Quantifying Transport in Chaotic Rayleigh-Benard Convection

The transport of a scalar species in a complex flow field is important in many areas of current interest such as the combustion of premixed gases, the dynamics of particles in the atmosphere and oceans, and the reaction of chemicals in a mixture. There has been significant progress in understanding transport in steady periodic flows such as a ring of vortices. In addition, transport in turbulent flow has an extensive literature. Here we focus on the transport of a scalar species in a three-dimensional time-dependent flow field given by the spiral defect chaos state of Rayleigh-Benard convection. We use a highly efficient and parallel spectral element approach to simultaneously evolve the Boussinesq equations and the reaction-advection-diffusion equation in large cylindrical domains with experimentally relevant boundary conditions. We explore the active and passive transport of a scalar species in a chaotic flow field to quantify the transport enhancement for a range of Lewis and Damkholer numbers.