This Early Technology Project aims to develop and demonstrate the use of a bio-inspired surface pattern, i.e. herringbone riblets, in delaying the onset of laminar-turbulent transition process in hypersonic flow through a series of carefully designed wind tunnel experiments. Herringbone riblets are inspired by the micro-scale structures on the secondary flight feathers of birds (Figure 1a). Due to the directional orientation of these riblets, herringbone riblets are capable of generating weak localised secondary motions in the near-wall region along their streamwise extent which will profoundly modify the characteristics of the boundary layer (Figure 1b).
Our experiments will be undertaken in the High-Supersonic Tunnel at Mach 5 at The University of Manchester (UoM) in two stages. At the Proof of Concept stage, the experiments will be conducted on a hollow cylinder model to enable the suitable geometry and location of these riblets to be identified. At the Technology Demonstration stage, a cone-flare model mimicking the basic shape of a hypersonic vehicle will be tested on which riblets with geometry and location identified from the first stage will be applied. The surface patterns will be produced using a patented advanced laser manufacturing technique developed at UoM.
It is expected that this project will deliver a new passive flow control technology which is potentially suitable for delaying the laminar-turbulent transition process on hypersonic vehicles. A delay of the transition process will lead to a significant reduction in aerodynamic heating and drag experienced by a hypersonic vehicle, which could lead to an increased payload and safer vehicle operation.
