Simulation of Unsteady, Turbulent Base Flow for Ariane-5 Wind Tunnel Configurations by Detached Eddy Simulation

Abstract

Concerning the requirements of future rocket technologies, which are the cost-efficient access to orbit as well as an increase in system reliability, a deeper insight into the unsteady phenomena during the ascent of the launchers is essential. Especially unsteady interactions of flow separation and the turbulent launcher wake may play an important role for the design of future main stage propulsion systems. In conjunction with fluid-structure interactions between nozzle and flow-field resonance phenomena can play an important role, so the described interactions need to be properly predicted by CFD tools. This so called buffeting coupling phenomenon is, due to its turbulent transient character, one of the main challenges during ascent. In the present study of Ariane-5 wind tunnel models of varying komplexity, a detailed numerical simulation of the afterbody with a realistic aerodynamic representation of different model geometries is carried out using unsteady Detached Eddy Simulation (DES) to predict the turbulent flow field. A number of buffeting reduction devices, investigated in wind tunnel campaigns by unsteady pressure and PIV measurements, were simulated by unsteady calculations and compared with the experimental results. Furthermore good agreement with ONERA simulations of the clean configuration without struts and buffeting reduction devices is found as long as differences in the post-processing are taken into account. The essential features of the interaction process between flow field and turbulent shear layer are well captured and an insight into the flow physics in the investigated region is carried out.