Coupling of a Simplified Stability-Based Transition Transport Model with the Negative Spalart-Allmaras Turbulence Model

Kurzfassung

The laminar-turbulent transition plays a direct role on drag production, and thereby directly impacts on the aerodynamic efficiency and the aircraft operation cost. Therefore, the availability of reliable tools for the transition prediction is of primary interest for computational fluid dynamics (CFD) as a suitable aircraft design tool. Accurate numerical transition prediction can be achieved applying the eN method based on linear stability theory (LST). However, the strong complexity of the approach which requires non-local quantities, and streamlines as well as wall-normal integrations makes its implementation challenging on complex geometries requiring high user expertise. Alternatively, transition transport models (TTM) like the γ-Reθt model [1] are more flexible, robust, and user-friendly, but their accuracy highly depends on the applied transition criterion and the local modeling of the required boundary-layer parameters. In [2] a new γ-based one-equation transition transport model was implemented in the DLR TAU code. The new model applies the LST-based transition criterion from [3] and an improved local modeling of the integral parameters of the boundary layer that takes into account pressure-gradient effects. First, the new TTM has been coupled to the Menter shear stress transport (SST) turbulence model and it yields very satisfactory transition prediction results [2, 4] showing, in many cases, a very good agreement with the results obtained with the eN method. Therefore, the application of this new TTM has recently been extended to the negative Spalart-Allmaras (SA-neg) turbulence model [5], and the coupling approach as well as the simulation results will be presented during the STAB workshop.