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Instabilities of the separated wake flow in the base region of a space launcher

Instabilities of the separated wake flow in the base region of a space launcher . PhD Candidate: Valeria Gentile Department: AWEP Section: Aerodynamics Supervisor: F. Schrijer , B. van Oudheusden Promoter: F. Scarano Start date: 03-12-2012 Funding: Tinker Bell Scholarship. Background

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Instabilities of the separated wake flow in the base region of a space launcher

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  1. Instabilities of the separated wake flow in the base region of a space launcher PhD Candidate: Valeria Gentile Department: AWEP Section: Aerodynamics Supervisor: F. Schrijer, B. van Oudheusden Promoter: F. Scarano Start date: 03-12-2012 Funding: Tinker Bell Scholarship • Background • Due to the abrupt change in geometry on the base, the flow past a space launcher is characterized by a massive separation. • During the lift-off at transonic speeds, the resulting turbulent flow can excite structural modes and generate unsteady side loads both on the base and on the nozzle (buffeting). • Aim of the research • In order to containstructuralproblemswithout over-designing the launcher, itisnecessary to investigate the effects of differentgeometricconfiguration and flow regimes on the separated flow. • Particularattentionisaddressed to the case of Ariane 5. • Proper Orthogonal Decomposition (POD) were used to identify the most energetic modes associated to the motion of the wake. Progress Tomographic PIV was used to investigate the flow field behind a simple truncated base rocket model at uncompressible regime. Different flow velocities were considered in a range including both laminar and turbulent regimes. The main purpose was to studythe spatial organization of turbulent structures inside the wake in the plane parallel to the base of the model (Azimuthal Plane). POD Mode m=1- 0.25 diameters past the base Aerospace Engineering POD Mode m=2-0.25 diameters past the base Axial Velocity Field -0.25 diameters past the base – V=20m/s Ariane 5 Lift- Off ResearchMethodology The flow field in the separatedwakebehind the launcherisstudiedconsideringdifferentgeometricconfigurations and different flow regimes. The effect on the organization and coherence of turbulent structures are considered. The flow fieldbehind the launcherisobtained by means of Paticle Image Velocimetry (PIV). POD Mode m=3- 0.25 diameters past the base Axial Velocity Field 1.0 diameters past the base - V=20m/s POD Mode=4- 0.25 diameters past the base Objectives Theresults obtained for the uncompressible case are to be used for next experiments at transonic regime. Modifications of the basis and the after- body of the model are to be considered in order to obtain a geometric configuration closer to the one of Ariane5. Coherent structures downstream of a cylinder with a cylindrical after- body at high subsonic regime(Deck and Thorigny, 2007) Axial Velocity Field 1.75 diameters past the base - V=20m/s

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