CFD study of vorticity patterns and sound generation in simplified aft-finocyl geometries

The generation of vorticity patterns, in simplified aft-finocyl geometries of interest, is investigated by means of 2D-axisymmetric ILES CFD simulations with a 2nd order TVD scheme. The development of vortical shear layer structures is observed along the propellant surface and across the finocyl region. These structures are found to induce sustained pressure oscillations as due to the coupling of vorticity and acoustic modes of the chamber. The qualitative and quantitative characterization of the pressure oscillations phenomenon, in terms of both amplitude and frequencies, is a challenging problem, indeed it results to be strongly affected by mesh level, order of accuracy an sub-grid model of ILES approach.