Hypersonic Boundary/Shear Layer Transition for Blunt to Slender Configurations - A NASA Langley Experimental Perspective

摘要

Heating augmentations and temperature increases resulting from boundary layer/shear layer transition during hypersonic flight through the atmosphere of Earth or other planets impose critical constraints on the design of vehicle thermal protection systems and are well documented in the literature. Laminar-to-turbulent transition effects on local surface heat transfer determine thermal protection system material selection, placement, and thickness. In terms of vehicle performance, transition can influence vehicle aerodynamics and scramjet propulsion system performance. The development of numerical tools for the reliable and rapid prediction of boundary layer transition on complex vehicle shapes, however, continues to be hindered by the lack of a practical capability to model the complex physics associated with the transition process. Therefore, until a credible approach to transition prediction is identified that can be implemented in a rapid assessment framework, vehicle designers will continue to rely heavily on empirically derived transition prediction strategies derived from ground-based measurements. With an emphasis on hypersonic boundary layer transition, the focus of the present paper is to highlight recent aerothermodynamic studies in NASA Langley Research Center's conventional hypersonic wind tunnels (as opposed to high enthalpy, impulse facilities) in support of agency access-to-space and planetary entry programs. Configurations of interest include the Shuttle Orbiter and proposed advanced space transportation concepts (reusable and partially reusable crew launch/return vehicles, single and multiple stage-to- orbit rocket /airbreathing propulsion system concepts, hypersonic cruise vehicles, and planetary aerocapture /entry vehicles). Characterization of surface heating on complex shapes and deflected control surfaces and fluid dynamic phenomenon, such as flow separation and wake closure, are addressed.