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-   -   immersed boundary method of Markus Uhlmann (https://www.cfd-online.com/Forums/main/101532-immersed-boundary-method-markus-uhlmann.html)

dishengbin May 7, 2012 04:51

immersed boundary method of Markus Uhlmann
 
1 Attachment(s)
Hello, everyone.
I’ve tried the immersed boundary method proposed by Ulhmann (Uhlmann, M. (2005). "An immersed boundary method with direct forcing for the simulation of particulate flows.”). I have doubt about the determination of Lagrangian markers (requires ds=dx)the mathematical expressions are in the attachment. Can anybody explain the reason? Thank you very much!

dishengbin May 8, 2012 21:34

anybody kowns the reason? thank you in advance:)

arjun May 9, 2012 00:06

Quote:

Originally Posted by dishengbin (Post 360000)
anybody kowns the reason? thank you in advance:)

i can't open .docx so i can't comment.

dishengbin May 9, 2012 00:45

Quote:

Originally Posted by arjun (Post 360022)
i can't open .docx so i can't comment.

hi Arjun, thanks for your reply. I do not know how to add mathematical equations in the message:). My doubt is why the distance of the markers is required to be equal to the cell length? thank you .

arjun May 9, 2012 05:05

Quote:

Originally Posted by dishengbin (Post 360025)
hi Arjun, thanks for your reply. I do not know how to add mathematical equations in the message:). My doubt is why the distance of the markers is required to be equal to the cell length? thank you .

I have experience with writing immersed boundary codes so i thought I might be able to help.
But I haven't read the original paper you quote and I do not have access to it. I thought your docx might give me some hints to what you are talking about but I can not open that either.

Anyway, if I have to just guess blindly, my guess is that he require ds=dx etc because of ease of interpolation (creating a interpolation function) or ease of marking solid and fluid points. Solid marking is tough and time consuming task if grid is not uniform or if grid is unstructured.

dishengbin May 9, 2012 06:44

Quote:

Originally Posted by arjun (Post 360051)
I have experience with writing immersed boundary codes so i thought I might be able to help.
But I haven't read the original paper you quote and I do not have access to it. I thought your docx might give me some hints to what you are talking about but I can not open that either.

Anyway, if I have to just guess blindly, my guess is that he require ds=dx etc because of ease of interpolation (creating a interpolation function) or ease of marking solid and fluid points. Solid marking is tough and time consuming task if grid is not uniform or if grid is unstructured.

Thanks for your explanation. Yes, you are right, he requires ds =dx, http://www.sciencedirect.com/science...21999105001385
(i'm not sure whether you can access it)
In equation (9b), dv = dx*dy = ds*dx(dy). in 2D case. But in the flow past a stationary circular cylinder, when I use more or less markers, the drag/lift force varies significantly. In some other papers , dv is replaced by ds. So could you let me know the reason? thanks


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