DDES of Aeropropulsive Flows Based on an Extended k-ε RANS Model

摘要

Aeropropulsive flows may contain localized separated flow regions whose analysis using RANS methodology may be inadequate, particularly so for massively separated flows having unsteady/oscillatory features. DES-type methods provide for the improved analysis of these local regions, and can often demarcate the zones to be analyzed using RANS or LES methodology in an automated fashion. The DDES implementation described utilizes an extended k-E model in RANS regions containing a number of unique features catered to analyzing aeropropulsive flows. Several aeropropulsive cases of interest are considered for which test data is available. Cases include: a supersonic base flow calculation; a transverse supersonic air jet interacting with a subsonic airtstream; and two angled fuel simulant jets (M_j = 2.S helium jet and M_j = 1.0 ethylene jet) injected into a M_∞ = 2.0 airstream. The results obtained for the supersonic base flow case as well for the transverse air jet in a crossflow case, both compare favorably with the experimental measurements. The predictions for the helium injection case also agree reasonably well with the experimental data. The ethylene case case was not as well predicted which may be due to the RANS representation of the approach boundary layer for this low momentum ratio case (as also pointed out by other investigators).