Ricerc@Sapienza

A delayed detached eddy simulation of a sub-scale cold-gas dual-bell nozzle flow at high Reynolds number in transition operation mode will be carried out at nozzle pressure ratio NPR=49.2. In this regime, the over-expanded flow exhibits an asymmetric flow separation in the inflection region that could lead to the generation of content of aerodynamic side loads comparable to conventional bell nozzles used for space launchers. The nozzle wall-pressure signature will be analyzed in the frequency domain and compared with the experimental data available in the literature for the same geometry and flow conditions. The Fourier spectra in time and space (azimuthal wavenumber) will be studied in order to assess the role of the asymmetric shock movement and its connection with the possible development of a helical mode inside the nozzle. This could confirm the damping of the inflection point on the aero-acoustic interaction between the separation shock and the detached shear layer.