Evaluation AC1-09
Vortex breakdown above a delta wing with sharp leading edge
Application Challenge AC1-09 © copyright ERCOFTAC 2024
Comparison of Test Data and CFD
An overview is given of the computational results obtained by the different partners.
In terms of the mean pressure coefficient, the different computations are reasonably clustered in the vicinity of the experimental data (Figure \ref{fig-cp}). The largest difference with the experiment is found at the first station ($x/c_r = 0.2$), where all computations show a clear suction peak due to the main vortex (and some also a smaller peak due to secondary separation), whereas the experiment shows a plateau. In the computations, the main vortex starts to develop immediately from the apex. In the experiment, however, it seems that the vortex starts further downstream along the leading edge, more resembling the vortex development of a round leading edge. Possibly, this may be related to the relative bluntness of the leading-edge angle. There may also be a Reynolds number effect, because at a higher Reynolds number ($Re_\text{mac} = 2\cdot 10^6$), the experiment does show a clear suction peak (Furman and Breitsamter, 2009). At the other four stations, the computed pressure distributions compare reasonably well with the experiment in terms of the location of the main suction peak and the level of the pressure plateau outboard of the main peak, indicating no or only weak secondary separation. The level of the suction peak is underpredicted at the station $x/c_r = 0.6$ where the experiment shows vortex breakdown, but the computations do not (see below). At the other stations, the suction peak in most computations is close to or just below the experiment.
Contributed by: J.C. Kok, H. van der Ven, E. Tangermann, S. Sanchi, A. Probst, L. Temmerman — '
© copyright ERCOFTAC 2024