Numerical study on self-sustained oscillation characteristics of cavity flameholders in a supersonic flow

摘要

Self-sustained oscillation characteristics of two-dimensional cavity-based flameholders in a cold supersonic flow were investigated in the present numerical study. The unsteady flowfields were calculated using hybrid Reynolds-averaged Navier–Stokes/large eddy simulation (RANS/LES) method. The key cavity parameters that were varied include cavity aft wall angle and cavity length to depth ratio. The hybrid model favourably captured the large scale unsteady characteristics and revealed the evolution process of cavity free shear layer. Pressure fluctuation spectra agreed well with theoretical predictions. The hybrid RANS/LES data indicate that cavity shape and size both have significant effects on the oscillation characteristics. As the cavity length to depth ratio decreases, oscillation frequency corresponding to maximum oscillation amplitude shifts to higher values. Most of the oscillation modes are greatly suppressed as the cavity aft wall angle decreases. Contrast to the steep aft wall cavity, only higher frequency modes remain in the oscillation of the cavity with small aft wall angle.