[dishengbin]

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]

anybody kowns the reason? thank you in advance

[arjun]

Originally Posted by dishengbin

anybody kowns the reason? thank you in advance

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

[dishengbin]

Originally Posted by arjun

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]

Originally Posted by dishengbin

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]

Originally Posted by arjun

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