Question about AeroVSP Analysis with Rotating Propellers

[مريم راشد‎]

Dear OpenVSP Team,

I’m currently modeling a quadplane with 5 propellers in OpenVSP, and I’m using the AeroVSP analysis tools to compute the full set of aerodynamic derivatives (stability and control derivatives).

The issue I’m facing is that whenever I try including the propellers in the analysis, the results don’t show. It seems that the range of angle of attack (AOA) disappears once I select the option to rotate the blades.

I also tried running an analysis for the Default single propeller example provided in OpenVSP, but I still couldn’t find the aerodynamic stability derivatives (e.g., C_L, C_{m\alpha}, etc.).

Is there any alternative way to keep the blades rotating while still being able to run the analysis over a range of alpha values?

I’ve attached screenshots that illustrate the problem. Any guidance would be greatly appreciated.

Best wishes,

Maryam Alkhateri

[Brandon Litherland]

VSPAERO does not compute the "steady" stability derivatives in unsteady mode.  The steady stability derivatives are only for steady solutions (not for unsteady rotating blade solutions).

First, think of how long it would take to run all 7 (or more) cases for each unsteady run of the propellers.

Second, the stability derivatives tend to be based on small, linear perturbations about some fixed case.  The unsteady nature of rotating blades would induce significant error in the solution. You would likely want to average the solution of several revs and then perhaps use those results to manually derive the stability values.

Finally, consider the time scale of the rotating blades versus reasonable changes in aircraft attitude.  For smaller propellers/rotors turning slowly, say 2400 RPM, that's 40 rev/second.

If you want to capture propeller effects in your model while computing stability derivatives, use actuator disks.