Large Eddy Simulation of Impinging Jets in Crossflow

摘要

Large Eddy Simulations and RANS predictions have been carried out for a generic primary zone type jet configuration, for which significant IDA experimental data is available. It consists of an annular passage feeding a row of ports mat issue jets into a confined crossflow. A bleed flow of 50% past the ports in the feed annulus and a jet to cross flow ratio of 5 are set-up in order to be representative of annulus fed primary jets. Time averaged inlet boundary conditions have been taken from experimental data and have had time-correlated fluctuations with the correct RMS values and time scales imposed on them. Calculations have been performed on a modest PC cluster using the CFD-ACE+ flow solver package. Results show that LES is able to surpass RANS quantitatively and qualitatively. At the time-average impingement point of the jets the LES predicted normal stresses are in considerably better agreement with experimental data than is RANS, which is to be expected considering the limitations of k-e models relying upon linear stress-strain relationships. Phenomena impossible to capture using RANS are also well predicted by LES, such as bi-modal pdf 's that have been witnessed at the time average stagnation point where the cross flow and jet back flow meet. By solving for a conserved scalar it has also been possible to examine mixing rates within the recirculation zone.