Resolution Requirements for Numerical Simulations of Buoyant Plumes

High-fidelity computational predictions of buoyant plumes in natural and built environments are constrained by the difficulty of modeling complex physics across wide temporal and spatial scale ranges. Plume structure and dynamics are governed by coupled nonlinear interactions between turbulence, buoyancy-driven flow, and, in the case of reacting flows, flame chemistry. These multi-physics phenomena typically span an enormous range of spatial and temporal scales and are intricately connected to various canonical flow instabilities, including Rayleigh Taylor and Kelvin Helmholtz instablities. In this talk, we outline recent efforts to use adaptive mesh refinement (AMR), where the grid is resolved at small scales only in regions of high dynamical and physical significance, for the study of buoyant plume structure, dynamics, and evolution in a range of contexts. We place particular focus on the fundamental changes in flow dynamics that occur with different levels of spatial resolution, specifically related to the accurate representation of Rayleigh Taylor instablities. These instablities affect the frequency at which many buoyant plumes oscillate, or "puff", and we show that simulations with insufficient resolution are likely to incorrectly predict the resulting puffing frequency. We end by highlighting challenges faced in the application of AMR to simulations of buoyant plumes, including future research directions.