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Can I just use a coarse mesh as my final mesh size? |
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January 16, 2021, 05:41 |
Can I just use a coarse mesh as my final mesh size?
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#1 |
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Join Date: Feb 2019
Posts: 69
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I am testing my model, specifically for RANS and it is able produce good result except for anisotropic shear stress (uv) profile where the oscillation is rampant. I can eliminate these oscillation by using a coarser mesh but I am wondering whether is this the right thing to do and does reviewer reject this practice?
However, I also partly have no idea what is the 'appropriate' mesh size. For instance, when I was working on 2D backward test case, my coarsest mesh was >60k cells. However I came across a journal where they use 61 x 41 grid cells and now it make me wonder whether am I over-estimating the required mesh density. Besides it does make sense to not use such a high mesh density as I am working on RANS and high mesh density will capture unsteady effects which will make prevent RANS from converging. In that case, is it okay to use a coarser mesh for my research and is there a standard number? For instance, for 2D case (e.g. backstep, hills), can I just use mesh number on the order of thousands? |
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January 16, 2021, 06:10 |
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#2 | |
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Sayan Bhattacharjee
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If the methods used in the reference paper, and your experiments, are the same, they could be acceptable; but personally, I would like to create a denser mesh for my own sake, and ensuring that there isn't a high difference between the results of the coarse and fine grids. |
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January 16, 2021, 06:26 |
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#3 | |
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Filippo Maria Denaro
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First of all, the quality of the mesh does not depend only on the total number of nodes, you have to specify the details of the flow problem. However, a reviewer will ask you for a grid refinement assessment until a grid independent solution is reached. RANS produces a solution largely driven by the turbulence model, thus you have to demonstrate that the grid resolution is enough fine to let only the model acts. And not at all, a high mesh density will not capture unsteady effects. That depends on the proper formulation for solving transient problems. |
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January 16, 2021, 06:37 |
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#4 | ||
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January 16, 2021, 06:41 |
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#5 | |
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However, may I asked what is the general acceptable number of mesh cells for 2D case? This is because, when I test my model at very high mesh cell number (e.g. >100k), the general flow field (e.g. flow separation) does not vary much compared to low mesh cell number (e.g. >1k), except that the uv profile becomes highly oscillatory at high mesh density. In that case, is it okay to just stick to the thousand range as I do not have to deal with the issue of uv profile oscillation? |
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January 16, 2021, 06:49 |
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#6 | |
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Filippo Maria Denaro
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Again, is not the total number of nodes that defines the quality or the good level of resolution. That depends on the geometry, Reynolds number, type of BCs at the wall. A reviewer of a relevant journal would not accept only a number of cells. For some 2D flow problems a 100k number could be ridiculous. |
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January 16, 2021, 23:21 |
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#7 | |
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January 16, 2021, 23:48 |
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#8 | |
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Kira
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Just as an aside; this would depend on when the paper was published, but have you considered reaching out to the author(s) and asking for the data? Some may give you the velocity profiles, others may not, but the only way to know for sure is to ask. If anyone ever contacted me about something like that for my work, I would be inclined to assist them. |
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January 17, 2021, 06:11 |
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#9 | |
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Filippo Maria Denaro
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Submitting an article to a journal means you propose a new methodology or you apply a standard methodology to a new flow problem. The former case requires you compare your results to the best result you found in literature. |
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Tags |
fluent, mesh, rans modelling, separate flow, turbulence |
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