Steady-state and unsteady Reynolds-averaged Navier-stokes modelling of cold jets-in-hot crossflow in a cylindrical duct for non-impinging, impinging, and strongly impinging jets

摘要

The objective of this study is to demonstrate that strongly impinging jets-in-crossflow (JIC) will result in a counter flowing jet that will probably be unsteady. This numerical study was conducted in a 360° (complete cylindrical duct) computational domain using a steady-state Reynolds-Averaged Navier Stokes, RANS, and time-dependent URANS at various momentum-flux ratios J. Asymmetry in a steady-state RANS solution is very likely to be an indication of the flow's instability and unsteadiness. RANS predictions clearly show asymmetry in cases of strongly impinging jets. RANS solutions show that steady-state solutions are not appropriate if the flow is, or is suspected to be, unsteady. RANS and URANS solutions for computational domains <360° will require boundary conditions at the edges of the computational domain and will not correctly represent the flow if it is unsteady even if the RANS solution converges. The results of this study are consistent with, and extend, the experimental and numerical results published earlier that were motivated by mixing in gas turbine combustors.