A free triangular jet(TJ1)and its counterpart initially passing a short circular chamber(TJ2)are numerically modeled using large eddy simulation(LES).This paper compares the near-field characteristics of the two jets ...A free triangular jet(TJ1)and its counterpart initially passing a short circular chamber(TJ2)are numerically modeled using large eddy simulation(LES).This paper compares the near-field characteristics of the two jets in detail.To enable some necessary experimental validations,the LES conditions of TJ1 and TJ2 are taken to be identical to those measured by Xu et al.(Sci.China Phys.561176(2013))and England et al.(Exp.Fluids.4869(2010)),respectively.The LES predictions are found to agree well with those measurements.It is demonstrated that a strong swirl occurs near the chamber inlet plane for the TJ2 flow.At the center of the swirl,there is a cluster of three sink foci,where each focus is aligned midway between the original triangular apexes.In the vortex skeleton constructed from the time-averaged flow field,the vortices arising from the foci are helically twisted around the core of the jet.As the flow passes through the chamber,the foci merge to form a closed-loop“bifurcation line”,which separates the inward swirling flow and the outward oscillating jet.This global oscillation is regarded as a source node near the centerline of the chamber.If the chamber is removed for a“free”jet,i.e.,TJ1,a cluster of three pairs of counter-rotating foci is produced and the net swirl circulation is zero,so the overall oscillation of the jet does not occur.展开更多
基金National Natural Science Foundation of China(Grant Nos.51879022,51979045,and 51906029)the Fundamental Research Funds for the Central Universities,China(Grant Nos.3132019197,3132020187,and 3132019037)+1 种基金the Projects for Dalian Youth Star of Science and Technology,China(Grant No.2018RQ12)the China Postdoctoral Science Foundation(Grant No.2019M661084).
文摘A free triangular jet(TJ1)and its counterpart initially passing a short circular chamber(TJ2)are numerically modeled using large eddy simulation(LES).This paper compares the near-field characteristics of the two jets in detail.To enable some necessary experimental validations,the LES conditions of TJ1 and TJ2 are taken to be identical to those measured by Xu et al.(Sci.China Phys.561176(2013))and England et al.(Exp.Fluids.4869(2010)),respectively.The LES predictions are found to agree well with those measurements.It is demonstrated that a strong swirl occurs near the chamber inlet plane for the TJ2 flow.At the center of the swirl,there is a cluster of three sink foci,where each focus is aligned midway between the original triangular apexes.In the vortex skeleton constructed from the time-averaged flow field,the vortices arising from the foci are helically twisted around the core of the jet.As the flow passes through the chamber,the foci merge to form a closed-loop“bifurcation line”,which separates the inward swirling flow and the outward oscillating jet.This global oscillation is regarded as a source node near the centerline of the chamber.If the chamber is removed for a“free”jet,i.e.,TJ1,a cluster of three pairs of counter-rotating foci is produced and the net swirl circulation is zero,so the overall oscillation of the jet does not occur.
