Introduction
The present thesis work has been developed in the framework of the EXPERT Program (Euro-pean eXPEerimental Re-entry Test-bed), developed by ESA (Euro(Euro-pean Space Agency) with impor-tant European research centers and industry, among which the von Karman Institute for Fluid Dynamics, where the present work has been carried out.
EXPERT is an ESA in-flight aerothermodynamics research program. Its aim is to design and instrument a generic configuration for in-flight measurement of the effects of hypersonic flight at high altitudes, using state-of-the-art instrumentation. It will provide ESA and the European sci-entific community with high-quality data on critical aerothermodynamic phenomena encountered during high-speed flight. The experiments address the following phenomena: natural and roughness-induced transitions, catalicity and oxidation, shock-wave and boundary-layer interaction, plasma spectroscopy, flap efficiency and instrumentation, real-gas effects in hypersonic conditions, hot struc-tures for hypersonic flight and their instrumentations intermetallic materials for hot strucstruc-tures, and base flows.
In particular the aim of this thesis work is the investigation of the effect of a Backward Facing Step or briefly BFS (i.e. a negative step in the direction of the flow, figure 1) on the boundary layer transition on the EXPERT vehicle.
Figure 1: Backward Facing Step In chapter 1 an overview of the Expert Program is reported.
Chapter 2 contains a review of the theorethical background necessary to read the following chapters: this review has also been the first part of the thesis work, i.e. a theorethical and bibliographical research about Hypersonic Flows and Boundary Layer Transition.
Chapter 3 includes a bibliographical and general discussion about the flow around a Bakcward Facing Step, focusing on the compressible and hypersonic case.
The following two chapters contain the main part of the thesis work: the study of the effect of a BFS for the VKI1 H3 Hypersonic Wind Tunnel (working at M=6). Chapter 4 includes the first part
of the thesis work: it is the study of transition correlation applied to CFD simulations: simulations reproduce VKI H3 Wind Tunnel testing conditions and real Flight conditions and have been carried
1von Karman Institute for Fluid Dynamics, Belgium
out at ESTEC (Leiden) and at VKI). This study is useful for extrapolation to flight methodologies. Chapter 5 includes the experimental campaign results carried out in the VKI H3 Hypersonic Wind Tunnel.
In chapter 6 eventually some considerations about extrapolation to flight conditions methodologies are reported.
