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Issue with curved non-slip wall in fluid dynamic model
Posted 16 oct. 2009, 06:45 UTC−4 1 Reply
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I am trying to model the power produced by a tidal turbine in an open channel flow using the 2D Navier stokes application. The main subdomain has inlet and outlet boundaries as well as a non-slip base and a symmetry boundary at the top. This provides a good estimate for the device performance but, it is well known that the free surface deforms so that the downstream flow is shallower than the upstream.
I have developed a technique to vary this free surface and then create a new model with the top surface defined by a series of lines (defined using the curve geometry tool). This "free surface" should then constrain the flow in a realistic way. This does not seem to work though because as soon as the free surface changes direction the tangential velocity goes to zero and I end up with what appears to be a non-slip wall (see attached image). I have tried replacing the symmetry boundary with a non slip boundary but this phenomenon still occurs.
Does anyone know of any way of avoiding this problem, possibly by using a different technique for defining the curve of the free surface or some other technique? I am currently using linear elements but could easily switch to higher order elements.
Thank you for your time,
Ross McAdam
I have developed a technique to vary this free surface and then create a new model with the top surface defined by a series of lines (defined using the curve geometry tool). This "free surface" should then constrain the flow in a realistic way. This does not seem to work though because as soon as the free surface changes direction the tangential velocity goes to zero and I end up with what appears to be a non-slip wall (see attached image). I have tried replacing the symmetry boundary with a non slip boundary but this phenomenon still occurs.
Does anyone know of any way of avoiding this problem, possibly by using a different technique for defining the curve of the free surface or some other technique? I am currently using linear elements but could easily switch to higher order elements.
Thank you for your time,
Ross McAdam
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1 Reply Last Post 19 oct. 2009, 18:36 UTC−4
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Posted:
1 decade ago
Hi
Changing and adapting dynamically the geometry will be much easier in V4, but you still need to wait some months for that.
In the mean time, if you are not using the ALE (but I'm afraid you are already usiging it) you could perhaps managed to deform your geomtry with the ALE application, as used for some examples of adaptive geometry in the documentations.
But for these approaches I have not enough experience to really propose you something practicle.
Sorry for that, good luck anyhow, I like your idea of analysis
Ivar
Changing and adapting dynamically the geometry will be much easier in V4, but you still need to wait some months for that.
In the mean time, if you are not using the ALE (but I'm afraid you are already usiging it) you could perhaps managed to deform your geomtry with the ALE application, as used for some examples of adaptive geometry in the documentations.
But for these approaches I have not enough experience to really propose you something practicle.
Sorry for that, good luck anyhow, I like your idea of analysis
Ivar