Abstract
Particle-laden buoyant jets (PBJ) are free-convective flows that contain particles. Many studies have examined pure thermal plumes, discussing a symmetric self-similar structure that is common in the plume literature. Other studies have studied the fallout properties of particles embedded in plumes. Many contaminant transport models use a Gaussian, self-similar plume profile and treat particles only as a passive tracer. There is however no evidence in the literature of the simultaneous examination of both particle loading and temperature on the flow regimes of a PBJ. Twenty-five numerical simulations were implemented using the LANL HIGRAD numerical model, to systematically study the resulting flow regimes as the temperature and particle loading of a PBJ were systematically varied. A supplemental experiment was carried out in the laboratory, with three simulations carried out that were dynamically similar to the experiment. The comparison between experiment and simulation indicated that the model did not create turbulence as close to the domain floor as in the experiment, and further tuning is required. With awareness of this inconsistency, the twenty-five simulation results produced results of significant interest. Only two of the twenty-five simulation results produced the self-similar, Gaussian profile that is observed in the plume literature. Four of the twenty-five cases produced a no collapse PBJ scenario. The remaining cases produced either a partial collapse or full collapse of the PBJ. The use of the Grashof and buoyant Richardson numbers to characterize the flow regimes did not produce consistency with the resulting flow regime. A modified multiphase Richardson number however, accounting for particle density within a control volume, showed consistency with the resulting flow regime and indicates promise for further research and perhaps operational use. PBJ are physically relevant to a variety of particle-laden convective flows including volcanoes, industrial emissions, and contaminant transport. These results are of interest to a number of stakeholders including the DOE, DOD, DHS, and emergency management communities.
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