We analyse laminar thermal plumes and their interactions originating from line sources using two-dimensional simulations for a range of Rayleigh numbers ( \(\hbox {Ra}_f\) , which is based on the constant heat flux supplied at the source), spanning from \(10^4\) to \(10^8\) . Initially, a single-plume system is examined by systematically varying \(\hbox {Ra}_f\) within the range of \(10^4\) to \(10^8\) . Subsequently, we explore a two-plume system, wherein the separation between the sources is within a range of four to twelve times the radius (R) of the cylindrical heater. Additionally, we have explored an equivalent single-plume scenario with an effective \(\hbox {Ra}_f\) of \(10^6\) . The analysis establishes an empirical correlation for the cap-tip velocity ( \(v_\textrm{c}\) ) and the steady-state average temperature of the heater with \(\hbox {Ra}_f\) . Notably, we observe that the sensitivity of these parameters to variations in \(\hbox {Ra}_f\) is comparatively lower when compared to that in the case of point source heaters. Furthermore, the merged plume, which manifests in the case of the two-plume system, exhibited heightened stability for larger source separations. This increased stability is due to the diminished generation of vorticity and velocity fluctuations along the plume stem. Interestingly, we observe that the cap-tip velocity of the merged plume remained unaffected by the source separations. Following the merging of plumes, the two-plume system displays lateral mass ejections that increase with the source separations. These lateral mass ejections facilitate augmented heat transfer in the lateral direction, though at the expense of compromised heat transfer in the downstream direction.
