Experimental and computational investigations of hypersonic flow about compression ramps

Abstract

Comprehensive results of a joint experimental and computational study of the two-dimensional flow field over flat plate/compression ramp configurations at Mach 14 are presented. These geometries are aimed to simulate, in a simplified manner, the region around deflected control surfaces of hypersonic re-entry vehicles. The test cases considered cover a range of realistic flow conditions with Reynolds numbers to the hinge line varying between 4.5 × 105 and 2.6 × 106 (with a reference length taken as the distance between the leading edge and the hinge line) and a wall-to-total-temperature ratio of 0.12. The combination of flow and geometric parameters gives rise to fully laminar strong shock wave/boundary layer interactions with extensive separation, and transitional interactions with transition occurring near the reattachment point. A fully turbulent interaction is also considered which, however, was only approximately achieved in the experiments by means of excessive tripping of the oncoming hypersonic laminar boundary layer. Emphasis has been placed upon the quality and level of confidence of both experiments and computations, including a discussion on the laminar-turbulent transition process and the associated striation phenomenon. The favourable comparison between the experimental and computational results has profided the grounds for an enhanced understanding of the relevant flow processes and their modelling. Particularly in relation to transitional shock wave/boundary layer interactions, where laminar-turbulent transition is promoted by the adverse pressure gradient and flow concavity in the reattachment region, a method is proposed to compute extreme adverse effects in the interaction region avoiding such inhibiting requirements as transition modelling or turbulence modelling over separated regions.

Numerical simulation of Görtler vortices in hypersonic compression ramps

“…The flow passing a compression ramp is a classic example of shock-boundary layer interaction. Two-dimensional computational results of these configurations compare poorly with experimental data, specially when large regions of separated flows are present [1,28,37]. Generally, there is an under prediction of the heat transfer over the ramp and an over estimation of the extent of the separation bubble.…”

“…Generally, there is an under prediction of the heat transfer over the ramp and an over estimation of the extent of the separation bubble. These discrepancies have been associated with three-dimensional effects [10,29,32] and transition at reattachment [1,37]. In most of the experiments involving shock-boundary layer interaction at hypersonic speeds, significant spanwise heat transfer variations were reported [17,37,39].…”

“…These discrepancies have been associated with three-dimensional effects [10,29,32] and transition at reattachment [1,37]. In most of the experiments involving shock-boundary layer interaction at hypersonic speeds, significant spanwise heat transfer variations were reported [17,37,39]. These take the form of a striation pattern, which may indicate the presence of Gö rtler-type vortices [12], arising from the curvature of the streamlines at reattachment.…”

Three-dimensional supersonic flow around double compression ramp with finite span

“…Numerical simulation of supersonic flow over a doublecompression ramp with finite span is a challenging topic not only because of the three-dimensional complexity [1][2][3][4], but also due to turbulent transition inside the separation bubble [5,6], and/or numerical difficulties [7]. In his study of shock-shock interactions between an oblique shock and a bow shock over a cylinder, Edney [8] identified six different types of shock-shock interactions.…”

Gun Tunnel Studies of Shock-Wave/Boundary-Layer Interactions; Laminar, Transitional and Turbulent

“…A good example of this approach is the ogive-cylinder-flare model of Wideman et al 45 shown in figure 2. It is also recognised 29 , however, that an axisymmetric configuration cannot guarantee (time-averaged) two-dimensionality, in particular the formation of cellular (streamwise) structures or Goertler-type vortices especially once flow separation is involved 9,22,29,30,35,40 . Figure 3 shows a rearward-facing step separated flow, generated at the base of a sting-supported circular section cone and conducted in the Imperial College Gun Tunnel.…”