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Modeling a water turbine using actuator disc theory

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Hello, I'm trying to model the flow in a (simplified) tidal channel. For now there is one turbine placed in the channels (this might be extended to two or more). With this model I hope to study the flow trough the channel under different load conditions of the turbine(s).

As many documents suggest a simple and reliable model is the use of an actuator disc. This disc imposed a force on the flow dependent on the flow speed (the force can be computed using other tools). I'm trying to perform a steady state simulation where the force of the turbine on the flow is constant.

My question is what is the best way to model this force on the flow? There are different method's these are the one's I've come up with but other suggestions are welcome.

My first idea would be to create a line and add a force condition. Unfortunately the line (in the form of Bezier Poligon) does not allow me to create a boundary condition. Is there another way to model this force?

Second option would be to create a turbine rectangle and a difference (the inside of the rectangle is empty). Creating a turbine 'inlet' and 'outlet' boundary. This allows boundary conditions to be set (either in the form of pressure or a stress force). The problem is however that the velocity that exits the domain via the turbine 'outlet' must re-enter via the turbine 'inlet' (or vise versa). How do i correctly impose this constraint?

For the simulation i'm using laminar, single phase, incompressible flow in 2D.


2 Replies Last Post Apr 10, 2013, 8:32 a.m. EDT
Frank van Gool COMSOL Employee

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Posted: 1 decade ago Apr 5, 2013, 10:52 a.m. EDT
Dear Boris,

If you update to the latest version 4.3a, you should be able to select either the "interior fan" boundary condition. Or you can use the "volume force" domain condition.
Is this what you are looking for?

Best regards,
Frank
Dear Boris, If you update to the latest version 4.3a, you should be able to select either the "interior fan" boundary condition. Or you can use the "volume force" domain condition. Is this what you are looking for? Best regards, Frank

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Posted: 1 decade ago Apr 10, 2013, 8:32 a.m. EDT
Dear Frank,

I've tried the "Volume Force" condition on the "turbine" domain and now the pressure and velocity profiles match the expectation.

Thanks a lot,
Boris
Dear Frank, I've tried the "Volume Force" condition on the "turbine" domain and now the pressure and velocity profiles match the expectation. Thanks a lot, Boris

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