Calculating the effective angle of attack on a propeller blade section using the flow field query
Ben Jables
Hi all,
I'm working on calculating the effective angle of attack () on a propeller blade section in VSPAERO. My goal is to find the angle between the local chord and the effective velocity vector, which includes the propeller's induced velocities.
I've been using the Flow Field Query (as described here: Flow Field Query) to find the local velocity vector at various points along the blade's camberline. As expected, querying near the VLM panel edges shows the effect of the vortex singularities, resulting in very high induced velocities.
To get a more stable result, I'd like to query the flow field at the VLM panel control points. This leads to my first question:
How can I find the coordinates of the VLM panel control points? I'm thinking of either extracting them from the degengeom files or using the Python API, but I'm not sure of the exact method.
My plan is to then determine the distribution of local velocity vectors along the camberline at these control points. With this, I can evaluate the velocity at a representative point for the blade section, like the three-quarter-chord point.
However, I anticipate a potential issue. The flow field query at a control point will likely include the induced velocity from the bound vortex of that same panel. This would mean the resulting velocity vector will be parallel to the camberline to satisfy the no-penetration condition, making it unsuitable for determining the effective angle of attack.
This brings me to my main question:
Is my proposed method a valid way to calculate the effective angle of attack for a propeller blade section in VSPAERO? Or is there a more direct or recommended approach?
Any insights or suggestions would be greatly appreciated. Thanks!