Discrepancies in side force and rolling moment

Questions, suggestions, feature requests, bug reports, feedbackCategory: QuestionsDiscrepancies in side force and rolling moment
Aaditya WangikarAaditya Wangikar asked 3 months ago

I’ve used Uniform Density Triangular panel method. For T6 analysis along with VPW, there is a close agreement of drag force and pitching moment with the CFD results. However, there is a deviation between side force and rolling moment. What can be done to reduce the errors.

1 Answers
André Deperroistechwinder Staff answered 3 months ago

In the case of the side force, the main cause of discrepancy could be that you are looking at the variables CY and Fy_FF which are evaluated in the far-field plane and not by summation of pressure forces. The former may not account properly for forces acting on the fuselage. Fy_sum latter can be plotted in the polar graphs.
The other cause of discrepancy which affects both the side force and the lateral moments Cl and Cn is the inviscid pressure forces acting on the fuselage where it connects to the wings, and on the tip of the wings. These are areas of high velocity gradients and high pressures which in the real case are damped by viscosity. The display of panel forces in the 3d view will tell if this may be the cause of the problem.
There is already an option to exclude altogether the fuselage forces in the evaluation of moments. The next upcoming version of flow5 will also include an option to exclude the forces acting on the wing tips.
Hope this helps.