Parametric study of inlet conditions for LES of forced plume interacting with a ceiling*

Present work concerns LES of forced plume interacting with a ceiling in OpenFOAM. Different inlet types are used for parametric study, starting with a constant inlet velocity & temperature, to using a non-uniform spatially varying profiles from experiment. Velocity, temperature and turbulence quantities are compared at both near- and far-field from the inlet for radial profiles, along with axial profiles at different radial locations. Moreover, boundary layer profiles at the ceiling layer are also studied. The turbulent velocities obtained from both the inlet-types are really low in near-field, with plume remaining intact without any mixing until it hits the ceiling, resulting in an over-predicted vertical velocity along the centreline.

To address the issue, a turbulent inlet is adopted which generates artificial fluctuations over the mean velocity profile. These fluctuation scales are calculated based on the maximum/mean values of turbulent velocities from experimental data. This resulted in a proper mixing and entrainment, which increased the turbulence levels near the inlet simultaneously slowing down the plume. Different inlet velocities are considered to check the validity of this concept