate that a gradient-transport scheme can be applied to the vertical and spanwise scalar flux components. ► The streamwise scalar flux is characterized by a counter-gradient transport mechanism in the wake region close to the obstacle. ► The wake profiles of scalar fluctuations and the shape of probability density functions do not suggest a significant flapping movement of the scalar plume. ► The evaluation of scalar dispersion models must include a careful assessment of the computed mean velocity field and Reynolds stress tensor. ► Algebraic models provide an improved prediction of the mean concentration field as compared to the standard eddy-diffusivity model.