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Weird velocity profile in boundary layer

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Old   March 15, 2011, 07:26
Default Weird velocity profile in boundary layer
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Greg Melling
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Hi,
I am trying to simulate flow around a cylinder with pimpleFoam. I'm trying to resolve the junction vortex but i've realised the calculated velocity profile is very odd. It is not logarithmic as expected. BC on the wall is uniform 0. I have run the model with wall functions and without, with coarse mesh and fine mesh and always get the same weird profile, where the flow velocity is maximum just above the bed!!?? i cannot understand why, i've tried pretty much anything i could think of, changed BCs, used potential foam, with/without wall functions, different meshes and i always get this to some extent.... i've taken the cylinder out and just run a channel but still get that signature, albeit less pronounced. sometimes the maximum flow velocity is larger than my input velocity U=0.441 ??
does anyone have an idea what might be wrong. I've attached 2 screenshots for clarification (x axis is z and y-axis is U, its how paraview plots it). would be endlessly grateful for any ideas, i'm at my wits end, it doesnt make any sense. could also post the case if needed...
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File Type: jpg withcyl.jpg (16.3 KB, 24 views)
File Type: jpg simplechannel.jpg (15.5 KB, 21 views)
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boundary conditions, boundary layer., velocity

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