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-   -   Dynamic Mesh (http://www.cfd-online.com/Forums/openfoam-meshing/64919-dynamic-mesh.html)

ezzieyguywuf May 28, 2009 13:52

Dynamic Mesh
 
Hey guys,

I am very very new to openFOAM and CFD in general. I would like to model the flow of air around a Vertical Axis Wind Turbine (VAWT). In this case, the flow of air is what is causing the mesh to move, while at the same time (I assume) the mesh is having an effect on the air flow. Is this case possible to model in openFOAM and if so can I have some guidance in setting this up?

Wolfgang

marico May 29, 2009 03:19

Hi Wolfgang,

I can only speak in general without experience for that topic:
Your problem looks like if you have to set up a rotating cylindrical mesh with all the Turbine Walls inside and a static mesh with the surrounding airflow (where the rotating cylinder is substracted), in an abstract way the same like in:

http://openfoamwiki.net/index.php/Si...vaned_diffuser

One problem could be the speed, which in your case is dependent on airflow! Probably there exists already a solution, but I dont know. Normally it is defined as constant, if I'm up to date.

Marco

ezzieyguywuf September 27, 2009 00:15

Thanks for your reply Marico. I'd like to bump this to see if anyone can provide further support. I am currently taking a graduate level intro-to-cfd course at university (to establish the necessary background for this kind of thing) but could still use some help.

http://en.wikipedia.org/wiki/File:Savonius-rotor_en.svg

That link has a good image of what I wish to model. The boundary would just be the "S" shaped wings, not the whole diameter of the circle.

Thanks for any help guys!

ericnutsch December 11, 2009 21:09

Vertical Axis Turbine
 
I am in the process of learning how to model a vertical axis turbine in OpenFOAM.
I plan to use a rotating reference frame.

You cannot have the wind tell the turbine how fast to turn(well...you could, but it is not computationaly feasible; plus you would have to write your own script). CFD predicts flow and pressures based on a gemometry(or rotating geomerty). It itterates the flow based on the geometry to give you surface pressures. You can then use those pressures to determine your torque at a given velocity. These two values give you power output. If you run your simulation for a few different rpms for a given velocity you can graph them with a trendline, differentiate for the optimum, and find the maximum power rpm of your turbine. The turbines free-wheel speed would occur when the power production equals zero.

Hope that helps. Good luck to you! Let us know how the project goes.


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