HiSST: International Conference on High-Speed Vehicle Science & Technology 26–29 November 2018, Moscow, Russia Two-Equation Transition Model Based on Intermittency and Empirical Correlations Jeroen Van den Eynde 1 & Johan Steelant 2 Abstract A two-equation correlation-based transition model is presented to predict the onset and development of the laminar-turbulent transition process for boundary layers. It uses one equation for the intermittency- transport, and another for the transport of a transition onset criterion. It uses some elements from the Langtry-Menter intermittency-based γ -Re θt transition model, but introduces a physics-based rationale for the intermittency production and destruction. The model has been validated for a number of subsonic to hypersonic boundary layer cases and is able to correctly predict the transition onset location and typical skin friction overshoot. Keywords: transition, modelling, intermittency, empirical Nomenclature Latin C – Model constant C f – Skin friction coefficient C p – Pressure coefficient c – Velocity D – Diffusion term E – Dissipation term k – Turbulent kinetic energy K – Pressure gradient parmeter M – Mach number n – Spatial coordinate normal to streamline P – Production term Pr – Prandtl number PRC – Pressure relaxation factor p – Pressure q – Dynamic pressure ˙ q – heat flux Re θt – Transition momentum Reynolds number r – Recovery factor S ij – Strain rate tensor St – Stanton number s – Spatial coordinate along streamline T – Temperature Tu – Turbulence level u, U – Velocity v – Wall-normal velocity x – Spatial coordinate Greek α – Onset parameter β – Turbulent spot growth δ – Boundary layer thickness γ – Intermittency µ – Dynamic viscosity ν – Kinematic viscosity ˆ nσ – Spot growth parameter θ – Momentum thickness τ – Shear stress ρ – Density Superscripts ’– Fluctuating value – Favre-averaged Subscripts i, j – Components of vector ∞ – Freestream value ad – Adiabatic c– Critical value; Compressible e– Edge value inc – Incompressible l– Laminar value t– Turbulent value; Value at transition onset r– Recovery w– Value at the wall 1 Research Fellow, ESA/ESTEC, 2200AG Noordwijk, The Netherlands (Jeroen.Van.den.Eynde@esa.int) 2 Senior Aerothermodynamicist, ESA/ESTEC, 2200AG Noordwijk, The Netherlands (Johan.Stee- lant@esa.int) HiSST 2018-1300826 Two-Equation Transition Model Based on Intermittency and Empirical Correlations Page | 1 Copyright © 2018 by the author(s)