Large Eddy Simulation of Compressible Subsonic Turbulent Jet Starting From a Smooth Contraction Nozzle

详细信息    查看全文

• 作者：Abbas Ghasemi ; Aaron Pereira ; Xianguo Li
• 关键词：Starting jet ; Large eddy simulation ; Hairpin vortices ; Vortex ring ; Rib vortex
• 刊名：Flow, Turbulence and Combustion
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：98
• 期：1
• 页码：83-108
• 全文大小：
• 刊物类别：Engineering
• 刊物主题：Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer; Automotive Engineering;
• 出版者：Springer Netherlands
• ISSN：1573-1987
• 卷排序：98

文摘

Compressible subsonic turbulent starting jet with a relatively large Reynolds number of significant practical importance is investigated using large eddy simulation (LES), starting from a smooth contraction nozzle. The computational domain of truncated conical shape is determined through the comparison of the time-averaged numerical solution with the particle imaging velocimetry measurements for the steady jet. It is shown that the starting jet consists of a leading vortex ring followed by a quasi-steady jet, and the instantaneous velocity field exhibits contraction and expansion zones, corresponding to the high pressure (HP) and low pressure (LP) regions formed by the convecting vortex rings, and are related to the Kelvin-Helmholtz instability. The thin boundary layer inside the smooth contraction nozzle evolves into a shear layer at the nozzle exit and develops with the downstream penetration of the jet. Using λ₂ criterion, the formation and evolution of the vortical structures are temporally visualized, illustrating distortion of vortex rings into lobed shapes prior to break-down. Rib-shape streamwise vortex filaments exist in the braid region between a pair of consecutive vortex rings due to secondary instabilities. Finally, formation and dynamics of hairpin vortices in the shear layer is identified.