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Question on applying exponentially stretched grid in the vertical direction. |
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December 19, 2023, 05:24 |
Question on applying exponentially stretched grid in the vertical direction.
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#1 |
New Member
DENGGEFEI
Join Date: Dec 2023
Posts: 16
Rep Power: 3 |
hello,
I want to transform a code( Rans-2DV-WENO-SIMPLIC- sigma Coordinate) into a vertical streched version to statifity the y+ condition in deep waters. The original code use a uniform mesh in the vertical, the vertical grid number is 8000 to meet y+=100 in my simulation, which is too expensive. Therefore, I should apply the vertical stretched version. But I have no idea how to use the exponentially stretched grid. Could some one be so nice to tell me how to deal with it? Is there any example to study? I think there should be a transform function, so the compution domain is uniform, and the scheme used in the original code still works. thanks in advance |
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December 19, 2023, 08:42 |
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#2 |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,897
Rep Power: 73 |
Why do you want to compute the discrete derivatives in the computational plane? Use the formula for non uniform grid.
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December 19, 2023, 09:50 |
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#3 |
New Member
DENGGEFEI
Join Date: Dec 2023
Posts: 16
Rep Power: 3 |
Hello FMDenaro, the original code apply a geometric multigrid with red-black SOR method to solve possion function, and the advection is sloved by the WENO scheme. In the computational plane(uniform grid)these scheme may work. This is why i want to do calculations in the computational plane. Very thanks to you.
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December 19, 2023, 10:47 |
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#4 | |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,897
Rep Power: 73 |
Quote:
https://www.researchgate.net/publica...-uniform_grids But you need to transform the equations from the physical to the computational plane. This is a topic you can find in the classic textbooks about structured grid generations. |
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December 19, 2023, 11:03 |
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#5 |
New Member
DENGGEFEI
Join Date: Dec 2023
Posts: 16
Rep Power: 3 |
Thanks very much, FMDenaro.
I hope tp do the exponentially stretched grid in the sigma coordinate. In the physical domain, the bottom is the sea bed and the up is the free-surface. In the computational domain 1 (for the original code), the bottom is 0 and the up is 1. This transformation is clear and many model does this. However, when I want to use stretched grid in the computational domain 1, and by some transformation like sigma-transformation, the stretched grid will be uniform in the computational domain 2 (for the stretched code version), and the scheme used in the original code can be easily applied into the stretched one. |
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December 19, 2023, 11:09 |
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#6 | |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,897
Rep Power: 73 |
Quote:
yes, but there is the fact you need the metric, that is the Jacobian for the derivatives. |
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December 19, 2023, 22:59 |
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#7 |
New Member
DENGGEFEI
Join Date: Dec 2023
Posts: 16
Rep Power: 3 |
Thanks very much.I will learn from your suggestion
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Tags |
rans, stretched grid |
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