Openvsp beginner

[Gladys See]

Hi everyone, thank you for having this space. I’m an aerospace engineering student with a final year project aiming to analyse the aerodynamic of C-130 Hercules with winglet configuration using OpenVSP software to investigate the aerodynamics forces and propeller wake effect of the aircraft with winglets installed onto the aircraft wings.

Would you be able to advice me on the specs of the propellers used on the C130 herk as I’m not able to find that online. 

Also I tried using the CFD MESH but running it crashes the whole program. Would you be able to guide me on why this is happening and why the geometry tool pop up doesn’t appear?

Sorry about the silly questions, I’m alittle lost on how to navigate the software. I’m working on this project alone and have not used OpenVSP before. 

Im a student from Singapore, would anyone be able to guide me through if you have time on zoom or teams if possible. 

I’ve been struggling and really hope to pass this final year of university. Thank you for your time in reading this.  

[Rob McDonald]

The best advice is to start simple and add complexity as you build confidence.

In your case, that probably means start with just a wing.  Run that wing through whatever process and analysis you want to perform.  Once you've worked out the bugs, add a tail, run that through the process.  Then a fuselage.  Run that through the process.  Then add an actuator disk or a propeller -- depending on what tools you are using.  Adding propulsive components can be complex in many tools.  I would do all this with simplified geometry first -- then come back with more realistic geometry matching your target case.  Once again, start simple and work up in complexity.

Detailed propeller geometry is seldom supplied.  This is one big advantage to using the actuator disk model in OpenVSP -- you can specify the thrust and power coefficients for a propeller and the flow can be simulated without needing the detailed geometry.

Why are you trying to run CFDMesh?  What analysis tool are you going to use after that?  CFDMesh might not be the right tool.  CFDMesh is very picky about a lot of things -- the start simple and work to complex is the best way to figure out what it doesn't like about your file.  If you build some experience, you can probably figure out the problem and a way around it.  If you want to post your file here, someone may be able to help you.  However, without more information, I don't think anyone can help.

Best of luck,

Rob

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[Gladys See]

Hi Rob, 

Thank you so much for your advise and prompt reply.  
I`m having an issue regarding the visual of the rotor wakes. 
As you can see (from the picture below), I have created a model with the rotor as disk but when I tried running it on VSPAERO, there are no wakes showing up on the viewer. 
Is there a way to show the wake at view? 
I have sent the file as well for your viewing if needed. 

[Rob McDonald]

It looks to me like you are making good progress.

The actuator disk does not have its own trailing vortices -- those only happen in VSPAERO when you model unsteady rotating blades.

You should see some effect of the actuator disks on the movement of the wing trailing wake lines -- it can be subtle, so a view from the front may help to see it.

Also, you will see an effect from the actuator disks on the spanwise load distribution.

Rob

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[Gladys See]

Hi Rob, 

Thank you for the prompt reply! 
Can I ask, how do you model an unsteady rotating blades? 
What parameters do I need to change in order to do so as i would like to see the wake effect of the disk. 

[Rob McDonald]

You first go to the propeller and change their representation from 'Disk' to 'Blades'.  To do it right, you now need to know lots of details about the design of the propeller.

When you switch representations, the VSPAERO GUI will change available options -- On the advanced tab, for propeller representation, select 'Rotating Blades'.  instead of the 'Disk' tab, you will now have access to the 'Propeller' tab with a bunch of options.  The most important one here is RPM. 

Here is a simple example you can play with.  It probably should have more spanwise resolution in the area of the propwash.

Rob

 

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