Numerical Investigation of Laminar-Turbulent Boundary-Layer Transition for an Ogive Geometry at Mach 7: Wind tunnel and Flight Conditions

Numerical investigations were carried out for an ogive geometry with a blunted nose tip at zero angle of attack for atmospheric flight conditions at M = 7.1. These investigations are compared to those for the flow conditions of the hypersonic wind tunnel (H2K) experiments conducted by the German Aerospace Center (DLR), also at M = 7.1. For this comparison, the Mach and unit Reynolds numbers for both flight and wind tunnel conditions are the same allowing for a direct comparison of how a change from wind tunnel to flight conditions affects the linear and nonlinear transition regimes. Linear Stability Theory (LST) calculations revealed that while both first and second mode waves experience significant amplification under wind tunnel conditions, only second mode waves are present under flight conditions. Similar to the investigations for the wind tunnel conditions, primary wave saturation and transition onset calculations were carried out for the flight conditions to determine whether large amplitude second mode waves can reach amplitudes sufficient for transition onset. Secondary instability calculations showed that the so-called fundamental resonance leads to strong secondary amplification, making this a relevant mechanism that could lead to transition for the ogive geometry under atmospheric flight conditions. Based on the primary and secondary instability investigations, high-resolution "controlled" transition simulations have been set up and are currently underway.