Advanced Flow Conditions tab

[Leonardo Ungureanu]

Hello, I introduced actuator disks in my project and now I have to set up the Advanced Flow Conditions tab (3.46.0 Version). Do Vinf and Rho have a specific unit? Or should it be simply consistent with how I built the geometry? I set up all the dimensions in meters, so Vinf is in m/s?
I would also like to better understand how these two parameters influence the behaviour of the actuator disk, but I couldn't find any tutorial or documentation related. Is there any?

Thank you, 

Best Regards, 

L. Ungureanu

[Rob McDonald]

Yes, Vinf and Rho need to be consistent with the rest of your model.

When your distances are in m, your velocity should be in m/s.  Density should be in kg/m^3.

The actuator disk needs V and rho to be able to take propeller thrust coefficient (CT), and dimensionalize it into thrust to the figure out the corresponding strength of the actuator disk (in terms of vorticity).

The GUI will let you specify the disk parameters in a variety of ways (say, T, rpm, eta), and V, rho will also be used when converting between those quantities to get what VSPAERO actually needs as input.

Rob

[Tad Chichester]

Something to consider when you are specifying the density AND you are using slugs and inches as your units. The sea level value of density in those units is 1.146e-07. If you run VSPAERO using the GUI and input that value, it writes that density to the *.vspaero file in a floating point format with 6 decimal places (%.6f). To six decimal places that is 0.000000, which means it has no effect at all on the solution. If you want VSPAERO to use 1.146e-07 (or any other small number) you have to edit the *.vspaero file by hand and run from the command line.

TC

R.H.L. “Tad” Chichester

[Rob McDonald]

Wow, good catch.

Looks like I need to change that format specifier to some variant of %g instead of %f.

Rob