Integrated Experimental-Numerical Analysis of High-Agility Aircraft Wake Vortex Evolution

The presented investigation includes a combined experimental numerical approach to quantify the wake vortex system of a high-agility aircraft from the near field up to the far field. Detailed near-field data are obtained by low-speed wind-tunnel tests on a delta-canard configuration of 1:15 scale. The measurements are performed at several angles of attack applying advanced hot-wire anemometry. For a wake distance of up to 16 wing spans, mean and turbulent velocity fields are measured. The upstream data are used to initialize implicit large-eddy simulations aimed to compute the velocity fields of the wake vortex system over a wake distance of up to 50 spans. Here, a validation case is shown comparing measured and calculated wake data over a distance from 4 to 16 spans, with the implicit large-eddy simulations initialized by the measured quantities at a position of two wing spans. Compared with the experimental data, the numerical results show the expected lateral and vertical movement of the wake vortex system due to the interaction of the single vortices. The distributions of axial vorticity, crossflow velocities, and turbulence intensities match well with the experimental data. In addition, the dissipation process can be observed, resulting in a reduction of circulation. In the context of this study, the measured and computed velocity fields will be used to determine unsteady aerodynamic loads acting on a fighter aircraft encountering the wake. This is of great importance as wake induction may result in critical structural dynamic loads.