Large Eddy simulation of annular plumes
摘要
Annular plumes discharged in stable and uniform environments of greater density than the initial plume density were simulated to detect and explain possible existing differences compared to available experimental data. Two cases were simulated numerically with exit velocities of 0.527 and 0.702 m/s; exit/ambient temperatures of 68.5/23 °C; outer/inner annular source diameters of 0.13/0.11 m; equivalent densimetric Froude numbers of 1.63 and 2.12 and Reynolds numbers of 2380 and 3171. These cases have recently been investigated experimentally (Stefanidou et al. in Environ Fluid Mech 23:965–1010, 2023, https://doi.org/10.1007/s10652-023-09943-z). For quasi-steady-state conditions, the annular plume is simulated by employing the Reynolds-averaged Navier–Stokes equations via the k–ε-realizable turbulence model and the large-eddy simulation (LES) via the wall-adapting local eddy viscosity (WALE) subgrid stress turbulence model of ANSYS© Fluent software. The results regarding the centreline mean velocity and mean relative concentration were compared with the above experimental measurements, with an exit velocity of 0.527 m/s, and proved that LES-WALE is better at predicting the annular plumes. Thus, the latter was used to simulate both above cases. In general, the predictions agree well with the measurements regarding the mean flow and mixing characteristics in the core region and the region beyond the core. The results for the turbulent intensities of velocities and temperature were also obtained for both the core and beyond the core regions. The transverse profiles of the mean axial velocity and mean relative concentration were used to determine the corresponding spreading coefficients, which were in good agreement with literature experimental data regarding equivalent round plumes.