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November 26, 2007, 14:46 |
how can I increase Y-plus in 2D geometry
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#1 |
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Hi I am simulating 2D geometry I saw my y+ value very law can anyone guide me how can i increase it?
rb |
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November 27, 2007, 04:42 |
Re: how can I increase Y-plus in 2D geometry
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#2 |
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Take a look at this to understand y+: http://www.cfd-online.com/Wiki/Dimen..._wall_distance
Y+ is the non-dimensional wall distance. The formula y+ = u(star) * y / kin_visk, says it all for you. If you wan't to increase y+ value then make the center of you first cell further from the wall. Or change the kinematic viskosity. The value of y+ in the first cell should be controlled in regard to what you are modelling. Take a search on y+ in forum and you will find loads of information. BR Kasper |
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November 27, 2007, 05:28 |
Re: how can I increase Y-plus in 2D geometry
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#3 |
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Hi thanks for the information you sent. I saw the formula for estimating the desire grid distance but it was mentioned for flow a flow over a flat plate? is it work for the case of pipe flow and how much the value of Ref. length in this case for y+=41 & diameter=77.92 mm?
rb |
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November 28, 2007, 02:55 |
Re: how can I increase Y-plus in 2D geometry
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#4 |
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I think the diameter could be the reference length, but I'm not sure. Use the grid spacing calculator: http://geolab.larc.nasa.gov/APPS/YPlus/#TOTAL
and insert y+=41 ref.length=0.07792m and your Re no. But why are you using y+=41? BR Kaspeer |
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November 30, 2007, 09:53 |
Re: how can I increase Y-plus in 2D geometry
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#5 |
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because I need to use the non-equilibrium wall function as wall treatment so I want set y+ over 30? Do you have another suggestions?
rb |
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