Turbulence modeling for leading-edge vortices: An enhancement based on experimental data

The aerodynamic characteristics of delta wings are dominated by the separation of large-scale vortices at the swept leading edge. The vortex typology and development depends on the flow condition and wing geometry. The numerical solution of vortex flows is routinely performed by means of Reynolds Averaged Navier-Stokes equations because of their consolidated numerical stability, computational efficiency, and good accuracy with regard to low and moderate angles of attack. However, high angles of attack generate more intense vortices and largely separated flows which weaken the prediction accuracy of traditional turbulence models. The employment of scale-resolving or more complex turbulence models is not considered attractive at the current state of computational efficiency requirements if a considerable amount of flow stages need to be calculated. In the context of the Advanced Aircraft Understanding via the Virtual Aircraft Model project, the enhancement of an one equation eddy-viscosity model is formulated by means of additional vortex source terms for improving the accuracy. The terms coefficients are obtained by an automated calibration based on experimental data as reference. The modified one equation turbulence model is applied to relevant test cases. The results show that a significant grade of accuracy improvement is achievable. Furthermore, in the framework of high agility aircraft, the methodology acquires further relevance because it synergizes with the availability of large data-sets that include several geometric and/or flow condition variations.