Confusion about PROP in OpenVSP

[a student]

Hello Everyone, I am a beginner of OpenVSP.

When I add a PROP Geom and set it as Disk， whether its rotation direction can be changed.For example, in the figure below, the rotation directions of the two propellers are both clockwise. Is it feasible to change the rotation direction of one of the propellers to counterclockwise?I want to test if the rotation direction of the propellers has an effect on the lift coefficient when multiple propellers are present.

Another question is whether the Num_Sections is default or can be changed when exporting the propeller as a Blade Element(.bem) file. If it is the default, how to determine the default value ; if it can be changed, where to change it.The output file is as shown below.

Thank You.

[Brandon Litherland]

It's been a while since I tested the VSPAERO GUI for reversing propeller directions or manually setting the rotation.  If you look at the Prop in Blade mode, the default is to turn 'right-handed' or clockwise viewed from behind.  The Rev flag under Design will reverse the blade geometry to a counterclockwise rotation.  Now the Disk mode, for some reason that I've forgotten to talk to Rob about (my bad), has the _indicated_ direction reversed from the Prop direction.  I think it has to do with the rotation being about the X-axis where positive follows the right-hand rule (counterclockwise) but the arrow indicating turn wasn't updated to reflect that.  Justin Gravett made it so the GUI will automatically set the proper turning direction in the VSPAERO input file regardless of the indicated direction so you don't have to set a negative RPM in Disk mode vs Prop.  So VSPAERO will see rotors turning in the direction indicated by Blade mode, regardless of what the disk direction shows.  Run a simple VSPAERO case with a disk and wing to see for yourself.

That's a long way of saying, just click the Rev button.  And, yes, you are very likely going to see a difference.

The .bem file uses the Prop wireframe to set the sections.  So Num_W (chordwise) will set how many airfoil points are written and Num_U sets how many stations.  Twelve is the default Num_U.