Zonal Detached Eddy Simulation of the Flow Around a Simplified Launcher Afterbody

Abstract

This paper presents the numerical investigation of the unsteady separated flow around a simplified space-launcher afterbody. A zonal detached eddy simulation is used to deal with the high-Reynolds-number flow. The geometry consists of a cylinder of finite length extended by another cylinder of smaller diameter for the central body, and two cylinders similar to the Ariane 5 launcher boosters on each side. The main purpose was to evidence the impact of the side cylinders on the flow characteristics of the isolated central body. To this end, instantaneous and statistical results are compared to those of the isolated central body. The flow topology with side cylinders is found to be dramatically different from that of the axisymmetric case. The mean and rms values for the pressure and velocity fields appear to be organized along the two planes of symmetry of the geometry. Besides, the levels of the mean wall-pressure coefficients are lower by 10% in the three-body configuration. Conversely, the maximum rms coefficients are higher by approximately 45% and located in four quadrants bounded by the planes of symmetry. In the plane normal to the boosters, the mean solid reattachment length is shorter than that of the reference case by 25%. Finally, a three-dimensional Fourier analysis is performed, which highlights that the spectral content organization strongly depends on the location around the emerging cylinder, leading to very different properties of the dynamic buffet loads. Such significant discrepancies in the instantaneous, statistical, and fluctuating flow features suggest that the expertise gained from the axisymmetric body experiments cannot be straightforwardly extended to three-dimensional geometries.