  A delayed detached eddy simulation of a sub-scale cold-gas dual-bell nozzle
flow at high Reynolds number and in sea-level mode is carried out at nozzle
pressure ratio NPR=45.7. In this regime the over-expanded flow exhibits a
symmetric and controlled flow separation at the inflection point, that is the
junction between the two bells, leading to the generation of a low content of
aerodynamic side loads with respect to conventional bell nozzles. The nozzle
wall-pressure signature is analysed 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)
show the presence of a persistent tone associated to the symmetric shock
movement. Asymmetric modes are only slightly excited by the shock and the
turbulent structures. The low mean value of the side-loads magnitude is in good
agreement with the experiments and confirms that the inflection point dampens
the aero-acoustic interaction between the separation-shock and the detached
shear layer.
