Coherent vertical structures in numerical simulations of buoyant plumes from wildland fires

摘要: The structure and dynamics of buoyant plumes arising from surface-based heat sources in a vertically sheared ambient atmospheric flow are examined via simulations three-dimensional, compressible numerical model. Simple circular asymmetric elliptical ring that representative wildland fires moderate intensity considered. Several different coherent vortical structures dominate the plume evolution evident simulations, these correspond well with those observed fires. For source, include: (i) counter-rotating vortex pair aligned trajectory is associated bifurcation plume, (ii) transverse shear-layer vortices on upstream face (iii) oriented wake form periodically alternating sign either side downstream edge base. streamwise apparent each flank, horizontal above head source. In all cross section represented poorly by self-similar Gaussian distribution.