Discrete Roughness Transition for Hypersonic Flight Vehicles

Abstract

The importance of discrete roughness and the correlations developed to predict the onset of boundary layer transition on hypersonic flight vehicles are discussed. The paper is organized by hypersonic vehicle applications characterized in a general sense by the boundary layer: slender with hypersonic conditions at the edge of the boundary layer, moderately blunt with supersonic, and blunt with subsonic. This paper is intended to be a review of recent discrete roughness transition work completed at NASA Langley Research Center in support of agency flight test programs. First, a review is provided of discrete roughness wind tunnel data and the resulting correlations that were developed. Then, results obtained from flight vehicles, in particular the recently flown Hyper-X and Shuttle missions, are discussed and compared to the ground-based correlations.

Heating Augmentation Due to Compression Pad Cavities on the Project Orion CEV Heat Shield

“…Ref. 20), boundary-layer transition is treated as a function of Re θ /M e (rather than just Re θ ) and the ratio of trip height (or in this case cavity depth) to boundary-layer thickness, H/δ.…”

IR thermography investigation on roughness induced transition in high-speed flows

“…In presence of a turbulent boundary layer the convective heat transfer rate can be 5 times higher respect to the laminar flows [3]. Therefore, the prediction of the laminar turbulent transition plays an important role for the vehicle's design and optimization [4]. On the other hand, in scramjet applications, artificial roughness elements are often employed for intentional tripping of the boundary layer on the forebody of the vehicle in order to prevent engine unstart and to minimize the flow non-uniformities at the entrance of the combustion inlet [5].…”

“…Laminar to turbulent prediction is typically performed by means of empirical correlation obtained by systematic experimental campaign in ground facilities and then extrapolated to the few in-flight data [4]. A systematic work was carried out in support of the Hyper-X program [9] and in the frame of the ESA EXPERT program [10,11].…”

A High Order Cut-Cell Method for Numerical Simulation of Hypersonic-Boundary Transition with Arbitrary Surface Roughness

“…For a reentry vehicle entering earth's atmosphere, it initially experiences a heating environment associated with a laminar boundary layer. Eventually with the attitude decreasing, the vehicle surface become rougher and the boundary layer become turbulent and the heating rate at the surface can be increased by a factor of four or more [2]. Thus the ability to understand and predict the roughness induced transition plays an essential role in thermal protection system (TPS) design process.…”