Numerical study of buoyant plumes from a multi-flue chimney released into an atmospheric boundary layer

A numerical study has been carried out of three-dimensional, full-scale, turbulent, buoyant plumes from a four-flue chimney in an atmospheric boundary layer. The simulations were based on the k− ε turbulence model and a finite-volume method. The investigation was aimed to verify the question of how closely the overall characteristics of merged plumes from a multi-flue chimney match those of an equivalent single plume. Therefore, the results for multi-flue plumes were compared with those for a single plume under the same release conditions for volume flow rate, momentum and temperature. The differences in the velocity, temperature and turbulence energy fields of a single plume and multiple plumes were mainly significant in the early stages of rise and spreading. The multiple plumes merged very quickly and by ten diameters downstream only small differences between the plumes’ cross-sections could be distinguished. Comparisons of the rise heights showed that the arrangement of the individual flues within the chimney, with respect to the cross-wind, affects the rise height of the merged plumes. One of the multi-flue cases, which allowed the cross-wind penetration between the adjacent plumes, resulted in a lower rise height of the merged plume, while one other case, which provided a greater shielding, led to a rise height which was in agreement with the plume from the single-flue chimney. The rise heights were compared with empirical data.