Investigation of Hypersonic Flow in the VKI H3 Wind Tunnel: from Facility Characterization to Boundary-Layer Interaction over Low-Temperature Ablators

This work deals with the characterization, in terms of operating conditions, of the H3 hypersonic wind tunnel of the von Karman Institute for Fluid Dynamics (VKI), thus providing a detailed and structured benchmark for the evaluation of testing capabilities in hypersonic wind tunnels, and with the experimental study of the interaction between the boundary layer and the ablation process of low temperature ablative materials. The flow characteristics of the test section of the H3 WT have been assessed by using a pitot rake, for a wider range of operating conditions with respect to previous calibrations. A CFD analysis of the diffuser-ejector system has been carried out to assess its performance, and an experimental test campaign has been performed in order to validate the CFD analyses and completely characterize the facility operating conditions. Finally, a series of experiments with models of increasing size and different shapes has been carried out to determine the blockage effect in the tunnel test section. The H3 WT is then employed to study the boundary layer interaction with the ablative process on low temperature ablative models. These models have been built after having appropriately designed the sintering system. The Planar Laser Induced Fluorescence method has been applied to visualize the flow behavior: a laminar-turbulent transition due to the ablation process has been observed, together with the main flow structures.