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Old   May 20, 2011, 09:22
Default Multiple Rotors
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Michel Van de gaer
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Hello,

I'm fairly new to OpenFOAM and CFD simulations and I'd like to ask some questions and hope to get some directional advice on how to simulate a setup of multiple propellors.

The idea I'm working on is very basic, 16 rotors are placed in a circle, and drive by an internal motor, and RC controlled. The goal is to see if the whole formation would spin around its axis like a wheel, and move sideways forward through water, like drill.

I have been constructing a mechanical model to figure it out, but recently I've encountered some difficulties and thought of making the switch to a computer simulation. See pictures and clip below to get an idea.

The concept is based on a wild idea of how would physics-particles, such as electrons or photons would move through an Aether (the Vacuum) if they had any structure. More than a year ago I posted some rather naïve questions of CFD simulations at the speed of light on this forum and got some good advice to try to use Blender 3D.

Now I have tried Blender and even designed the model you can see in the pictures with it, but couldn't find a way to do a simulation with their physics engine, that's why I'm passing by OpenFOAM again to hopefully get some new advice from you experts.

So what I would like to know if its possible to simulate the motion of these propellors in a medium with OpenFOAM, and if it's doable, regarding rendering times, with a 'normal' computer?

Looking forward to hear from you,

greetings,

m.

--

Clip: http://youtu.be/VTwqssM8yfE


A little sketch of the original idea:




The mechanical model in action:




How it's driven by little motors from the inside:




The technical design:








For a CFD simulation a basic setup would be sufficient:



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Old   September 15, 2016, 03:25
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Hi Michael,

Interesting post. I've formulated an aether based theory for the EM fields:

http://www.cfd-online.com/Forums/ele...-openfoam.html

I think it will not be too difficult to implement this in OpenFoam, but I have to check that out further. I guess it's not too difficult, although we will have to simulate both compressible waves as well as incompressible rotating magnetic fields....
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Old   September 15, 2016, 07:46
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Very complex geometry you have there, but thankfully it can be simplified. Only model one of the rotors in OpenFOAM, then apply a wedge boundary condition to either side of it. That's equivalent to having a ring of them.

I've not worked with a blockmesh that changes over time (aren't there tutorials for this?) nor imported models; someone else will have to help you with that. I'd worry that you might have trouble using both an imported model and modeling motion at the same time. But again.. I have no experience in that regard.

Another possibility is just to focus on an individual rotor. You could model just one bladed section of said rotor as a wedge, have it be static and just give the outer boundary condition as water moving tangentially to it (because a still rotor in swirling water is the same as a swirling blade in still water, right?). You could then print the forces on your rotor to see which way it wants to move.
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Old   September 15, 2016, 08:37
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Hi KarenRei,

Thanks for your suggestions, but this is rather an old post (2011) that resurfaced due to a recent comment. In the mean time I have had some help and did the simulations with SPH particles in a simplified version, and it worked. Here's one example:

https://www.youtube.com/watch?v=ndQDWQmgejc
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