Flow around a wing: improvement of physical comprehension by using a DES model.

The flow around a wing is usually well represented by a RANS simulation in cruise conditions, because the zones with flow separations are absent or very small. But, as the angle of attack increases, because of the request of higher lift values, the separated flow zones become important, and the flow is more complex. In these conditions, a RANS approach, also with an unsteady solution, could be not satisfactory. Therefore, we decided to investigate this aspect, by comparing the results of an unsteady RANS solution with a DES solution. In the paper, the setting of both cases are described, as well as the comparison in terms of global coefficients, local distributions and field vorticity distributions. The results show that, at low angle of attack, not significant differences between the RANS and DES solutions occur. On the contrary, at higher angles of attack, the flow highlights a different behaviour (some results are shown in the following figures), with the DES approach that seems to give a more realistic representation of the flow itself. It is important to note that the difference between RANS and DES results is so considerable that also the lift, drag and pitching moment are significantly changed. Finally, it is possible conclude that the use of a DES approach appears an improvement to evaluate the aerodynamics characteristics of a wing close to the stall conditions, a relevant problem for the aerodynamics design of an airplane.