Reynolds and Richardson Number Dependence of Near-Field Flow Behavior for Axisymmetric Buoyant Jets and Plumes

The large-scale structures that form in the near-field of axisymmetric buoyant jets and plumes play an important role in the entrainment and mixing properties of the flow. As such, characterizing the dynamics of these structures is essential to building reduced-order models (ROMs) that accurately capture these dynamics without resolving the broad range of scales that occur in the flow. With accurate ROMs, we will be able to better predict flow properties and optimize flow configurations. In order to do this, here we conduct high-resolution numerical simulations using adaptive mesh refinement of axisymmetric non-reacting helium jets and plumes spanning different Richardson (Ri) and Reynolds (Re) numbers. We first review the flow kinematics, showing that, as the flow becomes more turbulent via increases in Ri and Re, the ambient fluid penetrates further into the core of the flow, ultimately with sufficient strength to form a mean recirculation zone just above the inlet. We then explore the dynamics through the mean and turbulent kinetic energy transport equations, which allows us to probe the dynamical causes of the production, transport, and removal of kinetic energy. The balance between budget terms is compared for each simulation and examined for different Ri and Re.