Fluidic control of transition in a dual-bell nozzle

The application of dual-bell nozzles to existing space launchers offers the possibility to significantly increase their payload capability. This benefit is related to the ability of this kind of nozzles to switch between a low-altitude and a high-altitude working mode. However, the transition between the working modes introduces several problems like for example the possible development of high side-loads and a significant jump in the thrust magnitude. Furthermore, the natural transition takes place earlier with respect to the ideal case and this limits the performance gain. Among the different strategies proposed to control the transition, the injection of a secondary flow close to the inflection point represents a promising solution. In this work, the use of fluidic control is investigated by means of numerical simulations. After a preliminary calibration of a modified version of the Spalart-Allmaras turbulence model, the effects of the injection on the transitional nozzle pressure ratio are investigated.