Hi,
I am working on a student project using FlightStream to obtain a full set of stability derivatives for a light GA aircraft, similar in configuration to a Cessna 172.
I have been able to produce good results for lift, drag, and side force derivatives, but the pitching, rolling and yawing moments and their associated derivatives are off significantly. I have tried the following without success:
- Tested with and without viscous coupling, and axial/crossflow separation
- Tested laminar, transitional-turbulent and turbulent
- Tested with and without compressibility
- Running with the wing-tail only (no fuselage)
- Simplifying geometry and re-meshing with CCS and TFI meshing tools, with/without growth schemes
I have tried moving the coordinate system around (which is my aircraft CG), but the moment coefficients remain several orders of magnitude off unless I place the CG 1m above the aircraft. I'm really not sure what is wrong and any help would be appreciated!
Derivative | FlightStream Result | Expected Value | Units |
|---|
CL_alpha | 4.81 | 4.4 | 1/rad |
Cm_alpha | -1.1743 | -0.6 | 1/rad |
CY_beta | -0.34 | -0.4 | 1/rad |
Cn_beta | 0.4161 | 0.06 | 1/rad |
Cl_beta | -1.1149 | -0.09 | 1/rad |
