Problem with X13
 

Hello

I am trying to analyze floating body using reef3d.
I’m confused about X13 Rigid body dynamics representation, What's the difference between X13 1 and X13 2? I find that the Ze(X13 1，REEF3D_6DOF_E_force.dat) is not the same as the Fz (X13 2，REEF3D_6DOF_forces_0.dat), I mean they're all resultant force in z direction of the object. So what's the difference between these two options?

With best regards
Allison

As described in the User Guide,
X 13 1 follows the older implementation for the handling of fluid-floating body interface in REEF3D (Bihs and Kamath, 2017, IJNMF 83 (12), 905-916, doi: 10.1002/fld.4333) using the Ghost cell immersed boundary method.

X 13 2 is the new implementation for the same, using a direct forcing ghost cell method, following Martin et al. 2021, Appl. Oce. Res. 106, doi: 10.1016/j.apor.2020.102410.

Thank you so much , I have read two articles, and I ' m confused about "a direct forcing ghost cell method” following Martin et al. 2021, Appl. Oce. Res. 106. I find in the article, it uses the direct force to deal with fluid-structure interaction, where does the "ghost cell" idea reflect?

With best regards
Allison

Hi,


as my colleague has already tried to explain, these are two different implementations.



The ghost cell immersed boundary method is described in Bihs and Kamath, 2017, IJNMF 83 (12), 905-916, doi: 10.1002/fld.4333.

It is though recommended to use X 13 2 which is the continuous direct forcing method following Martin et al. 2021, Appl. Oce. Res. 106, doi:10.1016/j.apor.2020.102410. Here, no ghost cells are required.



I hope this helps.


Kind regards,
Tobias

Hi，

Thank you so much ,Now I have a general understanding that these are two different approaches, I used to confused the description about "a direct forcing ghost cell method"
Now I'm trying to learn more about this method

With best regards
Allison