How to decide the number of grid lines in boundary layer
Hi,
May I ask how to decide how many grid lines(at the direction proportional to the wall) do I need(to resolve boundary layer well)? Of course grid independence study is always good practice. But I always need a first guess of this number to have my first grids before the grid independence study. Thank you very much. |
That depends on the order of your scheme and on the type of flow you are considering. Impossible to answer in general....
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If you are performing a RANS or URANS simulation the standard approach is to settle on the distance of the first point off the wall based on an acceptable y+ value, and then keep any grid stretching ratio below 1.2. The resulting simulation should always be reviewed after the fact to ensure that the actual value of y+ is still acceptable and the boundary layer is well-resolved.
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After running problem in solver. you will get actual value of Y+ . before running also we can calculate by Y+ estimatation calculater in CFD online(Rough). based on calculation you can find first cell distance.
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If I use laminar model(no model), do I need to have Y+ smaller or equal to 1? Thank you. |
please post your problem brief. whether its Heat transfer or only fluid flow problem. I will send some data based on that. that data will answer your question. .
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Just wondering: If it's for heat transfer, Y+ will need to be below 1, right? |
Based Turbulence models Y+ limitation is there for each models(like K-omega ,K-epsilon). if u want caputure flow parameter along vertical. u have make fine mesh near wall.For Y+ consideration i will refer and answer your question later .
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Hi
I have a question like Anna. Anna did you find an answer to your question about importance of y+ in laminar cases? and is it important that flow be compressible or incompressible? thanks. |
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