Direct numerical simulation of the near field dynamics of a rectangular reactive plume

✍ Scribed by X. Jiang; K.H. Luo

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 438 KB
• Volume: 22
• Category: Article
• ISSN: 0142-727X
• DOI: 10.1016/s0142-727x(01)00123-0

✦ Synopsis

Spatial direct numerical simulation (DNS) is used to study the near ®eld dynamics of a buoyant diusion ¯ame established on a rectangular nozzle with an aspect ratio of 2:1. Combustion is represented by a one-step ®nite-rate Arrhenius chemistry. Without applying external perturbations at the in¯ow boundary, large vortical structures develop naturally in the ¯ow ®eld, which interact with the ¯ame and temporally create localized holes within the reaction zone in which no chemical reactions take place. The interaction between density gradients and gravity plays a major role in the vorticity generation of the buoyant plume. At the downstream of the reactive plume, a more disorganized ¯ow regime characterized by small scales has been observed, following the breakdown of the large vortical structures due to three-dimensional (3D) vortex interactions. Analysis of energy spectra shows that the spatially developing reactive plume has a tendency of transition to turbulence under the eects of combustion-induced buoyancy. The buoyancy eects are found to be very important to the formation, development, interaction, and breakdown of vortices in reactive plumes. In contrast with the relaminarization eects of chemical exothermicity via viscous damping and volumetric expansion on non-buoyant jet diusion ¯ames, the tendency towards transition to turbulence in reactive plumes is greatly enhanced by the buoyancy eects.