Not able to do VSPAero analysis for 2D square inlet engine nacelle.

[Shaik Hyder Pasha]

I'm quiet new to OpenVSP and VSPAero, I would like to perform vspaero analysis on an aircraft with square engine inlet. But, the result manager doesn't display anything and the Viewer Console shows various error, but the most prominent error is,

"There were 104 loops that we could not find upwind edges for...

Mag: 0.000000"

To provide some context, I have designed engine nacelle using fuselage geometry with Loop design policy. All the parameters in skinning are kept zero (again, due to me being new to openvsp and the model looked good enough with those parameters). The final geometry I achieved is shown in the image below:

I did try to use a different approach, such as using a wing geometry and creating axial symmetry along x-axis, but again this would only work as long as the cross section of the wing is aerofoil, if I change it to a rounded rectangle cross section, the same error would occur.

I would like to perform analysis with the first model rather than the second one as I have more finer control over the geometry taper and rotation. So, it would be helpful if you can provide any suggestion to do so.

Regards,

Hyder

[Rob McDonald]

Please attach the file that you are trying.

I tried something similar to your first example and had no issues.  We can't help without more information.

Rob

[Shaik Hyder Pasha]

Thanks for the response Rob,

Here's the model I have been working on,

Hyder

[Rob McDonald]

I ran your 'Engine Nacelles' component (isolated) in panel mode at a single flight condition and it worked fine.

This geometry probably did not do well when collapsed VLM mode.

You also were originally running a sweep of Mach numbers that spanned sub to supersonic.  Supersonic is only supported by the VLM - which is going to struggle with this duct arrangement.

Rob

[Shaik Hyder Pasha]

You are right Rob, the panel method worked if we isolate the engine nacelles and perform analysis, even this does not show trailing wakes in viewer. 

My parameter of interest is total (Aircraft+engine nacelle) induced drag at Mach 1.6. 

Should I do VLM analysis on Aircraft and Panel method on Engine separately and then just add the induced drag obtained together?

Hyder

[Rob McDonald]

I think you'll be able to generate a combined model.

The nacelles aren't contributing to induced drag because we aren't attaching wakes to their trailing edge.  We currently only attach wakes to wings and to bodies of revolution with airfoil cross sections...

Since you need supersonic, you're stuck with the VLM for now.

Including the nacelle without modeling the propulsion effects probably isn't a great idea.  I would just run the model without the nacelles as VLM and use that for the induced drag.

Rob

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[Shaik Hyder Pasha]

Thanks for the suggestion Rob,

I'm sorry if I am asking the most obvious or know question, but just out of curiosity, can we model propulsion effect for nacelle in OpenVSP?? Because I have seen a section mentioning 'Engine definition' in Design tab of fuselage Geometry but I don't know what it does.

Hyder

[Rob McDonald]

Not at this time.

The Engine Definition stuff is described in a presentation at last year's Workshop.

Rob

[Shaik Hyder Pasha]

Understood,
Thanks Rob!