Transitional Shock-Wave / Boundary Layer Interaction behind a Roughness Element
Interactions of shock-waves with boundary layers are a common feature in highspeed flight. Depending on the nature of the incoming boundary layer such interactions may lead to large unsteady thermal and pressure loads which may reduce the aerodynamic performance and the structural integrity of hypersonic vehicles. Despite numerous investigations our current knowledge of the fundamental physical mechanisms involved in unsteady shock-wave/boundary-layer interactions (SBLI) is far from complete and a number of aerospace applications would benefit from a deeper understanding of the subject. Most of the research efforts in this field have been directed to the analysis of shock-waves interacting with nominally twodimensional turbulent boundary layers . Flows over high-speed vehicles and, in particular, inside the intakes of their air-breathing propulsion systems are very complex and include interactions of shock-waves with three-dimensional transitional boundary layers. The transition process is very sensitive to flow conditions and geometric parameters. Experiments have shown that small roughness elements, less than a millimetre in height, can lead to early breakdown to turbulence even in a quiet environment . In high-speed flows, transitional boundary layers can also be affected by the interaction with shock-waves through mechanisms which are largely unknown. A detailed study of three-dimensional transitional SBLI will help understand how shock-waves affect the transition process at high-speeds. The limited number of studies available in the literature on transitional SBLI show that for strong interactions (in the convective instability regime) small-amplitude disturbances experience strong amplification across the separation bubble due to the instability of the separated shear layer . In addition, transitional interactions induce higher levels of unsteadiness and stronger thermal loads than in the fully turbulent case [4, 5].
KeywordsBoundary Layer Direct Numerical Simulation Skin Friction Turbulent Boundary Layer Separation Bubble
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- 5.Murphree, Z.R., Jagodzinski, J., Hood, E.S., Clemens, N.T., Dolling, D.S.: Experimental Studies of Transitional Boundary Layer Shock Wave Interactions. AIAA paper 2006-326 (2006)Google Scholar