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Drag and lift calculation in Arbitrary Mesh Interface simulation |
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#1 |
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Hello everyone, I have a simple question about lift and drag calculation in OpenFOAM. Obviously, in a simulation with no moving mesh it is straightforward to specify LiftDir and DragDir (lift direction vector and drag direction vector, respectively). But in case of sliding mesh, that is, those directions are changing with respect to time, so How can we specify the lift and drag directions in this case?
Update: I want to clarify the question because someone got it wrong. What I mean exactly is: in case of say rotating airfoil about some axis, horizontal axis wind turbine, vertical axis wind turbine ...etc) obviously the body is moving so in this case how to specify the lift and drag directions? Last edited by anon_q; April 20, 2018 at 17:31. |
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#2 | |
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Uwe Pilz
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Quote:
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Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950) |
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#3 |
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No please I guess you can understand what I mean. Of course I mean a body within a dynamic mesh (rotation, oscillation,...etc). In my example I've a rotating airfoil about some axis. Can you imagine lift and drag for no object??!!!
Last edited by anon_q; April 20, 2018 at 17:27. |
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#4 | |
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Bruno Santos
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Greetings to all,
I've arrived at this thread, coming from here: https://github.com/blueCFD/Core/issues/98 - from which the following additional questions+information are relevant: Quote:
This way it's possible to change the lift and drag directions for each already recorded time step and use a function object entry in accordance to each time step. The annoying part is that the lift and drag directions have to be known for each time step and manually defined... @Evren, a few questions:
Bruno
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#5 |
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Thank you very much dear Bruno,
For an example let's say we want to calculate force coefficients (Cl, and Cd) for the following simulation of vertical axis wind turbine: https://www.youtube.com/watch?v=6o4L...ature=youtu.be The surface is not changing but the mesh is composed of a rotating zone and a fixed zone |
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#6 |
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Bruno Santos
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So that means that the positions are predefined and can be calculated directly based on the rotation speed?
My concern is if the rotation/movement speed was meant to change with the flow itself... |
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#7 |
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In my case the rotation speed is constant, the position of the airfoils as a function of time are known.
Last edited by anon_q; April 22, 2018 at 16:04. |
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#8 |
Retired Super Moderator
Bruno Santos
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Quick answer: Unfortunately I didn't have more time beyond the following attached example:
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