Supersonic axisymmetric base flows are prototypical for flows behind projectiles and missiles, For these flows, drag reduction can be achieved by means of passive control of the near wake. Thereby, large (turbulent) coherent structures play a dominant role. The objective of the present investigation is to elucidate if and how successful passive flow control techniques modify these structures. To this end, first Direct Numerical Simulations (DNS) for a Reynolds number of ReD = 100,000 and Mach number of Ma =2.46 were performed using a high-order accurate and highly parallelized research code which was developed at the University of Arizona. Thereby, roughly 52 million grid points were employed. The DNS data serve to visualize typical structures of the unsteady flow field and to verify that the use of less computational costly RANS/LES methods is applicable for this flow. Two of these methods, the Flow Simulation Methodology (FSM) and Detached Eddy Simulations (DES), were then employed to investigate the supersonic base flow at ReD =3.3 × 106 and Ma = 2.46 using between 460,000 and seven million grid points. For the DES, the commercial CFD-code Cobalt was employed. This unstructured grid solver allowed then to perform simulations with boat-tailing. The obtained mean flow data are compared to available experimental results.@en

Drag reduction by means of flow control is investigated for supersonic base flows at M = 2.46 using direct numerical simulations and the flow simulation methodology. The objective of the present work is to understand the evolution of coherent structures in the flow and how flow control techniques can modify these structures. For such investigations, simulation methods that capture the dynamics of the large turbulent structures are required. Direct numerical simulations are performed for transitional base flows at ReD = 30,000. Because of the drastically increased computational cost of direct numerical simulations at higher Reynolds numbers, a hybrid methodology (flow simulation methodology) is applied to simulate base flows with flow control at ReD = 100,000. Active and passive flow control techniques that alter the near wake by introducing axisymmetric and longitudinal perturbations are investigated. A detailed analysis of the dynamics of the resulting turbulent structures is presented.@en