CFD investigations of Axi-symmetric steady state nozzle plume flow for the Volvo S6 and Vulcain2 nozzle

Kurzfassung

In the afterbody region of the Ariane 5 ECA launcher, the flow around the launcher interacts with the plumes of the propulsion systems, i.e. the plumes from the \mbox{Vulcain-2} engine and from the solid rocket boosters. A dedicated experiment or analysis to evaluate the influence of the plumes on buffeting has not been performed up to now. However, the good agreement of the wind tunnel results obtained from the model without plumes to the flight data of Ariane 5 indicates that, for the investigated flight situations, the plume influence is limited. Nevertheless, the experimental investigation of the plume influence on buffeting remains an important topic and its simulation seems mandatory whenever the base configuration is modified. The design of a sub-scale nozzle that uses a different working gas, but behaving as closely as possible to the full-scale launcher in terms of base flow, is a very challenging task. It can only be solved by taking considerable compromises into account since only low total temperatures are available in wind tunnels. For example air condensation and thick nozzle walls are required for pressure measurements to give a few design constraints in such a facility. Since perfect similarity is impossible to realise, a numerical study was proposed in prior to the wind tunnel tests to assess how representative the plume flow flight conditions can be realised. The results will be used to decide whether modifications of the existing models would be needed or if a new model is required. They will furthermore provide the basis to prepare a research program focusing on the experimental investigation of the plume effect on buffeting. Apart from detailed three-dimensional unsteady CFD-studies, the described work package is supported by 2D axis symmetric numerical computations of the plumes, carried out by the DLR TAU-code in order to characterise the shear layers emanating from the nozzle lip. In the scope of the work-package 8000 of the ESA-TRP on buffeting coupling a study of both configurations was carried out which is the objective of the following report.