Effective boundary conditions for rough reactive walls in laminar boundary layers

In order to gain computational time and simplicity, transfer over rough and heterogenous surfaces is most often modelled using the concept of an effective (flat) surface. In this paper, we are particularly interested in mass transport by convection and diffusion over rough, heterogeneous and reactive surfaces and we propose a model using first-order effective properties. The resolution of “local closure problems  ” given by a domain decomposition technique, allows to link flow and surface parameters to effective properties of the modelled fluid/solid interface: δδ, the effective surface position, and keffkeff, the effective reaction rate. The effect on δδ and keffkeff of the surface chemical and geometric properties, as well as the flow characteristics, is then analysed, giving some indications for possible estimates in specific cases. Finally, the obtained model is validated by comparison to direct numerical simulations.