Large eddy simulation of unconfined turbulent swirling flow  

作　　者：ZHANG HongDa HAN Chao YE TaoHong ZHANG JiMin CHEN YiLiang 

机构地区：[1]Department of Thermal Science and Energy Engineering, University of Science and Technology of China

出　　处：《Science China(Technological Sciences)》2015年第10期1731-1744,共14页中国科学（技术科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.51176178&91441117);the Key Program of National Natural Science Foundation of China(Grant No.50936005)

摘　　要：Large eddy simulations(LES) were performed to study the non-reacting flow fields of a Cambridge swirl burner. The dynamic Smagorinsky eddy viscosity model is used as the sub-grid scale turbulence model. Comparisons of experimental data show that the LES results are capable of predicting mean and root-mean-square velocity profiles. The LES results show that the annular swirling flow has a minor impact on the formation of the bluff-body recirculation zone. The vortex structures near the shear layers, visualized by the iso-surface of Q-criterion, display ring structures in non-swirling flow and helical structures in swirling flow near the burner exit. Spectral analysis was employed to predict the occurrence of flow oscillations induced by vortex shedding and precessing vortex core(PVC). In order to extract accurately the unsteady large-scale structures in swirling flow, a three-dimensional proper orthogonal decomposition(POD) method was developed to reconstruct turbulent fluctuating velocity fields. POD analysis reveals that flow fields contain co-existing helical and toroidal shaped coherent structures. The helical structure associated with the PVC is the most energetic dynamic flow structure. The latter toroidal structure associated with vortex shedding has lower energy content which indicates that it is a secondary structure.

关 键 词：Cambridge swirl burner large eddy simulation proper orthogonal decomposition vortex shedding and breakdown precessing vortex core 

分 类 号：O357.5[理学—流体力学] TK223.23[理学—力学]