# Question regarding 2D depth and force acting on mo

Hello guys!

I've been trying to find information in some of the pdf's but I just can't figure this out and searching the forum a bit.

I started wondering about how I was able to export mass and volume from a 2d simulation? I did not specify any depth? This is my case:

Basically a box of fluid inside a box, and then a moving box in the middle.

Secondly my method for calculating the force acting on the moving box (in the middle) during movement is by using F = ma on the particles of the moving box, since I have the assumption that these particles have to get a acceleration to overcome the forces of water and do the prescribed sinusdioal motion. Any comments or better approach on this?

Kind regards, Ahmed

• With regards to the first part of my question (depth of 2d simulation) I thought a bit and came to the realization that:

Volume = Area x Depth

So since I know the volume of the moving particles by exporting via PartVtk and that I know the area of the moving square, 0.01 m^2, I could calculate the depth. I ended up with a depth of 44 metres..

I am still confused how DualSPHysics can provide a volume in 2d (ie which depth it uses naturally, is it the 1 my I see in Freecad GUI?) but wanted to share some more of my thoughts if they were to help others in the future.

• Okay it was pretty basic, I just got confused by the exported data files - in 2D the units are just N/m, kg/m etc. - there is no need for an arbitrary depth as in FVM. Verified by simulating the floating test case in 3D and 2D.