(312e) Validation of Les Simulation of a Large Helium Plume

Large eddy simulations (LES) are performed for 1m in diameter Helium (He) plume. In a large He-plume, turbulence is generated by the buoyancy phenomenon which induces large scale mixing of air with Helium forming a large plume. One characteristic feature of these turbulent plumes is the generation of toroidal vortices which gives rise to a characteristic puffing motion. These puffing motions show a characteristic frequency (often referred as ?puffing frequency?) once the flow is statistically stationary. The simulations are validated by comparing the simulation results with experimentally recorded data for the He-plume at the FLAME facility in Sandia National Laboratory, Albuquerque. The velocity measurements are performed using Particle Image Velocimetry (PIV) technique and the He-concentration measurements are performed using Planar Laser Induced Fluorescence (PLIF) technique. The comparisons are performed for the time averaged mean velocity and concentration fields and for the rms velocity fields in the near source region i.e., X/Dp < 0.7 (here, Dp is the plume diameter). The simulations are performed at different grid resolutions and use two different sub-grid scale (SGS) models to study the effects of the resolution and SGS model in simulating the flow dynamics of the plume. The puffing frequency observed from the simulations is also compared with the one recorded during the experiments.