Computing flare dynamics using large eddy simulations

Computing the dynamics of flares is motivated by the increased need for efficient and safe flaring of unwanted gases during hydrocarbon and petrochemical processing. To understand the unsteady flame shape dynamics, Large Eddy Simulations (LES) are used to study natural gas flares in the presence of crosswind. Different flare regimes are created by the competing forces of the jet inertia, flare buoyancy, and crosswind inertia. These regimes are studied by performing LES simulations which include different flare jet velocities, crosswind velocities and flare tip diameters. As the ratio between the flare jet to crosswind momentum decreases for constant flare tip diameters, the computed flame shape is changed from a buoyancy dominated regime to a fully wake stabilized regime. These simulation results are in agreement with the flame shapes observed in wind tunnel experiments reported in the open literature. With this confidence in the simulation tool, a parametric study is carried out to understand the effect of flare tip diameters and velocities typical of large-scale industrial flares. In addition to the jet to crosswind momentum ratio, the individual velocity magnitudes also play a significant role in changing the flame regimes. This study shows the capability of the LES method to predict dynamics of flare flame shape.