Fowler Flap Continued

[Dennis Haimerl]

The CL_max in the load distributions are correlating with the point were the lift curve becomes nonlinear. In VLM you must enter a 2D cl_max for this to occur, otherwise the lift curve slope continues to climb roughly linearly. The spanwise distributions do bunch up if a 2D cl_max is entered. The delta CL does diminish as the flap deflection is increased as yBrandon stated, it just doesn’t diminish as quickly as expected at the higher deflections. The expected 2D cl_max for 10, 20, 30 & 40 deg. deflections are 1.9, 2.4, 2.9 & 3.25, respectively, with the expected 3D CL_max values being a little lower. Assuming CL_max occurs at the point were the lift curve slope becomes nonlinear, the 3D CL_max values generated using VLM are 2.2, 2.7, 3.1 & 4.0.

I think a better solution to my CL_max issue than I originally stated for the 30 and 40 deg. deflection would be to adjust the 2D cl_max until the VLM results match the actual CL_max I am expecting. I understand the difficultly in predicting the onset of separation, hence my decision to start by comparing to wind tunnel data.

Apparently, I was using version 3.53 when I had issues loading the viewer. It seems to be working fine in 3.36.0. The Cp data did load by using the "Slice Latest *.adb File" button. The Cp plots are pretty much as expected. Is there a way to retrieve the wake coordinate data from the binary *.adb file?

Maybe in a newer version a “Save Results To (folder)” button could be added to make it easier to keep track of multiple configuration results. I think I’m getting too old to want to learn a seventh programming language for manipulating data files, though what I’ve seen of Python reminds me of Borland’s Turbo Pascal.

I’ll post more as I refine my method. Thanks for the help.

[Brandon Litherland]

There is also the option to write the Results data to file using the "Export to *.csv" button.  This will include the data that the Results Manager uses to display and plot such as spanloading, wake iteration step history, etc.

There is not a way to interact with the ADB file manually and we generally discourage folks from trying.  Dave Kinney, the VSPAERO author and developer, reserves the right to change that format as needed to make improvements and add features so whatever translator you might come up with would potentially break on a new release.  If you need wake information, slices or survey points are your best bet, with slice being the easiest to implement.  The format of the <model>.case.<caseNum>.quad.<quadNum>.dat file written out from a quad tree slice of a solution is "Node Number, X, Y, Z, U, V, W, Cp".  The first line tells direction (2=Y, etc.), slice location, Vref, and Vmax (used to try and bound Cp in a reasonable range).  On the other hand, if you're only looking to pull the velocities along the leading edge of the tail or some small sample, you can use Survey Points.  See a prior Groups post here: https://groups.google.com/g/openvsp/c/8TF3DCy7BWA.