There are three modifications which will change slightly the results:
- the calculation of the downwash and induced angle for the VLM method has been corrected; it was twice what it should be. These values were for information only and have no impact on other calculated values, which explains why the error went undetected for many years. Thanks to Philippe for reporting this one.
- the calculation of the damping ratio for natural modes has been corrected; was formerly lambda.real()/omega_damped instead of lambda.real()/omega_natural; no excuses there.
- the calculation method of stability derivatives is now made with centered differences rather than forward differences. The only noticable impact should be for the derivative Xw which changes significantly. However this derivative seems to have low influence on the eigenvalues, and the flight modes should be almost unchanged.
Hi everyone,
v6.33 is now available for download.
There are three modifications which will change slightly the results:
- the calculation of the downwash and induced angle for the VLM method has been corrected; it was twice what it should be. These values were for information only and have no impact on other calculated values, which explains why the error went undetected for many years. Thanks to Philippe for reporting this one.
- the calculation of the damping ratio for natural modes has been corrected; was formerly lambda.real()/omega_damped instead of lambda.real()/omega_natural; no excuses there.
- the calculation method of stability derivatives is now made with centered differences rather than forward differences. The only noticable impact should be for the derivative Xw which changes significantly. However this derivative seems to have low influence on the eigenvalues, and the flight modes should be almost unchanged.
For those who need them, the VC++ dll for win64 can be installed directly from Microsoft's web site:
https://www.microsoft.com/en-us/download/details.aspx?id=48145
Feel free to continue to make suggestions and to report bugs. I still have the goal to make xflr5 crash-proof ultimately.
André
Last edit: André 2017-03-27
Dear André,
thank you for implementing the correct formulation of a bell-shape lift distribution function!
best regards,
eMJay