A Particle-Induced Transition Model for Hypersonic Flows*

Particles are inevitably present in the atmosphere and various prior research studies have provided some evidence that they may play an important role in the laminar-to-turbulent boundary layer transition process observed on hypersonic vehicles. This presentation introduces a newly developed model for particle-induced transition of hypersonic boundary layer flows. This model uses some of the key findings of previous particle-induced transition studies employing stability investigations and direct numerical simulations. It considers the particle concentration, particle size and density, the receptivity process, the relevant boundary layer instability mechanisms, as well as laminar wavepacket and turbulent spot spreading rates. The details of the model are discussed and demonstrated for two transition scenarios: a Mach 9.5 flow over a 14-degree wedge and one trajectory point of the HiFIRE-1 flight test. Finally, the model will also be used to explore sensitivities of particle-induced transition with respect to particle properties and some of the assumptions used for the receptivity process as well as nonlinear breakdown regime.